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Cited by 200Phytoestrogen effects and researchThyroid Disorders and TreatmentsSoybean genetics and cultivation

Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: A review of the relevant literature

Messina, Mark, Redmond, Geoffrey·2006·Thyroid
DOI 10.1089/thy.2006.16.249
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Abstract

Soy foods are a traditional staple of Asian diets but because of their purported health benefits they have become popular in recent years among non-Asians, especially postmenopausal women. There are many bioactive soybean components that may contribute to the hypothesized health benefits of soy but most attention has focused on the isoflavones, which have both hormonal and nonhormonal properties. However, despite the possible benefits concerns have been expressed that soy may be contraindicated for some subsets of the population. One concern is that soy may adversely affect thyroid function and interfere with the absorption of synthetic thyroid hormone. Thus, the purpose of this review is to evaluate the relevant literature and provide the clinician guidance for advising their patients about the effects of soy on thyroid function. In total, 14 trials (thyroid function was not the primary health outcome in any trial) were identified in which the effects of soy foods or isoflavones on at least one measure of thyroid function was assessed in presumably healthy subjects; eight involved women only, four involved men, and two both men and women. With only one exception, either no effects or only very modest changes were noted in these trials. Thus, collectively the findings provide little evidence that in euthyroid, iodine-replete individuals, soy foods, or isoflavones adversely affect thyroid function. In contrast, some evidence suggests that soy foods, by inhibiting absorption, may increase the dose of thyroid hormone required by hypothyroid patients. However, hypothyroid adults need not avoid soy foods. In addition, there remains a theoretical concern based on in vitro and animal data that in individuals with compromised thyroid function and/or whose iodine intake is marginal soy foods may increase risk of developing clinical hypothyroidism. Therefore, it is important for soy food consumers to make sure their intake of iodine is adequate.

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  • Individuals with normal thyroid function and iodine intake should be able to safely consume soy foods/protein.

    “individuals with normal thyroid function and iodine intake should be able to safely consume soy foods/protein [150].”

    From Plant Proteins: Assessing Their Nutritional Quality and Effects on Health and Physical Function (2020) · cites this paper as [150]

  • Even in hypothyroid individuals on thyroid replacement medication, reasonable intake of soy foods may still be acceptable if the dose of levothyroxine is either increased or timed such that it does not coincide with soy intake.

    “even in this situation, the reasonable intake of soy foods may still be acceptable if the dose of levothyroxine is either increased or timed such that it does not coincide with the soy intake [150,151].”

    From Plant Proteins: Assessing Their Nutritional Quality and Effects on Health and Physical Function (2020) · cites this paper as [150]

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Authors
Messina, M., & Redmond, G.
Affiliations
  • Loma Linda University (US)
  • Hormone Center of New York, New York, New York.
ORCID
Messina, Mark
Venue
Thyroid
Publisher
SAGE Publications
Published
2006-03
Volume
16
Issue
3
Pages
249-258
ISSN
  • 1050-7256 (ISSN-L)
  • 1557-9077
DOI
10.1089/thy.2006.16.249
OpenAlex
W2147572477
Cited by
200
References
124
Citations by year
2026: 6 · 2025: 4 · 2024: 7 · 2023: 8 · 2022: 15 · 2021: 12 · 2020: 16 · 2019: 9 · 2018: 10 · 2017: 7 · 2016: 10 · 2015: 7 · 2014: 15 · 2013: 9 · 2012: 8
FWCI
6.96
Type
journal article
Language
en
Open access
closed
Licence
www.liebertpub.com/nv/resources-tools/text-and-data-mining-policy/121/ (tdm)
Locations
  • Thyroid (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Pathology and Forensic Medicine › Phytoestrogen effects and research
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
  • Life Sciences › Agricultural and Biological Sciences › Plant Science › Soybean genetics and cultivation
Keywords
soy protein, soy isoflavones, thyroid function, hypothyroidism, thyroid hormone absorption, iodine intake, soy products, postmenopausal women
MeSH terms
Adult, Aged, Female, Humans, Hypothyroidism, Isoflavones, Male, Middle Aged, Thyroid Gland, Soybean Proteins

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