Soy
Cosse de Soja, Cosse de Soya, Daidzein, Daidzéine, Dolichos soja, Edamame, Estrogène Végétal, Fermented Soy, Fève de Soja, Fève de Soya, Fibre de Soja, Fibre de Soya, Frijol de Soya, Genestein, Genistein, Génistéine, Glycine gracilis, Glycine hispida, Glycine max, Glycine soja, Haba Soya, Haricot de Soja, Haricot de Soya, Hydrolyzed Soy Protein, Isoflavone, Isoflavone de Soja, Isoflavone de Soya, Isolated Soy Protein, Isolated Soybean Protein, Lait de Soja, Lait de Soya, Legume, Miso, Natto, Phaseolus max, Phytoestrogen, Phyto-œstrogène, Plant Estrogen, Protéine de Haricot de Soja Isolée, Protéine de Haricot de Soya Isolée, Protéine de Soja, Protéine de Soya, Protéine de Soja Isolée, Protéine de Soya Isolée, Shoyu, Soja, Soja hispida, Soja max, Sojabohne, Soy Bean, Soy Fiber, Soy Germ, Soy Isoflavone, Soy Isoflavones, Soy Milk, Soy Protein, Soy Protein Isolate, Soya, Soya Bean, Soja Fermenté, Soya Fermenté, Soybean, Soybean Curd, Soybean Isoflavone, Soybean Isoflavones, Tempeh, Texturized Vegetable Protein, Tofu, Touchi.
Soy comes from soybeans. The beans can be processed into soy protein, which is a powder; soymilk, which is a beverage that may or may not be fortified with extra calcium from the soybeans; or soy fiber, which contains some of the fibrous parts of the bean.
Soy is taken by mouth for high cholesterol, high blood pressure, and preventing diseases of the heart and blood vessels. It is also used for type 2 diabetes and kidney disease associated with diabetes, asthma, as well as preventing weak bones (osteoporosis), preventing joint pain and stiffness in people with arthritis, and slowing the progression of kidney disease. Soy is also taken by mouth to prevent different kinds of cancer.
Soy is also taken by mouth for treating constipation, diarrhea, Crohn's disease, hepatitis C, metabolic syndrome, fibromyalgia, weight loss, enlarged prostate, as well as decreasing protein in the urine of people with kidney disease, improving memory and mental function, improving muscle strength, and treating muscle soreness caused by exercise.
Women take soy by mouth for breast pain, preventing hot flashes after breast cancer, menopausal symptoms, premenstrual syndrome (PMS), and migraine headaches during menstruation.
Soy is used as a milk substitute in infant feeding formulas, and as an alternative to cow's milk. It is fed to infants who are unable to process the sugar galactose, who are lactose intolerance, who have a condition called hereditary lactase deficiency, or who have infant colic.
Soy is applied to the skin to improve photo-aged skin or wrinkled skin.
Soy is applied inside the vagina to treat vaginal swelling due to decreased lubrication and thinning vaginal tissue (vaginal atrophy).
In foods, soybeans are eaten boiled or roasted. Soy flour is used as an ingredient in foods, beverages, and condiments.
The active ingredients in soy are called isoflavones. A study of the quality of commercially available soy supplements suggests that less than 25% of products contain within 90% of labeled isoflavone content. Paying more for a product doesn't necessarily guarantee that the content shown on the label is accurate.
How does it work?
Soy contains "isoflavones" which are changed in the body to "phytoestrogens." Phytoestrogen molecules are similar in chemical structure to the hormone estrogen. In some cases, these phytoestrogens can mimic the effects of estrogen. In other cases, these phytoestrogens can block the effects of estrogen.
Possibly Effective for...
- Breast cancer. Eating a high-soy diet is linked to a slightly reduced risk of developing breast cancer in some women. Asian women who eat a high-soy diet seem to have a lower risk of breast cancer than those who eat less soy. But most research shows no benefit in Western-culture women. It's possible that women of Western culture do not eat enough soy to see any benefit. The effects of soy on breast cancer risk also seem to vary depending on a woman's age and menopausal status. Women who eat a high-soy diet during adolescence seem to have a reduced risk of breast cancer. This suggests that early exposure to soy might protect against breast cancer later in life. In women already diagnosed with breast cancer, eating a high soy diet is linked to a reduced risk of breast cancer recurrence. But there is no reliable evidence that taking a soy isoflavones supplement reduces breast cancer growth.
- Diabetes. Most evidence suggests that consuming soy products reduces blood sugar levels in people with diabetes. However, not all research shows a benefit. In general, dietary soy, soy fiber, and fermented soy seem to lower blood glucose, while processed soy products, such as isolated soy protein, may not work.
