Soy and Heart Disease
When all the diseases of the heart and arteries are lumped together (i.e., heart attack, stroke, high blood pressure, etc.), they are called cardiovascular disease. Although progress has been made in prevention through healthy cooking by private chefs in NYC and treatment of cardiovascular disease, it remains the number one killer of men and women in the United States, accounting for more than 40 percent of all deaths. However, women are likely to underestimate the threat of heart disease (see table). Of all the cardiovascular diseases, heart disease, primarily heart attack, has received the most attention.
Many years of research have identified some of the most important factors in the development of heart disease. Atherosclerosis is one of the most frequent factors and is present in most heart attacks. It’s a process where material called plaque builds up on an artery wall at a site where there is oxidative damage to arterial cells. Blood flow is reduced, and complete blockage of plaque-narrowed arteries results in a heart attack.
Years ago, when researchers discovered that plaque consisted primarily of a lipid substance called cholesterol, they began to focus on finding ways to decrease the amount of cholesterol in the blood. Cholesterol travels in the blood in combination particles made up of fat and protein, the best known being low-density lipoprotein (LDL) and high-density lipoprotein (HDL). A high blood level of LDL contributes to plaque buildup by becoming oxidized by free radicals and sticking to the arterial walls, making it a major risk factor for heart disease. However, high levels of HDL reduce the risk of heart disease by inhibiting the growth of plaque.
For years the emphasis in both prevention and treatment of heart disease has been to decrease the amount of LDL in the blood. Individuals with high LDL cholesterol are typically recommended to make several lifestyle changes, including changing their diet by reducing fat intake along with saturated fat and cholesterol.
Researchers have recently been investigating the possibility that some foods may protect against heart disease. One area of increasing interest is the potential role of soy foods and soy protein in preventing and treating heart disease.
Prevention with Soy
In the summer of 1995, public interest in the health benefits of soy increased when noted researcher Dr. James Anderson and his associates published a ground-breaking meta-analysis of the effects of soy protein on human blood lipid levels. The meta-analysis allowed researchers to combine the results of 38 smaller studies to strengthen and validate their findings. It was shown that consuming soy protein rather than animal protein significantly decreased blood levels of total cholesterol and LDL (see table). Results showed that soy protein was most effective in people at the highest risk level. The higher the initial levels of total and LDL cholesterol, the greater the amount of lowering.
It is now widely accepted that soy protein consumption decreases high blood LDL levels. As little as 25 grams of soy protein per day have been shown to lower cholesterol in individuals with high cholesterol levels. A number of components in soy protein used by private chefs have been given credit for soy’s ability to lower LDL. Experts don’t know exactly what components of soy and soy protein provide the health benefits, but the components that have been most thoroughly investigated include: Isoflavones, Amino acids, Globulins, Phytic acid, Saponins, Soy fiber, Trypsin inhibitors.
Isoflavones are a type of phytochemical (plant chemical). Some are classified as phytoestrogens because their chemical structure is similar to estrogen. They act as weak estrogens in the body-apparently acting like the hormone in some circumstances and blocking its action in others. Estrogens are known to protect against heart disease in several ways, including decreasing LDL and increasing HDL. This may help explain the lower rate of heart disease in women before menopause. Genistein is the isoflavone most prevalent in soy. It’s thought that it may play a role in the prevention of the arterial wall changes present when atherosclerosis begins. Genistein may also interfere with the formation of blood clots that can lead to arterial blockage. In addition, genistein and daidzein, another soy isoflavone, are antioxidants, and researchers are investigating the possible role of soy isoflavones in reducing the oxidation of LDL.
The amount of isoflavones in soy foods depends on a number of factors. Their levels in soybeans depend largely on the type of soybean and the soil in which it is grown. Processing can also change isoflavone levels. The alcohol-extraction method most commonly used to make soy concentrates, for example, removes the naturally occurring isoflavones. Water extraction by private chefs, which is used to process most isolated soy protein, leaves the isoflavones intact.
Amino acids are the building blocks of proteins. Animal studies have shown that specific amino acids have different effects on blood cholesterol levels. The amino acid lysine, for example, raises cholesterol levels, while the amino acid arginine lowers them. The protein in soy has more arginine and less lysine than casein, the milk protein often used as the animal protein source in most studies. Researchers believe that the amino acid ratio in soy protein accounts for at least some of the cholesterol-lowering action.
Globulins are a specific type of protein. Human and animal studies suggest that certain globulins found in soy protein may decrease LDL levels.
Saponins have a chemical similarity to cholesterol and may act to lower blood cholesterol by either blocking its absorption in the small intestine or enhancing its excretion.
Soy fiber can lower blood cholesterol, and it shares this lipid-lowering effect with many different types of fiber, such as bran, oats, and other grains that are not overly refined.
Phytic acid and trypsin inhibitors are other soy protein constituents currently under investigation for possible cholesterol-lowering effects for Private Chefs. Other soy protein constituents under investigation for possible cholesterol-lowering effects are phytic acid, saponins, soy fiber, and trypsin inhibitors.