Improve your Cholesterol Score with Soy

I've written before about one of several nutritional studies on soy protein and its effect on LDL cholesterol (the bad stuff) and total cholesterol levels. A recent Canadian study in the American Journal of Clinical Nutrition (2006;83(2):244-51) theorized that isoflavones, a plant chemical with estrogen-like qualities, might be one of the significant factors in soy's association with reduced cholesterol levels.

For this study, 35 men were recruited who were between the ages of 20 and 40, whose Body Mass Index was stable and between 19 and 29, and were otherwise free of serious medical conditions, including allergies to milk or soy protein.

The men were placed in three groups. Each group was given one of three types of protein powders to supplement their regular diet: low-isoflavone soy protein, high-isoflavone soy protein, or milk protein. None of the subjects knew which protein powder they were receiving, although all of the men were carefully instructed to avoid foods containing high amounts of isoflavones, including soy, flaxseed, beans and legumes, and to minimize their consumption of milk and calcium-fortified beverages and alcoholic beverages.

After supplementing their regular diet with one of the protein powders for 57 days, the subjects then stopped consuming the protein powders for a month, in what is called a "washout period" - to clear their systems of the effects of the supplementation. After that month, the subjects were then switched to another of the protein powders for 57 days, making the study into what is known as a crossover design. Again there was a month-long washout period, and then a third type of protein powder for 57 days. Throughout the trial the subjects did not know which type of protein supplement they were taking when.

After each 57-day trial, the subjects' blood was tested for serum cholesterol levels. In a particularly interesting result, the researchers found that although the subjects' total cholesterol was not much changed between the three arms of the study, the ratio of total cholesterol to HDL was decreased for those on the soy-protein regimens, regardless of whether the protein was high in isoflavones or low in isoflavones. The same was true for the other parameters that we consider to be more protective, including LDL to HDL.

What this means for you

It's pretty clear that soy protein is good for both your cholesterol and your blood pressure. There's a lot of ways to get soy in your diet. One of my favorites is shelled soy beans (edamame) and I keep a bag in my freezer. The Cashew Chicken uses them and so does the Ginger Chicken with Edamame recipe. I also love soy burgers and will often have them when I am traveling, as a good alternative when there's nothing healthy on the menu.

First posted: July 18, 2006