- Kidney disease in people with diabetes. Research shows that eating soy protein in place of animal protein as part of the diet might help prevent or treat kidney disease in people with diabetes. But some early research shows that drinking soy milk doesn't help.
- Diarrhea. Feeding infants formula supplemented with soy fiber, alone or together with rehydration solution, seems to reduce the duration of diarrhea compared to cow's milk formula or rehydration solution alone. However, in some studies formula supplemented with soy was no more beneficial than cow's milk formula. In adults, early evidence suggests that taking soy fiber does not decrease the incidence of diarrhea.
- Trouble digesting the sugar galactose (galactosemia). Feeding a soy-based formula to infants who have galactosemia seems to be helpful.
- Trouble digesting the sugar lactose (hereditary lactase deficiency). Feeding a soy-based formula to infants who have hereditary lactase deficiency seems to be helpful.
- High cholesterol. Eating soy protein in place of other dietary protein or using soy fiber products seems to slightly reduce total cholesterol and "bad cholesterol" (low-density lipoprotein (LDL) cholesterol). Soy protein that contains higher amounts of an ingredient called isoflavones might work better than soy protein with little or no isoflavones. Also, soy might work better in people with high cholesterol that is more severe. Supplements containing purified soy isoflavones don't seem to work. Soy doesn't seem to lower triglycerides. Also, most research shows that soy doesn't increase "good cholesterol" (high-density lipoprotein (HDL) cholesterol).
- Kidney disease. Taking soy protein by mouth seems to reduce protein in the urine in people with kidney disease. It also seems to reduce levels of certain nutrients and waste products, such as phosphorus and creatinine. These molecules can build up in the blood of people with long-term kidney disease.
- Trouble digesting the sugar lactose (lactose intolerance). Feeding a soy-based formula to infants who have lactose intolerance seems to be helpful.
- Menopausal symptoms. Eating soy protein or taking concentrated soy isoflavone extract seems to help hot flashes caused by menopause in some people. Taking soy products providing 100-200 mg of isoflavones in two or three divided doses per day might work better than taking lower or less frequent doses. In addition, using products that contain at least 15 mg of the specific isoflavone called genistein seem to work better than products that provide less genistein. Taking soy also seems to improve depression and body weight in women after menopause. It's unclear if soy reduces vaginal dryness or itching that is associated with menopause. Soy does not seem to help hot flashes in women with breast cancer.
- Osteoporosis. Most evidence suggests that soy protein or soy extract can increase bone mineral density (BMD) or slow BMD loss in women near or beyond menopause. It appears that soy products need to contain at least 75 mg of an ingredient called isoflavones in order to work. Soy might also reduce the risk of fractures in some women. Soy does not seem to affect BMD in younger women.
Possibly Ineffective for...
- Enlarged prostate (benign prostatic hyperplasia; BPH). Taking isoflavones isolated from soy doesn't seem to improve urination or other symptoms in people with an enlarged prostate.
- Breast cancer-related hot flashes. Research shows that drinking a beverage containing soy or taking tablets containing soy extract does not reduce hot flashes in breast cancer survivors.
- Colorectal cancer. Research suggests that taking soy protein does not reduce the progression of colorectal cancer.
- Muscle soreness caused by exercise. Taking soy isoflavone extract by mouth before exercising does not seem to prevent muscle soreness.
- Fibromyalgia. Drinking a soy protein shake containing soy isoflavones does not appear to improve physical function or symptoms of depression in people with fibromyalgia.
- Rheumatoid arthritis. Early research suggests that consuming a liquid diet containing soy protein (Top Up) does not improve pain, stiffness, or joint swelling in people with rheumatoid arthritis.
Insufficient Evidence to Rate Effectiveness for...
- Asthma. Early evidence suggests that people with asthma who eat soy foods have increased lung function, but taking supplements containing an ingredient in soy called isoflavones doesn't appear to improve lung function or reduce asthma episodes in adults or children with poorly controlled asthma.
- Heart disease. Some evidence suggests that postmenopausal women, but not men or pre-menopausal women, who eat a lot of soy in their diet might have a reduced risk of stroke, heart attack, or heart disease-related death.
- Mental function. There is conflicting evidence about the effect of soy on mental function. Some evidence suggests that eating more soy improves short-term and long-term memory. However, other research suggests that soy does not improve mental function, including memory. Some soy formulations might work better than others.
