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Cited by 21Muscle metabolism and nutritionNutrition and Health in AgingExercise and Physiological Responses

A 12-Week Randomized Double-Blind Placebo-Controlled Clinical Trial, Evaluating the Effect of Supplementation with a Spinach Extract on Skeletal Muscle Fitness in Adults Older Than 50 Years of Age

Open access
Pérez-Piñero, Silvia, Ávila-Gandía, Vicente, Rubio Arias, Jacobo A., Muñoz-Carrillo, Juan Carlos, Losada-Zafrilla, Pilar, López-Román, Francisco Javier·2021·Nutrients
DOI 10.3390/nu13124373PMC PMC8706266
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Abstract

The aim of a 12-week randomized double-blind placebo-controlled study was to assess the effect of daily supplementation with a natural extract of Spinacia oleracea L. (4 × 500 mg capsules/day; total 2 g per day) combined with a moderate-intensity training program (1 h session/3 times a week) on skeletal muscle fitness in adults over 50 years of age. Muscle strength assessed by isokinetic and isometric dynamometry improved significantly in the experimental (n = 23) and the placebo (n = 22) groups, but the magnitude of improvement was higher in the experimental group, with between-group differences in almost all variables, including isokinetic at 60° s−1 in knee extension, peak torque (p < 0.007); total work per repetition maximum (p < 0.009); isokinetic at 180°s−1 in knee extension, peak torque (p < 0.002); total work (p < 0.007); total work per repetition maximum (p < 0.005); average power (p < 0.027); isometric in knee extension, peak torque (p < 0.005); and average peak torque (p < 0.002). Similar findings were observed for muscle quality. Changes in quality of life (SF-36) were not found, except for improvements in the role physical (p < 0.023) and role emotional (p < 0.001) domains, likely as a result of the physical training sessions. A nutritional survey did not revealed changes in dietary habits. No adverse events were recorded. In subjects over 50 years of age, moderate-intensity strength training combined with daily supplementation for 12 weeks with a natural extract of Spinacia oleracea L. improved muscle-related variables and muscle quality. Maintaining muscle health is a key component of healthy aging.

AI snapshot

Written from the paper’s full text.

TL;DR

In adults over 50 years, 12 weeks of daily spinach extract supplementation (2 g/day) combined with moderate-intensity resistance training improved muscle strength and muscle quality more than placebo plus training. No adverse events were recorded, and body composition changes occurred in both groups without significant between-group differences.

Key findings

  • Among 45 completers (23 experimental, 22 placebo), muscle strength improved in both groups but more in the spinach extract group, with between-group differences in isokinetic knee extension at 60° s−1 for peak torque (p < 0.007) and total work per repetition maximum (p < 0.009), and at 180° s−1 for peak torque (p < 0.002), total work (p < 0.007), total work per repetition maximum (p < 0.005), and average power (p < 0.027).
  • Isometric knee extension also showed between-group differences for peak torque (p < 0.005) and average peak torque (p < 0.002); muscle quality improved significantly within and between groups in all variables.
  • Body composition improved in both groups (fat mass decreased; lean and muscle mass increased), but between-group differences were not statistically significant. Sarcopenia percentage decreased from 65.2% to 52.2% in the experimental group and from 77.3% to 59.1% in the placebo group.
  • Quality of life (SF-36) showed no changes except role physical (p < 0.023) and role emotional (p < 0.001); no adverse events were recorded, and the nutritional survey showed no changes in dietary habits.

Methods

  • Single-center, randomized, double-blind, placebo-controlled trial with two parallel arms in adults aged 50–75 years, BMI < 32 kg/m2, not performing scheduled weekly exercise. Of 80 volunteers, 51 were randomized and 45 completed (23 experimental, 22 placebo); mean age 58.9 ± 6.1 years, with 8 men and 37 women.
  • Participants received either spinach extract (Spinacia oleracea L., 4 × 500 mg capsules/day; total 2 g/day) or identical placebo (maltodextrin) for 12 weeks, combined with supervised moderate-intensity resistance training (1 h/session, 3 times/week, 60–75% 1RM).
  • Outcomes included isokinetic and isometric dynamometry, handgrip strength, DEXA body composition, muscle quality, SF-36 quality of life, and a 24-h dietary recall. Analysis used per-protocol repeated-measures ANOVA with Bonferroni correction, significance set at p < 0.05.

Limitations

  • The paper states the trial was exploratory, had a reduced sample size, and lasted only 12 weeks; hormone replacement treatment was not specifically recorded as an exclusion criterion, dietary intake during the protocol was not controlled, and the gender analysis included a small number of men.
  • Evident from the text: the analysis was per-protocol, excluding dropouts; the sample was predominantly women (82.6% experimental, 81.8% placebo), limiting generalizability; and between-group differences were not significant for body composition, handgrip strength, or maximal dynamic force (1RM).

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3390/nu13124373

Cites

55 of 55 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 51 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The magnitude of improvement in muscle strength was higher in the experimental group than in the placebo group.

