One very important factor that impacts calcium balance and bone strength has received little attention. Human beings evolved on a diet consisting largely of fruits and vegetables supplemented with modest amounts of animal products. The metabolic residue from fruits and vegetables is highly alkaline due largely to their high potassium content and less so to their calcium and magnesium content. Foods of animal origin yield an acidic residue.
In modern diets, calories from fruits and vegetables have been displaced by grains, which yield a modestly acid residue. There has also been an increased consumption of animal products, some of which are metabolically very acid forming. As a result, the urine of modern humans is generally acidic, whereas that of our ancient ancestors was likely alkaline. Aging lowers the body’s ability to deal with more acidity.
A recent study by Dr. Dawson-Hughes examined the impact of adding sodium or potassium bicarbonate supplements to a typical modern diet in 171 subjects age 50 and older. This study found not only a decrease in calcium lost in the urine in response to the bicarbonate supplements but also a reduction in urinary N-telopeptide – a marker for more rapid bone breakdown. Sodium bicarbonate and potassium bicarbonate increase the alkalinity of blood and urine. Dr. Dawson-Hughes concluded that alkalinizing the urine “… had a favorable effect on bone resorption and calcium excretion. This suggests that increasing the alkali content of the diet may attenuate bone loss in healthy older adults.”1
Bottom Line: The evidence is more than sufficient to encourage Americans to consume more fruits and vegetables and cut way back on foods like meats, eggs, and cheeses that acidify the blood and urine. Those with already weakened bones should replace some of the grain products in their diets with potatoes and yams. While salt has little impact on acid-base balance it increases calcium loss and is best limited in those with thinning bones.
By James J. Kenney, PhD, RD, FACN
1. J Clin Metab. 2009;94:96-102
Judy’s passion for cooking began with helping her grandmother make raisin oatmeal for breakfast. From there she earned her first food service job at 15, was accepted to the world-famous Culinary Institute of America at 18 (where she graduated second in her class), and went on to the Fachschule Richemont in Switzerland where she focused on pastry arts and baking. After a decade in food service for Hyatt Hotels, Judy launched Food and Health Communications to focus on flavor and health. She graduated with Summa Cum Laude distinction from Johnson and Wales University with a BS in Culinary Art, holds a master’s degree in Food Business from the Culinary Institute of America, 2 art certificates from UC Berkeley Extension, and runs a food photography studio where her love is creating fun recipes.
Judy received The Culinary Institute of America’s Pro Chef II certification, the American Culinary Federation Bronze Medal, Gold Medal, and ACF Chef of the Year. Her enthusiasm for eating nutritiously and deliciously leads her to constantly innovate and use the latest in nutritional science and Dietary Guidelines to guide her creativity, from putting new twists on fajitas to adapting Italian brownies to include ingredients like toasted nuts and cooked honey. Judy’s publishing company, Food and Health Communications, is dedicated to her vision that everyone can make food that tastes as good as it is for you.