Soy (Glycine max)



Soy (Glycine max)

Original Article:  http://www.mayoclinic.com/health/soy/NS_patient-soy
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Soy (Glycine max)

Natural Standard® Patient Monograph, Copyright © 2013 (www.naturalstandard.com). All Rights Reserved. Commercial distribution prohibited. This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice. You should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Background

Soy (Glycine max)

Soy is a subtropical plant, native to southeastern Asia. This member of the pea family (Fabaceae) grows from one to five-feet tall and forms clusters of three to five pods, each containing two to four beans per pod. Soy has been a dietary staple in Asian countries for at least 5,000 years, and during the Chou dynasty in China (1134-246 B.C.), fermentation techniques were discovered that allowed soy to be prepared in more easily digestible forms such as tempeh, miso, and tamari soy sauce. Tofu was invented in 2 nd -Century China.

Soy was introduced to Europe in the 1700s and to the United States in the 1800s. Large-scale soybean cultivation began in the United States during World War II. Currently, Midwestern U.S. states produce approximately half of the world's supply of soybeans.

Soy contains protein, isoflavones, and fiber, all thought to provide health benefits. Soy is an excellent source of dietary protein, including all essential amino acids. Soy is also a source of lecithin or phospholipid. Soy isoflavones and lecithin have been studied scientifically for numerous health conditions. Isoflavones such as genistein are believed to have estrogen-like effects in the body, and as a result are sometimes called "phytoestrogens."

Common sources of soy isoflavones include roasted soybean, green soybean, soy flour, tempeh, tofu, tofu yogurt, soy hot dogs, miso, soy butter, soy nut butter, soy ice cream, soy milk, soy yogurt, tofu pups®, soy cheese, bean curd, seitan, and soy noodles. Soybean flour is found in Spanish sausage products (chorizo, salchichon, mortadella, and boiled ham), doughnuts, and soup stock cubes. Although processed soy foods (e.g., veggie burgers, tofu pups®, meatless dinner entrees, chicken-free nuggets, soy "ice creams" and energy bars) are usually high in protein, they typically contain lower levels of isoflavones.

Soy protein has also been investigated for benefit in terms of other cardiovascular disease risk factors, reducing menopausal symptoms, weight loss, arthritis, brain function, and exercise performance enhancement. Dietary soy may decrease the risk of breast cancer in women and prostate cancer in men, as well as other types of cancers. In general, the supportive evidence for use of phytoestrogens as treatments for menopause, cardiovascular disease, osteoporosis (weak bone mass), and cancer is limited. The use of soy formula has been investigated in the treatment of diarrhea in infants and is an effective and safe alternative to cow's milk formula in most infants. Due to limited human study, there is currently not enough evidence to recommend for or against the use of soy for weight reduction.

Related terms

Abalone®, beta-conglycinin, bioactive peptides, bowman-birk inhibitor, coumestrol, daidzein, daizuga-cha (Japanese), dark soy sauce, dietary soy protein, edamame, equol, Fabaceae (family), flavonoids, fortified soy milk, frijol de soya, functional proteins, genistein, genistin, Glycine max, greater bean, haba soya, hydrolyzed soy protein, isoflavone, isoflavones, isoflavonoid, Isomil®, kuromame-cha (Japanese), kuromame-cha Gold (Japanese), kuromame-soy milk drink (Japanese), lecithin, legume, lignans, margarine, miso, Mull-Soy®, natto, Nursoy®, okara, phosphatidylserine, phytate, phytoestrogen, plant estrogen, PtdSer, S-PtdSer, shoyu, shoyu polysaccharides, soja, sojabohne, soya, soya-based food, soya protein, soya sauce, soybean, soybean-barley paste, soybean oil, soy milk, soy fiber, soy flour, soy food, soy isoflavones, soy lecithin, soy milk, soy nuts, soy oil, soy phosphatidylcholine complex (IdB 1016), soy phosphatidylinositol (PI), soy product, soy protein, soy protein isolate, soy sauce, Supro®, Ta-tou , tempeh, texturized vegetable protein, tofu, yuba.

Evidence

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.

