As we age, our muscle and whole-body protein metabolism slows down. (Medical Reference 1) Fortunately, these changes can be offset by exercise, which provides a variety of health benefits for people of any age. However, our bodies require a good source of energy or fuel for exercise to provide its full benefits.
It has been reported that the branched-chain amino acids (BCAAs), leucine, isoleucine, and valine, are oxidized to provide an important energy source during exercise. (Medical Reference 2) In addition, the BCAAs, especially leucine, can enhance protein synthesis after exercise and while at rest (Medical References 3-9) and may help prevent muscle breakdown and soreness associated with exercise. (Medical References 10, 11) In addition to their benefits on protein synthesis and exercise, it has been suggested that BCAA may support better immune function in athletes. (Medical Reference 12)
Soy protein has been shown to be an excellent source of BCAAs. (Medical Reference 13) The requirements of the BCAAs for human growth and development are 66, 28, and 35 mg/gram of protein for leucine, isoleucine, and valine according to the Food and Agricultural Organization/World Health Organization. (Medical Reference 14) Isolated soy protein has been reported to contain 82, 49, and 50 mg/gram of protein for these BCAAs, levels well above above human requirements. Thus, the amino acid pattern of soy protein provides adequate levels of each essential amino acid for normal growth and development. Interestingly, soybeans are the only vegetable to meet these requirements.
In summary, the high quality of soy protein and its BCAAs content make soy an excellent protein food source for good health and exercise. The FDA recommends 25 grams of soy protein per day, as part of a diet low in cholesterol and saturated fat, to reduce risk of heart disease.
By Dr. Aaron Tabor, MD
Medical Research Director
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