To keep muscles strong, the 'garbage' has to go, says a study, "Autophagy Is Required to Maintain Muscle Mass," published online in the December 1, 2009 issue of Cell Metabolism, a Cell Press journal. In order to maintain muscle strength with age, cells must rid themselves of the garbage that accumulates in them over time, just as it does in any household, according to that new study. In the case of cells, that waste material includes spent organelles, toxic clumps of proteins, and pathogens.
The researchers made their discovery by studying mice that were deficient for a gene required for the tightly controlled process of degradation and recycling within cells known as autophagy. Those animals showed profound muscle atrophy and muscle weakening that worsened with age.
"If there is a failure of the system to remove what is damaged, and that persists, the muscle fiber isn't happy," said Marco Sandri, according to the December 1, 2009 news release, "To keep muscles strong, the 'garbage' has to go." Sandri (at the time of the news release) is with the University of Padova in Italy. Damaged and misfolded proteins pile up along with dysfunctional mitochondria, distended endoplasmic reticulum, free radicals, and other aberrant structures. Eventually, some of those muscle cells die, and "the muscles become weaker and weaker with age."
The muscle wasting observed in the mice seems to bear some resemblance to certain forms of muscle-wasting diseases, Sandri said, according to the news release. He now suspects that this kind of mechanism may offer insight into some of those still-unexplained conditions, as well as the muscle weakening that comes with normal aging (a condition known as sarcopenia).
Sarcopenia, also known as muscle wasting, also shows up in older adults
Researchers knew before that excessive autophagy could also lead to muscle loss and disease. The new findings highlight the importance of maintaining a normal level of autophagy to clear away the debris and keep muscles working properly. Although the discovery seems to make perfect sense in retrospect, it wasn't what Sandri's team had initially anticipated.
"We thought if you reduced autophagy it might protect against atrophy," he said, according to the news release. "Instead, it's the opposite. We realized, OK, of course, if you don't remove the damage, it triggers weakness."
The findings may have clinical implications, he says, according to the news release. There has been interest in developing therapies to block proteins' degradation for treating certain muscle-wasting disorders. But in some cases, at least, "it may be better to activate autophagy and remove the garbage in the cells," Sandri said, according to the news release. The researchers think similar treatments might combat aging sarcopenia as well, noting that another study has shown a decline in the efficiency of autophagy during aging. You also may be interested in another research work by different researchers, "Putting the Brakes on Dietary Fat Breakdown."
How do you avoid the reduction of lean body mass with a concomitant increase in fat mass as you age? Do your muscles really turn to fat as you get older?
The changes often impact health and functional capacity in ways that are negative. One solution is to turn to the burgeoning field of nutritional metabolism. Sarcopenia, the gradual loss of muscle mass is what seniors want to avoid happening too fast or postpone it for as long as possible as the years pass.
This relatively new area is a branch of nutrition science that most consumers haven't heard about too much in the news. One of the areas of study is sarcopenia, or the gradual loss of muscle mass, is a common consequence of aging, and poses a significant risk factor for disability in older adults. As muscle strength plays an important role in the tendency to fall, sarcopenia leads to an increased risk of fractures and other injuries.
Eat more fruits and vegetables and less excess cereal grains and meat
For seniors losing muscle mass, modifying the diet to include more fruits and vegetables is likely to benefit both bones and muscles because of the alkalizing effects. Too many cereal grains and meat in the diet does the opposite, creates an acid effect which weakens muscle mass in aging individuals. The goal is to prevent falls and fractures.
The International Osteoporosis Foundation (IOF) Nutrition Working Group has published a new review which identifies nutritional factors that contribute to loss of muscle mass, or conversely, are beneficial to the maintenance of muscle mass. The Group reviewed evidence from worldwide studies on the role of nutrition in sarcopenia, specifically looking at protein, acid–base balance, vitamin D/calcium, and other minor nutrients like B vitamins.
"The most obvious intervention against sarcopenia is exercise in the form of resistance training," explains Professor Jean-Philippe Bonjour, co-author and Professor of Medicine at the Service of Bone Diseases, University of Geneva, in the January 18, 2013 news release, Which nutritional factors help preserve muscle mass, strength and performance in seniors? "However, adequate nutritional intake and an optimal dietary acid-base balance are also very important elements of any strategy to preserve muscle mass and strength during ageing."
The review discusses and identifies the following important nutritional factors that have been shown to be beneficial to the maintenance of muscle mass and the treatment and prevention of sarcopenia:
Protein intake plays an integral part in muscle health. The authors propose an intake of 1.0–1.2 g/kg of body weight per day as optimal for skeletal muscle and bone health in elderly people without severely impaired renal function.
As many studies indicate a role for vitamin D in the development and preservation of muscle mass and function, adequate vitamin D should be ensured through exposure to sunlight and/or supplementation if required. Vitamin D supplementation in seniors, and especially in institutionalized elderly, is recommended for optimal musculoskeletal health.
Avoiding dietary acid loads: Avoid too many cereal grains and too much meat
Excess intake of acid-producing nutrients (meat and cereal grains) in combination with low intake of alkalizing fruits and vegetables may have negative effects on musculoskeletal health. Modifying the diet to include more fruits and vegetables is likely to benefit both bones and muscles.
Emerging evidence also suggests that vitamin B12 and/or folic acid play a role in improving muscle function and strength. As well, the Review discusses non-nutritional interventions such as hormones, and calls for more studies to identify the potential of antioxidants and anti-inflammatory compounds in the prevention of sarcopenia.
Dr. Ambrish Mithal, co-author and Chair and Head of Endocrinology and Diabetes division at Medanta, New Delhi underlined the need for further research in the field, according to the news release. "Strategies to reduce the numbers of falls and fractures within our ageing populations must include measures to prevent sarcopenia. At present, the available evidence suggests that combining resistance training with optimal nutritional status has a synergistic affect in preventing and treating sarcopenia," explained Mithal in the news release. "We hope that further studies will shed light on other effective ways of preventing and treating this condition."
You can read the original study, "Impact of nutrition on muscle mass, strength, and performance in older adults." Osteoporos Int. May 24, 2013. Authors are A. Mithal & J.P. Bonjour, S. Boonen, P. Burckhardt, H. Degens, G. El Hajj Fuleihan, R. Josse, P. Lips, J. Morales Torres, R. Rizzoli, N. Yoshimura, D. A. Wahl, C. Cooper, B. Dawson-Hughes, and for the IOF CSA Nutrition Working Group. For more information, check out the International Osteoporosis Foundation.
Or you can check out a PDF file article, "Nutrition, Muscle Mass, and Muscular Performance in Middle Age and Beyond, by Catherine D Johnson. PhD, RD,LD. Also see the news release, "Which nutritional factors help preserve muscle mass, strength and performance in seniors?"