    “but the magnitude of improvement was higher in the experimental group”
    • Also stated in: § 3.3. Muscle Function · plain
      “but the magnitude of improvements was higher in the experimental group (Table 3)”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Participants in both groups adhered similarly to the training program.
    • Rests on an assumption: The placebo (maltodextrin) has no effect on skeletal muscle fitness.
  • Findingown data

    Similar findings to muscle strength were observed for muscle quality.

    “Similar findings were observed for muscle quality.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Participants in both groups adhered similarly to the training program.
    • Rests on an assumption: The placebo (maltodextrin) has no effect on skeletal muscle fitness.
  • Findingown data

    Muscle strength assessed by isokinetic and isometric dynamometry improved significantly from baseline in both the experimental (spinach extract) and placebo groups.

    “Muscle strength assessed by isokinetic and isometric dynamometry improved significantly in the experimental (n = 23) and the placebo (n = 22) groups”
    • Also stated in: § 3.3. Muscle Function · plain
      “Muscle function improved significantly at the end of the study as compared with baseline both in the experimental and the placebo groups”
    Quote in the paperSubstantial claim
  • Findingown data

    No adverse events were recorded.

    “No adverse events were recorded.”
    Quote in the paperNot a substantial claim
  • Findingown data

    At 180° s−1 knee extension, between-group comparisons were statistically significant for all variables.

    “although at 180° s−1 knee extension, between-group comparisons were statistically significant for all variables.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Participants in both groups adhered similarly to the training program.
    • Rests on an assumption: The placebo (maltodextrin) has no effect on skeletal muscle fitness.
  • Classified as probably not a substantial claim. 41
  • May combine two claims. 37

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    A nutritional survey did not reveal changes in dietary habits.

    “A nutritional survey did not revealed changes in dietary habits.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Changes in quality of life (SF-36) were not found, except for improvements in the role physical (p < 0.023) and role emotional (p < 0.001) domains.

    “Changes in quality of life (SF-36) were not found, except for improvements in the role physical (p < 0.023) and role emotional (p < 0.001) domains”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The consumption of the spinach extract or placebo for 12 weeks was associated with a reduction of fat mass and an increase in lean and muscle mass in both study groups.

    “The consumption of the spinach extract or placebo for 12 weeks was associated with a reduction of fat mass and an increase in lean and muscle mass. In both study groups, differences in these parameters at the end of the study as compared with baseline were statistically significant when body composition was evaluated by DEXA.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    The total amount of nitrate consumption from the intervention was 14.18 mg/day.

    “total amount of nitrate consumption 14.18 mg/day”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Within-group and between-group differences in muscle quality were statistically significant in all variables.

    “As shown in Table 4, within-group and between-group differences were statistically significant in all variables.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Participants in both groups adhered similarly to the training program.
    • Rests on an assumption: The placebo (maltodextrin) has no effect on skeletal muscle fitness.

  • May combine two claims.

    Findingown data

    Statistically significant between-group differences were observed for all muscle function variables, except for total work and average power in isokinetic dynamometry testing at 60° s−1 knee extension.

    “As shown in Table 3, statistically significant between-group differences were observed for all muscle function variables, except for total work and average power in isokinetic dynamometry testing at 60° s−1 knee extension”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Participants in both groups adhered similarly to the training program.
    • Rests on an assumption: The placebo (maltodextrin) has no effect on skeletal muscle fitness.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    The content of nitrates in the active product was 7088 mg NO3/kg.

    “The content of nitrates was 7088 mg NO3/kg and total amino derivatives expressed as pipecolic acid (died extract) 2.9%.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The use of the study products (active spinach supplementation or placebo) was associated with general improvements in the perception of HRQoL, with significant within-group differences at the end of the study compared with baseline in the role physical and role emotional domains.

    “The use of the study products, either active spinach supplementation or placebo was associated with general improvements in the perception of HRQoL, with significant within-group differences at the end of the study as compared with baseline in the two domains of the role physical and role emotional (Table 6).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In men, the strength developed by the experimental group was higher than the strength that could be developed by the placebo group; an increase in muscle quality was also observed.

    “The strength developed by the experimental group was higher than the strength that could be developed by the placebo group; an increase in muscle quality was also observed.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The study products were well tolerated and no adverse effects were recorded.

    “The study products were well tolerated and no adverse effects were recorded.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The percentage of patients with sarcopenia at the end of the study decreased from 65.2% to 52.2% in the experimental group and from 77.3% to 59.1% in the placebo group.

    “Finally, the percentage of patients with sarcopenia at the end of the study decreased from 65.2% to 52.2% in the experimental group and from 77.3% to 59.1% in the placebo group.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    In women, increases in muscle mass of the lower limb were similar in the two study groups, but improvements in muscle strength were higher as compared with placebo.