- Crohn's disease. Research suggests that taking soy by mouth, along with standard treatment, increases bowel movements and improves symptoms, such as fatigue and body weight, in people with Crohn's disease.
- Endometrial cancer. Eating more soy might lower the risk of endometrial cancer. Endometrial cancer is less common in Japan, China, and other Asian countries where the usual diet is low in calories and high in soy and whole grain foods, vegetables, and fruits. However, some soy foods seem to lower the risk of endometrial cancer better than others. It's too early to know if soy supplements affect endometrial cancer risk.
- Hepatitis C. Early research suggests that taking soy protein reduces the buildup of fat in the liver and lowers biomarkers linked with liver damage in patients with hepatitis C.
- High blood pressure. Most research shows that eating soy protein can reduce systolic blood pressure (the top number in a blood pressure reading) by about 4-8 mmHg and diastolic blood pressure (the bottom number) by about 3-5 mmHg in people with pre-high blood pressure or slightly high blood pressure. However, this is a relatively small reduction.
- Colic in infants. Early research suggests that feeding infants a soy-based formula might reduce the duration of colic symptoms in infants who have trouble digesting cow's milk. However, higher-quality research suggests that feeding infants a soy-based formula does not improve the duration of crying in infants with colic. Also, soy-based formula doesn't seem to improve crying compared to the drug dicyclomine.
- Lung cancer. Men and women who consume a higher amount of dietary phytoestrogens, such as isoflavones from soy, seem to be less likely to develop lung cancer than people who consume smaller amounts. Soy seems to prevent lung cancer more in men than women. However, some research suggests that only non-smokers, not smokers, who eat soy have a lower risk of developing lung cancer.
- Breast pain (mastalgia). Drinking soymilk might reduce monthly breast pain in some women.
- Memory. Some research suggests that a high-soy diet might slightly improve performance on memory tests.
- Metabolic syndrome (a condition that increases risk for diabetes and heart disease). Eating a soy nut diet appears to reduce blood sugar and decrease "bad"cholesterol (low-density lipoprotein (LDL) cholesterol) in postmenopausal women with metabolic syndrome better than a soy-protein diet or a DASH diet.
- Migraines. Research suggests that taking a combination of soy isoflavones, dong quai, and black cohosh reduces the frequency of migraines associated with menstruation.
- Muscle strength. Research suggests that taking soy protein can increase lean tissue mass in people participating in resistance training. Other research suggests that consuming a specific soy protein product (Supro) can increase body mass and strength and reduce fatigue in athletes. However,conflicting research shows that soy protein might not improve strength.
- Osteoarthritis. Early research shows that taking soy protein can improve motion, pain, and quality of life in people with osteoarthritis. However, taking milk-based protein also seems to have these effects.
- Sun-damaged skin. Research suggests that applying a soy moisturizer to the skin can improve skin color, fine lines, and texture.
- Premenstrual syndrome (PMS). Research suggests that taking soy protein for two menstrual cycles can reduce cramps and swelling associated with PMS.
- Prostate cancer. Research regarding the effect of soy on prostate cancer risk is conflicting. Men who eat an Asian diet, which contains 10 times more soy than the average American diet, seem to have a lower risk of prostate cancer. However, it is unclear whether it is the soy in the diet of Asian men or other factors (such as genetic differences or differences in dietary fat) that protect against prostate cancer. Some research shows that taking soy protein can reduce the risk of prostate cancer in at-risk men. However, there is conflicting evidence about whether soy can affect the progression of prostate cancer. Soy protein doesn't seem to reduce hot flashes in prostate cancer patients.
- Thyroid cancer. Diets that include plenty of soy seem to be linked to a reduced risk of thyroid cancer.
- Vaginal irritation due to decreased lubrication and thinning vaginal tissue (vaginal atrophy). Applying a vaginal gel containing soy extract seems to reduce vaginal dryness and pain and improve vaginal tissue in postmenopausal women with symptoms of vaginal atrophy.
- Weight loss. Some research suggests that eating a soy-based, low-calorie diet can reduce weight in obese and overweight people more than a low-calorie diet alone. Eating foods containing soy fiber might also improve weight loss. Replacing meat protein with soy protein in the diet might improve weight loss in women, although conflicting data exists. Supplementing with soy-based meal replacements doesn't seem to improve weight loss or prevent weight gain. Soy protein doesn't seem to improve weight loss when eaten as part of a free-choice diet.
- Wrinkled skin. Consuming soy isoflavones seems to improve the elasticity of skin and the appearance of fine wrinkles.
- Other conditions.
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).
