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The Acid Factor

From a dietary standpoint, muscle growth results when anabolic factors predominate over catabolic factors. Anabolic factors include a hormonal milieu favorable to promoting gains in muscular size and strength—such as higher levels of testosterone and growth hormone and a controlled release of insulin at the right time. The primary catabolic hormone is cortisol, secreted from the cortex area of the adrenal glands, which sit just on top of the kidneys. A high-protein diet is also vital for encouraging anabolism in muscle because the components of protein foods, amino acids, are directly involved in muscle protein synthesis. Amino acids also help curb the effects of cortisol.

Cortisol is released when the body is under high stress and has a protective role in that regard. In fact, a lack of cortisol can lead to death if a massive stress event, such as shock, ensues. Exercise itself is a form of stress that’s beneficial under the right conditions. The body reacts to exercise by upregulating the muscular and cardiovascular systems. On the other hand, the body also has a finite capacity for that. Excess stress can overwhelm the body’s defenses, leading to disease. Overtraining constitutes excess stress, which results in a loss of muscle because the body can’t cope with an overabundance of induced stress.

A less recognized cause of muscle loss, which is common among many bodybuilders, involves alterations in the body’s acid-alkaline balance. The body functions best within a certain range of pH, which is a measure of acidity. Every bodybuilder is familiar with the burn induced by an intense set. The burn is caused by a buildup of hydrogen ions, signaling that the end of that particular set is near. Energy-producing enzymes in muscle fail under high-acid conditions, leading to muscular contraction failure. The body is also affected, however, by systemic acidity.

While high acidity often happens during pathological conditions, such as a heart attack or kidney failure, a more subtle form often isn’t immediately recognized. Systemic metabolic acidity relates to diet, specifically an imbalance between high-acid-producing and alkaline-based foods. Most high-protein foods, along with cereal and wheat products, are high acid. Protein generates acid because of the presence of certain amino acids that contain sulfur—methionine, cysteine and taurine. The sulfur content of the aminos encourages the production of acid, mainly highly caustic sulfuric acid.

The body normally neutralizes the excess acid with various buffers, which include bicarbonate, phosphate and carnosine in muscle. The buffer system is aided by the intake of foods rich in alkaline minerals, such as potassium, magnesium and calcium. Alkaline foods are mainly fruits and vegetables.

What happens when you eat a high-protein diet and no alkaline foods? Studies show that most people lean toward a high-acid diet, mainly because they don’t eat enough fruits and vegetables. As people age, their kidney function declines, and the kidneys are the primary organ that excretes excess acid. As a result, many older people are in a chronic state of mild acidosis. Other studies show that obese people on fat-loss diets are also susceptible to becoming mildly acidic. The higher acid levels that result from such diets can lead to a loss of muscle, which in turn results in a lower resting metabolic rate—which just about ensures a regain of the lost bodyfat. Other studies show that supplying a buffer, such as potassium bicarbonate, stops the loss of muscle. An easier way to do that would be to just eat more fruits and vegetables.

In response to a higher acid level in the body, cortisol levels rise, leading to a breakdown of muscle tissue. When the amino acids that are released from muscle enter the blood, they travel to the liver, where they are converted into glutamine. The kidneys use glutamine to synthesize ammonia. The ammonia molecules readily accept acid protons and are then excreted as ammonium ions, which leads to acid excretion and lower blood acidity. That’s a primary buffering system of the body, but it also explains the connection between high body acidity and loss of muscle.

The scenario gets worse with age, as kidney function often declines by an average of 40 percent in older people. A recent study found that older adults who eat more alkaline-based foods, as determined by excretion of potassium, a primary alkaline mineral, experience less loss of muscle than those who eat only high-acid foods. The authors suggest that seniors who eat fruits and vegetables in addition to enough protein will stave off the loss of muscle that leads to frailty.

Another interesting recent study focused on 1,136 young women, age range 18 to 22, to identify any association between an acid/alkaline imbalance and cardiovascular risk factors. The study found positive links between high-acid food intake and high blood pressure, increased total and low-density-lipoprotein cholesterol and, surprisingly, a larger waist, which is associated with the metabolic syndrome. Those effects were thought to be related to an increased amount of cortisol induced by high-acid food intake, coupled with a loss of minerals that act as buffers in the body, such as calcium and citrate.

What does it all mean to a hard-training bodybuilder? As I’ve pointed out in regard to low-carb dieting, one of the main problems with following a high-protein, low-carb diet is the increased acidity. Some claim that such diets lead to loss of muscle, often incorrectly attributing it to a lack of carbs. It’s not the carbs—it’s the high acidity; high acid favors more cortisol.

The cure is simple: Eat more fruits and vegetables. Those who don’t should get enough alkaline minerals, such as potassium and magnesium, as well as citrate, to offset the higher acidity of a high-protein diet. Eating more alkaline foods is far better, though, because they provide other nutrients often lacking in high-protein diets, such as fiber. —Jerry Brainum

Hughes-Dawson, B., et al. (2008). Alkaline diets favor lean tissue mass in older adults. Am J Clin Nutr. 87:662-665.

Murakami, K., et al. (2008). Association between dietary acid-base load and cardiometabolic risk factors in young Japanese women. Brit J Nutr. 18:1-10.

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