Study: Increasing soy in your diet may lower your cancer risk
|Strengths and limitations||Clinical trials|
|What does this mean for me?||Related resources|
|Questions for your doctor|
STUDY AT A GLANCE
What is this study about?
This study is a review of recent research that looked at whether the amount of soy and certain substances found in soy, can lower cancer risk and death due to cancer.
Why is this study important?
Soy is an important source of protein for many people. It is often used as a meat substitute, and some cultures use soy products in many of their foods. Some groups, including the American Heart Association, recommend eating 25 milligrams of soy, which is less than 3 ounces of tofu, per day to prevent heart disease and other illnesses.
Past studies looking at the link between eating soy and cancer risk have had different findings. In this study, researchers looked at several recent studies to better understand whether a diet that includes soy can lower cancer risk and death due to cancer.
Researchers looked at the results of 81 studies. The number of participants in studies varied from just over 1,000 to almost 500,000. A total of 4.15 million participants were included in this analysis. Follow-up varied by study, ranging from 2 years to over 19 years.
Most of the studies used a food frequency questionnaire. This questionnaire listed the foods and beverages that are being studied, such as soy foods, soy milk, miso soup and other foods that contain soy were listed in questionnaires. Participants recorded how often they had each type of food or drink over a specific period of time. Some questionnaires asked about the portion size. One question, for example, asked “How often do you eat three or more ounces of tofu?”
The average lifetime risk for cancer is about 40 percent. Researchers found that people who eat a diet that is rich in soy can decrease this to about 36 percent.
Researchers also found that a higher intake of isoflavones, which are compounds found in soy, can further decrease a person’s lifetime risk of any cancer to 34 percent.
When researchers looked at cancer risk reduction by cancer type, the reduction in cancer risk varied. For example, about 6.6 percent of people will develop lung cancer at some point in their lifetime. Soy was shown to reduce the lifetime risk of lung cancer to 4.4 percent. Soy modestly reduced the lifetime risk for other cancers. (see table below).
When researchers looked specifically at soy isoflavones, the lifetime risk reduction was similar to that for soy (see table below).
Soy and soy isoflavones cancer risk reduction varied by cancer type.
|Cancer||Lifetime risk||Lifetime risk for people who eat soy||Lifetime risk for people who eat isoflavones|
Researchers did not observe a link between soy or soy isoflavones and death due to cancer in the general population or in patients diagnosed with cancer.
Strengths and limitations
- This study is a , a study that reviews the results of many previous studies. Looking at multiple studies together can sometimes strengthen the results of single studies that are assessed alone.
- Some studies had a follow-up of almost 20 years.
- The studies controlled for some factors that may impact outcomes, such as demographics, lifestyle and dietary factors. However, there may be other factors that were not looked at that could impact results.
- Participants were asked how much soy they ate. The studies did not verify the accuracy of what participants reported. When researchers measure the type and amount of different foods eaten, the results are likely to be more accurate.
- The observed cancer risk reduction may not be solely due to soy but to other dietary or lifestyle components. For example, people who ate a lot of soy may have had other factors that also reduced their cancer risk.
- Different cooking and processing methods of soy products consumed may influence the availability of soy isoflavones and protein.
- The studies reviewed in this analysis did not look at high-risk populations, such as people with an inherited mutation and those with a strong family history of cancer. Therefore, it is unclear if these results would be similar for a high-risk group of people.
Past studies of the effect of soy on cancer risk showed mixed or unclear results. The findings of this study support including soy as a part of a healthy diet to reduce the risk of cancer. These results also suggest that soy isoflavones likely contribute the most to cancer risk reduction.
The researchers and other experts think that the benefits of soy, especially soy isoflavones, in preventing cancer is because soy protects the body from damage that is caused by inflammation.
What does this mean for me?
This study suggests that eating soy is safe and may be beneficial. A higher intake of soy and soy isoflavones may reduce your overall risk of cancer as well as your risk for specific cancer types. However, while significant, the risk reduction for all cancer and specific cancer types is small.