    “Analysis of these variables in women revealed that increases in muscle mass of the lower limb were similar in the two study groups, but improvements in muscle strength were higher as compared with placebo [45].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [45] Roberts, 2020, Sex differences in resistance training: A systematic review and meta-analysis, J. Strength Cond. Res. source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    Subjects assigned to the active product showed improvements of muscle function of greater magnitudes than those treated with placebo, with between-group significant differences in all variables in dynamometry testing at 180° s−1 and isometric dynamometry at 90° position.

    “Subjects assigned to the active product showed improvements of muscle function of greater magnitudes than those treated with placebo, with between-group significant differences in all variables in dynamometry testing at 180° s−1 and isometric dynamometry at 90° position.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In women, gains in muscle quality were higher in the experimental group but statistically significant differences by gender were not found.

    “Gains in muscle quality were higher in the experimental group but statistically significant differences by gender were not found.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Participants in both groups adhered similarly to the training program.
    • Rests on an assumption: The placebo (maltodextrin) has no effect on skeletal muscle fitness.

  • May combine two claims.

    Findingreasoning

    There was a significant decrease of fat mass in both study groups and an increase in muscle mass.

    “Moreover, there was a significant decrease of fat mass in both study groups and an increase in muscle mass.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In men, consumption of the active product induced a higher increase in muscle mass in the lower limb than placebo, resulting in higher muscle strength and a greater increase in muscle quality.

    “In men, consumption of the active product induced a higher increase in muscle mass in the lower limb than placebo, resulting in higher muscle strength and a greater increase in muscle quality.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Participants in both groups adhered similarly to the training program.
    • Rests on an assumption: The placebo (maltodextrin) has no effect on skeletal muscle fitness.

  • May combine two claims.

    Findingcitation

    There was a significant decrease in fat mass in both groups, but this change was not clinically significant (2.1% in the placebo group and 1.4% in the experimental group).

    “We found a significant decrease in fat mass in both groups, but this change was not clinically significant (2.1% in the placebo group and 1.4% in the experimental group) [43].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [43] Han, 2016, A clinical perspective of obesity, metabolic syndrome and cardiovascular disease, JRSM Cardiovasc. Dis.

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    After training, there was an increase of muscle mass of 1.5% in the experimental group and 1.1% in the placebo group, but statistically significant between-group differences were not observed.

    “After training, there was an increase of muscle mass of 1.5% in the experimental group and 1.1% in the placebo group, but statistically significant between-group differences were not observed.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    82.6% of participants in the experimental group and 81.8% in the placebo group were women.

    “It should be noted that 82.6% of participants in the experimental group and 81.8% in the placebo group were women.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Results of laboratory tests were within the normal ranges.

    “Results of laboratory tests were within the normal ranges.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Our study identified relevant ergogenic properties, in contrast to Wilborn et al. where no ergogenic effects were observed.

    “In contrast to the results of an early study by Wilborn et al. [27], in which no ergogenic effects were observed, our study did identify relevant ergogenic properties.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [27] Wilborn, 2006, Effects of methoxyisoflavone, ecdysterone, and sulfo-polysaccharide supplementation on training adaptations in resistance-trained males, J. Int. Soc. Sports Nutr. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    In both groups there are significant differences in the evolution of the role emotional, and there is a greater increase in the role emotional in favor of the spinach extract treatment.

    “Although in both groups there are significant differences in the evolution of the role emotional, there is a greater increase in the role emotional, in favor of the spinach extract treatment”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    No adverse events associated with daily ingestion of the active product were observed for 12 weeks, and laboratory test results were within normal limits.

    “No adverse events associated with daily ingestion of the active product were observed for 12 weeks, and laboratory test results were within normal limits.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Improvements were observed in all domains of the SF-36 questionnaire, with statistically significant differences within groups at the end of the study compared to baseline in the role physical.

    “In relation to the changes observed in HRQoL, improvements were observed in all domains of the SF-36 questionnaire, with statistically significant differences within groups at the end of the study compared to baseline in the role physical”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    No changes in macronutrient intake were observed during the study period.

    “In addition, no changes in macronutrient intake were observed during the study period.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The main findings showed significant improvements in muscle strength assessed by isokinetic and isometric dynamometry and muscle quality, as well as a reduction of fat mass and an increase in muscle mass.

    “The main findings showed significant improvements in muscle strength assessed by isokinetic and isometric dynamometry and muscle quality, as well as a reduction of fat mass and an increase in muscle mass.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In the French SU.VI.MAX cohort, a one-point increase in a five-component healthy lifestyle index was related to an 11% higher probability of healthy aging in adults aged 45-60 years.

    “In an analysis of data of 2203 participants, of the French ”Supplémentation en Vitamines et Minéraux Antioxydants” cohort, aged 45–60 years, a one-point increase in a five-component healthy lifestyle index (weight, smoking status, physical activity, alcohol consumption and diet) was related to a 11% higher probability of healthy aging”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [15] Atallah, N., Adjibade, M., Lelong, H., Hercberg, S., Galan, P., Assmann, K.E., and Kesse-Guyot, E. (2018). How healthy lifestyle factors at midlife relate to healthy aging. Nutrients, 10. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Exercise and physical activity are countermeasures against muscle aging and attenuate age-related decreases in skeletal muscle performance.

