“Young men think old men are fools; but old men know young men are fools.”
-George Chapman (1559-1634)
Much has been written about nutrition in the pages of magazines over the decades. I’m sure many readers who began reading muscle magazines when they were teenagers are now entering their 30’s and 40’s. Countless pages have been devoted to describing nutritional protocols to maximize gaining muscle and losing fat. But I submit to you that we have all been fools, not just the young as George Chapman implies, for we have neglected the fact that there are fundamental metabolic differences between different age groups of people. Despite this fact, hardly any nutritional recommendations for maximizing muscle have taken age into account! In this young fool’s opinion it is time that we all examine optimal anabolic eating for YOUR age addressing each of the macronutrients.
We might as well get the big issue of protein intake out of the way first. I’m not going to waste a bunch of ink explaining why protein is important. If you have ever read MD you know high protein meals increase muscle protein synthesis and increasing muscle protein synthesis over time leads to more muscle. The question is, how does age affect this anabolic response to protein? Research suggests that younger individuals are very sensitive to the anabolic effects of amino acids (1-3). As we age however, we become less sensitive to the anabolic effects of amino acids. Several researchers have shown that comparatively large doses of amino acids are required to maximize the anabolic response in the elderly as opposed to young subjects (1,2,5-9). It appears the decreased response in the elderly may be explained by a decrease in the muscle cell content and activity of mTOR and p70S6K, two kinases involved in directing protein synthesis (2,5). In accordance with this research, it has been demonstrated that old subjects require a greater amount of amino acids, specifically leucine, (the amino acid responsible for stimulating protein synthesis) to maximize protein synthesis as opposed to young subjects (7-9). Furthermore, it appears that the decreased anabolic response in the elderly may be due, at least in part, to increased production of reactive oxygen species (ROS) with age. ROS have been shown to decrease mTOR activity and inhibit protein synthesis (10). There is hope however, as it has been demonstrated that supplementing with a combination of anti-oxidants (rutin, vitamin E, vitamin A, zinc, and selenium) can restore the anabolic effect of a meal to the same level as the young (11)! So make sure you eat plenty of protein high in leucine (like whey) and keep room in that pill box of yours for some anti-oxidants grandpa!
<20 years old: 0.7-1g/lb bodyweight
21-40 years old: 0.9-1.2g/lb bodyweight
41-65 years old: 1.1-1.4g/lb bodyweight
>65 years old: 1.3-1.5g/lb bodyweight
Carbohydrates are another macronutrient that differentially impact anabolism as people age. The primary way by which carbohydrates influence anabolism is by increasing insulin secretion. Young individuals are very sensitive to the anabolic effects of insulin and in their case carbohydrates alone may be sufficient to increase protein synthesis and also inhibit protein degradation (12). Recall that Net Muscle Gain = Muscle Protein Synthesis – Muscle Protein Degradation, so insulin is both anabolic and anti-catabolic in young individuals.
In adult subjects, carbohydrates fail to increase protein synthesis when they are consumed alone (13). Carbohydrates do have a synergistic effect on protein synthesis with amino acids in adults and can induce a greater anabolic response when combined with protein as opposed to consuming protein alone (14). It also appears that insulin will still inhibit protein degradation in adults, and therefore, is anti-catabolic with the potential to optimize the anabolic effects of amino acids (15). Though little data is available in the elderly, it is clear that physiological increases in insulin that would be induced by consuming carbohydrates alone will not stimulate muscle protein synthesis (14). It does appear that co-ingestion of carbohydrates with amino acids does provide a small anabolic advantage over amino acids alone in the elderly, however (14). Since carbohydrates do not provide the same anabolic advantage to the elderly as they do other age groups and because aging reduces insulin sensitivity it is likely that elderly muscle heads will want to consume less carbohydrates than young or adult individuals ().
