A body of more than fifty scientific studies has prompted the Food and Drug Administration to endorse the heart benefits of soy foods. On October 25th, 1999, the agency authorized manufacturers of foods that contain soy protein to state on the label that the food helps reduce the risk of coronary heart disease (CHD). The decision was based on a determination that soy protein lowers both total blood cholesterol and low-density lipoproteins (LDL), or "bad" cholesterol.
CHD is the number one cause of death in the United States. High total cholesterol and high LDL cholesterol levels are proven risk factors for CHD. Studies have shown that consuming twenty-five grams of soy protein per day lowers cholesterol levels. However, you would have to eat a lot of tofu, soy milk, or soy-based meat alternative foods to consume twenty-five grams of soy protein a day. Since miso has about twenty times as much isoflavones, it should only take about a gram of miso protein to have the same cholesterol lowering effect as at least four servings of other non-fermented soy foods. This is about one teaspoon of miso or the amount needed to make just one cup of miso soup.
Besides lowering cholesterol directly, isoflavones seem to reduce blood clotting, which can reduce the risk of heart attacks and stroke. Finally, isoflavones may prevent the multiplication of cells that make up artery plaque. Research has shown that it may take much less soy protein to prevent plaque and blood clot formation than to reduce cholesterol.
Besides isoflavones, there are other ingredients in soybeans and miso that can play a role in managing cholesterol levels in the blood. In fact, soybeans are one of nature's best sources of lecithin and linolenic acid, which have been shown to play an important role in cholesterol metabolism.