The growing popularity of soy products in U.S. and European diets has raised considerable controversy. While the soy-rich diets of Asia generate documented health benefits, questions persist about the safety of soy in some products.

To make sense of this debate, it helps to understand the nature of dietary compounds called phytoestrogens—plant-based compounds whose chemical structure resembles estrogens, the female sex hormones of mammals. Also called isoflavones, phytoestrogens are most prevalent in soybeans and red clover.

Phytoestrogens have been linked to better heart health and reduced risk of breast and prostate cancers. They can help with osteoporosis and menopausal symptoms and may possibly improve cognitive functions. For all these benefits, however, the question of whether we should consume more soy-based products or add soy supplements to our diets has not been fully resolved.

Konstanin Yakimchuk, MD, PhD, senior researcher and expert medical and scientific writer of the Karolinska Institutet in Stockholm, Sweden, explains the fundamentals of the phytoestrogens at the root of the soy-safety debate.

Effects on Inflammation and Metabolic Diseases

Experimental data show that phytoestrogens—including genistein, one of the main soy isoflavones—may be useful for treating inflammation, one of the basic mechanisms of metabolic syndrome, atherosclerosis, arthritis, obesity and diabetes (Yu et al. 2016). Just two servings of soy foods can increase blood flow in heart vessels and improve the health of heart muscle. Phytoestrogens also widen blood vessels, reduce blood pressure, decrease blood cholesterol levels and prevent atherosclerosis in blood vessels (Rietjens, Louisse & Beekmann 2017). Note, however, that these plant hormones can suppress the human immune system, which could pose risks (Masilamani, Wei & Sampson 2012).

Soy for Postmenopausal Women

Researchers have found that supplementing diets with 30 milligrams of genistein daily can suppress osteoporosis in postmenopausal women. That dosage mirrors the regular intake of isoflavones in the traditional Eastern diet. Moreover, several studies suggest that isoflavones may reduce hot flashes and other postmenopausal symptoms (Messina 2014).

Societies with high consumption of soy foods or isoflavones also see a lower prevalence of breast cancer and other hormone-regulated cancers (Rietjens, Louisse & Beekmann 2017). However, some studies have reported an increase in abnormal growth of breast tissue after short-term intake of isoflavones (Rice & Whitehead 2006). Thus, the benefits of soy in women’s diets must be weighed against its potential risks.

Soy’s Impact on Men

Phytoestrogens also improve men’s health in several ways. Consider the impact on prostate cancer, the second-leading cause of cancer deaths in U.S. men. Notably, Asian populations with a high intake of soy are less affected by prostate cancer. Moreover, multiple studies in Asia, the U.S. and Europe have found that regular consumption of soy products decreases the risk of prostate cancer (Applegate et al. 2018). However, intake of isoflavones extracted from red clover has been linked to prostate cancer cell death by the process known as apoptosis (Reiter, Gerster & Jungbauer 2011).

Some Cautions

Many scientists agree that the data on health benefits of soy-derived isoflavones suggest potential preventive and therapeutic applications. But in spite of this healthy optimism in the scientific community, phytoestrogens should be valued and used with caution.

No matter how promising some studies may sound, the potential effects of plant hormones on male and female reproductive systems are not fully understood (Bennetau-Pelissero 2016). Excessive soy intake may cause an imbalance in the menstrual cycle, and several studies have associated decreased sperm count and erectile dysfunction with high intake of soy products. Soy protein is also one of the main triggers of food allergies.

It’s clear that more studies are needed before we can solve the puzzle of phytoestrogens. More research is needed to determine exactly which populations might best profit from isoflavone supplementation. You will want to consider what type and amount of soy (if any) you want to consume based on your individual health needs and family history.

A new study on insomnia in postmenopausal women suggests that consuming refined carbohydrates may keep you awake. The findings were published online in The American Journal of Clinical Nutrition.

Investigators analyzed food diaries from more than 50,000 participants in the Women’s Health Initiative and looked at whether women with a higher dietary glycemic index were more likely to develop insomnia.

Previously, researchers have been unable to confirm whether refined carbs trigger insomnia or whether insomnia causes individuals to eat more sweets. In this study, investigators sought to determine the role of carbs in creating sleep problems by looking for the emergence of insomnia across different types of diet.

The link they discovered between high glycemic diets and insomnia can be attributed to the quick spike in blood sugar after eating highly refined carbohydrates, like added sugars, white bread, white rice and soda. An increase in blood sugar causes the body to release insulin and other hormones—such as adrenaline and cortisol—that interfere with sleep.

The study also found that women whose diets contained higher amounts of vegetables, fiber and whole fruits were less likely to develop insomnia.

“Whole fruits contain sugar, but the fiber in them slows the rate of absorption to help prevent spikes in blood sugar,” said the study’s senior author, James Gangwisch, PhD, assistant professor of clinical psychiatric social work at Columbia University Vagelos College of Physicians and Surgeons, in a ScienceDaily press release “This suggests that the dietary culprit triggering the women’s insomnia was the highly processed foods that contain larger amounts of refined sugars that aren’t found naturally in food.”

While the research focuses primarily on postmenopausal women, the effects of carbs on blood sugar are true for most people and suggest the study has broader applications.

“Based on our findings, we would need randomized clinical trials to determine if a dietary intervention, focused on increasing the consumption of whole foods and complex carbohydrates, could be used to prevent and treat insomnia,” said Gangwisch.

True, some people did not win the genetic lottery with respect to gaining pounds, but that doesn’t mean they can’t tweak their diets to stave off weight creep. A study in The American Journal of Clinical Nutrition involving more than 14,000 adults over a 20-year period discovered that increasing one’s intake of fruits and vegetables can be protective against a genetic susceptibility to obesity. The impact was more robust in people whose genes strongly edged them toward obesity, and the most effective choices for overriding fat genes were berries, citrus fruits and leafy green vegetables.