Alkaline Diets to Protect Against Muscle Loss with Age

As we age, the ability of our kidneys to excrete acid declines. To buffer acid, our kidneys produce ammonia, a base, from the amino acid glutamine, which it can effectively pull from our muscles. So, part of the muscle breakdown as we age may be our body’s attempt to maintain its pH balance, its acid to base ratio. As acid levels rise, our adrenal glands release stress hormones like cortisol, which degrade our muscle proteins, releasing glutamine and other amino acids our liver can turn into glutamine, which then allows our kidneys to generate ammonia to neutralize the acid. What can we do to help keep our kidneys from dipping into the protein stores from our musculature? We can eat an alkaline—base-forming—diet.

The concept that muscle loss was an adaptive response to acidosis (acid overload) arose from the realization that excess acid appeared to be the most important factor in a wide range of muscle wasting syndromes, whether from kidney failure, infection, trauma, or chronic diarrhea. This was subsequently established by demonstrating that induction of acidosis led to both a decrease in muscle protein formation and an increase in protein breakdown. Most convincingly, the correction of acidosis led to a reversal of muscle loss in conditions, such as kidney disease or ketogenic weight loss diets. (Ketones are acidic, themselves.).

Even just eating a standard American diet can result in an excess of acid. Animal protein tends to have higher levels of sulfur-containing amino acids, such as methionine, which are metabolized in the body to sulfuric acid. Fruits and vegetables, on the other hand, are generally base forming, metabolized to alkaline residues, such as potassium bicarbonate, which help neutralize acids in our kidneys from excess acid production from animal foods. So, the net dietary acid load is determined by the balance of acid-inducing foods (primarily meats, cheeses, and eggs) and base-inducing foods, alkaline-forming foods (such as fruits and vegetables).

Ancient human diets largely consisted of unprocessed plants; so, they likely produced more base than acid in the kidneys of our ancestors. Humans evolved eating these alkaline diets, these base-forming diets, over millions of years. Most contemporary diets, on the other hand, produce acid in excess. What if you removed that extra dietary acid? Researchers at UC San Francisco used potassium bicarbonate supplements to effectively neutralize the dietary acid load in a small group of postmenopausal women. They not only showed a significant increase in blood pH (demonstrating that the dietary acid-forming foods had been perturbing the body’s acid/based balance), but correcting the diet-induced acidosis led to a reduction in protein loss from the body.

We can counter the chronic low-grade acidosis with advancing age due to declining kidney function by eating an acid neutralizing diet, that is, one with more vegetables and less meat. A cross-sectional analysis of thousands of older men and women found that those who ate about six or more servings of vegetables a day only had about half the odds of low muscle mass, attributed to the “alkalizing effects of vegetables.” A higher alkaline dietary load in general was found to be positively associated with muscle mass, and those reaching the recommended minimum daily intake of potassium (found most concentrated in greens and beans) had nearly a decade of aging’s more lean mass. For much of human history, we ate so many plants that we got upward of 10,000 mg of potassium every day, but now we eat such potassium-deficient diets that less than two percent of Americans reach even close to half that, the recommended daily intake of 4,700 mg.

High dietary acid loads, on the other hand, have been associated with a higher prevalence of frailty in snapshots in time and declines in muscle mass over time, perhaps explaining the studies that found muscle mass preservation associated with plant but not animal or total protein intake. This could also explain why Mediterranean-type diets have been associated with lower odds of frailty, as much as nearly 60 percent lower odds of frailty. Mediterranean diets have been estimated to be even more alkaline-producing than your average vegan diet due predominantly to the higher vegetable intake.

Other diet quality scoring systems have also appeared protective against frailty. Since less meat and more fruits and vegetables tend to be characteristic of healthier diets in general, how do we know acid/base dynamics have anything to do with it? Because you can give people bicarbonate supplements and get a significant improvement in muscle performance. Older women given potassium bicarbonate supplements for three months experienced a 13 percent increased double leg press peak power output compared to placebo (in comparison, strength-training exercises could be expected to increase power in a similar timeframe by 15 percent to 141 percent). Or we can just eat an acid neutralizing diet in the first place. Ten to twelve servings a day of fruits and vegetables was able to increase time-to-exhaustion during high-intensity treadmill running by an impressive 21 percent, but with so many other healthy components in whole fruits and vegetables, it’s unknown how much of that could be attributed to their alkaline nature.