WOMEN'S HEALTH
December 22, 2008

Buffering Acid Protects Bones

Neutralizing the metabolic acidity of the proteins and sugars typical of the American diet can help reduce bone loss.

Neutralizing the metabolic acidity of the typical American diet can effectively reduce bone loss in older individuals, according to research from Tufts University.

The bicarbonate offsets the acidity that is created when the proteins and sugars that characterize the typical Western diet are metabolized.

A three−month course of bicarbonate supplements, which are known for their acid−buffering properties, significantly reduced evidence of bone loss in study subjects over the age of 50 compared to treatment with an acid−neutral supplement or a placebo. The results will be published in the January issue of the Journal of Clinical Endocrinology & Metabolism.

During the study period, urinary N−telopeptide (a marker of bone resorption) and calcium excretion levels decreased in the individuals who were randomized to treatment with 67.5 mmol/day of either sodium bicarbonate or potassium bicarbonate, while increasing in those who received either potassium chloride or placebo. All study subjects also took supplements of calcium and vitamin D, which previously have been demonstrated to improve bone health.

The bicarbonate offsets the acidity that is created when the proteins and sugars that characterize the typical Western diet are metabolized. High acidity levels can trigger bone resorption, as neutralizing minerals are released from the bone into the bloodstream, particularly in older adults.

At the start of the study, urinary net acid excretion was strongly positive in all subjects, reflecting the acidity of patients' diets (vegetarians were excluded). At the end of the study, the mean NAE level was near zero in those who had taken bicarbonate but did not change significantly in the other two groups.

"Bicarbonate had a favorable effect on bone resorption and calcium excretion." said Bess Dawson−Hughes, MD, lead author of the study. "This suggests that increasing the alkali content of the diet may attenuate bone loss in healthy older subjects."

Although the study specifically analyzed the effect of adding bicarbonate to the diet in pill form, the authors theorized that similar results might be achieved by reducing dietary proteins and sugars and increasing consumption of alkaline−producing vegetables and fruits such as broccoli, kale, collard greens, raspberries, nectarines and melons.

However, the Tufts group found no significant effect of dietary potassium on bone health, in contrast to the findings of a 2005 study from the University of Aberdeen in which bone mineral density level was positively correlated with self−reported potassium intake. The Tufts authors suggested that the potassium−rich diets in the Aberdeen study were also likely to have been rich in alkaline−producing fruits and vegetables, which would have positively affected BMD even if potassium itself did not.

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