Low-carb diets may cause atherosclerosis, impaired blood vessel growth

August 25th, 2009 - 1:13 pm ICT by ANI  

Washington, Aug 25 (ANI): While low-carbohydrate/high-protein diets have been known to help individuals to lose weight rapidly, researchers have now found that such diets may lead to atherosclerosis and impaired blood vessel growth.

Led by a scientific team at Beth Israel Deaconess Medical Center (BIDMC), the study has shown that mice placed on a 12-week low carbohydrate/high-protein diet had a significant increase in atherosclerosi- a buildup of plaque in the heart’s arteries and a leading cause of heart attack and stroke.

The findings also showed that the diet led to an impaired ability to form new blood vessels in tissues deprived of blood flow, as might occur during a heart attack.

The study also found that standard markers of cardiovascular risk, including cholesterol, were not changed in the animals fed the low-carb diet, despite the clear evidence of increased vascular disease.”It’s very difficult to know in clinical studies how diets affect vascular health. We, therefore, tend to rely on easily measured serum markers [such as cholesterol], which have been surprisingly reassuring in individuals on low-carbohydrate/high-protein diets, who do typically lose weight. But our research suggests that, at least in animals, these diets could be having adverse cardiovascular effects that are not reflected in simple serum markers,” said senior author Dr. Anthony Rosenzweig.

The researchers found that the increase in plaque build-up in the blood vessels, and the impaired ability to form new vessels, were associated with a reduction in vascular progenitor cells, which some hypothesize could play a protective role in maintaining vascular health.

“A causal role for these cells has not yet been proven, but this new data is consistent with the idea that injurious stimuli may be counterbalanced by the body’s restorative capacity. This may be the mechanism behind the adverse vascular effects we found in mice that were fed the low-carb diets,” explained Rosenzweig.

The researchers embarked on the study after seeing heart-attack patients who were on these diets - and after observing Rosenzweig himself following a low-carbohydrate regimen.

The investigators proceeded to study a mouse model of atherosclerosis.

These “ApoE” mice were fed one of three diets: a standard diet of mouse “chow” (65 percent carbohydrate; 15 percent fat; 20 percent protein); a “Western diet” in keeping with the average human diet (43 percent carbohydrate; 42 percent fat; 15 percent protein; and 0.15 percent cholesterol); or a low-carb/high-protein diet (12 percent carbohydrate; 43 percent fat; 45 percent protein; and 0.15 percent cholesterol).

They observed the mice after six weeks, and again at 12 weeks to find that just like in humans, the mice fed the low-carb diet gained 28 percent less weight than the mice fed the Western diet.

However, further probing revealed that the animals’ blood vessels exhibited a significantly greater degree of atherosclerosis, as measured by plaque accumulation- 15.3 percent compared with 8.8 percent among the Western diet group.

The investigators looked at the animals’ endothelial or vascular progenitor cell (EPC) counts, which could play a role in vessel regrowth and repair following injury.

“Examinations of the animals’ bone marrow and peripheral blood showed that the measures of EPC cells dropped fully 40 percent among the mice on the low-carb diet - after only two weeks,” said Rosenzweig.

Importantly, the findings pointed out that there can be a disconnect between weight loss or serum markers and vascular health, and that vascular health can be affected by macronutrients other than fat and cholesterol - in this case, protein and carbohydrates.

Rosenzweig said: “This issue is particularly important given the growing epidemic of obesity and its adverse consequences. For now, it appears that a moderate and balanced diet, coupled with regular exercise, is probably best for most people.”

The research has been published in the Proceedings of the National Academy of Sciences (PNAS). (ANI)

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