High protein, low carbohydrate diets such as the one promoted by Atkins, have been the source of much criticism from the nutrition community but while many nutritionists agree that the diet may not be nutritionally balanced, the new study suggests that protein may decrease bone resorption, a process that make bones stronger.
It had been thought that high protein (and reduced cereal grain) diets would increase urinary excretion of the mineral calcium, known to be essential to bone health.
The study, published in the March issue of the Journal of Clinical Endocrinology & Metabolism (89:1169-1173), looked at 32 men and women over 50 who were randomised to either a high or low protein intake diet for nine weeks and who were already including the recommended 800 milligrams of calcium in their diet.
The subjects were also advised to reduce their intake of carbohydrates to balance calorie leves with higher protein intake.
Changes in urinary calcium excretion in the two groups did not differ significantly over the course of the study. But those who increased their dietary protein by an average of 58 grams of protein a day had 25 per cent higher levels of bone growth factor and lower levels of a marker of bone resorption compared with controls, report Bess Dawson-Hughes and colleagues at the Bone Metabolism Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in the US. Both these factors indicate healthy bone status.
"In contrast to the widely held belief that increased protein intake results in calcium wasting, meat supplements, when exchanged isocalorically for carbohydrates, may have a favourable impact on the skeleton in healthy older men and women," write the researchers.
The findings confirm results reported last year from a study on 15 postmenopausal women. The women consumed about 600 milligrams of calcium per day, half the recommended intake, and either a low-meat or high-meat diet. Even with low-but-average calcium intake, the volunteers could eat twice the recommended dietary allowance of protein, mostly as meat, and not have an adverse effect on calcium retention or on biomarkers for bone breakdown, said the researchers.
A survey last year estimated that around 3 million people in the UK have tried the Atkins diet while in the US about 59 million adults are currently 'controlling their carbs', according to figures from the Valen Group.
Dr Dawson-Hughes did however warn that the new study "does not support the high protein, low carbohydrate approach to weight loss".
"There are many nutrients that contribute to healthy bones and a balanced diet, rich in fruits, vegetables, whole grains and protein is one of the best ways to ensure healthy bones throughout a lifetime," she added.