The study did bring good news to those favoring tomato-rich diets as it found the fruit could help to protect at-risk postmenopausal women from breast cancer by increasing hormones which play a role in metabolism and cancer risk. Those same hormones are decreased by soy.

Writing in the Journal of Clinical Endocrinology & Metabolism, the new longitudinal cross-over study examined the effects of lycopene- and isoflavone-rich diets on serum adipokines – which play a vital role in regulating fat and sugar metabolism.

Led by Dr Adana Llanos from Rutgers University, the explained that breast cancer risk rises in postmenopausal women as their body mass index climbs. As such lifestyle changes or interventions that modify the metabolism of sugar and fat may help to reduce body fat and the risk of cancer.

Study Details

The team assessed the effects of both tomato-rich and soy-rich diets in a group of 70 postmenopausal women.

For 10 weeks, the women ate tomato products containing at least 25 milligrams of lycopene daily, while in a second 10-week period they consumed at least 40 grams of soy protein daily.

Before each test period began, the women were instructed to abstain from eating both tomato and soy products for two weeks.

Participants following the lycopene-rich diet were found to have higher levels of adiponectin — a hormone involved in regulating blood sugar and fat levels.

The soy diet, however, was linked to a reduction in participants’ adiponectin levels.

Adiponectin Levels May Be A Red Flag For Obesity In The United States and Soy May Be Part of The Problem

The study supports previous evidence which strongly correlates soy isoflavones with insulin resistance. In the Journal Metabolism, researchers found that isoflavone-containing soy protein increased insulin resistance to a glucose challenge and decrease plasma adiponectin, whereas isoflavone-depleted soy protein decreased body weight.

Current estimates are that 50% of the adult population of the United States is obese. About half of the obese population also suffers from pre-diabetes or the metabolic syndrome. Insulin resistance and obesity are key features of the metabolic syndrome and Type 2 diabetes mellitus. One potential mechanism involves the production of adiponectin levels in adipose tissue.

There is now growing evidence that environmental stressors, including chemicals present in food, air and water, may affect energy balance. A study in Toxicol Lett found that chemical-induced alterations by soy isoflavones in adiponectin concentrations imply that changes in adipose tissue metabolism occasioned by exposure to these dietary estrogens, and perhaps other estrogenic agents, possibly contribute to deficiencies in reproductive capacity attributed to these compounds.

Soy isoflavones are firmly being established as well known influential compounds on insulin action by means of their well-known receptor-mediated estrogenic activity. The problem is, they work against physiological mechanisms that advance health and rather act to prevent those mechanisms from flourishing.

Because almost 90% of soy beans are now considered genetically modified, and since most soy food products come from unfermented sources, this is one legume well worth leaving off your plate.

Dr. Marianna Pochelli is a Doctor of Naturopathic Medicine specializing in the treatment of disease through superfoods and herbal strategies. She actively promotes detoxification, colon cleansing, and a vegetarian lifestyle using living foods as a platform to health.