Soy protein is the new hype these days. Everywhere you look there is soy. Tofu, Soy-Um, Quaker instant oatmeal Nutrition for Women, and Clif bars are just a few things I have in my house that contain soy protein. If the label indicates that soy is an ingredient, does it mean that it is good for you? If this were the case, then Pop Tarts, which include soy, would be considered healthy. We all know that they are not considered healthy. However, there are complete lines of soy food that can be found at Trader Joe's that are good for you. Over the last couple of years researchers are finding more and more reasons why soy protein should be in YOUR diet. According to the MSNBC website, there has been an increase of 200% in the consumption of soy in the United States since 1995.

Soy protein , derived from the soya bean, was originally cultivated in Asia. It is considered a complete protein, meaning that it contains all nine of the essential amino acids our body requires. Amino acids are the building blocks for the synthesis of proteins into skeletal muscles. There are 24 amino acids that, when constructed properly, make human proteins. Of these 24 amino acids, 9 of them your body cannot produce so you most obtain from the foods you eat. When there is a deficiency in any of these 9 amino acids the rebuilding process becomes less efficient. Your muscles require protein to repair, rebuild and grow. It is also an excellent source of Fiber, Iron, B-Vitamins, and Essential Omega-3 Fatty Acids. Fiber is important because it helps reduce cholesterol and makes fats less likely to be absorbed in to the body.

Soy protein contains branched-chain amino acids (BCAA's) which are an important energy source during exercise. In the first 20 minutes of a workout, glucose is broken down through glycolosis to produce the energy your body needs. After 20 minutes of exercising, the glucose is exhausted and the fatty acids and BCAA's become the major energy source. It has been found that BCAA's have and increased up take by muscles and has an increased rate of oxidation during exercise. This is important because BCAA's are metabolized in your muscle rather than in your liver. This is why it is recommended to eat protein after working out, because the BCAA's help to restore the decrease in protein production lost during exercise. Proteins are what your body uses to create muscle mass. Protein also contributes to 16% of the nitrogen in your body. During endurance activity nitrogen is removed from the BCAA's. The body loses nitrogen through urea, feces and sweat.

Soy protein has been found to reduce exercise oxidative stress. Soy protein contains isoflavones, which are antioxidants that combat against cell damage. Antioxidants are free radical "scavengers" that directly combat free radicals and work synergistically in restoring normal function to all body tissue. They help the body to recover more quickly. Isoflavones have been found to cause less muscle soreness by decreasing muscle inflammation.

Soy protein changes the way the liver creates and metabolizes cholesterol differently than that of meat protein. Isoflavonnes protect low-density lipoproteins (LDL's) from oxidation and raises high-density lipoproteins (HDL's) in the blood. LDL's are considered "bad" cholesterol while HDL's are considered "good" cholesterol. LDL's transport triacylglycerols and cholesterol from the liver, via the blood, to the tissues where it deposits the cholesterol for cell building. The problem lies when there is too much of a build up on the artery wall causing the arteries the clog. HDL's transport endogenous cholesterol from the tissues to the liver. It removes the cholesterol from the tissues, extracting it from the cell surface membranes and moves it back to the liver for re-processing or excretion. In the extrahepatic tissues, tissue outside the liver, LDL's can be broken down into HDL's. The liver as bile acids disposes of the surplus of cholesterol; the only significant mechanism the body has for disposing the water-insoluble substance.

Two important amino acids your body naturally produces are glutamine and arginine. Glutamine buffers lactic acid build-up to reduce fatigue. It also enhances nitrogen balance, promotes protein synthesis and improves the immune system. Arginine promotes anabolic activity that results in muscle formation. Both of these amino acids are essential during metabolism stress.

You have to be careful when buying soy protein products. Products that say they contain soy are not the same as soy protein. In order for a product to be considered beneficial for your health it must contain at least 6.25g of soy protein, no more than 20mg of cholesterol, no more than 480mg of sodium, less than 1g of saturated fat and no more than 3g of total fat. This is the standard FDA health claim. The RDA recommended daily intake of protein is 0.8g per kg of body weight (1kg is equal to 2.2g), but depending on your needs can be up to 2.0g per kg of body weight. The FDA recommends 25g of soy protein a day to help reduce cholesterol. Soy protein has been found to help the body protect against cardiovascular disease, osteoporosis (by protecting the bones from becoming weak), and certain cancers. It helps against obesity buy decreasing the amount of LDL’s circulating in the blood. Soy protein has also been found to decrease the risk of breast cancer by regulating the estrogen levels in women.

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References:
Voet, D.; Voet, J.; Pratt C., Fundamentals of Biochemistry, 1999, p 262,567, 605.

Cooper Amy, "Soy Protein, Gale Encyclopedia of Alternative Medicine, January 1, 2001.

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