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Summary:  | Soy has been suggested for many conditions including high cholesterol, cardiovascular health, menopausal symptoms, and diarrhea. It is also used in some infant formulas. Soy may have similar effects to the hormone estrogen. The amount of soy found in foods is generally considered safe, although allergic reactions have been reported. |
Scientific Evidence: | Uses These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. | Grade* | | Dietary source of protein | A
| | High cholesterol | A
| | Diarrhea (acute) in infants and young children | B
| | Menopausal hot flashes | B
| | Breast cancer prevention | C
| | Cancer treatment | C
| | Cardiovascular disease | C
| | Cognitive (mental) function | C
| | Colon cancer prevention | C
| | Crohn's disease | C
| | Cyclical breast pain | C
| | Diarrhea in adults | C
| | Endometrial cancer prevention | C
| | Gall stones | C
| | High blood pressure | C
| | Kidney disease | C
| | Menstrual migraine | C
| | Obesity, weight reduction | C
| | Osteoporosis, post-menopausal bone loss | C
| | Prostate cancer prevention | C
| | Stomach cancer | C
| | Type 2 diabetes | C
| | Improved body composition and physical performance in postmenopausal women | D
| | *Key to grades: A: Strong scientific evidence for this use; B: Good scientific evidence for this use; C: Unclear scientific evidence for this use; D: Fair scientific evidence against this use (it may not work); F: Strong scientific evidence against this use (it likely does not work). |
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Safety: | Avoid if allergic to soy. Breathing problems and rash may occur in sensitive people. Soy, as a part of the regular diet, is traditionally considered to be safe during pregnancy and breastfeeding, but there is limited scientific data. The effects of high doses of soy or soy isoflavones in humans are not clear, and therefore are not recommended. There has been a case report of vitamin D deficiency rickets in an infant nursed with soybean milk (not specifically designed for infants). People who experience intestinal irritation (colitis) from cow's milk may experience intestinal damage or diarrhea from soy. It is not known if soy or soy isoflavones share the same side effects as estrogens, like increased risk of blood clots. The use of soy is often discouraged in patients with hormone-sensitive cancers, such as breast, ovarian or uterine cancer. Other hormone-sensitive conditions such as endometriosis may also be worsened. Patients taking blood-thinning drugs like warfarin should check with a doctor and pharmacist before taking soy supplementation. |
Possible side effects: | Acute migraine headache, bloating, constipation, damage to the pancreas, damage/bleeding of the intestine walls, decreased thyroid hormone and increased thyroid stimulating hormone (TSH) levels, diarrhea, eczema, growth failure, increased serious intestinal side effects in infants, nausea, stomach and intestinal difficulties, vomiting. |
Interactions: | Soy contains "phytoestrogens" (plant-based compounds with weak estrogen-like properties) like isoflavones. In laboratory studies, it is not clear if isoflavones stimulate or block the effects of estrogen, or both. Researchers do not know if soy or soy isoflavone supplements increases or decreases the effects of estrogen on the body, such as the risk of blood clots. It is unclear if taking soy alters the effectiveness of birth control pills containing estrogen. Researchers do not know what the effects of soy phytoestrogens are on the anti-tumor effects of selective estrogen receptor modulators (SERMs) like tamoxifen. The effects of aromatase inhibitors like anastrozole (like Arimidex), exemestane (like Aromasin) or letrozole (like Femara) may be reduced. Soy protein may interact with blood-thinning drugs like warfarin (like Coumadin). Calcium and phosphate levels may be altered. Avoid with herbs or supplements with similar effects. The effects of soy protein or flour on iron absorption are not clear. People using iron supplements or soy products should consult a qualified healthcare practitioner to follow blood iron levels. Some experts believe that there may be a potential interaction between soy extract and Panax ginseng, but this possible interaction has not been well-studied. |
Dosing: Adults (18 years and older): | 17-50 grams of soy protein have been taken by mouth daily. Isoflavone content has ranged from 60-90 milligrams daily. |
Children (younger than 18 years): | Not enough scientific data available. Please check with a pediatrician and pharmacist before using soy in children. | | In infants and young children (2-36 months-old), Hyprovit formula, Isomil formula, Nursoy formula or powder, and Prosobee formula taken by mouth have been studied. |
  | Natural Standard Monograph(www.naturalstandard.com)
Copyright 2007 Natural Standard Inc. Commercial distribution or reproduction prohibited.
| The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions. Natural Standard evidence-based flashcard. Copyright 2007 (www.naturalstandard.com). Commercial distribution prohibited. This flashcard is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions. While some complementary and alternative techniques have been studied scientifically, high-quality data regarding safety, effectiveness, and mechanism of action are limited or controversial for most therapies. Whenever possible, it is recommended that practitioners be licensed by a recognized professional organization that adheres to clearly published standards. In addition, before starting a new technique or engaging a practitioner, it is recommended that patients speak with their primary healthcare provider(s). Potential benefits, risks (including financial costs), and alternatives should be carefully considered. The below monograph is designed to provide historical background and an overview of clinically-oriented research, and neither advocates for or against the use of a particular therapy. |
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