Low-carb diets linked to vascular disease

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H et M/photocuisine/Corbis

H et M/photocuisine/Corbis

Ever wonder how all that fat and protein in a low-carb diet could be good for you, even though you’re losing weight? A new study today in the journal Proceedings of the National Academy of Sciences suggests that, well, in fact, it isn’t.

Mice that were fed a high protein, high fat diet — designed to resemble a human low-carb diet in terms of the proportion of calories derived from different macronutrients — gained less weight than mice fed either a standard lab diet or a diet designed to resemble humans’ typical Western diet. (Both those latter two groups gained about the same amount of weight.) But the low-carb group had far worse vascular health. They had more atherosclerosis (hardening of blood-vessel walls) and they had what seemed to be an impaired ability to generate new blood vessels. In humans, these are considered major risk factors for heart attack and stroke.

Even more surprising, the changes in vascular health didn’t seem related to changes in the indicators that doctors typically look at to determine cardiovascular risk in humans — things like cholesterol. Instead, for the same cholesterol levels and the same markers of oxidative stress (the harmful process that antioxidants help to prevent), the low-carb dieters had more blood-vessel damage. The researcher hypothesize, therefore, that a low-carb diet may not actually cause more vascular damage in the first place, but may instead limit the body’s ability to repair damage once it’s done. It appears that mice on the low-carb diet may have produced fewer endothelial progenitor cells, cells that help the vascular system regenerate.