Proteins consist of long chains of amino acids held together by peptide bonds. The chains of amino acids that make up a protein can be quite long, sometimes hundreds of amino acids in length. Proteins can be broken down into shorter chains of amino acids called peptides. Every time you eat a protein, stomach acid and digestive enzymes in the stomach and intestines break down these proteins to peptides. Peptides can be as long as 50 amino acids in length or as short as 2 amino acids.
One type of peptide called soy peptides are derived from soy protein. These peptides are found naturally in soybeans as a part of soy protein. Soy peptides are released when hydrochloric acid in the stomach breaks them down. They can also be produced using enzymes to break down the bonds between amino acids in a laboratory. A variety of biologically active peptides have been isolated from soybeans that appear to have health benefits. Some have the ability to act as antioxidants, protecting cells against damage from exposure to oxygen, while others have an anti-inflammatory effect, reducing inflammation that contributes to a variety of health problems.
Peptides derived from soybeans also have blood pressure and cholesterol-lowering benefits, which may explain why diets high in soy may lower the risk for heart disease. In addition, soy peptides may lower the risk for obesity by reducing the body's ability to store fat and by stimulating the breakdown of fat stores. They also may reduce the risk for certain types of cancer, especially colon and liver cancer.
More recently it was discovered that soy peptides reduce exercise-related fatigue in athletes. This isn't surprising since peptides contain amino acids. These amino acids slow down the breakdown of other muscle proteins during exercise. They also appear to increase lean body mass in bodybuilders. Soy peptides are also easier to digest than milk protein and are well tolerated as a nutritional supplement.
Soy peptides also have skin anti-aging benefits. Peptides are frequently added to skin care products because of their ability to alter the activity of cells. For example, some peptides signal cells in the dermis called fibroblasts to produce more collagen. Collagen is a protein that gives skin support and keeps it firm and wrinkle-free. Collagen levels decline with age, which is one reason wrinkles form and skin loses the firmness it had in youth. Research also shows that soy peptides increase the synthesis of glycosaminoglycans, or GAGs, chains of polysaccharides linked to a central protein, in the dermis of the skin. An example of a GAG is hyaluronic acid. Glycosaminoglycans have the ability to hold onto water, which helps to keep skin hydrated. GAG levels decrease with age, and soy peptides may be one way to preserve them.
Due to their anti-aging benefits, soy peptides are added to some anti-aging skincare products to boost collagen synthesis and increase production of glycosaminoglycans as well as reduce inflammation and oxidative damage. When skin is exposed to ultraviolet light and pollutants in the environment, free radicals form that can damage skin cells and activate enzymes that break down collagen. Soy peptides can prevent some of this damage by donating electrons to these free radicals so they can't do their damage.
Soy peptides may also help to fade areas of increased pigmentation due to sun damage as well as lighten under-eye circles. A small study showed that women who used a moisturizer containing soy peptides twice daily reported more even skin pigmentation, less blotchiness and improved skin texture as well as an improvement in fine lines and wrinkles. That's why soy peptides can be found in some facial moisturizers, eye creams and other anti-aging skin care products.
Is it safe? Soy peptides appear to be safe when applied topically and rarely cause skin irritation even for people with sensitive skin. In fact, they help to reduce skin irritation due to their anti-inflammatory effect. They have an anti-aging effect and can make skin look smoother and more evenly pigmented while reducing the appearance of fine lines and wrinkles.