Soy
OTHER NAME(S): Glycine max, soy, soybean, soya bean
Overview
Soy refers to the beans obtained from a plant called Glycine max. Soybeans are a common food and are used to make many other foods, including tofu, miso, soy milk, and soy sauce. Soybeans are also used to make dietary supplements. Soy supplements are often used for managing menopause symptoms and menopause-related health problems, but their benefits are not well defined. Common side effects may include gas or an upset stomach. Before taking soy supplements, make sure to tell your health care provider about any health conditions you have or medicines you are taking, especially if you have breast cancer or any other hormone-sensitive cancer.
Uses
What is soy used for?
Soy (Glycine max) is commonly used to help manage menopause symptoms and certain health problems related to menopause, including high cholesterol and osteoporosis. However, its benefits for most uses are not well defined.
Note: The FDA has not reviewed soy for safety and effectiveness, and it is not approved by the FDA. Learn more about dietary supplements here.
How does soy work (mechanism of action)?
Soy refers to the beans obtained from the soy plant (Glycine max). Soybeans are a common food and are also used to make various food products, including tofu, miso, soy sauce, soy milk, and soy nuts. Soybeans contain protein, fat, and various chemicals, including soy isoflavones. Soybeans are also used to make dietary supplements.
Soy isoflavones, such as daidzein and genistein, are sometimes known as “phytoestrogens” (plant estrogens). They may mimic some of the effects of estrogen in the body, which could help with managing some of the health problems that come with menopause. Some studies show that taking soy supplements may help reduce menopause-related hot flashes by a small amount. They may also help reduce bone loss after menopause.
It is not clear what dose of soy is most likely to provide benefits for menopause or which substances in soy are most important. As the amounts of each chemical in a specific soy product may vary, the effects of soy supplements may change depending on which specific product you are taking. Also, these benefits are only seen with soy supplements. Eating soy as part of the diet is not likely to help with menopause-related health problems.
Over the years, there has been controversy over whether eating soy can affect your risk for breast cancer. Most research shows that eating soy-based foods does not increase the risk for breast cancer, even in people who have had breast cancer or currently have breast cancer. But the risks of soy supplements are not well understood. If you have had or currently have breast cancer, speak to a health care provider before taking soy supplements.
How should I store soy?
You should store soy according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.
Side Effects
What are the most common side effects of soy?
The most common side effects of soy are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.
- Gas
- Upset stomach
There may be other side effects of soy that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.
What are the serious side effects of soy?
While less common, the most serious side effects of soy are described below, along with what to do if they happen.
Severe Allergic Reactions. Soy may cause allergic reactions, which can be serious. Stop taking soy and get help right away if you have any of the following symptoms of a serious allergic reaction.
- Breathing problems or wheezing
- Racing heart
- Fever or general ill feeling
- Swollen lymph nodes
- Swelling of the face, lips, mouth, tongue, or throat
- Trouble swallowing or throat tightness
- Itching or skin rash
- Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
- Nausea or vomiting
- Dizziness, feeling lightheaded, or fainting
- Stomach cramps
- Joint pain
Precautions
Who should not use soy?
Allergies to Ingredients. People who are allergic to any of the following should not take soy.
- Daidzein
- Genistein
- Glycine max
- Soy
- Soya bean
- Soybean
- Any of the ingredients in the specific product
Your pharmacist can tell you all of the ingredients in the specific soy products they stock.
What should I know about soy before using it?
Soy is available in various forms as a food and dietary supplement. Soy products cannot be marketed to treat or cure a disease.
Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.
Keep soy out of the reach of children.
Herbal products, such as soy, naturally contain many different chemicals. The amount of each chemical in a specific soy product can change for many reasons, including the area where the plant was grown, the weather during growth, the time of year when it was harvested, and the way that the bean was processed. If you switch to a new bottle or a different brand, you may not have the same effects or side effects because of this variability. Read the product label closely and talk to your health care provider if you have questions or concerns.
Some dietary supplements that contain soy are made from the entire soybean. However, other supplements may only contain certain substances from soy, such as its proteins or isoflavones. Each of these substances causes different effects and side effects. Read the product label closely to check which substances are found in that product.
The FDA has not tested soy products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.
What should I tell my health care provider before using soy?
Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if soy is right for you.
In particular, make sure that you discuss any of the following.
Peanut Allergy.Some people who have an allergy to peanuts may also have an allergy to soy. If you have a peanut allergy, talk to your health care provider before taking soy.
Other Current and Past Health Conditions.Tell your health care provider if you have any of the following.
- Breast cancer
- Other hormone-sensitive cancers, such as ovarian or uterine cancer
Other Medicines and Supplements.Soy may interact with other medicines and supplements. Before taking soy, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.
Pregnancy. It is not known if or how soy could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.
Breastfeeding. Some of the chemicals in soy, such as daidzein and genistein, pass into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.
Interactions
Does soy interact with foods or drinks?
There are no known interactions between soy and foods or drinks.
It is unknown if drinking alcohol will affect soy.
Does soy interact with medicines (drug interactions)?
Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.
In particular, make sure that you discuss if you are using hormone replacement therapy or any medicines that contain hormones before taking soy.
Soy may alter the blood levels of some medicines. Tell your health care provider about all medicines that you take or have recently taken.
The interactions between soy and medicines are not fully understood. As with most dietary supplements, research on drug interactions with soy is incomplete. Always check with your health care provider before taking soy with any medicines.
Dosing
What should I do if I accidentally use too much soy?
If you or someone else has used too much soy, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.
Soy is available in many different foods and as a dietary supplement. Read the product label closely and speak to a health care provider about how to take soy safely. Do not take double or extra doses, even if you miss a dose.
References
- American Institute for Cancer Research: “Soy: Intake Does Not Increase Risk for Breast Cancer Survivors.”
- Drugs and Lactation Database (LactMed) [Internet]: “Alfalfa.”
- European Medicines Agency: “Assessment report on Glycine max (L.) Merr., semen.”
- Food Allergy Research & Education: “What is Soy Allergy?”
- Memorial Sloan Kettering Cancer Center: “Soy.”
- National Center for Complementary and Integrative Health: “Cholesterol Management at a Glance,” “Soy,” “Menopausal Symptoms and Complementary Health Approaches: What the Science Says.”
- National Cancer Institute: “Soy,” “Soy isoflavones,” “Soy protein isolate.”