Consuming foods containing soy protein or taking soy protein products is LIKELY SAFE. Taking dietary supplements with soy extracts is POSSIBLY SAFE when used short-term (up to 6 months). Soy can cause some mild stomach and intestinal side effects such as constipation, bloating, and nausea. It can also cause allergic reactions involving rash and itching in some people. Some people might experience tiredness. Soy might also affect thyroid function. However, this seems to occur primarily in people who are iodine deficient.
Long-term use of high doses of soy extract is POSSIBLY UNSAFE. There is some concern that taking high doses might cause abnormal tissue growth in the uterus. However, eating large amounts of soy does not seem to have this effect.
Children: Soy is LIKELY SAFE for children when used in amounts commonly found in food or infant formula. Using soy formula does not seem to cause health or reproductive problems later in life. However, soymilk that is not designed for infants should not be used as a substitute for infant formula. Regular soymilk could lead to nutrient deficiencies.
Soy is POSSIBLY UNSAFE when used as an alternative to cow's milk in children who are allergic to cow's milk. Although soy protein-based infant formulas are often promoted for children with milk allergy, these children are often allergic to soy as well.
Don't give children soy in amounts larger than what is found in food or formula. Researchers don't know whether soy is safe for children at higher doses.
Hay fever (allergic rhinitis): People with hay fever are more likely to be allergic to soy hulls.
Asthma: People with asthma are more likely to be allergic to soy hulls. Avoid using soy products.
Breast cancer: The effects of soy in people with breast cancer are unclear. Some research finds that soy might "feed" certain breast cancers because it can act like estrogen. Other studies have found that soy seems to protect against breast cancer. The difference in effects might have something to do with the amount taken. Because there isn't enough reliable information about the effects of soy in women with breast cancer, a history of breast cancer, or a family history of breast cancer, it's best to avoid using soy until more is known.
Cystic fibrosis: Soymilk can interfere with the way children with cystic fibrosis process protein. Don't give these children soy products.
Diabetes: Soy might increase the risk of blood sugar levels becoming too low in people with diabetes who are taking medication to control blood sugar.
Endometrial cancer: Long-term use of concentrated soy isoflavone tablets might increase the occurrence of precancerous changes in the tissue lining the uterus. However, conflicting evidence exists. Use supplements containing soy isoflavones cautiously if you are at risk for endometrial cancer. Soy foods are likely safe.
Under-active thyroid (hypothyroidism): There is a concern that taking soy might make this condition worse.
Kidney stones: There is some concern that soy products might increase the risk of kidney stones because they contain large amounts of a group of chemicals called oxalates. Oxalates are the main ingredient in kidney stones. Another concern is that people with serious kidney disease aren't able to process some of the chemicals in soy. This could lead to dangerously high levels of these chemicals. If you have a history of kidney stones, avoid taking large amounts of soy.
Milk allergy: Children who are very allergic to cow's milk might also be sensitive to soy products. Use soy products with caution.
Kidney failure: Soy contains a chemical called phytoestrogens. Very high levels of phytoestrogens can be toxic. People with kidney failure who use soy products might be at risk for blood levels of phytoestrogens becoming too high. If you have kidney failure, avoid taking large amounts of soy.
Urinary bladder cancer: Soy products might increase the chance of getting bladder cancer. Avoid soy foods if you have bladder cancer or a high risk of getting it (family history of bladder cancer).
Medications for depression (MAOIs)Interaction Rating: Major Do not take this combination.
Fermented soy products such as tofu and soy sauce contain tyramine. Tyramine is an amino acid that is involved in blood pressure regulation. Tyramine is broken down by monoamine oxidase. Some medications for depression (MAOIs) can decrease the breakdown of tyramine. Consuming more than 6 mg of tyramine while taking one of these medications can increase the risk of serious side effects such as blood pressure getting too high. The amount of tyramine in fermented soy products is usually small, often less than 0.6 mg per serving; however, there can be variation depending on the specific product used, storage conditions, and length of storage. Storing one brand of tofu for a week can increase tyramine content from 0.23 mg to 4.8 mg per serving. If you take one of these medications, avoid fermented soy products that contain high amounts of tyramine.
Some of these medications include phenelzine (Nardil), tranylcypromine (Parnate), and others.
Antibiotic drugsInteraction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Antibiotics are used to reduce harmful bacteria in the body. Antibiotics can also reduce friendly bacteria in the intestines. Friendly bacteria in the intestines seem to help increase the effectiveness of soy. By reducing the number of bacteria in intestines, antibiotics might decrease the effectiveness of soy. But it is too soon to know if this interaction is a big concern.
