Fiber Against Frailty

There appears to be a microbiome “signature” of frailty. Stool samples from frail people show a striking lack of bacterial diversity, especially of fiber-eating “good bacteria” like Lactobacillus. Fecal transplant studies that I present at see.nf/musclefiber consider this a cause, not a consequence, of the condition, and intervention studies show that in people randomized to consume high-fiber foods, prebiotics, or certain probiotics, performance improved. I conclude that it is probably better to promote the growth of our own fiber-eaters by feeding them fiber. This has the dual benefit of reducing protein putrefaction toxins such as indoxyl sulfate, which are thought to play a role in muscle wasting.

Healthy Base

As we age, our kidneys’ ability to excrete acids declines. To buffer the acids, the kidneys produce the base ammonia from the amino acid glutamine, which they simply take from the muscles. When the acid level rises, the adrenal glands release stress hormones like cortisol that break down muscle proteins, releasing glutamine and other amino acids. The liver can convert these into glutamine, which then enables the kidneys to generate ammonia to neutralize the acid. Some of the muscle loss in aging could therefore be the body’s attempt to maintain its pH balance (acid-base balance). Potassium bicarbonate supplements have been shown to improve muscle performance, but as I lay out in detail in see.nf/muscleph, you can eat in an acid-neutralizing (alkaline or alkalizing) way and thereby prevent the kidneys from tapping into the protein reserves of our muscles.

Reduce Dietary Acid Load

Note in the table below that not all plant foods are alkalizing and not all animal foods are equally acid-forming. Fish, including tuna, forms the most acid, followed by pork, poultry, cheese, and beef. (Eggs, in the same amount, are even more acid-forming than beef, but you don’t eat as many of them at one time.) Some grain products can be mildly acid-forming, such as bread and rice, but pasta, interestingly, is not. Beans are clearly acid-reducing, but not as strongly as fruit and even sour fruits like citrus. Vegetables form the most base. However, beans and other legumes are the only major protein sources that are base-forming rather than acid-forming.

A strictly plant-based diet is not acid-forming but alkaline and raises urine pH significantly, whereas a plant-based diet on only some days of the week reduces the acid load but does not eliminate it. That said, even vegans have to eat their vegetables.

Salt intake also appears to increase the production of stress hormones via an acid-base mechanism, which would explain why high-salt diets are linked to diminished muscle function. Therefore, we should also eat as few processed foods as possible, which in the United States are the source of about 75 percent of sodium intake.

Reduce Acid

The imbalance of acids and bases in food affects more than just muscle health. Before they learned to hunt or could mine salt, our ancestors ate a neutral or base-forming diet for millions of years. The shift to acid-forming food resulted in a host of diseases, including osteoporosis, type 2 diabetes, high blood pressure, kidney stones, depression, anxiety, gout, and kidney failure. When mice were given alkaline water to drink, their telomeres lengthened, and their survival rate increased compared to controls, leading to articles like: “Is NaHCO3 [baking soda] an anti-aging elixir?” In see.nf/bakingsoda I explain why it’s better to get your alkalization from the produce section.

Which Fruits and Vegetables Best Preserve Muscles?

Higher consumption of fruit and/or vegetables is associated with half the risk of developing sarcopenia, nearly half the risk of being able to walk only slowly, and about a one-third lower likelihood of weak grip strength and poor physical performance. But the only three fruits or vegetables for which I found intervention studies on this topic are blueberries, garlic, and spinach. As I discuss in see.nf/musclefoods, all three increase muscle quality, performance, mass, and/or strength.

Muscles Without End

In aging rodents, coffee also prevents muscle loss. I discussed coffee’s role in boosting autophagy in the chapter on autophagy. Muscle tissue has one of the highest autophagy rates, which is essential for its integrity. Mice with an autophagy deficit experience a severe loss of muscle mass and strength, so “autophagic failure” with aging could play a role in age-related declines in muscle mass. This prompted scientists to put diluted coffee in old mice’s water bottles. The mice that sniffed the coffee (and drank it) had, after just one month, 13 percent more muscle mass in the hind limbs and 18 percent greater grip strength than others randomized to drink only water. I know what you’re thinking now: The mice on caffeine must have been running like crazy on the wheel. But: no. The muscle gain occurred without a change in activity level.

Epidemiologic studies found an association between higher coffee consumption and higher physical performance, a greater muscle mass index, fewer functional disabilities at two or more cups of coffee per day, and less sarcopenia at three cups or more. But in observational studies, reverse causality often cannot be ruled out. Maybe people with limited mobility buy coffee less often or make it less often, or they have fewer opportunities to drink it socially. That’s where intervention studies come in.

A review of more than 20 meta-analyses on caffeine and physical performance found that caffeine has an ergogenic (performance-enhancing) effect on aerobic activity and on muscle strength, power, and endurance, based on studies going back more than 100 years. Most studies, however, were conducted in young men after a single acute dose equivalent to the caffeine in two cups of coffee, taken about an hour before the activity. Caffeine also appears to improve functional fitness, balance, and endurance in older men and women, but again after an acute dose. When young people drank three cups of coffee a day for a month, their lean mass increased by about a pound, while their fat mass decreased by one to two pounds. Coffee can make mice fat, but for older people there are not yet any findings on this.

A Powder Keg

Cacao beans may help as well. Three tablespoons of cocoa powder per day significantly improve walking performance. Unfortunately, the tastiest cocoa doesn’t work, as I examine in see.nf/cocoamuscles. Scientists randomized older adults to receive either natural cocoa, heavily alkalized cocoa, or a placebo. The alkalized cocoa worked no better than the placebo. Among the bitter compounds removed during alkalization are the flavonoid phytonutrients that are suspected to be responsible for the beneficial effect. But older men and women who consumed one tablespoon a day of natural, unprocessed cocoa for twelve weeks improved significantly in muscle mass index, grip strength, and all four physical function tests. And refreshingly, the study was not funded, like many others, by the chocolate manufacturer Hershey.