Timed Protein Intake

/ Posted 11.20.2009
Does it work for seniors?

Nearly all the frailty associated with aging is related to long-term loss of muscle, or sarcopenia. The major cause of muscle loss, which begins at around age 40, is lack of sufficient exercise, particularly resistance exercise. A reduction in the secretion of anabolic hormones, such as testosterone and growth hormone, also plays a role. As mass decreases, insulin sensitivity declines, since active muscles influence insulin activity by spurring glucose uptake into muscle. The loss of effective insulin activity compounds the muscle loss burden, since insulin helps prevent excess muscle tissue breakdown.

The cure is simple and readily available—effective nutrition along with resistance exercise, mainly lifting weights. In regard to nutrition, however, it has become clear that changes occur over the years in the way that the body handles nutrients—which must be taken into consideration. One example has to do with protein intake past age 40. The usual advice for optimal protein intake is to eat small protein meals every two to three hours. Yet older adults of both sexes show better protein uptake with fewer meals.

People are often told to take in protein both before and after weight-training sessions in order to maximize the anabolic response. More recent studies show that you can get maximum benefits from as few as six grams of essential amino acids. “Essential” amino acids must be supplied in the diet, while the body can synthesize the remaining dietary amino acids from essential aminos and other sources. Here again you see differences between the young and the old. While essential amino acid intake before and after exercise boosts anabolic effects in young people, in older people whey protein appears to work equally well. That isn’t surprising, since whey is chock full of essential amino acids, containing 16 percent branched-chain aminos, which are the ones most related to increased muscle protein synthesis with exercise.

A recent study examined the effects of getting protein before and after training in a group of 26 men, average age 72. The men, who were placed in either a placebo group or a protein group, participated in a 12-week weight-training regimen, in which they exercised three days a week. Those in the protein group got 10 grams of protein before training and another 10 grams immediately afterward. Note: All the subjects were getting sufficient protein in their normal diets. The protein was a casein hydrolysate, or predigested casein milk protein supplement.

Taking in protein before and after training did not further enhance the anabolic skeletal muscle response that occurs with regular weight training in the protein-replete older men. Both the placebo and protein groups showed similar muscle gains, occurring mainly in the lower body. As expected, most of the muscle gains involved an increase in type 2 muscle fiber thickness, which is significant because those are the muscle fibers most prone to loss with age and lack of exercise. That loss is primarily responsible for the weakness and frailty associated with aging.

So weight training alone provides a “fountain of youth.” It appears that following a strategic, timed protein intake before and after weight training doesn’t add to gains in muscular size and strength in elderly men who already get enough protein.

—Jerry Brainum

1 Verdijk, L.B., et al. (2009). Protein supplementation before and after exercise does not further augment skeletal hypertrophy after resistance training in elderly men. Am J Clin Nutr. 89:608-16.

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