According to Bess Dawson-Hughes, professor of medicine at Tufts University School of Medicine, having too much acid in the bloodstream may occur if you consume a high acid-load diet and have reduced kidney function, leading to bone and muscle breakdown. According to a 1995 publication in the "Journal of the American Dietetic Association," in the early 1990s, German scientists developed a physiologically-based calculation model to estimate acid load on the kidneys for some of the most commonly eaten foods. This calculation model has been validated and is known as potential renal acid load or PRAL. Acid-promoting foods include proteins and grains or starches.
The PRAL score is directly associated with urine acidity or urine pH value. The higher the value, the more acid-producing the food. The scale has evolved to include more foods but at the time of development, ranged from an average maximum of 23.6 mEq/100 g to an average minimum of approximately -3 mEq/100 g. Eating too many refined grains promotes an acidic environment in the bloodstream. Examples of foods in this category include rice, cereal, pasta, crackers, flour tortillas, cookies, doughnuts, cupcakes and similar foods. While carbohydrate-rich whole grains are important for a healthy diet, the typical American consumes too many refined grains, many of which are in the form of snack foods. Foods with a positive potential renal acid load or PRAL need to be balanced with those with a negative load. A 1/2-cup of white rice has a score of 2.7 while one peach has a score of -2.4, according to an article published in November 2010 in the the Center for Science in the Public Interest or CSPI publication, the Nutrition Action Healthletter.
Amino acids, or the building blocks of protein, make up protein-rich foods, such as meat. Certain amino acids contain sulfur, which is essential for proper bodily functions. While essential, sulfuric compounds promote acidity in the bloodstream, according to research published in December 2003 in the "American Journal of Clinical Nutrition." The acid-producing quality of a protein food depends on how many sulfur-containing amino acids it contains. These amino acids exist in both plant and animal protein sources. While both plant and animal proteins contribute to an acidic environment, plant protein foods generally come in the form of beans, which are also slightly alkaline. According to CSPI, a 5-oz. raw portion of lean beef or pork has a PRAL score of 11.2 and skinless chicken, a score of 12.4. These are healthy, lean protein foods, but it is about balancing them with alkaline-promoting foods, such as fruits and vegetables, or neutral foods, such as olive oil.
Dairy and Eggs
While dairy foods, such as milk, yogurt, cheese and eggs appear to have a lower PRAL score than meats, the serving size is smaller, especially for cheese and eggs. A 1/2-cup of cottage cheese has a PRAL score of 9.6 and 1 oz. of hard cheese, such as cheddar, a score of 5.4. One large egg, the equivalent in protein of 1 oz. of meat, poultry or fish, has a PRAL score of 4.1. Soft cheeses, as well as other dairy products, such as milk, yogurt and ice cream, have a lesser tendency to promote acidity. Per 1-cup serving, ice cream, milk and yogurt have a PRAL score ranging from 0.8 to 2.0.
- "Nutrition Action Healthletter"; Bad for Bones? The Latest on Food and Fractures; B Liebman; Nov 2010
- Pubmed: Potential Renal Acid Load of Foods and Its Influence on Urine pH
- American Journal of Clinical Nutrition: Contribution of Dietary Protein and Inorganic Sulfur to Urinary Sulfate
- Journal of the American College of Nutrition: Dietary Acid-Base Balance, Bone Resorption, and Calcium Excretion
- Jupiterimages/Photos.com/Getty Images
This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.