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Soy

What does the research say about Soy?

2 health outcomes synthesised

Research on Soy spans 2 health outcomes, with the strongest evidence focusing on reduced breast cancer recurrence (3 studies). Studies most commonly use isoflavone doses of 25-50 mg/day (equivalent to 2-3 servings of traditional soy foods) in women with breast cancer or postmenopausal women. The evidence strength across both outcomes is currently rated as low, indicating preliminary conclusions.

Strongest evidence: The most consistent findings are for reduced breast cancer recurrence, where all 3 studies reported beneficial effects (effect size moderate to large). The effective dose range is 25-50 mg isoflavones per day (about 2-3 servings of traditional soy foods), primarily in women with breast cancer or survivors, including estrogen receptor-positive cases.

Mixed or weaker evidence: For reduced menopausal symptoms, evidence is weaker: 2 of 3 studies show small-to-moderate benefit at 60 mg isoflavones/day, but 1 neutral study found no significant effect. Both outcome areas have low evidence strength, meaning conclusions are preliminary.

Effective dose patterns: Both outcomes converge on isoflavone doses in the 25-60 mg/day range. The menopausal symptom studies used 60 mg/day, while breast cancer recurrence studies used 25-50 mg/day (2-3 servings of traditional soy foods).

Population insights: Research primarily involves women: postmenopausal women for menopausal symptoms, and women with breast cancer or survivors (including estrogen receptor-positive and postmenopausal) for recurrence outcomes.

Notable caveats: Both syntheses are based on only 3 studies each, so evidence should be considered preliminary. There is a risk of publication bias in the breast cancer literature (null results less likely to be published). The menopausal symptom data has limited generalizability due to a single study providing median duration data.

Frequently asked

  • What is Soy good for according to research?
    Current research suggests soy intake may help reduce breast cancer recurrence (3 studies, all beneficial) and may improve menopausal symptoms (2 of 3 studies show benefit). However, both evidence bases are small and rated as low strength.
  • What dose of Soy is typically used in studies?
    For breast cancer recurrence, studies used approximately 25-50 mg isoflavones per day (2-3 servings of traditional soy foods). For menopausal symptoms, the most-studied dose was 60 mg isoflavones per day.
  • Who benefits most from Soy?
    Research focuses on women: postmenopausal women for menopausal symptoms, and women with breast cancer or survivors (including estrogen receptor-positive and postmenopausal) for reducing recurrence risk. No studies addressed benefits in men or other populations.
  • Are there caveats or limitations in the research on Soy?
    Yes. Both syntheses include only 3 studies each, making conclusions preliminary. The breast cancer research may be affected by publication bias (null results less likely published). The menopausal symptom evidence has limited generalizability due to a single study providing the duration data.
  • Does Soy help with menopausal symptoms?
    Two of 3 studies report small-to-moderate beneficial effects of soy isoflavones (60 mg/day) on menopausal symptoms in postmenopausal women, but one neutral study found no significant effect. The evidence strength is low, and conclusions should be considered preliminary.
  • Does Soy reduce breast cancer recurrence?
    All 3 studies found beneficial effects of soy intake on reducing breast cancer recurrence, with moderate-to-large effect sizes. The evidence is limited by a small number of studies and potential publication bias. The dose range is 25-50 mg isoflavones daily.

Most-studied combinations with Soy

most supplement research is combination research
Also studied with:Soy Protein (3), natto (2), Red Clover (3)

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