Several decades ago, western nutrition had little interest in acid-base balance, yet it was a central theme in macrobiotic eating and in eastern approaches to health. Things have changed and western scientists now recognize dietary patterns can put an immense burden on the body to restore an optimal acid-base balance. Our kidneys, in partnership with our lungs, must maintain the acidity or pH of our body fluids within a very narrow range (7.35-7.45). A pH of 0 to 7 is acidic (with the lowest numbers being more acidic); numbers above seven indicate increasingly alkaline pHs.
Meats, dairy products and grains are acid-forming, meaning that after these foods are digested and metabolized, they influence body fluids and the urine to be acidic. This effect is related to the amounts of phosphorus, sulphur and protein in these foods. Buckwheat and quinoa are less acid-forming than wheat, rice and other cereal grains.
Vegetables and fruits are alkali-forming, counterbalancing the effects of animal products and grains. Although we may think of some fruits as acidic because of their sour taste, this acidity is quickly disposed of during digestion. Some fruits – plums, prunes, cranberries, rhubarb and sour cherries – are acid-forming because they contain organic acids that are not completely broken down to bicarbonate. However, the vast majority of fruits and vegetables have an alkaline effect, related to the presence of potassium, magnesium and calcium. Nuts and legumes tend to be mildly acid-forming. It is interesting to note that humans evolved on a diet much more alkali-forming than today’s eating patterns.
The table below shows the Potential Renal Acid Load (PRAL) of various food groups. In this system, the positive numbers above “0” indicate foods that acidify our bodies. The negative numbers make our system more alkaline. Diets centered on meats, cheeses, wheat and rice are heavily acid-forming. When you look at family meals, restaurant menus and the contents of supermarket shopping carts, it becomes obvious our diets tip the scales in an acid-forming direction. A diet providing plenty of vegetables and fruits is highly important in maintaining the slightly alkaline pH that sustains health.
|Potential Renal Acid Load of Food Groups (Food Group per 100g and PRAL)|
|Milk, dairy products||1.0 to 23.6*|
|Grains, grain products||3.5 to 7.0|
|Fruits, fruit juices||-3.1|
|*PRAL is particularly high for processed and low fat cheeses.|
To maintain our necessary pH range of 7.35-7.45, we need not avoid acidic foods entirely, but instead get a mix that is just slightly alkaline overall. The body manages best when it has plenty of vegetables and fruits to offset moderate amounts of acid-forming foods.
Diets high in acid-forming foods can have damaging consequences due to our cells being kept in an environment that is too acidic (mild metabolic acidosis). Impacts include the wasting of muscles, the formation of kidney stones, kidney damage and the dissolution of bone. With age, our bodies become even less able to manage the imbalance. In next month’s column, we will explore how acid-forming diets affect our muscles, bones and kidneys.
Also see Becoming Raw (Book Publishing Co) by Living Light nutrition instructors and Registered Dietitians Brenda Davis and Vesanto Melina. Learn more about raw food nutrition in our Advanced Vegan and Raw Nutrition Certification course.