“Nutritional research today is typically the blind leading the blind. People following nutritional belief systems like religion,” explains Dr. Fuhrman and this study claiming that high protein diets help preserve bone integrity during weight-loss is no different. From the University of Illinois at Urbana-Champaign:
The scientists recruited and randomized 130 middle-aged, overweight persons at two sites—the U of I and Pennsylvania State University. Participants then followed either the higher-protein weight-loss diet or a conventional higher-carbohydrate weight-loss diet based on the food-guide pyramid for four months of active weight loss followed by eight months of weight maintenance.
"Essentially we substituted lean meats and low-fat milk, cheese, yogurt, etc., for some of the high-carbohydrate foods in the food-pyramid diet. Participants also ate five servings of vegetables and two to three servings of fruit each day," Evans said.
Bone mineral content and density were measured with DXA scans of the whole body, lumbar spine, and hip at the beginning of the study, at four months, at eight months, and at the end of the 12-month period.
"In the higher-protein group, bone density remained fairly stable, but bone health declined over time in the group that followed the conventional higher-carbohydrate diet. A statistically significant treatment effect favored the higher-protein diet group," said Matthew Thorpe, a medical scholars (MD/PhD) student who works in Evans's lab and was the primary author of the study.
I asked Dr. Fuhrman about this research and here’s what he had to say. Take a look:
There are so many variables that the conclusions are simplistic. First of all, the vast majority of Americans are severely Vitamin D deficient and their higher protein group was given more Vitamin D fortified milk. Second, the intervention group was encouraged to eat more green vegetables and less sugar, bread and white potato, getting higher level of bone building nutrients, including Vitamin K, and thirdly, the intervention group, though eating less refined carbohydrates were only given a diet a little higher in protein (30 percent) which is not a very high protein diet.
All in all, if they are going to claim some benefit to lean muscle or bone for the higher protein diet, they have to control for Vitamin D, K and other bone supportive nutrients that were higher in the intervention group. Even though this was a poorly designed and poorly controlled study, I basically agree with what they found—that a moderate protein diet with more fruits and vegetable and less refined foods bread and pasta, with attention to more Vitamin D from fortified skim milk will result in better bone mass with dieting compared to a diet not paying attention to these details. However, I think the better results stem from numerous factors, and not likely from a higher percentage of protein and less carbohydrate.
No doubt, this report will whip the low-carb congregation into their usual zealotry.