Dietary source of protein
Soy products, such as tofu, are high in protein and are an acceptable source of dietary protein. 		A
High cholesterol
Numerous human studies report that adding soy protein to the diet can moderately decrease blood levels of total cholesterol and low-density lipoprotein ("bad" cholesterol). Small reductions in triglycerides may also occur, while high-density lipoprotein ("good" cholesterol) is altered in some, but not all, studies. Some scientists have proposed that specific components of soybean, such as the isoflavones genistein and daidzein, may be responsible for the cholesterol-lowering properties of soy. However, this has not been clearly demonstrated in research and remains controversial. It is not known if products containing isolated soy isoflavones have the same effects as regular dietary intake of soy protein. Dietary soy protein has not been proven to affect long-term cardiovascular outcomes, such as heart attack or stroke. 		A
Diarrhea (acute) in infants and young children
Numerous studies report that infants and young children (2-36 months old) with diarrhea who are fed soy formulas experience fewer daily bowel movements and fewer days of diarrhea. This research suggests that soy has benefits over other types of formula, including cow milk-based solutions. The addition of soy fiber to soy formula may increase the effectiveness. Better quality research is needed before a strong recommendation can be made. Parents are advised to speak with qualified healthcare providers if their infants experience prolonged diarrhea, become dehydrated, develop signs of infections (such as fever), or have blood in the stool. A healthcare provider should be consulted for current breastfeeding recommendations and to suggest long-term formulas that provide enough nutrition. 		B
Allergies (prevention of food allergies)
Soy formulas are commonly used by infants with sensitivities to milk-based formulas. There is currently little evidence to support the use of soy formulas for preventing food allergies. Further research is needed in this field. 		C
Antioxidant
There is some evidence in support of soy increasing antioxidant status in humans. In general, diets high in plant foods may offer antioxidant benefits. Further research is required in this field before recommendations can be made. 		C
Bowel/intestinal disorders
The effect of soy on erosive-ulcer lesions of the alimentary tract has been examined in limited study. Overall, the effects of soy products appear beneficial. Further study is required before recommendations can be made. 		C
Cancer (prevention and treatment)
Several large population studies have asked people about their eating habits and reported that higher soy intake (such as dietary tofu) is associated with a decreased risk of developing various types of cancers, including breast, prostate, and colon cancer. However, other research suggests that soy does not have this effect. Until better research is available, it remains unclear if dietary soy or soy isoflavone supplements increase or decrease the risk of these cancers. 		C
Cardiovascular disease
Dietary soy protein has not been shown to affect long-term cardiovascular outcomes, such as heart attack or stroke. Research does suggest cholesterol-lowering effects of dietary soy, which in theory, may reduce the risk of heart problems. Soy has also been studied for blood pressure-lowering and blood sugar-reducing properties in people with type 2 diabetes, although the evidence is not definitive in these areas. In women with suspected cardiac ischemia, high levels of the soy isoflavone genistein have been associated with blood vessel problems. Further investigation is needed before a strong recommendation can be made. 		C
Cognitive function
It is unclear if soy isoflavone supplementation in postmenopausal women can improve cognitive function. Results from studies are mixed. 		C
Crohn's disease
Due to limited human research, there is not enough evidence to recommend for or against the use of soy as a way to prevent Crohn's disease. Further research is needed before a recommendation can be made. 		C
Cyclical breast pain
It has been theorized that the "phytoestrogens" (plant-based compounds with weak estrogen-like properties) in soy may be beneficial to premenopausal women with cyclical breast pain. However, due to limited human research, there is not enough evidence to recommend for or against the use of dietary soy protein as a therapy for this condition. 		C
Diabetes
Several small studies have examined the effects of soy products on blood sugar levels in people with type 2 ("adult-onset") diabetes. Results are mixed, with some research reporting decreased blood glucose levels and other trials noting no effects. Overall, research in this area is not well designed or reported and better information is needed. 		C
Exercise performance enhancement
Soy protein has been investigated as a source of protein with potential for benefit in exercise performance. In general, research findings suggest soy protein is better than no protein but is unlikely to be superior to other sources of protein. Further research is required in this field. 		C
Gallstones (cholelithiasis)
