Let’s say two experienced athletes of the same gender and body weight are training for the same event. One is 35 years old and the other is 55 years old. Which athlete has the highest daily protein needs?
If you base your answer on the current Recommended Dietary Allowance (RDA) for protein intake for adults in the United States and Canada, you would say neither – their protein needs are the same: 0.8 grams per kilogram of bodyweight per day (g/kg/day).
If you based your answer on what is typically recommended for endurance athletes, you would still think they are the same because many coaches and dietitians use 1.2-1.4 g/kg/day for adult endurance athletes.
But the 55-year-old athlete is likely experiencing sarcopenia (age-related loss of muscle mass), especially if he/she isn’t including resistant exercise in his/her training schedule. In 10 years, that athlete will probably also develop anabolic resistance, a condition that affects many older individuals, including masters athletes. Do either of these conditions affect the protein requirements of these athletes?
The correct answer is yes. A growing body of evidence is suggesting that the protein needs of endurance athletes increase as they age, on a gram per kilogram basis, because of the effects of sarcopenia and declining rates of muscle protein synthesis (MPS). To offset declining MPS rates, some experts are calling for an increase in the RDA for protein intake to be 1.4-1.6 g/kg/day or even higher.
Keep in mind that muscle mass is mostly regulated by a balance between MPS and muscle protein breakdown (MPB).
When MPS exceeds MPB for long and frequent periods of time, muscle growth or hypertrophy is the result. Conversely, when there is a net negative protein balance, where MPB exceeds MPS, a reduction in muscle mass occurs, also known as atrophy.
These recent studies also suggest that the amount of protein at each meal is equally important to total protein intake for the day. Thus, the concept of a “meal threshold” for protein has been suggested to optimize MPS rates. Why? Because many older people eat very little protein at breakfast and lunch and then have a large protein serving at dinner. When large boluses of protein are consumed at once, the excess amino acids are usually oxidized or excreted rather than used for MPS.
The best way to optimize MPS rates and maintain muscle function is to distribute the protein throughout the day into three meals and two to three snacks. To ensure adequate intake, experts are recommending that younger adult athletes consume between 20-25 grams of protein per meal (0.25 g/kg/meal) and older athletes should aim for 30-40 grams of protein per meal (0.4 g/kg/meal).
However, many older people find it difficult to consume this much protein. To make it easier, Dr. Stuart Phillips at McMaster University recommends a high-protein snack one to two hours before bedtime as a method for meeting the higher protein requirements.
According to Phillips, pre-sleep feeding is a time when protein provision may increase MPS rates during the night. One study showed that 40 grams of protein before bed stimulated MPS and improved net protein balance overnight. (5). Another study showed that a pre-sleep beverage (27.5 g protein, 15 g carbohydrate, 0.1 g fat) augmented muscle mass, muscle fiber area, and strength gains compared to a placebo beverage.
Dr. McMaster made a nifty little video to explain the importance of pre-sleep feeding (it's also a promotional video for a protein powder). I am not promoting Ascent protein powder but thought the video was helpful in understanding how pre-sleep feeding can help build or maintain muscle mass.
Protein quality affects MPS rates as well. Amino acid composition differs between protein sources, which determines the magnitude of the anabolic effect. Studies of MPS rates in those doing resistance exercise suggest that whey protein impacts MPS rates more than soy protein because whey has a higher concentration of leucine, a branched-chain amino acid (BCAA), that is known to stimulate MPS.
In fact, there appears to be an intracellular leucine trigger whereby a critical quantity of leucine is necessary for the activation of a pathway known as mammalian target of rapamycin complex (mTORC1)(8). Proteins with higher levels of leucine appear to activate this pathway whereas lower-leucine proteins do not. The mTORC1 pathway is stimulated within 30 minutes of consuming of a high-leucine meal with maximum MPs rate peaking between 60 and 90 minutes after the high-leucine meal. Thus, regular consumption of high leucine protein is likely to augment MPS rates and muscle function in older athletes.
For masters athletes over the age of 60, anabolic resistance makes it even more difficult to maintain muscle mass and function. Proposed mechanisms underlying anabolic resistance and the resultant need for higher protein intake for older athletes include the following:
- decreased postprandial (during or after dinner or lunch) availability of amino acids,
- lower postprandial perfusion of muscle,
- decreased muscle uptake of dietary amino acids,
- reduced anabolic signaling for protein synthesis,
- reduced digestive capacity
Hope Barkoukis, Ph.D., RD, recently summarized the recent round of studies on protein intake:
Under conditions of energy balance, the quantity of dietary protein ingested daily is critical for metabolic functioning, but equally important is the amount of meal dietary protein to stimulate optimal MPS.
The quantity of meal dietary protein needed to optimize the skeletal muscle anabolic response appears to be influenced by the leucine content.
Meals providing protein in greater amounts than necessary for maximal mTORC1 signaling do not provide additional anabolic benefit, but rather result in enhanced amino acid oxidation of the excess protein.
Older adults appear to have an anabolic resistance, a term referencing the need to consume a greater amount of essential amino acids to achieve maximal MPS compared with younger adults.
This means athletes over the age of 40 should aim for 20-40 grams of protein at each meal. The following food sources have 20 grams of protein:
- Beef, lean: 2.75 ounces
- Eggs, 3
- Most whey protein powders, 1 scoop
- Salmon, 2.5 ounces
- Greek yogurt, 1 cup
- Kidney beans, 7/8 cup
Boirie, Y. Physiopathological mechanisms of sarcopenia. J Nutr Health Aging. 2009; 13: 717–723.
Moore RD, Churchward-Venne TA, Witard O, et al. Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. J Gerontol A Biol Sci Med Sci. 2015;70:57-62.
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