Soy foods, such as  tofu and soy milk, have been recognised for their high-quality protein and healthy fats for a long time.

Over the last 25 years, scientists have been taking a closer look at soy for its role in preventing and treating chronic diseases. They have found that soy can lower the risk of heart disease, breast cancer, and prostate cancer. It can also help with hot flashes, kidney function, mood improvement, and skin health.

The Power of Isoflavones

One reason why soy is so beneficial for us, is because it is packed with isoflavones.

Isoflavones are plant compounds that act like estrogen in the body.

Some people worry about soy because of these isoflavones, thinking that consuming soy might have negative effects. However, most of the concerns that the media panicked and screamed about for quite a while, came from animal studies. Research on humans shows that soy is safe and extremely beneficial.

The inhabitants of one of the Blue Zones (areas in the world where people are known to live with minimal ill health and actively up to 100 and over) called Okinawa, men and women consume large amounts of soy products. They have no breast cancer- actually, no cancer at all! Healthy blood pressure levels, no hot flushes and are free from modern diseases all round (and the women have beautiful skin).

Soy Protein: High-Quality and Nutrient-Rich

Soybeans are special because they’re higher in fat and protein and lower in carbohydrates than other beans. This makes them a great source of protein, similar to animal protein. Soy protein contains all 9 amino acids such as animal protein – but it doesn’t contain cholesterol and it low in saturated fats.

Traditional soy foods such as tofu and tempeh also have good protein digestibility.

Carbohydrates in Soy

Soybeans have fewer carbs compared to other beans. This can be good for people with diabetes or those on a keto diet.

The few carbs found in soybeans are oligosaccharides, which are types of sugars that promote the growth of healthy gut bacteria. These sugars can sometimes cause gas, but many soy products like tofu and tempeh have lower amounts because of processing.

Healthy Fats

Soybeans contain healthy fats, with a good balance of monounsaturated and polyunsaturated fats. They are also a good source of both essential fatty acids, omega-6 and omega-3.

Vitamins and Minerals

Soybeans are rich in various vitamins and minerals, especially potassium, which many people don’t get enough of. The nutrient content can vary depending on how the soy food is made. For example, natto, a traditional Japanese soy food, is extremely high in vitamin K2 due to fermentation.

Iron absorption from soy is good iron in soy is well absorbed because it is mainly in the form of ferritin, and people can adapt to the presence of phytate.

The Special Role of Isoflavones

Isoflavones in soy act like a milder form of estrogen, binding to estrogen receptors in the body. This can have different effects in different tissues. For example, while estrogen affects both estrogen receptors equally, isoflavones prefer one type over the other. This selective action means they can have estrogen-like effects in some tissues and not others, making them useful for specific health benefits without the risks associated with estrogen therapy.

Cardiovascular Benefits

Soy protein can help lower bad LDL cholesterol and slightly raise good HDL cholesterol. These changes can significantly reduce the risk of heart disease. The effect is modest, but still meaningful, especially considering that small reductions in cholesterol can lead to notable decreases in cardiovascular events.

Blood Pressure

Eating more protein, especially soy protein, can slightly lower blood pressure. Even a small drop in systolic blood pressure (2-5 mmHg) can reduce the risk of stroke by 6-14% and heart disease by 5-9% .

Some studies show significant drops in blood pressure with soy protein. One study had postmenopausal women eating 25 grams of soy protein from soy nuts, while another had men drinking one litre of soymilk daily. Both groups saw big drops in blood pressure.

The exact reason why soy protein lowers blood pressure isn’t known yet, but it helps – and all natural forms of healing is good!

Endothelial Function (Vasodilation)

The endothelium is a thin layer of cells lining our blood vessels, playing a crucial role in cardiovascular health. When these cells become dysfunctional – this can lead to cardiovascular events (CVEs).

Two meta-analyses found that soybean isoflavones improve endothelial function in postmenopausal women, especially those with impaired function at the start.

Arterial Stiffness

Arterial stiffness relates to how well arteries can expand and contract with each heartbeat. It’s a good predictor of future cardiovascular events. The best measure of arterial stiffness is pulse wave velocity.

