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.

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

Evidence gradeCondition to which grade level applies
A

Dietary source of protein

Soy products, such as tofu, are high in protein and are an acceptable source of dietary protein.
A

High cholesterol

Human research reports that adding soy protein to the diet can moderately decrease total cholesterol and low-density lipoprotein ("bad" cholesterol). The most benefit has been seen when all animal protein is substituted with soy, especially in soy products that contain isoflavones. The reductions in cholesterol may last as long as the diet is continued.
B

Diarrhea (acute) in infants and young children

Research reports that infants with diarrhea who are fed soy formula have less diarrhea than those fed milk formula. This only applies to children that are unable to eat solid food. Further research is needed before a conclusion 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

High blood pressure

Research in humans generally shows that soy lowers blood pressure. Further research is needed to determine the ideal soy preparation for lowering blood pressure.
B

Menopausal symptoms (hot flush)

Research shows that soy reduces hot flash occurrence in menopausal women. Further research is needed before a strong conclusion can be made.
C

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 conclusions can be made.
C

Bowel/intestinal disorders

The effect of soy on ulcers in the bowel/intestinal tract has been examined in limited study. Overall, the effects of soy products appear beneficial. Further study is required before conclusions can be made.
C

Cancer (prevention and treatment)

Limited human research shows that soy may decrease the risk of cancer, including breast, prostate, and colon cancer. However, confounding factors including dietary and lifestyle habits, culture, and genetics must be considered. Further research is needed before a conclusion can be made.
C

Cognitive function

It is unclear if soy supplementation in postmenopausal women can improve cognitive function. Results from studies are mixed. Further research is necessary.
C

Crohn's disease

From limited human research, it is unclear if soy helps with Crohn's disease. Further research is needed before a conclusion can be made.
C

Cyclical breast pain

Limited research shows that soy may decrease cyclical breast pain, which is pain linked to the menstrual cycle. Further research is needed to draw conclusions.
C

Diabetes

Human research demonstrates mixed results of soy products for blood sugar levels in people with type 2 diabetes. Overall, better quality research is needed in this area.
C

Exercise performance

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 a lack of protein but is unlikely to be superior to other sources of protein. Further research is required in this field.
C

Fibromyalgia

Limited evidence shows that soy lacks benefit for physical function and depression symptoms in fibromyalgia. Further research in this area is needed before any firm conclusions can be made.
C

Gallstones

There is insufficient evidence regarding the use of soy as a therapy for gallstones. Further research is needed before a conclusion can be made.
C

Heart disease

Research suggests cholesterol-lowering effects of dietary soy, which in theory, may reduce the risk of heart problems. However, in limited research soy lacked an effect on blood vessel function and increased the levels a heart disease risk marker. Further investigation is needed before a conclusion can be made.
C

Infantile colic

There is currently a lack of scientific evidence regarding the use of soy formula for fussiness and gas in infants with cow's milk allergy. Further research is warranted.
C

Inflammation

Sufficient evidence is lacking regarding the use of soy protein for inflammation associated with hemodialysis (a treatment given when kidneys fail, to remove waste from the blood). Further research is needed.
C

Iron deficiency anemia

There is currently a lack of sufficient evidence regarding the use of soy-based formula in the treatment of iron deficiency anemia in children. Further research is needed.
C

Kidney disease

Sufficient evidence is lacking regarding the use of soy in the treatment of kidney diseases, such as nephrotic syndrome. Further research is necessary. 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 (non hot-flush)

Overall, evidence suggests that soy products containing isoflavones may help reduce various menopausal symptoms. More study is needed to confirm this use.
C

Menstrual migraine

An herbal combination containing soy may help prevent menstrual migraine attacks. Further research is needed before a conclusion can be made.
C

Metabolic syndrome

Treatment with soy protein and soy nuts was evaluated in patients with metabolic syndrome. Benefits were found in terms of decreased cholesterol levels from consuming soy. Further research is required in this field to draw conclusions.
C

Motility disorders (problems with digestion)

In limited research, the addition of soy polysaccharide to non-regular diets improved stool consistency. It is unclear if soy polysaccharide would be superior to other fiber sources in this regard. Further research is warranted.
C

Osteoarthritis

Osteoarthritis is a form of arthritis caused by the breakdown of cartilage and resulting in symptoms of pain and decreased range of motion of joints. Early research suggests that intake of soy protein may be associated with reduced symptoms of osteoarthritis. Further research is needed before conclusions can be made.
C

Physical functioning and well-being in the elderly

Early evidence suggests that increased dietary intake of soy is associated with a decreased risk of physical disability in healthy older women. Further high quality research is needed for conclusions to be made.
C

Premenstrual syndrome (PMS)

Sufficient evidence is lacking regarding the use of soy in managing symptoms of PMS. Further high-quality clinical research is needed in this area before any firm conclusions can be made.
C

Rheumatoid arthritis

There is currently insufficient evidence regarding the use of soy as a treatment for rheumatoid arthritis. High-quality clinical research is needed in this area.
C

Skin aging

Research shows that combination products containing soy extract have demonstrated improvements in wrinkles and skin quality. More research is needed with soy products alone before a conclusion can be made.
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 research investigated whether soy protein could be used to increase walking performance in patients with incomplete spinal cord injury. Further research is needed to make a conclusion.
C

Thyroid disorders

Early research suggests that soy supplements lack an effect on thyroid function. More research is needed.
C

Tuberculosis

According to early research, soy may improve tolerance of antimicrobial drugs that are used to treat tuberculosis. Further research is needed to make conclusions.
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 (broken down) proteins. Further research is required in this field.
C

Weight loss

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 conclusion can be made.
F

Osteoporosis

Human research shows that soy lacks an effect on bone mineral density in post-menopausal women and healthy adults. However, more research is needed.

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, asthma, atherosclerosis (hardening of the arteries), ADHD, blood clots, bone fractures, breast enlargement, clogged arteries, colon inflammation, constipation, cystic fibrosis (mucus build-up in organs), diabetic nerve pain, estrogen-like activity, fall prevention, fever, growth, headache, hepatitis (liver inflammation), immune function, improving health outcomes, infertility, insect repellant, malnutrition, melasma (skin discoloration), nosebleed, polycystic ovary syndrome (cysts in ovaries), prostate enlargement (BPH), respiratory problems (cough, phlegm), vaginitis (vaginal inflammation), wound healing.

This evidence-based monograph was prepared by The Natural Standard Research Collaboration

www.naturalstandard.com