EstrogensInteraction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Large amounts of soy might have some of the same effects as estrogen. But soy isn't as strong as estrogen pills. Taking soy along with estrogen pills might decrease the effects of estrogen pills.
Some estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.
LevothyroxineInteraction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Levothyroxine is used for low thyroid function. Soy can decrease how much levothyroxine your body absorbs. Taking soy along with levothyroxine might decrease the effectiveness of levothyroxine. The dose of levothyroxine may need to be adjusted if soy is being used regularly, such as in soy-based formulas. If soy is used occasionally, levothyroxine and soy should be taken at least 4 hours apart.
Some brands that contain levothyroxine include Armour Thyroid, Eltroxin, Estre, Euthyrox, Levo-T, Levothroid, Levoxyl, Synthroid, Unithroid, and others.
Medications for diabetes (Antidiabetes drugs)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Soy can decrease blood sugar levels. Diabetes medications are also used to lower blood sugar. Taking soy along with diabetes medications might cause your blood sugar to be too low. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.
Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, metformin (Glucophage), pioglitazone (Actos), rosiglitazone (Avandia), and others.
Medications for high blood pressure (Antihypertensive drugs)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Soy protein might reduce blood pressure. Using soy with drugs that lower blood pressure might increase the effects of these drugs and may lower blood pressure too much.
Some medications for high blood pressure include captopril (Capoten), enalapril (Vasotec), losartan (Cozaar), valsartan (Diovan), diltiazem (Cardizem), amlodipine (Norvasc), hydrochlorothiazide (HydroDiuril), furosemide (Lasix), and many others.
ProgesteroneInteraction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Bone loss might occur in women with osteoporosis who combine progesterone with soymilk containing isoflavones.
Tamoxifen (Nolvadex)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Some types of cancer are affected by hormones in the body. Estrogen-sensitive cancers are cancers that are affected by estrogen levels in the body. Tamoxifen (Nolvadex) is used to help treat and prevent these types of cancer. Soy seems to also affect estrogen levels in the body. By affecting estrogen in the body, soy might decrease the effectiveness of tamoxifen (Nolvadex). Do not take soy if you are taking tamoxifen (Nolvadex).
Warfarin (Coumadin)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Warfarin (Coumadin) is used to slow blood clotting. Soy has been reported to decrease the effectiveness of warfarin (Coumadin). Decreasing the effectiveness of warfarin (Coumadin) might increase the risk of clotting. It is unclear why this interaction might occur. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.
Water pills (Diuretic drugs)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Early research suggests that soy can increase urine production. The effects seem to be similar to those of "water pills." Taking soy along with "water pills" might increase the risk for side effects.
Medications changed by the liver (Cytochrome P450 2C9 (CYP 2C9) substrates)Interaction Rating: Minor Be cautious with this combination.Talk with your health provider.
Some medications are changed and broken down by the liver. Soy might increase how quickly the liver breaks down some medications. But it is too soon to know if this interaction occurs in all people or if it affects how well the medication works.
Some medications changed by the liver include carvedilol (Coreg), fluvastatin (Lescol), losartan (Cozaar), phenytoin (Dilantin), and many others.
The following doses have been studied in scientific research:
ADULTS: BY MOUTH:
- For type 2 diabetes:
- Touchi extract 300 mg three times daily for 3-6 months. Touchi is a traditional Chinese food prepared from soybeans.
- Fibrous soy hulls 26 grams daily for 4 weeks. Single doses of soy fiber 7-10 grams have also been used.
- 30 grams of soy protein, containing 132 mg of phytoestrogens, daily for up to 12 weeks.
- For high cholesterol: 20-50 grams per day of soy protein.
- For protein in the urine of people with kidney disease: a diet limited to 700-800 mg/kg soy protein daily has been used.
- For menopausal symptoms such as hot flashes:
- 20-60 grams per day of soy protein providing 34-80 mg isoflavones.
- concentrated soy isoflavone extracts providing 35-200 mg/day of isoflavones.
- Genistein, a soy isoflavone: 54 mg per day.
- For menopausal symptoms such as depression: 100 mg of soy containing 50 mg of isoflavones has been used along with sertraline 50 mg daily.
- To reduce body weight during menopause: Soy isoflavones <100 mg daily for up to 6 months have been used.
- For preventing weak bones (osteoporosis): 40 grams per day soy protein containing 2-2.25 mg isoflavones per gram has been used for 3-6 months. Soy extract 1 gram containing 80 mg of isoflavones has been used for one year.
- For diarrhea in infants: Soy fiber-fortified formula containing 18-20 grams of soy protein per liter.