A 2011 review by Pase et al. found that isoflavones reduce arterial stiffness based on five studies [153,154,155,156,157] Three more studies also support this finding, specifically in postmenopausal women  [158,159,160]

Effects on Cardiovascular Events

Cardiovascular disease like heart disease and stroke causes over 20% of deaths worldwide.

Studies show that replacing animal protein with soy protein in Western diets could further reduce LDL cholesterol and heart disease risk due to a better fatty acid profile. One estimate suggests that replacing 24 g of animal protein with soy protein could lower LDL cholesterol by about 4%.

Studies suggest that oils with both omega-6 and omega-3 fats reduce heart attack risk, which supports the heart health benefits of soy foods.

Bone Health

As women age, especially after menopause, their estrogen levels drop. This can lead to significant bone loss and an increased risk of fractures.

Research has found that soy foods can help with bone health due to the estrogen-like effects of isoflavones.

Two large studies in Asia found that women who consumed soy had about one-third lower risk of fractures. Whilst a US study among Seventh-day Adventists in the US, many of whom are vegetarians, found that postmenopausal women who drank soymilk had a lower risk of developing osteoporosis.

Studies using a novel method to assess bone calcium content showed that over 50 days, isoflavones (105 mg/day) increased bone calcium content by 7.6%,

Interestingly, doubling the dose of isoflavones didn’t improve bone calcium content as much as the lower dose. This suggests that moderate doses of isoflavones (50–100 mg/day) might be more effective for bone health.

Breast cancer

It is generally well known that breast cancer rates are lower in countries where people eat a lot of soy, compared to Western countries. As Asian countries have adopted more Western lifestyles, their breast cancer rates have increased. Studies suggest that eating more soy can reduce breast cancer risk by about one-third.

In recent studies by the Shanghai Women’s Health Study provided an interesting insight into the impact of timing of soy intake on breast cancer risk [238]. After a median follow-up period of 13.2 years, 1034 incident of breast cancer cases were identified among the 70,000 women enrolled in this study. When women were divided into three soy protein intake groups (low, medium, and high) it was found that high intake during both adolescence and adulthood significantly reduced breast cancer risk. However, consuming higher amounts of soy only during adolescence (and low soy intake during adulthood) was almost as protective.

Studies suggest the reason for this finding is that protective effects would have already been manifest against breast cancer among premenopausal women if they had consumed soy when young [238]..

One of my favourite doctors Dr William Li – has much to say about the benefits of soy and it’s cancer fighting abilities. 

Breast Cancer Patients

There was concern that soy foods might negatively affect the prognosis of breast cancer patients due to isoflavones’ estrogen-like effects. However, isoflavones are different from estrogen, and the evidence that estrogen therapy increases breast cancer risk is weak. In fact, the Women’s Health Initiative trial showed estrogen therapy significantly reduced the risk of invasive breast cancer.

Clinical data show that soy isoflavones do not have any harmful effects on breast tissue. The EFSA concluded that isoflavone supplements do not affect breast tissue in healthy postmenopausal women. Soy and isoflavone supplements also do not significantly affect reproductive hormones in women.

Prospective epidemiologic data show that post-diagnosis soy intake improves prognosis. A meta-analysis of five studies involving over 11,000 women with breast cancer found soy consumption after diagnosis was associated with reduced breast cancer recurrence and mortality. Soy was beneficial for both Asian and non-Asian women.

Prostate Cancer

Prostate cancer is the second most common cancer in men and the fourth most common overall. Rates are much lower in Asian countries where soy foods are commonly consumed compared to Western countries. Studies show that higher soy consumption is associated with up to a 50% reduction in prostate cancer risk.

Isoflavones do not affect testosterone levels in men, suggesting other mechanisms for their protective effects against prostate cancer. Studies indicate that isoflavones inhibit metastasis and may exert effects through binding to ERβ, which has anti-proliferative, pro-differentiative, and pro-apoptotic roles in prostate cells.

Kidney Function

The potential benefits of soy for kidney health are significant given the rising prevalence of renal disease, largely due to diabetes.

Studies have found that soy protein puts less stress on the kidneys compared to other high-quality proteins, which could reduce the risk of renal disease in susceptible individuals.

Replacing animal protein with soy protein may protect against diabetic nephropathy by decreasing hyperfiltration and glomerular hypertension.

