Lysine is an amino acid, one of the "building blocks" of protein. Your body uses 22 amino acids to make protein-based substances such as muscle, skin and enzymes. As an adult, you can make most of the amino acids needed to build protein within your body, but eight of them must come directly from dietary sources. Lysine is in this group of eight, which are called "essential" amino acids. A lack of dietary lysine slows down protein synthesis and results in various health issues.
Building Muscle Tissue
Like most amino acids, lysine is used to build muscle fibers and collagen, which is an elastic-like compound found in skin, cartilage and other connective tissues such as ligaments and tendons. Muscle tissue has a higher proportion of lysine compared to other amino acids, so lysine deficiency is especially detrimental to muscle growth, strength and repair. Muscle weakness, increased injury recovery time and sagging skin are common symptoms of lysine deficiency. Athletes sometimes take lysine supplements in efforts to build leaner muscle and reduce recovery times after workouts. Lysine also stimulates growth hormone production, which helps with muscle growth as well.
Synthesizing Enzymes, Hormones and Antibodies
In addition to muscle and connective tissues, enzymes, hormones and antibodies are also made from protein and rely partially on lysine for synthesis. Enzymes are important for metabolizing foods and precipitating biochemical reactions in your body. Hormones are important for regulating various aspects of the body, including mood, weight, sleep and energy levels. Antibodies are essential for the immune system, because they are able to “recognize and tag” foreign material in the blood and other tissues for destruction and elimination. Consequently, lysine deficiency also can result in poor metabolism, fatigue, hormone imbalance and compromised immunity.
Availability of Lysine
Lysine is found in low concentrations in the proteins of cereal grains such as wheat, and many other vegetable sources of protein. Furthermore, lysine is not fully biologically available in many foods, which means your body cannot metabolize and absorb it as well as other amino acids. Lysine deficiency is not common, but strict vegetarians are more at risk because lysine is much more plentiful in meats and other animal products. However, some decent plant sources of lysine include green leafy vegetables such as spinach and kale, cauliflower, soybeans, green beans, papaya, apricots, almonds and cashews.
Bodybuilders often take large amounts of amino acid supplements -- especially lysine and leucine -- to try to stimulate protein synthesis. Lysine supplementation has proven effective in helping injured muscles recover more quickly, but most people get more than enough dietary lysine for normal body functions that rely on protein synthesis. Too much supplemental lysine, such as more than 1,500 milligrams daily, increases your risk of nausea, diarrhea, high blood cholesterol levels and gallstone formation. Consult your doctor before taking lysine supplements.
- Exercise Physiology: Energy, Nutrition, and Human Performance; William D. McArdle, et al.
- Human Physiology: An Integrated Approach; Dee Silverthorn, et al.
- Advanced Nutrition and Human Metabolism; James L. Groff, et al.
- Natural Standard Herb & Supplement Reference: Evidence-based Clinical Reviews; Catherine E. Ulbricht, et al.
Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.