No one wants to grow old. However growing old, and the challenges that come alongside ageing, is something that most of us will face at some point. As we age we become more susceptible to a number of health conditions including: osteoporosis, arthritis, dementia and – the main focus of this article – sarcopenia (muscle wasting).
Sarcopenia is a complex condition, which is facilitated by the adoption of a more sedentary lifestyle and a less than optimal diet. Like any degenerative disease, sarcopenia is of most concern when it comes to the effect it can have on a person’s quality of life. As the condition advances there is a greater likelihood of falls and simple daily activities, for example getting out of bed, can become difficult.
Muscle loss and aging
Some muscle loss is considered as an inevitable yet undesirable consequence of aging. After reaching a peak in early adult years, skeletal muscle mass declines by 0.5–1.0% year on year, which begins at around 40 years of age (Padden-Jones et al., 2008). Matters can be made worse if an elderly person is bed ridden or disabled for a significant period of time, as this will accelerate the loss of lean tissue.
Interestingly, it’s not uncommon for the principles of sports nutrition, to cross over into recommendations for elderly populations, especially for the prevention of certain health conditions.
There are a number of studies supporting the notion that physical activity, and resistance exercise in particular, aids in the maintenance of muscle mass and function in aging populations (Freiberger et al., 2011). However, in older populations the ability to exercise is often compromised by physical disability, frailty, or disease. In this instance dietary modification could play a key role in prevention of sarcopenia.
As we age protein intake tends to decrease and we also appear to be less efficient at utilising protein from our diet. The root cause of this is likely a combination of factors including, increased satiety (fullness after a meal), dentition/chewing difficulties, changes in digestion, reduced ability to cook and mobility issues.
Currently it is recommended that the adult population consumes 0.8g of protein per kilogram of body weight. This recommendation is largely based on studies on short-term nitrogen balance in young adults (Rand et al., 2003).
Protein and muscle mass
Proteins are made up of amino acids, which are made largely of nitrogen. A positive nitrogen balance is associated with growth or anabolism, whereas a negative nitrogen balance is associated with catabolism or the breaking down of body tissues and structures.
Therefore to put it simply – the more protein that is metabolised the more likely an individual is to be in a positive nitrogen balance, which promotes a state of growth and repair.
A key consideration is the quantity of protein metabolised, and not just the total consumption, unless protein is digested and metabolised successfully, it will not be used by the body. A panel of experts have recommended a higher protein intake for elderly populations at risk of sarcopenia, advocating 1-1.5g per kilogram of body weight. On top of increasing total daily protein intake, the panel also advise that protein servings should be spaced out throughout the day (Morley et al., 2010). The panel also recognised that total energy consumption and vitamin D levels also play an important role in preventing sarcopenia.
Increasing protein though the diet could provide older individuals with the nutrients required to slow down or prevent muscle loss. Futhermore it has been suggested that an increase in protein could aid in other factors, including immune status, wound healing, blood pressure and bone health (Wolfe et al., 2008).
One issue with consuming more protein is the increased levels of satiety. It’s not uncommon that as we age our appetites decrease, so by consuming more protein and therefore increasing satiety it could potentially lead to other nutritional deficiencies. This means that if more protein is to be consumed to prevent sarcopenia, the diet as a whole must also be considered too. This could be achieved by ensuring that the protein sources and other foods in the diet are rich in all the macro and micronutrients required to maintain a healthy body. This would include all the food groups normally recommended: fruits, vegetables, wholegrains, unprocessed meat and fish, legumes and dairy.
In addition to total quantity of protein consumed evidence suggests that we must consider the quality of protein sources consumed. Similarly to active individuals seeking to build muscle mass, the amino acid leucine also appears to play an important role in the prevention of sarcopenia. The reason for this is the apparent role leucine has in the initiation of muscle protein synthesis (the production of muscle tissue). Leucine supplementation has been proposed as an intervention to prevent sarcopenia. This is not only based on its role regarding protein synthesis, but also that by consuming leucine in a supplement form it could potentially negate the issues regarding increased satiety. There have been some studies showing short-term benefits of leucine on muscle mass and exercise performance (Leenders & Van Loon, 2011). However, at the moment there appears to be a lack of definitive conclusion as to whether leucine as a supplement should be used to prevent sarcopenia. The principle reason for this is a lack of long-term evidence supporting its use (Van Loon, 2012). So even though leucine supplementation is not currently recommended, it’s perhaps something to consider moving forward as more studies are conducted.
What is important moving forward is to establish if leucine supplementation can be beneficial in the long term and also to determine if and what dosage may be required to be effective. More research is needed to establish this.
We must also not forget that there are a number of leucine rich foods, mainly from animal proteins, these can be found in the table below.
Sarcopenia is a complex condition where prevention is key. Once sarcopenia occurs it seems to activate a vicious cycle. As muscle is lost an individual is more likely to become sedentary, which in turn can increase the rate at which sarcopenia progresses. By staying active and consuming adequate amounts of good quality protein throughout the day, elderly populations give themselves a much better chance of preventing sarcopenia.
Freiberger, E., Sieber, C. and Pfeifer, K. (2011). Physical activity, exercise, and sarcopenia – future challenges. Wiener Medizinische Wochenschrift, 161(17-18), pp.416-425.
Leenders, M. and van Loon, L. (2011). Leucine as a pharmaconutrient to prevent and treat sarcopenia and type 2 diabetes. Nutrition Reviews, 69(11), pp.675-689.
Morley, J., Argiles, J., Evans, W., Bhasin, S., Cella, D., Deutz, N., Doehner, W., Fearon, K., Ferrucci, L., Hellerstein, M., Kalantar-Zadeh, K., Lochs, H., MacDonald, N., Mulligan, K., Muscaritoli, M., Ponikowski, P., Posthauer, M., Fanelli, F., Schambelan, M., Schols, A., Schuster, M. and Anker, S. (2010). Nutritional Recommendations for the Management of Sarcopenia. Journal of the American Medical Directors Association, 11(6), pp.391-396.
Paddon-Jones, D., Short, KR., Campbell, WW., Volpi, E., and Wolfe, RR. (2008). Role of dietary protein in the sarcopenia of aging. American Journal of Clinical Nutrition, 87, pp1562-1566.
Rand, WM., Pellett, PL and Young, VR. (2003). Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults. American Journal of Clinical Nutrition, 77(1), pp.109-127.
Van Loon, L. (2012). Leucine as a pharmaconutrient in health and disease. Current Opinion in Clinical Nutrition and Metabolic Care, 15(1), pp.71-77.
Wolfe, R., Miller, S. And Miller, K. (2008). Optimal protein intake in the elderly. Clinical Nutrition, 27(5), pp.675-684.
Xu, Z., Tan, Z., Zhang, Q., Gui, Q. and Yang, Y. (2015). The effectiveness of leucine on muscle protein synthesis, lean body mass and leg lean mass accretion in older people: a systematic review and meta-analysis. British Journal of Nutrition, 113(01), pp.25-34.