Positive nitrogen balance, muscle synthesis, and resistance training go hand-in-hand with dietary protein intake. For senior adults aiming to live healthy, ambulatory lives, some experts believe that additional amounts of protein–beyond what dietitians recommend–might prove beneficial. For those seeking to build lean muscle mass, however, current RDA for protein simply does not suffice. Learning the adaptations needed for older weightlifters can help us educate clients on how to remain strong and fit throughout their golden years, and specifically how to guide recommending protein for older clients.
Ages Bring Changes
Strength training for the maintenance of fitness typically does not require additional nutritional considerations. However, when striving to add lean muscle as the body ages, certain protein manipulations must occur. The process of aging itself does not cause a decline in muscle protein synthesis. Rather, the manner in which the body responds to workouts and protein consumption differs greatly over time. As the body inches toward the 60’s, 70’s, 80’s, and beyond, muscles prove more resistant to hypertrophy and strength gains.
Amino acid resistance refers to the reduced muscular response to protein consumption. Anabolic resistance takes into account how workouts no longer elicit the same muscle-building effect observed in one’s younger years. Around the age of 60, lean muscle tissue starts to resist the signaling mechanisms induced by both strength training and protein consumption.
The Numbers Game
Based upon currently known standards, a male in his 20’s can demonstrate muscle/strength gains on a meal plan including ~ 1.6 grams of protein/kg. of body weight. However, a male in his 70’s might not show any significant gains unless he consumes closer to 2.2 grams of protein/kg. of body weight.
One research study looked at 37 men around 71 years of age. The subjects ingested either 0, 10, 20, or 40 grams of whey protein following a leg training session. While 20 grams elicited muscle protein synthesis in the leg, 40 grams of whey protein induced even greater gains. Previous studies conducted only on a much younger subject sampling had indicated that 20 grams of protein conferred maximal gains, clearly not the case as we age.
A study published in May 2014 in the Journal of the International Society of Sports Nutrition recommended that most bodybuilders regardless of age may benefit from eating 2.3 to 3.1 grams/kg. body weight of protein daily. Previously, experts felt that such a high protein intake might strain the kidneys, a significant health risk for older adults. Current recommendations now suggest that protein intake as high as 35% of daily calories only poses a risk to this population in conjunction with previously diagnosed kidney impairment.
Leucine and the Aging Process
A current theory gaining popularity in scientific circles points to a “leucine threshold” as the controlling force in muscular development. The body must consume leucine through proper nutrition, since it lacks the ability to manufacture essential amino acids (EAA’s). Decades of studies have identified leucine as the EAA most responsible for inducing muscle protein synthesis.
Sadly, age affects the body’s amino acid sensitivity. Whereas 1-2 grams of leucine triggers muscle protein synthesis in a young athlete, his senior counterpart now must reach closer to 4 grams of leucine to realize the same potency. Hence, as we saw in the aforementioned example, 40 grams of protein (packed with leucine) now serves as the gold standard for muscle gains in older weightlifters.
Aging and Digestion
Older athletes must also take into consideration the digestion rate of proteins consumed immediately post-workout. A slower-digesting source such as the milk protein casein seems to generate greater gains in younger men. However, older male athletes exhibit greater muscle synthesis when choosing whey protein for post-exercise supplementation. Whey, long considered an ideal source of protein for bodybuilders, breaks down much faster in the body than casein, apparently serving older digestion more effectively.
Mounting evidence highlights the notion that current protein recommendations for older adults, around 0.8 g/kg/day, fail to optimize retention of muscle mass. A 3-month-long study of men and women aged 55 to 77 showed that consumption of only 0.8 g/kg/day of protein, even with ample leucine, led to an unfortunate physiological adaptation: a reduction in skeletal muscle. This situation causes the body to break down lean muscle mass to preserve nitrogen homeostasis, ultimately resulting in sarcopenia, frailty and an overall reduced quality of life.
Hormones, Macronutrients, and Timing
Aging also brings about changes in the body’s response to endogenous hormones. A meal consisting of mostly carbohydrates, and very little lean protein, appears to have a negative effect on muscle protein turnover in older adults, another reason to suggest that clients carefully outline their meal plans to include the optimal amounts of macronutrients corresponding to their age.
Researchers from the University of Arkansas for Medical Sciences published compelling data in the American Journal of Physiology/Endocrinology and Metabolism. Recruiting healthy athletic-minded subjects aged 52 to 75, these scientists sought to determine how four different eating plans might affect muscular health.
Subjects received random assignments to one of four groups: Two groups followed current RDA of 0.8 grams of protein/kg. of body weight. Half of these divided their protein equally between 3 daily meals; the rest consumed the majority at dinner (typical of most Americans). The other two groups ate twice the RDA, again either equally over 3 meals or predominantly in the evening.
At the end of the 4-day trial, no matter how/when throughout the day, researchers found that the more protein consumed, the better the hypertrophy. The Pennington Biomedical Research Center took this a step further, looking into high-calorie diets. The meal plans providing 15-25% of calories from protein enabled subjects to store 45% of any excess calories as lean muscle mass. Conversely, subjects receiving only 5% of their calories from protein ended up storing 95% of the excess as adipose tissue.
Protein for Older Adults and Healing
As we age, the rate of injury repair slows significantly. Beginning at age 60 or even earlier, adults who consume additional protein repair training-induced damaged muscle fibers more efficiently while also increasing lean muscle mass. Personal trainers who share this winning combination with senior clients may see them progress more effectively toward their goals.