Muscle wasting disease, known clinically as sarcopenia, is common among aging populations, especially those who are sedentary or nutritionally deficient. Loss of muscle can lead to poor balance, osteoporosis and falls that result in injury. One nutrient that appears to have a positive impact on slowing and reversing sarcopenia is zinc.
Sarcopenia
Sarcopenia is an age-related condition marked by loss of muscle mass and strength due to lack of physical activity and inadequate nutrition. Left unaddressed, sarcopenia leads to frailty and physical decline that can result in injury and disability. Age-related sarcopenia directly related to $18.5 billion in health care costs in the year 2000, according to an article in the "Nutritional Journal of Biochemistry." The Mayo Clinic's Dr. K. Sreekumran Nair, links sarcopenia to metabolic syndrome. He explains, "Muscle is one of the major organs involved in metabolism and in setting the body's metabolic rate and fuel-burning following a meal." Dr. Nair says sarcopenia leads to increased body fat, type II diabetes and markers for cardiovascular disease associated with metabolic syndrome.
Zinc
The Linus Pauling Institute notes that zinc is responsible for many aspects of cellular metabolism, including growth and development, the immune response and reproduction. Over 100 different enzymes are zinc-dependent, including the antioxidant enzyme copper-zinc superoxide dismutase. This plays an important role in muscle cell catabolism or growth. Loss of zinc from cell membranes makes them vulnerable to oxidative damage and impairs their function. Impaired function of muscle cells leads to their shrinkage, resulting in loss of strength and a slowed metabolism.
Antioxidants and Muscle
A 2009 study by researchers at the University of Texas Health Science Center at San Antonio observed sarcopenic mice lacking the antioxidant enzyme copper-zinc superoxide dismutase. They found a link between death of muscle cells and damage from oxidative stress that impaired the energy centers, or mitochondria, of cells. The scientists pointed to decreased protection from antioxidants as a key cause. The study's director, Dr. Holy Van Remmen, explains that the damaged mitochondria impact actions at the neuromuscular junction, interfering with the messages traveling from the central nervous system to the muscles, and impeding muscular contraction.
Sources and Dosage
The Linus Pauling Institute identifies adults over age 65 to be at risk for zinc deficiency due to a reduced capacity to absorb zinc, increased diseases that interfere with zinc utilization, and use of pharmaceutical drugs that increase zinc excretion. Zinc is naturally in many food sources, including red meats, shellfish, legumes, nuts and eggs. Oysters are exceptionally high, containing 76.3 mg of zinc per serving compared to just 6 mg in beef, the second-highest dietary source of zinc.
References
- University of Texas Health Science Center at San Antonio; Sarcopenia -- Muscle Loss Fnding May One Day Save Physiques
- Journal of Nutritional Biochemistry; Dietary implications on mechanisms of sarcopenia: roles of protein,amino acids and antioxidants; Jeong-Su Kim, et.al., June, 2009
- Linus Pauling Institute: Micronutrient Information Center: Zinc
- Mayo Clinic; "Discovery's Edge"; Slowing Aging by Fighting Muscle Wasting Disease
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