Harvard Study: Soy Counteracts Metabolic Syndrome

30/03/07 Obesity. High blood pressure. Abnormal cholesterol levels. Most of us intuitively recognize these as warning signs for health problems. Combine these risk factors in individuals with insulin resistance, however, and the cluster becomes metabolic syndrome -- a precursor to heart disease and type-2 diabetes. Now, new research co-authored by the Harvard University School of Public Health shows that adding soy to the diet may improve many problems associated with the metabolic syndrome above and beyond that of a healthy diet without soy.

The study evaluated both soy protein and soy nut consumption among postmenopausal women living with metabolic syndrome. Soy protein and soy nuts each exhibited a beneficial effect on components of the syndrome, but soy nuts had the strongest impact, perhaps because they provided soy protein as well as polyunsaturated fat and contained a higher amount of soybean isoflavones.

How much should we worry about metabolic syndrome? The condition afflicts up to 30 percent of the industrialized world's population, and will likely affect 50 to 75 million Americans by the year 2010. Alarmingly, this syndrome increases risk of heart disease by two to four times that of the normal population, and increases risk of type-2 diabetes by nine to 30 times. Research also suggests the metabolic syndrome may play havoc with the kidneys, liver, ovaries, ability to sleep and even dementia.

Published in the American Journal of Clinical Nutrition, the Harvard study, which was co-authored by researchers at Shaheed Beheshti University of Medical Sciences in Iran, used a randomized crossover design involving 42 Iranian postmenopausal women. All subjects consumed each of three different diets for eight week periods: a healthy diet that had previously been demonstrated to lower blood pressure, the same diet in which soy protein replaced the original protein source or the same diet in which soy nuts replaced the protein source.

The results showed that all three diets lowered LDL cholesterol but the decreases were significantly greater in the diets containing soy.Even more impressive, the soy-containing diets markedly improved insulin resistance, a hallmark of the metabolic syndrome. In this case, soy nuts had a greater effect than soy protein.

Dr. Mark Messina, a nutritionist and noted soyfood expert, commented, "The results of this study confirm the well-recognized role of soyfoods in reducing cholesterol levels and provide new evidence that soyfoods can potentially help millions of individuals with the metabolic syndrome by improving insulin resistance."