Recent research suggests that increasing intakes of amino acids can help people to avoid the problems of muscle wasting, known as sarcopenia, as they get older. Sarcopenia is the age-related, degenerative loss of skeletal muscle mass, strength and function. This loss of mass reduces the performance of the muscles. With the ever-increasing number of elderly people, sarcopenia is becoming an increasingly pressing health issue in the developed world. However, long-term amino acid supplementation could be effective in reducing the age-related muscle loss, as amino acids stimulate muscle protein synthesis.
Muscle loss occurs in people of all fitness levels, even master athletes. People who have less muscle mass to begin with, however, will pay a higher price, as they grow older. Women in particular face increased risks from lost muscle mass, as women have about one third less muscle mass than men.
As a person's muscle mass decreases, muscle strength declines and loss of physical function follows. As a consequence, the ability to do everyday activities, such as grocery shopping, housework and taking walks, declines. According to a national survey in the United Kingdom, 12% of people aged over 65 could not manage to walk outside on their own and 9% could not climb the stairs unaided.
If no action is taken to combat sarcopenia, people experience a 10% decline in muscle mass between the ages of 25 and 50 and a further 45% shrinkage by their eighth decade. The bicep muscle of a newborn baby has around 500,000 fibres, while that of an 80 year old will have just 300,000 fibres.
While loss of bone density renders the human skeleton more prone to fractures, it is mainly the gradual erosion of lean muscle, and the ensuing frailty, which leads to falls. Falls are a major cause of disability and the leading cause of mortality due to injury in people aged over 75 in the United Kingdom.
While sarcopenia cannot be halted completely, there are steps that can be taken to slow down its onset, making it possible for people to remain active well into their 80s. If a person was sedentary as a young adult and in middle age, they could even end up with more muscle mass and muscle strength in their later years, than in their 30s and 40s1.
Maintenance of muscle protein can be stimulated by increased amino acid availability. A study carried out in 2006, has shown that dietary amino acid supplementation appears to be effective in reducing the muscle loss that is associated with ageing, as essential amino acids stimulate muscle protein synthesis2. Therefore, long-term amino acid supplementation could be a useful tool in the prevention and treatment of sarcopenia.
1 Tufts Health & Nutrition Letter. Are you doing all you can to fight sarcopenia? March 2003.
2 Sheffield-Moore M et al. Amino Acid Supplementation and Skeletal Muscle Metabolism in Ageing Populations. Hormone Research. 66 (1): 93-97. 2006.