Is Soy Harmful to You? What the Science Has to Say

Soy may be the most contentious plant-based food on the market. Many individuals avoid soy because they believe it will lead to health problems like breast cancer, but others view it as a healthy meal.

So which is it? Here’s what you need to know about soy:

• Health Benefits

• Soy and Breast Cancer Risk

• Can Men Eat Soy?

• Are Some Soy Products Healthier Than Others?

WHAT IS SOY?

Humans have been cultivating and eating soybeans, a kind of legume, for at least 7,000 years. Soybeans are a nutrient-dense food that is high in protein, fibre, B vitamins, magnesium, and potassium. Products made from soybeans range from nutritious, less processed meals like soy milk and tofu to less nutritious varieties like soy oils and protein isolates.

HEALTH BENEFITS

Mark Messina, PhD, the executive director of the Soy Nutrition Institute and a former programme director at the National Cancer Institute, asserts that soy may significantly contribute to a healthy diet. Although there are thousands of studies on soy—so many that you can cherry-pick the ones you choose to support any argument—the overwhelming body of research shows a number of health advantages connected with eating the bean. According to Messina, soy "may make an essential contribution to a healthy diet."

SOY AND HEART HEALTH

Soy may offer protection against heart disease, according to research. Even after controlling for other risk variables including overall diet quality and body mass index, a 2020 research that looked at data from more than 200,000 people and showed that those who ate at least one dish of tofu per week were 18% less likely to acquire heart disease than those who rarely ate tofu. 

When the study's findings were announced, lead author Qi Sun, MD, a researcher at Harvard T.H. Chan School of Public Health, said: "People with an elevated risk of developing heart disease should evaluate their diets because other human trials and animal studies of isoflavones, tofu, and cardiovascular risk markers also have indicated positive effects."

Additionally, studies have shown that soy meals can decrease cholesterol and are devoid of the artery-clogging cholesterol. Soy reduced cholesterol levels by 3-4% in a Journal of Nutrition research.

Messina points out that consuming more soy products has the effect of "crowding out" foods higher in saturated fat like meat and dairy, which is another way that doing so can decrease cholesterol. This is in addition to soy's direct advantages for heart health.

Soy seems to help decrease blood pressure in addition to lowering cholesterol directly.

SOY AND CANCER

Research on human beings (as opposed to other animals) indicates that soy consumption may not raise cancer risk and may even reduce the risk of several malignancies. The American Institute for Cancer Research's Karen Collins, MS, RDN, CDN, FAND, states that "Population studies do not link soy consumption with increased risk of any cancer, and limited evidence suggests soy may protect against lung cancer in people who have never smoked tobacco, and either no effect or decreased risk of prostate cancer."

Eating soy foods was linked to a noticeably decreased risk of prostate cancer, according to a 2018 meta-analysis that examined the known literature on soy intake and the disease. Those who consumed the most soy had a 26% reduced risk of prostate cancer than men who consumed the least soy, according to a 2009 research.

Additionally, there is positive news regarding breast cancer. A plant-based dietician in Ojai, California, and the author of California Vegan, Sharon Palmer, MSFS, RDN, claims that cultures with higher soy consumption had lower rates of breast cancer. “Because moderate intake of soy is not linked to a rise in breast cancer risk, all of the major cancer organizations have removed cautions of soy from their consensus statements.”

WHY DO PEOPLE THINK SOY CAN RAISE BREAST CANCER RISK?

The idea that soy might raise the risk of breast cancer is one of the most prevalent ones. Two facts have given rise to these worries. The first is that soy is a particularly abundant source of isoflavones, which are naturally occurring plant substances known as phytoestrogens, or plant estrogens. Second, isoflavones promoted the development of cancers that react to the hormone oestrogen in one mouse model. Some people were convinced by this discovery that soy consumption raises the risk of breast cancer.

Messina points out that this misunderstanding omits a few crucial details, including: Mice have a different isoflavone metabolism from humans, and isoflavones are not the same as the hormone oestrogen. Furthermore, he says, "clinical investigations demonstrate neither soy diets nor isoflavones elevate indications of breast cancer risk."

In fact, observational studies reveal that women who consume soy after being diagnosed with breast cancer are less likely to pass away from their illness or even experience recurrence. Soy is safe for women with breast cancer to eat, according to groups including the American Cancer Society, American Institute for Cancer Research, and the World Cancer Research Fund International.

 

OTHER BENEFITS

Given that soy can lessen the negative effects of menopause, it may have particular advantages for women who are going through the menopause. A recent research in the journal Menopause found that hot flashes were reduced by 79% in women who followed a plant-based diet that contained 12 cup of cooked soybeans every day.

Soy increases cerebral blood flow in elderly men and women, which may be crucial for memory, according to a study from 2021 that was published in the American Journal of Clinical Nutrition. Adults in the research between the ages of 60 and 70 underwent two diet phases, one during which they consumed 25.5 grammes of soy protein (through soy nuts) per day for 16 weeks, and the other during which they did not. Researchers came to the conclusion that soy nut diet enhanced their cerebral function after MRI and several cognitive tests.

Even now, studies are being conducted to see whether soy may actually lessen wrinkles. According to a research published in the journal Phytotherapy Research, phytoestrogens, like those found in soy, can lessen the effects of ageing on the skin. And research has shown that soy protein may increase muscle growth and strength just as well as animal protein.

Another advantage of consuming soy is longer life. The residents of Okinawa, one of the world's five Blue Zones—areas where people not only live the longest but also the healthiest—rely heavily on tofu, which is produced from soybeans and water. According to Dan Buettner’s book, The Blue Zones Solution, people in Okinawa eat eight times more tofu than Americans, and Buettner ranks it in his top longevity foods from the region

CAN MEN EAT SOY?

Men can and ought to consume soy. According to Messina, soy has no feminising effects, meaning it has no impact on testosterone, sperm/semen, or gynecomastia. Soy meals did not alter male reproductive hormones like testosterone, according to a research published in 2021 in the journal Reproductive Toxicity. This conclusion supports that of an earlier meta analysis that was published in Fertility and Sterility. And as was already noted, some study has connected a high soy food intake with a markedly lower risk of prostate cancer.

ARE SOME SOY PRODUCTS HEALTHIER THAN OTHERS?

Unprocessed to heavily processed soy products are both available. Concentrate mostly on raw or lightly processed soy products to reap the greatest health advantages. According to Palmer, "the more entire the meal, the healthier it is in general because it keeps all of the natural nutrients in the plant food."

So how could a soy food pyramid appear, from healthiest to unhealthiest? Use this advice:

Unprocessed: Soya beans, edamame

Minimally processed: Soy milk, tofu, tempeh, soy nuts

Moderately processed: Miso, natto, soy yogurts

Highly processed: Extruded soy proteins (like soy protein isolate), soy oils and faux meats

HOW MUCH SOY SHOULD YOU EAT?

You shouldn't be hesitant to eat soy regularly in its unprocessed form because it is a nutrient-rich plant food that has been linked to a number of health advantages, as mentioned above. While tofu and tempeh may also be included in a nutritious plant-based diet, Forks Over Knives advises using them sparingly because they are processed, albeit little. Palmer estimates that she drinks fortified soy milk every day and occasionally eats tofu or tempeh, edamame, and soy-based yoghurt.