The researchers did not suggest an ideal amount of soy for cancer prevention. However, some professional organizations recommend eating 25 milligrams per day. Consult with your doctors and/or dietician before making changes to your cancer prevention plans or to your diet.
This research suggests that soy, particularly soy isoflavones, may reduce cancer risk. While soybeans are the richest source of isoflavones, they are also found in other legumes, including chickpeas, fava beans, pistachios and peanuts, as well as fruits such as currents and raisins. There may be other foods that you can add to your diet that are rich in isoflavones that reduce your overall cancer risk.
Fan Y, Wang M, Li Z, et al., Intake of Soy, Soy Isoflavones and Soy Protein and Risk of Cancer Incidence and Mortality. Frontiers in Nutrition. 2022. 9:847421.
Disclosure: FORCE receives funding from industry sponsors, including companies that manufacture cancer drugs, tests and devices. All XRAYS articles are written independently of any sponsor and are reviewed by members of our Scientific Advisory Board prior to publication to assure scientific integrity.
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The American Cancer Society (ACS) guidelines on exercise, nutrition and weight for cancer prevention recommend the following:
Diet and nutrition
- Follow a healthy eating pattern, including:
- foods that are high in nutrients in amounts that help you acheive and maintain a healthy body weight.
- a variety of vegetables, fiber-rich legumes (beans and peas) and whole fruits in a variety of colors. Consume at least 2½ to 3 cups of vegetables and 1½ to 2 cups of fruit each day, depending on your calorie requirements.
- whole grains rather than refined grains. At least half of the grains you eat should be whole grains.
- A healthy eating pattern that limits or does not include:
- red and processed meats.
- sugar-sweetened beverages.
- highly processed foods and refined grain products.
- It is best not to drink alcohol. People who choose to drink alcohol should:
- have no more than 1 drink per day (women) or 2 drinks per day (men).
- Exercise regularly.
- Adults should get at least 150 minutes of moderate-intensity activity (equal to a brisk walk) or 75 minutes of vigorous activity (heart rate is increased, breathing is faster and you are sweating) each week, preferably spread throughout the week.
- Physical activity has been shown to lower the risk of several types of cancer, including breast, endometrial, and colon. It also reduces the risk of other serious diseases including diabetes and heart disease.
- Achieve and keep a healthy weight.
- Being overweight or obese is a risk factor for many cancers, including breast, colon, endometrial and pancreatic. You can control your weight through regular exercise and healthy eating.
Other experts, including the following, also provide guidelines for exercise, nutrition and health:
- The Academy of Nutrition and Dietetics
- The United States Office of Disease Prevention and Health Promotion
- The American Institute for Cancer Research
- Should I eat soy to reduce my cancer risk?
- How much soy should I eat each day?
- What types of soy should I eat?
- Should I meet with a dietitian about my diet and using soy to reduce my cancer risk?
- Can you refer me to a dietitian?
The following are studies focused on nutrition and cancer prevention.
- NCT05094466: Parent and Family Obesity Intervention in Reducing Obesity Risk in Racial Ethnic Minority Families. This compares the effects of parent/caregiver-focused programs to family-focused programs in reducing obesity risk in racial ethnic minority families.
- NCT04374747: Fruit and Vegetable Intervention in Lactating Women to Reduce Breast Cancer Risk. This trial is for nursing mothers. This study will see whether eating at least 8 to 10 daily servings of fruits and vegetables reduces breast cancer biomarkers.
- NCT03448003: Comprehensive Lifestyle Change To Prevent Breast Cancer. This trial looks at how well lifestyle changes work to prevent breast cancer. Premenopausal women 18 years and older with intact breasts and ovaries are eligible.
- NCT04192071: Virtual Human Delivered Nutrition Module for Colorectal Cancer Prevention. This study will develop and test an interactive nutrition module for use with colorectal cancer screening to learn which messages and graphics promote understanding of cancer risk and promote screening.
Visit our Featured Research Page and Research Search and Enroll Tool to find additional studies enrolling people with or at high risk for cancer.