Chemical reactions in the body produce various acid and alkaline substances that may disturb the delicate balance between acidity and alkalinity required for life. In spite of an enormous acid load generated through the diet and normal metabolism, according to Eleanor Whitney and Sharon Rolfes in their book, "Understanding Nutrition," the body maintains a proper acid-base balance by constantly taking corrective actions to maintain a dynamic state of equilibrium.
Identification
The acid and alkaline balance in the body refers to the dynamic and delicately controlled state of equilibrium in the concentration of hydrogen ions in the blood. Acid-base status is measured by pH, the negative of the hydrogen ion concentration logarithm. The lower the pH, the stronger the acid and the higher the concentration of hydrogen ions. A higher pH reflects a more basic or alkaline solution.
Function
The acid-base balance in the blood must be tightly controlled between 7.35 and 7.45 pH for normal health. Acidosis occurs if the pH of arterial blood decreases to below 7.35 due to an increase in circulating acids or a reduction in bicarbonate levels. Alkalosis occurs if the pH of arterial blood increases to above 7.45 due to an increase in bicarbonate levels or a reduction in circulating acids. Compensating actions must occur to reestablish the acid-base balance and maintain it within the normal range.
Features
The body uses three different methods to regulate the pH balance of the blood, according to "Understanding Nutrition." Regulation by buffers serves as the first line of defense against changes in the pH balance. Bicarbonate, a base, neutralizes acid, and carbonic acid neutralizes alkaline substances. Regulation by the lungs provides a second line of defense. If too much acid builds up in the blood, the rate of respiration increases to exhale more carbon dioxide; if too much base or alkaline builds up, the rate of respiration slows down to retain more of the carbon dioxide.
The kidneys have the most effect on long-term control of pH balance. The kidneys constantly adjust the acid-base balance by selecting which substances to retain in the blood and which to excrete in the urine. The kidneys keep the acid burden in the body constant by fluctuating the acidity of the urine.
Risks
If the pH of the blood deviates from the narrow healthy range, protein damage can have life-threatening consequences. For example, a slight deviation in either direction from the normal pH range could damage enzymes so that they could not act as catalysts for chemical reactions or hemoglobin could not carry oxygen.
Considerations
Acids normally enter the body in food, acid precursors and toxins. For instance, foods containing protein, minerals and sulfur-containing amino acids affect the acid balance, according to T. Remer in the July-August 2000 issue of "Seminars in Dialysis." The body also generates acids through normal metabolism.
Disruption of the acid-base balance may accompany certain diseases and medical treatments, according to the book, "Krause's Food, Nutrition, & Diet Therapy." Protein energy malnutrition, trauma, illness and surgery can affect the acid-base balance by causing alterations in bodily fluids. Marked changes in the rates of chemical reactions can result. Maintaining the acid-base balance is crucial to life.
References
- "Understanding Nutrition, Ninth Edition"; Eleanor Noss Whitney and Sharon Rady Rolfes; 2002
- National Institutes of Health: Seminars in Dialysis: Influence of Diet on Acid-Base Balance
- "Krause's Food, Nutrition, & Diet Therapy, 10th Edition"; Mahan and Escott-Stump; 2000
Member Comments