Due to limited human research, there is not enough evidence to recommend for or against the use of soy as a therapy in cholelithiasis. Further research is needed before a strong recommendation can be made. 		C
Gastrointestinal motility
In limited available studies, the addition of soy polysaccharide to non-regular diets increased the moisture content of stool and decreased the number of liquid stools. It is not clear if soy polysaccharide would be superior to other fiber sources in this regard. 		C
High blood pressure
There is limited human research on the effects of dietary soy on blood pressure. Some research suggests that substituting soy nuts for non-soy protein may help improve blood pressure. Further research is needed before a firm recommendation can be made. 		C
Infantile colic
There is currently a lack of scientific evidence to recommend for or against the use of soy formula for fussiness and gas in infants with cow's milk allergy over a partially hydrolyzed cow's milk protein formula. 		C
Inflammation
There is currently a lack of scientific evidence to recommend for or against the use of soy protein on inflammation associated with hemodialysis (removal of waste products from the blood). 		C
Iron deficiency anemia
There is currently a lack of sufficient evidence to recommend for or against the use of soy-based formula in the treatment of iron deficiency anemia in children. 		C
Kidney disease (chronic renal failure, nephrotic syndrome, proteinuria)
Due to limited human study, there is not enough evidence to recommend for or against the use of soy in the treatment of kidney diseases, such as nephrotic syndrome. People with kidney disease should speak with their healthcare providers about the recommended amounts of dietary protein because soy is a high-protein food. 		C
Menopausal symptoms
Overall, evidence suggests that soy products containing isoflavones may help reduce menopausal symptoms, such as hot flashes. More study is needed to confirm this use. 		C
Menstrual migraine
A phytoestrogen combination may help prevent menstrual migraine attacks. Further research is needed before a strong recommendation can be made. 		C
Metabolic syndrome
Treatment with soy protein and soy nuts was evaluated in patients with metabolic syndrome and benefits were found in terms of plasma lipids in patients consuming soy nuts as part of the DASH (Dietary Approaches to Stop Hypertension) diet. Further research is required in this field in terms of soy protein supplementation. 		C
Obesity/weight reduction
Some research suggests that soy might be as effective as skim milk and more effective than a low-calorie diet alone in reducing weight. Other research has reported conflicting results. Further research is needed before a strong recommendation can be made. 		C
Osteoarthritis
Osteoarthritis is a form of arthritis caused by the breakdown of cartilage. Early research suggests that intake of soy protein may be associated with reduced symptoms of osteoarthritis. 		C
Osteoporosis
It has been theorized that "phytoestrogens in soy" (such as isoflavones) may increase bone mineral density in post-menopausal women and reduce the risk of fractures. However, more research is needed before a conclusion can be made. 		C
Quality of life
The effect of soy on quality of life has been investigated in limited study. Further study is required before recommendations can be made. 		C
Rheumatoid arthritis
There is currently insufficient evidence to recommend for or against the use of soy as a treatment for rheumatoid arthritis. 		C
Skin aging
It is unclear if aglycones, a form of soy isoflavone, can improve aged skin in middle-aged women when it is taken by mouth. More research is needed. 		C
Skin damage caused by the sun
A soy moisturizing cream may help improve signs of sun damage, including discoloration, blotchiness, dullness, fine lines, and overall texture. Because the cream contained other ingredients besides soy, more research with soy alone is needed. 		C
Spinal cord injury
Whey protein has traditionally been used as a protein source to increase body strength. Limited available study investigated whether soy protein could be used to increase ambulation performance in patients with incomplete spinal cord injury. There is currently not enough evidence to recommend for or against the use of soy as a treatment for increased endurance in individuals with spinal cord injury. 		C
Thyroid disorders
Early research suggests that soy supplements do not affect thyroid function. More research is needed. 		C
Tuberculosis
It has been suggested that soy may be beneficial for tuberculosis when taken with standard medications. According to early research, soy may improve the process of detoxification, have positive effects on the liver, reduce cell damage, and decrease inflammation. Therefore, soy supplements may allow patients to safely take higher doses of antimicrobial drugs that are used to treat tuberculosis. 		C
Weight gain (infants)
In limited study, weaning infants with cow's milk allergy to soy based formula resulted in reduced weight for age as compared with formulas containing hydrolyzed proteins (broken down). Further research is required in this field. 		C

