Depriving the Flames of Fuel

In the study in which subjects reduced their step count, the decline in activity was accompanied by an increase in inflammatory markers. For example, after two weeks the scientists found a 25-percent increase in C-reactive protein in the study participants. In cancer, inflammation triggers muscle wasting. And in old age? People who suffer from sarcopenia, pre-frailty, and frailty do in fact tend to have higher levels of systemic inflammatory markers such as C-reactive protein, which are independently associated with lower muscle mass and reduced upper- and lower-body strength. That led to the idea that anti-inflammatory food could help.

Meta-analyses of observational studies, including a representative sample of the US population, found that people with more pro-inflammatory diets are twice as likely to develop sarcopenia and frailty. Diets that rank at the very top of the Inflammatory Index are also associated with low grip strength, slow walking speed, and impairments in activities of daily living. Chronic inflammation is therefore thought to be an "important mechanism behind frailty," but observational studies do not investigate cause and effect.

The idea of an inflammation trigger would explain why saturated fats—the single most pro-inflammatory component of the Dietary Inflammatory Index—are associated with a higher risk of sarcopenia. People who consumed about 8 percent of their calories as saturated fats—consistent with the US federal recommendation of less than 10 percent, but more than the American Heart Association’s recommendation of less than 6 percent—lost only half as much fat-free mass as those who consumed 16 percent of their calories from saturated fats. In their case, the muscle loss corresponded to ten years of aging. That would be an explanation for why the leg muscles of CrossFit trainees who eat a ketogenic diet can shrink by up to 8 percent. More likely, however, their bodies begin burning their own proteins in the absence of the preferred fuel (carbohydrates). But where did all the protein that people ate go?

Human Protein Requirements

In my video see.nf/proteinhistory I trace the history of the enthusiasm for protein in the world of nutrition, which reached its peak with the so-called great protein fiasco, followed by a recalculation of human requirements in the 1970s and a massive correction downward. Yet to this day, some are obsessed with protein. Advocates of the Paleo diet, for example, try to justify protein requirements from an evolutionary perspective.

One food, however, has evolved over millions of years to contain the perfect amount of protein for us: human breast milk, with less than one percent by mass arguably the most protein-poor milk of all mammals on this planet. This is one of the reasons why cow’s milk can be so dangerous for infants. The protein content of breast milk has been described as "extremely low," but it is exactly where it should be—at the natural, normal level for our species.

The "low" protein content of human breast milk (about 6 percent of calories) does not mean that adults don’t need more. Older people couldn’t maintain their muscle mass on that. Adults can weigh ten times as much as infants, but we eat only about four to five times as much as they do, so our food has to have a higher protein concentration. Still, people generally consume about twice as much as they need. The recommended dietary allowance (recommended dietary allowance, RDA) is 0.8 grams of protein per kilogram of body weight for all adults regardless of age, which is roughly the ideal body weight in kilos multiplied by eight and then divided by ten. A person with an ideal weight of 50 kilos therefore needs up to 40 grams of protein a day. On average, they probably need only about 30 grams, which corresponds to 0.66 grams per kilo, but we round up to 0.8 because everyone is different and we want to capture most of the bell curve. As I explain in more detail in the chapter "Protein Restriction," most people likely suffer more from protein excess than from protein deficiency.

Some argue that older people should consume more protein than is officially recommended. It’s no wonder that this includes reviewers from the National Cattlemen’s Beef Association (association of American beef producers) and members of the Whey Protein Advisory Panel (whey protein advisory committee) of the National Dairy Council. They argue that age-related muscle loss could be the result of an "anabolic resistance" in older people, a diminished muscle-building response to strength training or protein intake, but most studies have been unable to find such a phenomenon. The most comprehensive study of protein requirements in healthy adults sees no difference in protein needs at older ages, and authorities in the United States, the EU, and worldwide agree. But even if older people don’t require more protein, they could still benefit from more. And what about unhealthy adults who already suffer from frailty or sarcopenia?

Do extra proteins increase muscle mass or strength?

I address this in depth in see.nf/muscleprotein, but basically no study of protein or amino acid supplementation for older men and women shows a significant improvement in fat-free body mass or upper- or lower-body muscle strength. Even the term "fat-free body mass" is misleading. Since high protein intake alone can cause liver and kidney swelling, the increase in total fat-free body mass may simply be the result of "enlarged internal organs" or fluid retention.

In non-frail older adults, additional intake of proteins or essential amino acids appears to have little to no effect on muscle mass, strength, or performance, whether taken alone or in combination with exercise. What about those who really need it—the sarcopenic, pre-frail, or frail? Among the first things doctors administer are "nutrition shakes" like Ensure, usually an industrially ultra-processed sweet sludge made of corn syrup, oil, and protein concentrates, often with artificial colors, flavors, and sweeteners. Pharma giants like Abbott Laboratories (maker of Ensure) spend millions of dollars annually on lobbying and campaigns to push these products in medicine, but a systematic review with meta-analysis of randomized clinical trials on such drinks for frailty published in 2021 found no benefit in the measured domains—muscle mass, muscle strength, muscle function, frailty, cognitive function, and mortality.

For decades, scientists have been searching for effective methods to treat sarcopenia, but so far only resistance training has worked over the long term. One of the largest and most thorough studies on treating pre-frail and frail adults was published in 2021. In hundreds of participants, within the framework of a 16-week strength-training program, the effects of leucine, whey protein, soy protein, creatine, and a combination of creatine and whey, or a placebo (cornstarch), were tested. The strength training itself was successful and led to an increase in muscle mass and function, but everything else flopped. None of the supplements mentioned provided any greater benefit for frail or pre-frail people than the cornstarch placebo.