Washington: Low-carbohydrate diets may help people lose weight, but they could prove deadly for those with a family history of heart disease, a new study has claimed.
In experiments on mice, researchers at the University of Alabama at Birmingham found that obese rats given a high-fat, low-carb diet -- comparable to what many humans consume – had more damaging and deadly heart attacks than those who were fed a low-fat diet.
Worse, the findings, presented at a meeting of American College of Cardiology in Chicago, suggested that this type of diet also impairs recovery immediately following a heart attack.
Although the low-carb diets do have benefits, people need to exercise caution while eating, the researchers advised.
"Right now, if I were considering a high-fat, low-carb diet, I would ask myself if the benefits outweigh the heart-attack issues this research has revealed," study author Steven Lloyd said.
"If I had heart disease or I was predisposed to having a heart attack, I would think carefully before starting this type of diet," Lloyd said.
According to researchers, carbohydrates from foods such as vegetables, nuts and grains have been the primary source of calories for most of the world`s people for millennia.
The World Health Organisation advocates a diet in which 55 percent to 75 percent of daily calories should come from carbohydrates; 15 percent to 30 percent from fats; and 10 percent to 15 percent from proteins.
For the study, Lloyd and his colleagues focused only on naturally occurring heart attacks in mice. They found that for obese rats on a high-fat diet, when a heart attack hit, it was larger and more punishing, causing more damage to the heart muscle and leaving less chance of recovery compared to equally obese rats on a low-fat diet.
One reason might be the role of fat in inducing oxidative stress and creating free radicals, which are highly reactive atoms and molecules that damage DNA and cellular walls, ultimately killing heart muscle cells, the researchers said.
Another reason, Lloyd said, could be that for the rats on a high-fat diet their hearts may have been starved for energy. Carbohydrates are the most efficient fuel when the heart is trying to recover from a damaging event, he said.
In the high-fat diet, the primary fuel is ketones from fat metabolism, which is adequate for a healthy heart but not a damaged one. The lack of glucose that would have been supplied by carbohydrates leaves the heart less able to heal itself, Lloyd said.
There is considerable scientific support for the low-carb diets as weight-loss programs. And Lloyd emphasised that his research does not suggest that high-fat, low-carb diets cause heart attacks.
Nevertheless, the long-term impact of high protein intake and fat on the heart and other organs is not well known.
Many advocates on both sides of the diet debate – the low-fat and low-carb camps -- have reached some common ground in recent years.
Both camps now emphasize "good carbs," which are complex carbohydrates found in whole grains and beans, as opposed to the simple carbs found in sugar, white bread and potatoes; and "good fats" such as the healthful omega-3 fatty acids found in some fish, and unsaturated fats found in poultry.