Let’s face it, getting old sucks! Hell I’m only 27 and sometimes I feel old. You get injured more easily, have less energy, and your metabolism slows down. Furthermore, metabolically speaking you become less insulin sensitive, less able to tolerate carbohydrates, and you also become less sensitive to amino acids. Several studies have demonstrated that elderly people require a greater amount of amino acids to maximize the anabolic response to a meal as compared to young people (1,2).
There seems to be some good news however! A recent study by Marzani et al. demonstrated that the defective anabolic response to a meal could be restored in elderly people taking an antioxidant mixture containing rutin, vitamin E, vitamin A, zinc, and selenium (3). Not only is this a big deal for helping to maintain muscle and maximize anabolism, but anti-oxidants have also been shown to increase insulin sensitivity (4). Therefore, anti-oxidants may have multi-faceted uses in preventing metabolic dysfunction associated with aging.
Not only does this research point out the importance of proper redox status, it also points to the need to address protein requirements across various demographics. These studies clearly show a difference in the effects of protein between young and old, and yet the recommendations for protein are the same for young and elderly even though there is ample evidence that the current recommendations are insufficient to prevent muscle loss associated with aging. I think it’s time for the people who make dietary recommendations to realize that metabolism is complex enough that one-size fits all recommendations no longer work, and that they will need to come up with more detailed recommendations for various demographics.
Cuthbertson D, Smith K, Babraj J, Leese G, Waddell T, Atherton P, Wackerhage H, Taylor PM, Rennie MJ. Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. FASEB J. 2005 Mar;19(3):422-4. Epub 2004 Dec 13.
2. Katsanos CS, Kobayashi H, Sheffield-Moore M, Aarsland A, Wolfe RR. A high proportion of leucine is required for optimal stimulation of the rate of muscle protein synthesis by essential amino acids in the elderly. Am J Physiol Endocrinol Metab. 2006 Aug;291(2):E381-7.
3. Marzani B, Balage M, Vénien A, Astruc T, Papet I, Dardevet D, Mosoni L. Antioxidant supplementation restores defective leucine stimulation of protein synthesis in skeletal muscle from old rats. J Nutr. 2008 Nov;138(11):2205-11
4. Lee WJ, Song KH, Koh EH, Won JC, Kim HS, Park HS, Kim MS, Kim SW, Lee KU, Park JY. Alpha-lipoic acid increases insulin sensitivity by activating AMPK in skeletal muscle.
Biochem Biophys Res Commun. 2005 Jul 8;332(3):885-91.