You’ll probably lose weight if you follow a popular type of diet that’s low in carbs and high in protein — but will you lose health, too? The controversy surrounding this type of eating plan is loud and seemingly endless, and here comes more research stirring that pot with a startling new finding about cardiovascular health.
The study started out as a straightforward effort to determine whether a low- carb/high-protein diet is healthful, says its senior author Anthony Rosenzweig, MD, director of cardiovascular research at the CardioVascular Institute at Beth Israel Deaconess Medical Center and professor of medicine at Harvard Medical School. Mice bred to have atherosclerosis were fed one of three diets for 12 weeks. One group ate a standard mouse chow with 65% carbohydrates, 15% fat and 20% protein …another group ate an approximation of the typical Western human diet with 43% carbs, 42% fat and 15% protein… and a third group ate an approximation of a typical human low-carb/high-protein weight loss diet with 12% carbs, 43% fat and 45% protein.
Not all the findings were surprising… as expected, the mice in the low-carb/high-protein group put on less weight as they matured than those on the Western diet, and their markers for vascular disease (including cholesterol and triglyceride levels)… oxidative stress… insulin and glucose levels… as well as some inflammatory cytokine levels were either no different or slightly better. So far so good… but the researchers got a big surprise when they examined the blood vessels themselves: The low-carb/high-protein eating mice had far more atherosclerosis as measured by plaque accumulation than the mice in the Western diet group.
Uh-oh — this could be big news for human dieters, so now the researchers had to try to find an explanation for this unexpected and worrisome finding. Since none of the standard vascular health markers (the things your doctor checks at your annual physical) indicated anything was amiss, the researchers theorized that something might have interfered with the mice’s natural ability to repair injuries to vessels and return them to normal function. The team focused on a special bone marrow cell thought to play a role in blood vessel regrowth and injury repair called EPC (endothelial progenitor cells) … and they found that in the low-carb/high-protein group, levels had indeed dropped 40% after only two weeks on the diet.
What does this mean for us non-mice? The study shows a correlation between reduction of the cells and an increase in arterial plaque, Dr. Rosenzweig said — and he believes this may be of great importance. Other studies have demonstrated that people with heart and cardiovascular disease tend to have fewer of these cells and that people who exercise have more of them, so now we must wonder, can a low-carb diet reduce EPC levels and possibly lead to or contribute to serious heart disease? More research is required, as we still don’t know whether this would happen in people… but it convinced Dr. Rosenzweig to go off the low-carb diet he was on!
If you’ve been keeping up with reading your Daily Health News, Dr. Rosenzweig’s research may remind you of another study, from Mount Sinai Medical School in New York City (Daily Health News, March 9, 2010, “The Brain-Shrinking Diet”). This earlier and unrelated study found brain shrinkage in mice fed a low-carb/high-protein diet — another finding that raises concerns about the potential for harm in such a diet. While it’s too early to draw conclusions, the two studies do ring some cautionary bells about diets loaded with protein and light on carbs. As Dr. Rosenzweig says, the best message for now is to stick with “all the things we know are good for us, including a balanced, nutritious diet with lots of fruits and vegetables.” Those are the kinds of carbs we all need to eat anyway.
