by David Baltimore, MD

As we begin this journey of understanding nutrition and learning how to better impart that knowledge in our patient care, it is important to remember that there are many signs and symptoms that practitioners should watch for as clues to what could be going on inside our patients.

Though well equipped with our education and experience to recognize these outward signs, recent studies have shown that vast numbers of practitioners are not confident in their abilities to guide their patients with nutritional advice on an ongoing basis. Over the course of the next year, this column will cover different aspects of nutrition such as: discussions about signs and symptoms you'll see in practice, the importance of long-chain omega fatty acids in the diet, food choices, metabolic and biochemical processes, and so much more.

But to begin this series, I'd like to start with key indicators of nutritional health that every doctor should be familiar with. These are pH balance, oxidative stress, and resistivity (mineral-mediated electrical conduction). This discussion will center on understanding pH and the body.

pH 101

The pH value ("potential of hydrogen") is the measurement of how acid or alkaline a solution or bodily fluid is. It is dependent upon the number of hydrogen ions present. Acidic measurements lie between 0-6.99, while alkaline measurements are between 7.01-14.00. The middle point, 7.00, is considered neither acidic nor alkaline. Water is an example of such a neutral substance.

Because pH changes as body fluids undergo physiological processes, optimal values of pH differ, depending whether you are testing blood, saliva, or urine.

Blood pH is the single most important reading, because it is affected by biocellular activity more directly than any other reading. The pH of venous blood is a reflection of three factors:

1. Respiratory rate. Respiratory alkalosis, for example, can be the result of chronic stress combined with improper breathing.
2. Oxygenation of the tissues. When oxygen is not being adequately taken up by the tissues, a higher percentage of it remains in the venous blood. Since oxygen is an alkalinizing substance, this results in an increase in the venous pH.
3. How effectively the tissues are using oxygen to generate energy. The most effective way for cells to produce energy from oxygen is through oxidative phosphorilation. This occurs in the mitochondria of the cells and involves the production of carbon dioxide. Note that the only other way to produce energy through oxygen is via the anaerobic metabolism of glucose, which does not produce CO₂. Therefore, effective energy production results in an increase in CO₂ production, whereas inefficient production results in a decrease. Venous pH is determined almost exclusively by the amount of carbon dioxide in the blood due to the following equation:

H₂O + CO₂ <=> HCO₃ + H+

In your patients, it can be observed that the higher the CO₂ concentration, the higher the hydrogen ion concentration, resulting in a lowered pH (more acidic). Conversely, the lower the CO₂ concentration, the lower the hydrogen concentration, and hence a higher pH (more bicarbonate). If blood becomes too acidic, more acid is excreted in the urine, and more CO₂ is expelled from the lungs. The opposite is set into motion is the blood becomes too alkaline.

Urine pH reflects the amount of acid residual that is being eliminated from the body. When significant interstitial acid accumulation has occurred, a normal urine pH of 6.8 can plummet to as low as 5.5. The dress of interstitial acid accumulation can be estimated by comparing the pH of the first morning urine to the pH of a specimen taken at least 30 minutes later. The second specimen should ideally show a significantly higher pH than the first. If it does happen to be nearly the same concentration for both specimens, it tells the practitioner that the degree of acidosis is quite marked.

Saliva values of pH are the most difficult to interpret of all the biocellular measurements of pH. They are influenced greatly by the measurements of the blood; thus, when interpreting the saliva values, one must do so by comparing the measurements to those of the blood. For the most part, saliva pH fluctuations can be attributed to digestive impairment.

Knowledge in Action

A tendency toward acidity, rather than alkalinity, will usually be seen in practice. This is primarily due to the fact that Western diets are full of refined carbohydrates and protein-rich foods. This creates acidity in the body, whereas most fruits and vegetables create alkalinity. This information can help direct your dietary recommendations to your patients.

The major clinical effect of acidosis is depression of the central nervous system. In the extreme cases in which the pH of the blood falls below 7.0, the patient can become disoriented and later comatose. Therefore, patients dying of diabetic acidosis, uremic acidosis, and other types of acidosis usually die in a state of coma.

In the case of slight metabolic acidosis, which is what we would more commonly see in everyday practice, specific symptoms or complaints can be very difficult to pinpoint, as acidic affects could span over many body systems. However, note that in metabolic acidosis, an increased rate and depth of respiration is caused by the high hydrogen ion concentration. Therefore, one of the outward signs of metabolic acidosis in your patient may be increased pulmonary ventilation (faster or deeper breathing in the patient). With acidosis depressing the function of the central nervous system, the toll that long-term slight acidosis could take on the patients' health and body function over time would be of concern to me as the practitioner.

The major clinical effect of alkalosis is over-excitability of both the central and peripheral nervous systems. In extreme cases, muscles will begin to go into a state of tetany. Extremely alkalotic patients may die of tetany of the respiratory muscles. Other symptoms may manifest themselves as extreme nervousness or convulsions.

Again, the long-term slightly alkalotic state could also take its toll on patient health and is what would be of concern to me as the practitioner.