Fruits and Vegetables are Alkaline Producing

The current typical Western diet is largely composed of acid-forming foods (proteins, cereals, sugars). Alkaline-producing foods as vegetables are eaten in much smaller quantities. Stimulants like tobacco, coffee, tea, and alcohol are also extremely acidifying.  The uses of artificial chemical sweeteners like NutraSweet, Sweet ‘N Low, Equal, or Aspartame are also acid forming chemicals. See Figure 1.  An imbalanced diet high in acidic-producing foods as animal protein, sugar, caffeine, and processed foods puts pressure on the body's regulating systems to maintain pH neutrality.  pH (potential of Hydrogen) is a measure of the acidity or alkalinity of a solution - the ratio between positively charged ions (acid-forming) and negatively charged ions (alkaline-forming.) The pH of any solution is the measure of its hydrogen-ion concentration. The higher the pH reading, the more alkaline and oxygen rich the fluid is.  The lower the pH reading, the more acidic and oxygen deprived the fluid is. The pH range is from 0 to 14, with 7.0 being neutral.  Anything above 7.0 is alkaline, anything below 7.0 is considered acidic.  Human blood pH should be slightly alkaline (7.35 - 7.45). Below or above this range means symptoms and disease.

Chronic Low Grade Acidosis Reduces Muscle Mass

So you may be asking how real this phenomenon of mild acidosis occurring with low consumption of vegetables is.   As early as 1987, researchers reported that when endurance runners were switched to a normal diet to a low carbohydrate diet resulted in the onset of a mild acidosis and suggested the acidosis may play a role in the fatigue process¹. Additionally, researchers reported in 1996 when subjects were switched from a normal diet (14.5% protein, 37.5% fat, 47.5% carbohydrates) to a Low Carb/high protein diet (33.6% protein, 64.4% fat, 2.2 carbohydrates) resulted in a mild metabolic acidosis.  After just 24-hours on the Low Carb diet, blood pH, bicarbonate, and base excess (In human physiology, base excess refers to the amount of acid required to return the blood pH of an individual to the normal value pH 7.4) were lower than on the normal diet.    Some researchers have suggested that high protein, low vegetable diets results in low grade chronic acidosis, habitual ingestion of typical net acid-producing diets might chronically sustain a slightly increased state of protein breakdown and consequent nitrogen wasting. Two studies have documented that normal healthy adults whom have their pH lowered to a mild acidic state resulted in increased amino acid breakdown and negative nitrogen balance^{4, 8}. Conceivably, low grade acidosis may account for the nitrogen wasting accounting for the normal progressive decrease in muscle mass as adults get older. Indeed, diet-dependent acidosis-induced muscle wasting might be amplified by age because diet-dependent metabolic acidosis tends to increase in severity with age^{14, 15}, which, in turn, appears to result from the normal age-related decline in the function of the kidney¹⁷. 

Proteins Increase Acidity

Proteins and cereal grains are metabolized to acidic residues, mainly sulfuric acid, and fruit and vegetables are metabolized to alkaline residues, mainly potassium bicarbonate.  Muscle wasting appears to occur when the body is in an acidic state.  When the body is an acidic state, Amino Acids are used as a substrate for the synthesis of glutamine.  Glutamine is then synthesized by the kidney to synthesize ammonia.  Ammonia molecules spontaneously accept protons and are excreted as ammonium ions; the excretion of ammonium thus removes the protons and lessens the effect of acidosis.  In other words, a "trade-off" occurs - the body loses protein, stored mostly in muscle, in order to help get rid of the positive net acid load.

New Study: Alkaline Diets Favor Muscle Mass

            Fruits and vegetables are generally considered alkaline.  A recent study released in the American Journal of Clinical Nutrition reported an alkaline diet favors muscle mass.  Since consumption of fresh fruits and vegetables have high potassium content; researchers enrolled 384 men and women and examined the relationship between dietary potassium and lean mass.  Results of the study indicate that a higher consumption of potassium rich foods was associated with greater lean body mass in older men and women.   The researchers suggested that a positive consumption of potassium rich foods may be counteracting the acid forming production of high protein foods, cereal grains, coffee, and other net acid-producing foods.  I am not suggesting switching to a vegetarian diet, but consumption of vegetables in conjunction with protein seems to favor muscle mass.

Neutralizing Ph Reduces Nitrogen Breakdown

Acidosis has been shown to have a detrimental impact on body protein metabolism and to promote negative nitrogen balance, protein wasting, and loss of body weight. Some in-vitro studies (test tubes) demonstrated that decreasing medium pH resulted in inhibition of protein synthesis in muscle cells¹². Experimental acidosis induced with doctors administer ammonium chloride (an acid forming solution) has been shown to result in negative nitrogen balance - an indication that body protein is being lost⁵. Acidosis can therefore induce protein wasting by inhibiting protein synthesis, stimulating protein degradation or by promoting a combination of the two processes. Several studies have investigated the impact of acidosis on whole-body protein turnover using tracer infusions of labeled Amino Acids. The results have consistently shown that metabolic acidosis stimulates the degradation of whole-body protein and promotes amino acid oxidation^6-9. The effects on protein degradation have been shown to result from a stimulation of the ATP-dependent ubiquitin-proteasome pathway - one of the major enzyme systems for proteolysis - by acidosis^10-11. Stimulation of proteolysis by acidosis is associated with activation of the ubiquitin-proteasome pathway at the muscle level and appears to be dependent on the concomitant presence of glucocorticoid hormones (cortisol), which may therefore represent important mediators of the proteolytic response.