Menopausal Symptoms

Hot flashes are the most common reason women seek treatment for menopausal symptoms, often lasting between 6 months to 20 years. The Study of Women’s Health Across the Nation found that hot flashes lasted an average of 11.8 years among women who began experiencing them during pre or perimenopause.

The low prevalence of hot flashes among native Japanese women and the interaction of isoflavones with ERs led to the hypothesis that soy foods can prevent or alleviate hot flashes.

A meta-analysis in 2012 found that soybean isoflavones significantly reduced the frequency and severity of hot flashes. Supplements providing more than 18.8 mg genistein were particularly effective.

Skin Health

Soy and isoflavones have shown wonderful results for skin health, especially in reducing wrinkles. Isoflavones, found in soy, can bind to estrogen receptors in the skin, potentially improving skin elasticity, moisture, pigmentation, and even hair health.

A few studies suggest that isoflavones help with wrinkles. One study had 40 postmenopausal women either eat their usual diet or add 20 grams of isoflavone-rich soy protein daily for three months. The group with the soy saw significant improvements in facial wrinkles, discoloration, and overall appearance. Another study with 26 premenopausal Japanese women found that 40 mg/day of isoflavones for three months significantly reduced fine wrinkles. Lastly, a 14-week study with 159 postmenopausal women showed a 10% reduction in wrinkles with an isoflavone drink, and the more wrinkles they had initially, the better the results.

Developmental Effects

Healthy eating habits in childhood are crucial as they often continue into adulthood and can lower the risk of chronic diseases. Although less research on soy involves children, some studies indicate that soy protein can lower LDL cholesterol in kids, just like in adults. Eating soy early in life might also reduce the risk of breast cancer.

Concerns about soy affecting hormone levels in children have been mostly unfounded. Limited studies show that soy does not impact hormone levels. While there is interest in how diet affects puberty, especially as puberty starts earlier in some cases, soy hasn’t been conclusively linked to these changes. Some studies even found no relationship between soy intake and the age of first menstruation in girls.

Fertility/Reproduction

There’s been debate about soy’s impact on fertility, especially given the high soy consumption in Asian countries. In women, soy might slightly lengthen menstrual cycles, which could potentially reduce breast cancer risk. Some evidence even suggests isoflavones might aid fertility, helping women undergoing reproductive treatments.

In men, studies on soy’s effect on sperm found that it improved sperm quality in a man with initially low sperm count.

Male Feminization

Two cases reported feminizing effects from high soy consumption, but these involved extremely high intakes (about nine times the average in older Japanese men) and unbalanced diets. Clinical studies show no effect of soy on estrogen or testosterone levels in men.

Thyroid Function

Concerns about soy affecting thyroid function come mainly from lab and animal studies. In people, studies show that soy does not affect thyroid function.

Effects on Endometrial Tissue

Endometrial cancer rates vary globally, with higher rates in the U.S. and Europe and lower rates in Asia. Research suggests that soy might lower endometrial cancer risk.

Conclusion

Adding tofu, soy milk, tempeh and miso to your daily diet (organic where possible) will lower your cholesterol, enhance your skin, protect you from breast or endometrial cancer as a woman and prostate cancer as a man. Help you with hot flushes as a menopausal and post-menopausal woman and decrease your chances of a heart attack.

It is loaded with good fats, protein, amino acids and isoflavones – I think you might want to rush out to the supermarket and get shopping like I did when researching this article because there was so much I didn’t know about soy – but I kept reading more and more good things so thought I should share!

For a thorough list of research material go to this site – it has every research link available https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5188409/

If you would like one on one  holistic beauty and wellness advice – book a glowing skin and wellness consultation via zoom with me!

Yvette xx

Thank you for reading my blog!

Hi! 

I am Yvette van Schie, I am a holistic beauty therapist, skin nutritionist, skincare developer and makeup artist. I am passionate about sharing real beauty advice with a whack of reality.

For over 30 years I have worked with the best in the beauty and health industry as a trainer, educator  and product formulator and I still do – so my knowledge is diverse – I am not blinkered when sharing my information with you because everyone I speak to shares what they know, and I turn it into easy to digest information because I want my readers to feel empowered to make their own decisions and to feel that they are fully in control of their beauty and well being.