Brain development, which begins in the womb and continues through puberty, also may be altered by estrogen in soy, Patisaul said. It is controlled by a well-organized combination of genes and hormones. Introducing compounds that mimic estrogen could throw off the balance, with long-term impacts on behavior and brain chemistry.
Studying the health outcomes of fetal or early infant exposure can be difficult, according to Benson Akingbemi , a developmental biologist at Auburn University. Reproductive changes are often not apparent until adulthood. Another difficulty is that infant formulas vary in isoflavone content depending on the type of soybean used and the conditions—such as soil type—that the beans were grown in, making dosage very hard to control. In , the American Association of Pediatricians reviewed all current scientific studies of the effects of soy formula on infants.
There is no conclusive evidence that it harms infant development, reproduction or endocrine function, stated the American Association of Pediatricians. Some researchers believe that waiting for proof from long-term human data may come at a price. Patisaul compares the effects of genistein to Bisphenol A , or BPA, the estrogenic compound found in plastic bottles that many scientists suspect can harm brain and reproductive development.
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See Subscription Options. Go Paperless with Digital. Get smart. Sign up for our email newsletter. Women from Asian countries appear to receive greater protective benefit from breast cancer with high soy intakes than American and European women, but this may simply be a difference in the amount of soy consumed. The Breast Cancer Family Registry was a prospective study following 6, women diagnosed with breast cancer and living in the U. Another prospective study followed 1, American women who were breast cancer survivors for six years.
The incidence of prostate cancer is highest in Western countries and lowest in Asian countries, where soy foods are a regular part of the daily diet. In addition, observational studies have found an increased risk of prostate cancer in Chinese and Japanese men who move to Western countries and adopt a Western diet, but not in those who continue eating a traditional diet. In a meta-analysis of 30 case-control and cohort studies from the U. A review of eight randomized controlled trials examined the effects of soy in men with or at risk of developing prostate cancer.
Two of these studies found that isoflavone supplements or dietary soy protein reduced the risk of prostate cancer in men at high risk of developing the disease. However, none of the studies found a significant effect on prostate specific antigen PSA levels. PSA is a protein produced by the prostate gland that is used to detect prostate cancer. There were no adverse effects reported with soy supplementation.
The authors discussed limitations of the review including the small number of participants, the short duration of studies less than one year , and variation in dosages and types of soy given.
Menopause has been linked with changes in mood and memory impairment. Thus, research has raised the possibility that eating soy foods might help prevent age-related memory loss or decline in thinking skills. Trials have yielded contradictory results, with some showing a benefit with soy isoflavone supplementation [28, 29] and others showing no benefit.
However the results overall were mixed, with other studies not demonstrating a benefit. This may have been due to differing dosages given or the types of cognition tests used. One large study in men found a detrimental effect on cognitive function. In a prospective cohort study of more than 3, Japanese-American men living in Hawaii, the highest intakes of tofu eaten almost daily at midlife ages were significantly associated with greater cognitive impairment and brain atrophy in late life compared with men with the lowest tofu intakes almost never eaten.
Because of this, the researchers stated that the findings were too preliminary to make recommendations. Soy may interfere with thyroid hormone medication used to treat hypothyroidism.
In one randomized double-blinded trial, 60 patients with a mild form of hypothyroidism called subclinical hypothyroidism were given low or high-dose phytoestrogen supplements both also contained 30 grams of soy protein , the amount that might be obtained from a vegetarian diet. The authors suggested that female vegetarian patients with subclinical hypothyroidism may need more careful monitoring of thyroid function.
However, the authors also found a benefit on of reduced cardiovascular risk factors in the high phytoestrogen group, with a significant reduction in insulin resistance, inflammatory markers, and blood pressure. The effect of soy on thyroid function needs further examination. The contents of this website are for educational purposes and are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
Never disregard professional medical advice or delay in seeking it because of something you have read on this website. The Nutrition Source does not recommend or endorse any products. Skip to content The Nutrition Source. Harvard T. The Nutrition Source Menu. Search for:. The Takeaway: Soy is a unique food that is widely studied for its estrogenic and anti-estrogenic effects on the body.
Studies may seem to present conflicting conclusions about soy, but this is largely due to the wide variation in how soy is studied. Results of recent population studies suggest that soy has either a beneficial or neutral effect on various health conditions. Soy is a nutrient-dense source of protein that can safely be consumed several times a week, and is likely to provide health benefits—especially when eaten as an alternative to red and processed meat.
Heart Disease Soy protein took center stage after research showed that it might lower levels of harmful cholesterol. Hot Flashes Hormone replacement therapy has traditionally been used as an effective treatment for hot flashes and other unpleasant symptoms that accompany menopause, but its long-term use carries concerns of an increased risk of some diseases including breast cancer and stroke.
Of all ethnicities, Asian American women tended to have the highest isoflavone intakes at about 6 mg. The authors noted that American women appeared to benefit from eating smaller amounts of soy. The most frequent sources of soy foods were not whole or minimally processed soy foods, but rather soy sauce, breakfast or diet drinks, tofu, diet bars, and soy protein isolate powder. The authors concluded that soy isoflavones eaten at levels comparable to those in Asian populations may reduce the risk of cancer recurrence in women receiving tamoxifen therapy and does not appear to interfere with tamoxifen efficacy.
However, the findings need to be confirmed because they were mainly in subgroups and could be due to chance. Prostate Cancer The incidence of prostate cancer is highest in Western countries and lowest in Asian countries, where soy foods are a regular part of the daily diet.
Memory and Cognitive Function Menopause has been linked with changes in mood and memory impairment. Starting to consume soya products at an earlier age may make soya more beneficial Credit: Getty Images. Meanwhile, clinical and population data shows daily soya intake can halve the frequency and severity of hot flashes even when the placebo affect is taken into consideration, says Mindy Kurzer, professor of nutrition at the University of Minnesota.
One paper argues that Chinese populations, for example, may be better able to digest and extract nutrients from soya because their ancestors have been eating it for thousands of years. This could explain why research has found that, while people who move from Asian countries to the US have an increased risk of breast cancer by the second generation, their risk remains lower than Westerners even when they adopt a Western diet. Soya intake could reduce the risk of cardiovascular disease Credit: Getty Images.
Early soya intake has also been found to reduce the risk of cardiovascular disease. In fact, population studies suggest isoflavone intake could be responsible for the different rates of cardiovascular disease between Asian and Western countries. This is because soya has been found to reduce levels of harmful low-density lipoprotein LDL cholesterol in the blood, which is a risk for heart disease.
But may have nothing to do with soya, per se — it could simply be because diets higher in soya are lower in unhealthier foods. There are also concerns soya could be linked to prostate cancer. Unprocessed soya, like edamame beans, has higher isoflavone levels than processed versions, like soya milk Credit: Getty Images. Isoflavone content varies in unprocessed soybeans, such as edamame beans, compared to processed soya foods — and the closer the food is to the soyabean, the higher its isoflavone levels.
Edamame has around 18mg of isoflavones per g, while soya milk has between 0. Soya has been extensively researched over the last few decades. Join one million Future fans by liking us on Facebook , or follow us on Twitter or Instagram.
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