    “Remarkably, exercise and physical activity are countermeasures against muscle aging and have been shown to attenuate age-related decreases in skeletal muscle performance [4].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [4] Askow, 2020, Of sound mind and body: Exploring the diet-strength interaction in healthy aging, Front. Nutr. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    An active lifestyle supported by appropriate dietary nutrition is crucial to preserve strong, healthy skeletal muscles.

    “There is evidence that an active lifestyle supported by appropriate dietary nutrition is crucial to preserve strong, healthy, skeletal muscles [5].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [5] Shin, 2018, Physical activity, benefits, and barriers across the aging continuum, Appl. Nurs. Res. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A relationship between healthier diets with nutrient adequacy and better muscle mass outcomes has been suggested.

    “In relation to diet as a modifiable factor, a relationship between healthier diets with nutrient adequacy and better muscle mass outcomes has been suggested [12].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [12] Waijers, 2007, A critical review of predefined diet quality scores, Br. J. Nutr. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    The improvements in role physical and role emotional domains of SF-36 were likely a result of the physical training sessions.

    “likely as a result of the physical training sessions”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Numerous studies have shown beneficial effects of various nutrients/nutraceuticals on skeletal muscle health and exercise performance through antioxidant, anti-inflammatory, or anabolic mechanisms.

    “Numerous studies related to the consumption of a large variety of nutrients/nutraceuticals have shown beneficial effects on different aspects of skeletal muscle health and exercise performance (strength and endurance capacity) through antioxidant, anti-inflammatory, or anabolic mechanisms, some of which are still poorly understood [16,17].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [16] Wang, Y., Liu, Q., Quan, H., Kang, S.G., Huang, K., and Tong, T. (2021). Nutraceuticals in the prevention and treatment of the muscle atrophy. Nutrients, 13. source

      Not checked in the free run.

    • cites [17] Deane, 2017, “Nutraceuticals” in relation to human skeletal muscle and exercise, Am. J. Physiol. Endocrinol. Metab. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Recommendations for resistance training in older adults include 2-3 sets of 3-4 polyarticular exercises involving large muscle groups at intensities of 70-85% 1RM, 2 to 3 times per week.

    “Recommendations of resistance training programs for older adults include 2–3 sets of 3–4 polyarticular exercises, involving large muscle groups at intensities of 70–85%, of 1 repetition maximum (1RM), 2 to 3 times per week [8].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [8] Gallardo, 2011, Short-term, light- to moderate-intensity exercise training improves leg muscle strength in the oldest old: A randomized controlled trial, J. Am. Geriatr. Soc. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Resistance training improves muscle strength and endurance and is used to improve physical fitness and functional performance in elderly people.

    “Resistance training is a form of exercise that improves muscle strength and endurance and is progressively gaining attention and interest as a method used to improve physical fitness and functional performance in elderly people [6].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [6] Li, 2020, Effects of resistance training on exercise capacity in elderly patients with chronic obstructive pulmonary disease: A meta-analysis and systematic review, Aging Clin. Exp. Res. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Healthy dietary patterns and adherence to healthy diets, such as the Mediterranean diet, are associated with improvements in different domains of self-reported quality of life in older adults.

    “In a systematic review of 15 studies, healthy dietary patterns and adherence to healthy diets, such as the Mediterranean diet, showed an association with improvements in different domains of self-reported quality of life in older adults [14].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [14] Govindaraju, T., Sahle, B.W., McCaffrey, T.A., McNeil, J.J., and Owen, A.J. (2018). Dietary patterns and quality of life in older adults: A systematic review. Nutrients, 10. source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Dietary nitrate (NO3−) supplementation has beneficial effects on muscle contractility and muscle efficiency, and improves muscle endurance during weightlifting exercise in healthy adults.

    “The ergogenic potential of dietary nitrate (NO3−) supplementation has shown beneficial effects on muscle contractility and muscle efficiency, as well as to improve muscle endurance during weightlifting exercise in healthy adults [32].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [32] San Juan, A.F., Dominguez, R., Lago-Rodríguez, Á., Montoya, J.J., Tan, R., and Bailey, S.J. (2020). Effects of dietary nitrate supplementation on weightlifting exercise performance in healthy adults: A systematic review. Nutrients, 12. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Spinach extract is characterized by a high content of phytoecdysteroids, particularly 20-hydroxyecdysone (20E), which have been shown to increase strength and muscle mass during resistance training, reduce fatigue, and facilitate recovery.

