Does Increasing Protein Intake Slow Age-Related Muscle Mass Loss?

Population studies have found that failing to meet the recommended daily intake of protein is correlated with a lower lean body mass and those exceeding the RDA associated with significantly greater lean body mass compared to those failing to meet the recommended intake. Greater protein intake has also been linked to greater grip strength over time, though not considered enough to be clinically meaningful. You don’t know if these correlations are even cause-and-effect though, until you put it to the test.

To see if increasing the protein intake for the elderly would help, Harvard researchers randomized older men with moderately impaired function to controlled diets offering the recommended 0.8 g/kg per day or bumping them up to 1.3g/kg a day with a whey and casein protein powder, with or without added testosterone. Six months later, there was no difference in lean mass, muscle strength, fatigue, walking speed, stair-climbing power, or any of the other measures of performance, function, or well-being with the added protein, whether combined with testosterone or not, suggesting that the recommended dietary allowance of 0.8 grams of protein per healthy kilogram of body weight, or about 50 grams a day, is sufficient to maintain lean body mass even in old age and does not support this thought that adding extra protein could promote bulking up additional lean mass.

Even studies that do show an increase in lean mass with protein supplementation doesn’t necessarily mean an increase in muscle mass. The field is said to be “plagued” with researchers referring to lean mass as an indication of muscle mass, but high protein intake alone can cause significant liver and kidney swelling; and so, an increase in total body lean mass may just be a reflection of “increased visceral organ size” or water retention, which also shows up as lean mass. For example, a 10-week randomized controlled trial found that elderly men on twice the protein RDA put on three pounds of lean mass over that of those just getting the RDA, but almost all the mass was in their trunk. When cross-sections of their thigh muscles were analyzed using CT scans, there was no significant difference between the two protein levels. Similarly, changes in muscle area measured by CT were found to be unrelated to protein intake in a prospective study that followed more than a thousand older adults over five years.

The gold standard for assessing muscle size is the use of MRI scans. Randomize hundreds of men and women over 65 years old to a year of a placebo control containing table sugar, versus a low-quality protein (collagen), versus whey protein, with or without low or high intensity resistance training, and the exercise group gained muscle, but the protein didn’t help at all. It made no difference in muscle size, strength, or performance. Even the whey protein, bumping them from average protein levels up to 1.5 g/kg, did no better than feeding them the equivalent of sugar pills—and the study was designed and paid for by a whey company! A two-year whey intervention—one of the largest, longest such studies ever run—similarly failed to show any benefits over placebo.

Put all these studies together on using protein or amino acid supplementation to preserve muscle mass and strength in older men and women, and overall, there was no significant improvement in lean body mass or upper or lower body muscle strength. That was without concurrent exercise, though. Maybe extra protein works when combined with strength training? Very few studies showed any benefit to adding protein or amino acid supplementation during resistance exercise, but enough trended in the right direction that if you put them all together, protein supplementation combined with resistance exercise held a small edge over resistance exercise alone among older individuals. After an average of 18 weeks of training, fat-free mass, handgrip, knee extension, and leg press strength each increased by an extra half pound on protein, though this did not translate into any significant improvement in muscle function (such as rising from a chair, stair climbing, or walking speed). Now here, “elderly” was defined as “over 50.” Restricting the scope to studies enrolling actual elderly individuals (average age 70 or older), resistance exercise training worked; however, they found no significant additive effects to protein supplementation on any outcome—lean mass, muscle strength, or functional abilities.

In non-frail older adults, extra protein appears to have little or no effect on muscle mass, strength, or performance when taken alone or added to an exercise regimen. OK, but what about in those who really need it: frail individuals? One of the first things doled out by doctors is a quote-unquote “nutrition shake,” like Ensure^®, which are typically ultra-processed sugary messes of corn syrup, oil, and protein concentrates, often laced with artificial colors, flavors, and sweeteners. Though Big Pharma giants, like Abbot Laboratories (makers of Ensure), spend millions of dollars a year in lobbying and campaign contributions to help make these products medicine’s go-to choice, if you look at the evidence, a systematic review and meta-analysis of randomized controlled trials on such drinks for the management of frailty found no discernable benefit for any measured outcomes—muscle mass, muscle strength, muscle function, frailty status, cognitive function, or mortality.

What about those suffering from sarcopenia, accelerated age-related muscle loss? A systematic review and meta-analysis concluded that protein was a wash across the board for improving muscle mass, strength, or performance among elderly sarcopenic individuals. The best studies on protein or amino acid supplements for unhealthy older adults with acute or chronic conditions also found no significant effect.

Researchers have been trying to find effective ways to improve muscle mass in older people for decades, and so far, only resistance exercise has consistently yielded benefits. One of the largest and most rigorous studies to treat pre-frail and frail adults was published in 2021. Hundreds were enrolled to test the effects of leucine, whey protein, soy protein, creatine, and a combination of creatine and whey versus a placebo control (corn starch) in the context of a 16-week resistance training program. The strength training itself worked, increasing muscle mass and function, but everything else flopped. No added benefit to frail or pre-frail individuals taking any of those supplements compared to taking a corn starch placebo. A similar trial of hundreds of sarcopenic men and women 75 and older given 40 grams of whey-enriched protein a day combined with exercise for an entire year with a 43-month follow-up found that all the extra protein did not slow the deterioration of muscle mass and physical performance significantly better than a placebo, all the more important since it is one of the largest and longest-lasting randomized controlled trials ever published on the subject.

Consumer Reports noted that an investigation of 134 top-selling protein powder products found virtually all tested positive for at least one heavy metal, building on their own study that concluded “You don’t need the extra protein or the heavy metals our tests found.”