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)

Grading rationale

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Alzheimer's disease, anorexia, anti-aging, antifungal, arthritis, atherosclerosis (hardening of the arteries), attention deficit hyperactivity disorder (ADHD), benign prostate hyperplasia, bone density, bone fractures, breast enlargement, colitis, constipation, cystic fibrosis, diabetic neuropathy, fall prevention, fever, growth, headache, hepatitis (chronic), immune function, improving health outcomes (general), infertility, insect repellant, kwashiorkor, malnutrition, melasma (skin discoloration), memory enhancement, nosebleed (chronic), osteosarcoma, polycystic ovary syndrome, respiratory problems (cough, phlegm), skin conditions, thrombosis (blood clotting), vaginitis, vasoregulator, wound healing.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (over 18 years old)

Soy is typically consumed as a protein drink, soy flour, isolated soy protein (e.g. Supro®), extract, fiber/cereal, or milk beverage. Studies have examined the effects of 10-106 grams of soy with an isoflavone content of about 40-120 milligrams taken daily for up to 12 months by mouth.

A dose of 20-106 grams of soy protein taken daily by mouth has been studied in people with high cholesterol. Isoflavone content has ranged from 60 to over 100 milligrams daily. Cholesterol and low-density lipoprotein levels have been reduced in people using these doses of soy protein. There is limited study of soymilk (400 milliliters daily) in pre-menopausal women, with reported benefits on cholesterol levels. Additional doses have been studied but are not recommended due to a lack of available scientific evidence.

Children (under 18 years old)

Due to potential safety concerns, a qualified healthcare provider should be consulted regarding the choice of infant formula.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Soy may act as a food allergen similar to milk, eggs, peanuts, fish, and wheat. Symptoms of an allergic reaction range from a runny nose to a sudden drop in blood pressure.

Side Effects and Warnings

Soy has been a dietary staple in many countries for more than 5,000 years and it does not appear to cause long-term toxicity. Aside from allergic reactions, limited side effects have been reported in infants, children, and adults.

Soy protein taken by mouth has been associated with stomach and intestinal difficulties, such as bloating, nausea, and constipation. Changes in stool quality have been reported. More serious intestinal side effects have been uncommonly reported in infants fed soy protein formula, including vomiting, diarrhea, growth failure, and damage/bleeding of the intestine walls. People who experience intestinal irritation (colitis) from cow's milk may also react to soy formula.

Based on human case reports and animal research, soy may affect thyroid hormone levels in infants. There have been rare reports of goiters (enlarged neck due to increased thyroid size). Hormone levels became normal again after stopping soy. Infants fed soy or cow's milk formula may also have higher rates of atopic eczema than infants who are breastfed.

Acute migraine headache has been reported with the use of a soy isoflavone product. Based on animal research, damage to the pancreas may theoretically occur from regularly eating raw soybeans or soy flour/protein powder made from raw, unroasted, or unfermented beans.

The use of soy is often discouraged in patients with hormone-sensitive cancers, such as breast, ovarian, or uterine cancer, due to concerns about possible estrogen-like effects (which theoretically may stimulate tumor growth). Other hormone-sensitive conditions, such as endometriosis, may also theoretically be worsened. In laboratory studies, it is not clear if isoflavones stimulate or block the effects of estrogen or both (acting as a "receptor agonist/antagonist"). Until additional research is available, patients with these conditions should be cautious and speak with a qualified healthcare practitioner before starting use.

It is not known if soy or soy isoflavones share the same side effects as estrogens, such as increased risk of blood clots. Early studies suggest that soy isoflavones, unlike estrogens, do not cause the lining of the uterus (endometrium) to build up.

There has been a case report of vitamin D deficiency rickets in an infant nursed with soybean milk (not specifically designed for infants). Patients should consult their qualified healthcare practitioners for current breastfeeding recommendations and use formulas with adequate nutritional value.

Pregnancy and Breastfeeding

Soy as a part of the regular diet is traditionally considered to be safe during pregnancy and breastfeeding, although scientific research is limited in these areas. The effects of high doses of soy or soy isoflavones in humans are not clear, and therefore are not recommended.

Recent study demonstrates that isoflavones, which may have estrogen-like properties, are transferred through breast milk from mothers to infants. High doses of isoflavones given to pregnant animals have resulted in tumors and reproductive changes in offspring, although this has not been tested in humans.