    “Spinach extract is another widely used food supplement or ergogenic aid, characterized by a high content of phytoecdysteroids, particularly 20-hydroxyecdysone (20E), which have been shown to increase strength and muscle mass during resistance training, to reduce fatigue and to facilitate recovery [20].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [20] Isenmann, 2019, Ecdysteroids as non-conventional anabolic agent: Performance enhancement by ecdysterone supplementation in humans, Arch. Toxicol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The signaling pathway of the ubiquitin-proteasome was suggested to be involved in the ecdysteroids-induced increase in protein synthesis, together with a downstream activation of the PI3K/Akt pathway.

    “the signaling pathway of the ubiquitin-proteasome was suggested to be involved in the ecdysteroids-induced increase in protein synthesis [28,29,30], together with a downstream activation of the PI3K/Akt pathway [31].”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [28] Syrov, 1984, Mechanism of the anabolic action of phytoecdisteroids in mammals, Nauchnye Doklady Vysshei Shkoly Biologicheskie Nauki

      Not checked in the free run.

    • cites [29] Gorelick-Feldman, J.I. (2009). Phytoecdysteroids. Understanding Their Anabolic Activity. [Ph.D. Thesis, The State University of New Jersey ]. Available online: https://rucore.libraries.rutgers.edu/rutgers-lib/25806/PDF/1/play/.

      Not checked in the free run.

    • cites [30] Hirunsai, 2016, Effect of 20-hydroxyecdysone on proteolytic regulation in muscle atrophy, In Vivo source

      Not checked in the free run.

    • cites [31] Cohick, 2010, Ecdysteroids elicit a rapid Ca2+ flux leading to Akt activation and increased protein synthesis in skeletal muscle cells, Steroids source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The ubiquitin-proteasome system (UPS) represents the major intracellular proteolysis machinery responsible for degradation of major contractile proteins and contributes significantly to muscle atrophy and sarcopenia in both animal and human models.

    “Although several proteolytic systems are involved in protein turnover in skeletal muscle, recent studies suggested that the ubiquitin-proteasome system (UPS) represents the major intracellular proteolysis machinery responsible for the degradation of major contractile proteins, and contributes significantly to muscle atrophy and sarcopenia in both animal and human models [22,23].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [22] Bialek, 2011, Distinct protein degradation profiles are induced by different disuse models of skeletal muscle atrophy, Physiol. Genom. source

      Not checked in the free run.

    • cites [23] Yimlamai, 2005, Clenbuterol induces muscle-specific attenuation of atrophy through effects on the ubiquitin-proteasome pathway, J. Appl. Physiol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Several studies failed to identify a frankly anabolic effect on total muscle mass by ecdysteroids.

    “Although several studies failed to identify a frankly anabolic effect on total muscle mass by ecdysteroids [25,26,27]”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [25] Lawrence, M.M., Zwetsloot, K.A., Arthur, S.T., Sherman, C.A., Huot, J.R., Badmaev, V., Grace, M., Lila, M.A., Nieman, D.C., and Shanely, R.A. (2021). Phytoecdysteroids do not have anabolic effects in skeletal muscle in sedentary aging mice. Int. J. Environ. Res. Public Health, 18. source

      Not checked in the free run.

    • cites [26] Cheng, 2013, Continuous infusion of 20-hydroxyecdysone increased mass of triceps brachii in C57BL/6 mice, Phytother. Res. source

      Not checked in the free run.

    • cites [27] Wilborn, 2006, Effects of methoxyisoflavone, ecdysterone, and sulfo-polysaccharide supplementation on training adaptations in resistance-trained males, J. Int. Soc. Sports Nutr. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Ecdysteroids have a protein-synthesis effect and influence on lipid and carbohydrate metabolism.

    “Ecdysteroids also have a protein-synthesis effect and influence on lipid and carbohydrate metabolism [18].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [18] Rondanelli, M., Rigon, C., Perna, S., Gasparri, C., Iannello, G., Akber, R., Alalwan, T.A., and Freije, A.M. (2020). novel insights on intake of fish and prevention of sarcopenia: All reasons for an adequate consumption. Nutrients, 12. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Doses of ecdysteroids higher than 5 μg/kg body weight were reported as active, while lower doses did not result in anabolic activities.

    “Doses higher than 5 µg/kg body weight were reported as active while lower doses did not result in anabolic activities [21].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [21] Hunyadi, 2008, Phytoecdysteroids and anabolic-androgenic steroids--structure and effects on humans, Curr. Med. Chem. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Ecdysteroids have purported adaptogenic and non-androgenic anabolic properties in mammals.

    “One of the most interesting properties of ecdysteroids in mammals is their purported adaptogenic and non-androgenic anabolic properties [24].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [24] Franco, 2021, A 20-hydroxyecdysone-enriched fraction from Pfaffia glomerata (Spreng.) pedersen roots alleviates stress, anxiety, and depression in mice, J. Ethnopharmacol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    The health-related quality of life was measured using a validated Spanish version of the short form-36 health survey (SF-36).

    “The health-related quality of life (HRQoL) was measured using a validated Spanish version of the short form-36 health survey (SF-36) [41].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [41] Alonso, 1995, The Spanish version of the SF-36 Health Survey (the SF-36 health questionnaire: An instrument for measuring clinical results. [Article in Spanish], Med. Clin.

