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Explaining the Acid Alkaline Theory of Eating

A popular and controversial theory related to osteoporosis and diet is that a diet high in acid forming foods will trigger the body's ability to self regulate and maintain a healthy blood pH and balance. The higher the acid load of the diet the harder the body has to work to maintain a normal blood pH. The body tries to defend against increasing acid by breaking down bone and muscle to obtain nutrients needed to buffer acid. This balancing system works by pulling the nutrients it needs from the body's mineral stores. If the imbalance is temporary the body is thought to be able to compensate. However, if the high acid diet is chronic and the kidneys are weakened with age this imbalance may result in a mild, but progressive, metabolic acidosis that adversely affects bones and becomes a significant problem. The issue is not that the blood becomes significantly acidic or that an individual in any way significantly changes the pH of their blood. The body has several mechanisms and buffer systems that prevent your blood from becoming too acidic and you cannot live if your blood pH is not within a certain critical range (7.35 to 7.45). The problem is that the body’s efforts to keep the body’s blood pH balanced when a person consumes a high acid, low alkaline diet on a chronic, long term basis may result in a loss of structural bone strength over time.

Some scientists believe dietary acid loads from Western diets may be a risk factor for osteoporosis. The acid load of a particular food is determined by what the food releases into the bloodstream upon metabolism not on the acidity of the food prior to metabolism. For instance, a lemon is acidic prior to metabolism but yields alkaline ash upon metabolism and is therefore considered to be an alkaline food when referring to the acid alkaline theory of eating. Grains like breads, cereals, rice, and pasta as well as meats, fish, egg yolks and cheeses release acids into the bloodstream upon metabolism. Fruits and vegetables break down to add alkali to the bloodstream which helps neutralize acid. Foods with higher acid loads don't have to be eliminated from the diet but they need to be eaten in moderation and adequately balanced with alkaline foods so the net effect is a more alkaline diet. The best way to reduce dietary acid load is to eat lots of fruits and vegetables with modest amounts of breads, cereals and pastas and adequate protein, but not excessive animal protein. 

There are numerous charts, food guides and books available on the acid and alkaline values of foods but the information differs according to the source and can result in confusion and frustration in meal planning. Trying to plan meals and eat by following these guides and charts is very difficult and often impractical. It is important to understand that some explanations of the dietary acid load theory are too simplistic and lack an understanding of the complexities involved in acid base balance.

At this point the best approach seems to be to plan meals according to the following guidelines. If you follow these general guidelines you should maintain a good alkaline balance in your diet: 

Have 1 serving of fruit or vegetable:

  • For every ounce of meat or egg eaten.
  • For every cup of milk, yogurt or beans eaten.
  • For every slice of bread or cup of pasta, grain or rice eaten.

Have 2 servings of fruit or vegetables:

  • For each ounce of cheese eaten.

While some research suggests high acid diets are detrimental to bones, other studies have failed to find a link between bone strength and the alkalinity of the diet. I'm not aware of any controversy around the suggestion to eat lots of fruits and vegetables so, regardless of what future research finds regarding the role of an alkaline diet in bone health, eating enough fruits and vegetables to keep your diet alkaline is bound to be beneficial. Just be sure to still get enough protein.

Photo used with permission from the Journal of the Academy of Nutrition and Dietetics. Photo by Amy Virus, MS,RD, LDN

posted on 3/18/2017