<20 years old: 2.2-3.2g/lb bodyweight
21-40 years old: 1.7-2.7g/lb bodyweight
41-65 years old: 1.2-2.2g/lb bodyweight
>65 years old: 0.7-1.7g/lb bodyweight
Keep in mind these recommendations are for maximizing muscle gain and will need to be adjusted accordingly for individuals wanting to lose bodyfat.
The difference in how dietary fat should be consumed as one ages should largely be influenced by the changes in carbohydrate intake with age. As outlined previously, one should gradually reduce carbohydrate intake throughout their life as they age. Therefore, someone who is younger and still sensitive to the anabolic effects of carbohydrates will be better off consuming lower fat with more carbohydrates, while an elderly individual will want to consume far less carbohydrates and fill in those calories instead with more protein and fat. Fat is a very important macronutrient and it’s important that one never let it fall too low so I never recommend anyone take their fat intake lower than 0.2g/lb of bodyweight, even if they are young and highly sensitive to the anabolic effects of insulin, it is still important to consume sufficient fat.
<20 years old: 0.25-0.4g/lb bodyweight
21-40 years old: 0.35-0.5g/lb bodyweight
41-65 years old: 0.45-0.6g/lb bodyweight
>65 years old: 0.55-0.7g/lb bodyweight
I want you to keep in mind that these are just general recommendations. Optimal macronutrient intake is based on numerous factors and it is always best to experiment to find out what will fit best with your individual metabolism. I do believe that this article will help everyone better understand how age can impact optimal macronutrient profiles and adjustments that can be made to best optimize these macronutrient profiles.
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2. 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.
3. Drummond MJ, Miyazaki M, Dreyer HC, Pennings B, Dhanani S, Volpi E, Esser KA, Rasmussen BB. Expression of growth-related genes in young and old human skeletal muscle following an acute stimulation of protein synthesis. J Appl Physiol. 2008 Sep 11.
4. Welle S, Thornton CA. High-protein meals do not enhance myofibrillar synthesis after resistance exercise in 62- to 75-yr-old men and women. Am J Physiol 1998; 274 (4 Pt 1):E677–E683.
5. Guillet C, Prod’homme M, Balage M, et al. Impaired anabolic response of muscle protein synthesis is associated with S6K1 dysregulation in elderly humans. FASEB J 2004; 18:1586–1587.
6. Katsanos CS, Kobayashi H, Sheffield-Moore M, et al. Aging is associated with diminished accretion of muscle proteins after the ingestion of a small bolus of essential amino acids. Am J Clin Nutr 2005; 82:1065–1073.
7. Katsanos CS, Kobayashi H, Sheffield-Moore M, et al. 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; 291:E381–E387.
8. Dardevet D, Sornet C, Bayle G, et al. Postprandial stimulation of muscle protein synthesis in old rats can be restored by a leucine-supplemented meal.J Nutr 2002; 132:95–100.
9. Rieu I, Balage M, Sornet C, et al. Increased availability of leucine with leucine-rich whey proteins improves postprandial muscle protein synthesis in aging rats. Nutrition 2007; 23:323–331.
10. Patel J, McLeod LE, Vries RG, Flynn A, Wang X, Proud CG. Cellular stresses profoundly inhibit protein synthesis and modulate the states of phosphorylation of multiple translation factors. Eur J Biochem. 2002 Jun;269(12):3076-85.
11. 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.
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13. Gautsch TA, Anthony JC, Kimball SR, Paul GL, Layman DK, Jefferson LS. Availability of eIF4E regulates skeletal muscle protein synthesis during recovery from exercise. Am J Physiol. 1998 Feb;274(2 Pt 1):C406-14.
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15. Rasmussen BB, Fujita S, Wolfe RR, Mittendorfer B, Roy M, Rowe VL, Volpi E. Insulin resistance of muscle protein metabolism in aging. FASEB J 2006; 20:768–769.
16. Kruszynska YT, Petranyi G, Alberti KG. Decreased insulin sensitivity and muscle enzyme activity in elderly subjects. Eur J Clin Invest. 1988 Oct;18(5):493-8.