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    The study protocol was approved by the Ethics Committee of Universidad Católica San Antonio de Murcia (code CE032003, approval date 27 March 2020) and registered in ClinicalTrials.gov (NCT04612127).

    “The study protocol was approved by the Ethics Committee of Universidad Católica San Antonio de Murcia (code CE032003, approval date 27 March 2020) (Murcia, Spain) and was registered in the ClinicalTrials.gov (accessed on 1 November 2021) (NCT04612127).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Participants were randomly assigned using a simple randomization procedure to the experimental group or the control group with the Epidat 4.2 software program.

    “Participants were randomly assigned using a simple randomization procedure to the experimental group (supplementation with the spinach extract nutritional product) or the control group (supplementation with placebo) with the Epidat 4.2 software program.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    The placebo capsules were identical-appearing to the active product.

    “Subjects in the control group received identical-appearing placebo capsules (maltodextrin) and followed the same regimen.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Randomization was performed by an independent researcher.

    “Randomization was performed by an independent researcher.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    All training sessions were supervised by a qualified sport-training monitor.

    “All training sessions were supervised by a qualified sport-training monitor.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    The analysis was based on the per-protocol (PP) data set.

    “The analysis was based on the per-protocol (PP) data set corresponding to those participants who met the inclusion criteria and finished the study at 12 weeks.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductown data

    The study was a single-center, randomized, double-blind, placebo-controlled study with two parallel arms.

    “This was a single-center, randomized, double-blind, placebo-controlled study with two parallel arms conducted at the Health Sciences Department of Universidad Católica San Antonio de Murcia (UCAM), in Murcia, Spain.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Written informed consent was obtained from all participants.

    “Written informed consent was obtained from all participants.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductcitation

    The sample size was calculated to require 23 subjects per group, increased to 25 per group assuming a 10% loss to follow-up.

    “Considering a standard deviation of peak torque of 15 Nm [39] for a precision of 11 Nm with an alpha risk of 5% and statistical power of 80%, 23 subjects in each group was needed, increasing to 25 subjects per group assuming a 10% loss to follow-up.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [39] Freitas, 2017, Acute physiological and performance responses to high-intensity resistance circuit training in hypoxic and normoxic conditions, J. Strength Cond. Res. source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Better muscle quality is an important contributor of muscle health and healthy aging.

    “Better muscle quality is an important contributor of muscle health and healthy aging [4,5].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [4] Askow, 2020, Of sound mind and body: Exploring the diet-strength interaction in healthy aging, Front. Nutr. source

      Not checked in the free run.

    • cites [5] Shin, 2018, Physical activity, benefits, and barriers across the aging continuum, Appl. Nurs. Res. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The analysis of gender effects for men should be interpreted cautiously because there were only eight men in the study.

    “although it should be noted that the analysis of gender effects for men should be interpreted cautiously because there were only eight men in the study.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The modifications in fat mass and muscle mass appeared in both groups, so they are the result of the physical training program carried out during the study.

    “As the modifications appeared in both groups, it is apparent that they are the result of the physical training program carried out during the study.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    All participants consumed a percentage higher than 80% of capsules.

    “All participants consumed a percentage higher than 80% of capsules.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Previous studies have reported that increase in muscle thickness in the upper body are greater and occur earlier compared to the lower extremity, during the first 12 weeks of a total body dynamic resistance training program.

    “Previous studies, however, have reported that increase in muscle thickness in the upper body are greater and occur earlier compared to the lower extremity, during the first 12 weeks of a total body dynamic resistance training program [46,48].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [46] Folland, 2007, The adaptations to strength training: Morphological and neurological contributions to increased strength, Sports Med. source

      Not checked in the free run.

    • cites [48] Abe, 2000, Time course for strength and muscle thickness changes following upper and lower body resistance training in men and women, Eur. J. Appl. Physiol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Both men and women respond to training with an improvement of strength and muscle mass.

    “Both men and women respond to training with an improvement of strength and muscle mass [46,50].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [46] Folland, 2007, The adaptations to strength training: Morphological and neurological contributions to increased strength, Sports Med. source

      Not checked in the free run.

    • cites [50] Tracy, 1999, Muscle quality. II. Effects of strength training in 65- to 75-yr-old men and women, J. Appl. Physiol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    All study participants were interviewed regarding medications and natural products, and this information was supervised by a sports medicine doctor who made final eligibility decisions.

    “However, all study participants were interviewed regarding what medications and pharmacological treatments and/or natural products were taken, and this information was supervised by the doctor (specialist in sports medicine) who made final decisions regarding the eligibility of participants.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Systematic reviews and meta-analyses have shown that dietary nitrate is a useful nutritional strategy to optimize muscular performance during resistance and endurance exercises in different training modalities.

