June 7, 2006
Low-carb diets not a threat to bone health
NEW YORK -- Contrary to concerns raised by animal studies, people on low-carb diets don't run a risk of weakening their bones, Florida researchers report.
Scientists had suspected that such diets might leach calcium out of the bones by causing the kidneys to excrete more acid, and research in animals had supported this possibility.To investigate whether this occurs in humans as well, Dr. John D. Carter and colleagues from the University of South Florida in Tampa had 15 people follow a low-carb diet for three months, comparing them to 15 age- and sex-matched "controls" who ate a normal diet.
As described in the medical journal Osteoporosis International, study participants ate less than 20 grams of carbohydrates daily for the first month of the diet, and less than 40 grams of carbs daily for the second and third months.
Carter and his team checked a number of measures of bone breakdown and bone formation at one month and at three months. They found no difference between the two groups in bone turnover, but the men and women on the low-carb diet lost an average of 6.39 kilograms (14 pounds) compared to 1.05 kg (2.3 pounds) for the controls.
"Although the relatively short observation period does challenge the generalizability of these findings, we suggest that a low-carbohydrate diet used for weight loss does not increase bone turnover in humans," Carter and his colleagues conclude.
In a press release accompanying the study, Carter stressed that he does not support low-carbohydrate diets for long-term weight maintenance, given that they may stress the kidneys and cause people to eat more fat and cholesterol.
SOURCE: Osteoporosis International, online May 24, 2006.