Diets high in protein and cereal grain produce an excess of acid in the body, which may increase calcium excretion, according to results to be published in the January issue of the Journal of Clinical Endocrinology & Metabolism.
"When it comes to dietary concerns regarding bone health, calcium and vitamin D have received the most attention, but there is increasing evidence that the acid/base balance of the diet is also important," said lead author Bess Dawson-Hughes from Tufts University in Boston.
Bone health is becoming a major segment of the supplements and functional foods market, as ageing populations and the additional strain from obesity swell the numbers affected by osteoporosis. Already the lifetime risk for a woman to have an osteoporotic fracture is 30-40 per cent and in men the risk is about 13 per cent.
As adults age they become less able to excrete the acid produced via dietary metabolism, explained Dawson-Hughes. Reacting to the increasing acid levels, the body counters this by bone resorption, a process by which bones are broken down, releasing minerals such as calcium, phosphates, and alkaline (basic) salts into the blood. Bone resorption weakens the bones and increases the risk of fracture.
Tufts researchers, in collaboration with scientists from Northeastern University in Boston, recruited 171 men and women aged 50 or older and randomly assigned them to receive supplements of potassium bicarbonate, sodium bicarbonate, potassium chloride or placebo for three months.
Dawson-Hughes and her co-workers report that only bicarbonate-receiving volunteers had significant reductions in calcium excretion, which indicated a reduction in bone resorption.
“When fruits and vegetables are metabolized they add bicarbonate, an alkaline compound, to the body," said Dr. Dawson Hughes. "Our study found that bicarbonate 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."
“Achieving alkali-producing diets would require drastic changes in food choices and be challenging in older people who tend to have long-established dietary patterns,” wrote the researchers.
“Should it be shown to be beneficial, an alternative approach may be to administer bicarbonate in supplement form or to lower the acid-producing capacity of selected foods through alkali fortification,” they added.
Source: Journal of Clinical Endocrinology & MetabolismJanuary 2009, doi:10.1210/jc.2008-1662"Treatment with Potassium Bicarbonate Lowers Calcium Excretion and Bone Resorption in Older Men and Women"Authors: B. Dawson-Hughes, S.S. Harris, N.J. Palermo, C. Castaneda-Sceppa, H.M. Rasmussen, G.E. Dallal