    “Systematic reviews and meta-analyses have shown that dietary nitrate is a useful nutritional strategy to optimize muscular performance during resistance and endurance exercises in different training modalities [54,55,56].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [54] Alvares, 2021, Effect of dietary nitrate ingestion on muscular performance: A systematic review and meta-analysis of randomized controlled trials, Crit. Rev. Food Sci. Nutr.

      Not checked in the free run.

    • cites [55] McMahon, 2017, The effect of dietary nitrate supplementation on endurance exercise performance in healthy adults: A systematic review and meta-analysis, Sports Med. source

      Not checked in the free run.

    • cites [56] Gao, 2021, The effects of dietary nitrate supplementation on endurance exercise performance and cardiorespiratory measures in healthy adults: A systematic review and meta-analysis, J. Int. Soc. Sports Nutr. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    All female participants were postmenopausal women, but the use of hormone replacement treatment was not specifically recorded as an exclusion criterion.

    “All female participants were postmenopausal women, but the use of hormone replacement treatment was not specifically recorded as an exclusion criterion.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Although similar improvements are observed in elderly men and women, the relative improvement in upper-body strength is greater in women, whereas greater hypertrophy and low-body strength are shown in males.

    “Moreover, although similar improvements are observed in elderly men and women, the relative improvement in upper-body strength is greater in women [45], whereas greater hypertrophy and low-body strength are shown in males [47].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [45] Roberts, 2020, Sex differences in resistance training: A systematic review and meta-analysis, J. Strength Cond. Res. source

      Not checked in the free run.

    • cites [47] Jones, 2021, Sex differences in adaptations in muscle strength and size following resistance training in older adults: A systematic review and meta-analysis, Sports Med. source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    The present findings should be interpreted taking into account the limitations of the study, including the exploratory nature of the trial, the reduced sample size, and the treatment period of 12 weeks only.

    “The present findings, however, should be interpreted, taking into account the limitations of the study, including the exploratory nature of the trial, the reduced sample size, and the treatment period of 12 weeks only.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Daily doses of 0.6 g leucine can induce robust muscle protein synthesis.

    “Daily doses of 0.6 g leucine can induce robust muscle protein synthesis, as observed in the study by Wilkinson et al. [53].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [53] Wilkinson, 2018, Effects of leucine-enriched essential amino acid and whey protein bolus dosing upon skeletal muscle protein synthesis at rest and after exercise in older women, Clin. Nutr. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Tracy et al. assessed the effects of strength training of short duration (9 weeks) in 65- to 75-year-old men and women, and found similar improvements in muscle mass and muscle quality, although older men appeared to have a greater capacity for absolute strength and muscle mass gains than older women.

    “These observations are in line with the study by Tracy et al. [51], who assessed the effects of strength training of short duration (9 weeks) in 65- to 75-year-old men and women, and found similar improvements in muscle mass and muscle quality, although older men appeared to have a greater capacity for absolute strength and muscle mass gains than older women.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [51] Tracy, 2006, Age and sex affect human muscle fibre adaptations to heavy-resistance strength training, Exp. Physiol. source

      Not checked in the free run.

66 of 66

  • The paper relies on this without support.

    Existing evidence on the association of dietary interventions and exercise training is limited.

    “However, the existing evidence is still limited, and further studies on the association of dietary interventions and exercise training are needed, in which clinical recommendations for the prevention or treatment of decline in muscle mass and quality could be based.”

  • The paper relies on this without support.

    Participants in both groups adhered similarly to the training program.

    “During the study period, they were also requested to be adherent with the exercise training sessions, which were scheduled 3 times a week, and the loss of three training days was only allowed.”
    “Training protocols were the same for the participants assigned to each study group.”

  • The paper relies on this without support.

    The placebo (maltodextrin) has no effect on skeletal muscle fitness.

    “Subjects in the control group received identical-appearing placebo capsules (maltodextrin) and followed the same regimen.”

  • The paper relies on this without support.

    Physical activity and nutrition are two modifiable lifestyle factors with direct impact on the health of older people.

    “Physical activity and nutrition are two modifiable lifestyle factors with direct impact on the health of older people”
4 of 4

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Consumption of spinach is not associated with adverse effects.

    “Furthermore, the consumption of spinach is not associated with adverse effects [162,171,172,173,174,175,176,177,178].”

    From Ecdysterone and Turkesterone—Compounds with Prominent Potential in Sport and Healthy Nutrition (2024) · cites this paper as [171]

    The Discussion reports no adverse events associated with daily ingestion of the spinach-extract product for 12 weeks, and laboratory results were within normal limits. The study concerned a specific supplement in adults over 50, so it does not establish that spinach consumption generally is free of adverse effects. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • Human studies on 20-hydroxyecdysone have produced inconclusive results: Isenmann et al. and Pérez-Piñero et al. observed performance-enhancing and anabolic effects, while Willborn et al. detected no effect.

    “Current studies in humans, however, are rather inconclusive. Isenmann et al. and Pérez-Piñero et al. were able to observe both performance-enhancing and anabolic effects through 20E application [7,24], whereas Willborn et al. were unable to detect any effect [25].”

