Potassium Guards Against Sodium-induced Bone Loss
Reference: Sellmeyer DE, Schloetter M, Sebastian A. Potassium citrate prevents increased urine calcium excretion and bone resorption induced by a high sodium chloride diet. J Clin Endocrinol Metab 2002;87:2008-12. Available at: http://jcem.endojournals.org/cgi/content/full/87/5/2008?ijkey=b46c2855f83d19e380eb6674c66c94e884ed56a0
Purpose of study: To study effects of dietary potassium citrate added to diets high in sodium, as commonly found in industrialized nations, in postmenopausal women. Postmenopausal women are at higher risk of osteoporosis, especially if consuming a high-sodium diet.
Type of study: Randomized, double-blinded placebo-controlled trial
Method used to conduct study: After three weeks in which 60 post-menopausal women adhered to a low-salt diet, they were provided sodium chloride pills, salt packets (for sprinking on food) and one cup of bouillon per day. They were randomized and either take potassium citrate (90 mmol/d) or placebo. Twenty-four-hour urine samples were analyzed to determine compliance after 12 days. When compliance was compromised, subjects were contacted to enforce regimen. After four weeks, urine samples and fasting blood samples were collected. Fifty two of the women completed seven-week study of which 26 had taken placebo and 26 potassium citrate. Exclusions at the beginning of the study included women who were less than 2 years past menopause, on bone metabolism medications or who had past history of bone disease.
Summary: Calcium excretion increased by 42+-12 mg/d (33%) from low-salt to high-salt diet in the women on placebo. Calcium excretion decreased by 8+- 14mg (4%) in women on potassium citrate. The results suggest that potassium citrate prevented bone resorption in response to salt increase in the diet.
The method is thought to be the natriuretic and chloruretic effects of potassium alkaline salts. These potentially reduce extracellular volume expansion associated with higher salt intake. The alkaline salts also reduce endogenous acid, increase blood pH and bicarbonate. Calcium excretion in the urine can change depending on acid production.
Critique: Examining effects of potassium through a placebo-controlled trial goes far to point out the intracellular cations biological effects on calcium excretion. The results are significant. The researchers took appropriate measures in assuring that the postmenopausal women were compliant in their diets. A seven-week study, however, may not be long enough to determine whether or not potassium citrate will make a significant difference in reducing risk of bone loss and hip fracture.
Nutritional implications and implications of future study: Post-menopausal women at risk for osteoporosis, especially who eat a high-sodium diet, should consider increases of dietary sources of potassium, which are mainly fruits and vegetables. For the benefit of post-menopausal women who may dislike fruits and vegetables and eat mainly processed foods, it may be wise to add potassium to these processed foods. Similar trials should be conducted to determine effects of potassium-added, high-sodium processed foods.