In one human study, male infants born to women who ingested soymilk or soy products during pregnancy experienced more frequent hypospadias (a birth defect in which the urethral meatus, the opening from which urine passes, is abnormally positioned on the underside of the penis). However, other human and animal studies have examined males or females fed soy formula as infants, and have not found abnormalities in infant growth, head circumference, height, weight, occurrence of puberty, menstruation, or reproductive ability.

Research in children during the first year of life has found that the substitution of soy formula for cow's milk may be associated with significantly lower bone mineral density. Parents considering the use of soy formula should speak with qualified healthcare practitioners to make sure the appropriate vitamins and minerals are provided in the formula.

Methodology

This patient information is based on a professional level monograph edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Monograph methodology

Selected references

  1. Allison DB, Gadbury G, Schwartz LG, et al. A novel soy-based meal replacement formula for weight loss among obese individuals: a randomized controlled clinical trial. Eur J Clin Nutr 2003;57(4):514-522.
  2. Berseth CL, Johnston WH, Stolz SI, et al. Clinical response to 2 commonly used switch formulas occurs within 1 day. Clin Pediatr (Phila) 2009;48(1):58-65.
  3. Campbell CG, Brown BD, Dufner D, et al. Effects of soy or milk protein during a high-fat feeding challenge on oxidative stress, inflammation, and lipids in healthy men. Lipids 2006 Mar;41(3):257-65.
  4. Fournier LR, Ryan Borchers TA, Robison LM, et al. The effects of soy milk and isoflavone supplements on cognitive performance in healthy, postmenopausal women. J Nutr Health Aging. 2007 Mar-Apr;11(2):155-64.
  5. Gasteyger C, Larsen TM, Vercruysse F, et al. Effect of a dietary-induced weight loss on liver enzymes in obese subjects. Am J Clin Nutr 2008;87(5):1141-1147.
  6. Hooper L, Kroon PA, Rimm EB, et al. Flavonoids, flavonoid-rich foods, and cardiovascular risk: a meta-analysis of randomized controlled trials. Am J Clin Nutr 2008;88(1):38-50.
  7. Izumi T, Saito M, Obata A, et al. Oral intake of soy isoflavone aglycone improves the aged skin of adult women. J Nutr Sci Vitaminol (Tokyo) 2007 Feb;53(1):57-62.
  8. Kerstetter JE, Wall DE, O'Brien KO, et al. Meat and soy protein affect calcium homeostasis in healthy women. J Nutr 2006 Jul;136(7):1890-5.
  9. Koo WW, Hammami M, Margeson DP, et al. Reduced bone mineralization in infants fed palm olein-containing formula: a randomized, double-blinded, prospective trial. Pediatrics 2003;111(5 Pt 1):1017-1023.
  10. Kreijkamp-Kaspers S, Kok L, Grobbee DE, et al. Effect of soy protein containing isoflavones on cognitive function, bone mineral density, and plasma lipids in postmenopausal women: a randomized controlled trial. JAMA 2004;292(1):65-74.
  11. Lichtenstein GR, Deren JJ, Katz S, et al. Bowman-Birk inhibitor concentrate: a novel therapeutic agent for patients with active ulcerative colitis. Dig Dis Sci 2008;53(1):175-180.
  12. MacGregor CA, Canney PA, Patterson G, et al. A randomised double-blind controlled trial of oral soy supplements versus placebo for treatment of menopausal symptoms in patients with early breast cancer. Eur J Cancer 2005;41(5):708-714.
  13. Nelson HD, Vesco KK, Haney E, et al. Nonhormonal therapies for menopausal hot flashes: systematic review and meta-analysis. JAMA 2006 May 3;295(17):2057-71.
  14. Romualdi D, Costantini B, Campagna G, et al. Is there a role for soy isoflavones in the therapeutic approach to polycystic ovary syndrome? Results from a pilot study. Fertil Steril 2008;90(5):1826-1833.
  15. Tice JA, Ettinger B, Ensrud K, et al. Phytoestrogen supplements for the treatment of hot flashes: the Isoflavone Clover Extract (ICE) Study: a randomized controlled trial. JAMA 2003;290(2):207-214.
Related terms
NS_patient-soy Portions of this document last updated: Sept. 1, 2012

THIS EVIDENCE-BASED MONOGRAPH WAS PREPARED BY
THE NATURAL STANDARD RESEARCH COLLABORATION
(www.naturalstandard.com)

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