    From How reliable is the labeling of a commercial phytosteroid product? A 12-week randomized double-blind training study (2025) · cites this paper as [24]

    The Results (sections 3.3–3.5; page unavailable) support a performance benefit: the spinach-extract group had greater gains in several measures of muscle function, and an exploratory analysis found greater lower-limb muscle-mass gains in men. But section 3.2 reports no significant between-group difference in overall muscle mass, and the intervention was a spinach extract containing 20E, not isolated 20E. The paper therefore does not establish the unqualified anabolic effect through 20E that the citing sentence attributes to it. (LLM, conf=0.89)

    Experimental — accuracy not yet measured

  • Perez-Pinero et al. reported that in over 50-year-old individuals, daily supplementation with Spinacia oleracea extract combined with moderate-intensity exercise increases muscle-related factors and muscle quality.

    “In a study on daily supplementation with S. oleracea extract, combined with moderate-intensity exercise, in over 50-year-old individuals, Perez-Pinero et. al. reported that spinach extract increases muscle-related factors and muscle quality [171].”

    From Ecdysterone and Turkesterone—Compounds with Prominent Potential in Sport and Healthy Nutrition (2024) · cites this paper as [171]

  • In comparison to Wilborn et al., the actual 20-hydroxyecdysone content was examined in the two other studies, but only Isenmann et al. also reported testing for prohibited substances and for anabolic effects in cell culture.

    “In comparison to the study by Wilborn et al., the actual 20E content was examined in the two other studies, but only Isenmann et al. also reported testing for the presence or absence of other prohibited substances and for anabolic effects in cell culture [7,24].”

    From How reliable is the labeling of a commercial phytosteroid product? A 12-week randomized double-blind training study (2025) · cites this paper as [24]

  • Pérez-Piñero et al. used a total daily dose of 3.2 mg (22.4 mg/week) of 20-hydroxyecdysone.

    “In contrast, the total daily dose in the study by Pérez-Piñero et al. was only 3.2 mg (22.4 mg/week) [24].”

    From How reliable is the labeling of a commercial phytosteroid product? A 12-week randomized double-blind training study (2025) · cites this paper as [24]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Muscle quality is described using reciprocal ratios

    Minor

    The discussion describes muscle quality as muscle mass divided by peak torque, but later defines it as strength divided by muscle mass. These are reciprocal measures, so an increase in one would be a decrease in the other.

1 of 1

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Gorelick-Feldman, J.I. (2009). Phytoecdysteroids. Understanding Their Anabolic Activity. [Ph.D. Thesis, The State University of New Jersey ]. Available online: https://rucore.libraries.rutgers.edu/rutgers-lib/25806/PDF/1/play/.

Cited by

Sorted by citations

Related

Authors
Pérez-Piñero, S., Ávila-Gandía, V., Rubio Arias, J. A., Muñoz-Carrillo, J. C., Losada-Zafrilla, P., & López-Román, F. J.
Affiliations
  • Universidad Católica de Murcia (ES)
  • Department of Education, University of Almería, E-04120 Almería, Spain
  • Sports Physiology Department, Faculty of Health Sciences, Campus de los Jerónimos s/n, UCAM Universidad Católica San Antonio de Murcia, E-30107 Murcia, Spain
  • Instituto Murciano de Investigación Biosanitaria (ES)
Corresponding author
Ávila-Gandía, Vicente
ORCID
Venue
Nutrients
Publisher
MDPI AG
Published
2021-12-06
Volume
13
Issue
12
Pages
4373
ISSN
2072-6643 (ISSN-L)
DOI
10.3390/nu13124373
PMC
PMC8706266
OpenAlex
W4200098590
Semantic Scholar
f5ef91d2776c45fef8873c397de2d3acffc3afe6
Cited by
21
References
55
Citations by year
2026: 6 · 2025: 4 · 2024: 8 · 2023: 2 · 2022: 1
FWCI
1.44
Type
journal article
Language
en
Open access
Licence
Locations
  • Nutrients (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Repositorio de Patentes de la Universidad de Almería (Universidad de Almería) (submittedVersion, cc-by-nc-nd)
  • RIUCAM (submittedVersion, other-oa)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
  • Health Sciences › Medicine › Physiology › Nutrition and Health in Aging
  • Health Sciences › Medicine › Rehabilitation › Exercise and Physiological Responses
Keywords
spinach extract, spinach, dietary supplementation, muscle strength, muscle quality, resistance training, older adults, healthy aging, isokinetic dynamometry, isometric dynamometry, quality of life
MeSH terms
Healthy Aging, Age Factors, Aged, Double-Blind Method, Female, Humans, Male, Phytotherapy, Middle Aged, Plant Extracts, Time Factors, Muscle, Skeletal, Spinacia oleracea, Dietary Supplements, Muscle Strength, Sarcopenia

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-10.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-10.

Statistics and arithmetic are recomputed, not judged.

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