Americans have been debating the risks and benefits of different diets, specifically low-fat versus low-carbohydrate diets, even decades before the Atkins Diet and the South Beach Diet swept the nation.
Now, a new study has answers to an old question: Is a low-carbohydrate diet bad for the heart?
No, suggests new research published in today's issue of the New England Journal of Medicine, and it's not any worse than a diet high in carbs.
The study, which involved more than 82,000 women from across the country over 20 years, confirms what previous research has suggested: Low-carbohydrate diets do not increase heart-disease risk.
Even though low-carb dieters might tend to eat more fats and other heart-unhealthy foods, over time their risk of coronary heart disease (CHD) did not exceed that of their counterparts who instead consumed a low-fat, low-cholesterol diet.
The study's researchers say the results suggest that low-carb diets are at least on equal footing with other forms of dieting when it comes to heart health.
"This study suggests that neither a low-fat dietary pattern nor a typical low-carbohydrate dietary pattern is ideal with regards to risk of CHD. Both have similar risks," said study researcher Tom Halton, a former doctoral student in the Department of Nutrition at the Harvard School of Public Health in Boston.
"However, if a diet moderately lower in carbohydrates is followed, with a focus on vegetable sources of fat and protein, there may be a benefit for heart disease," Halton said.
Backing the findings are data from three trials published in 2003, which showed that low-carb diets do not increase cardiovascular risk factors.
In those studies, the Atkins Diet, a bellwether regimen on the low-carb scene, was compared to a different diet emphasizing a low intake of fat and cholesterol.
The results? Those on the Atkins Diet actually had greater improvements in insulin sensitivity, HDL (good) cholesterol and triglyceride levels than did the low-fat, low-cal dieters.
The findings, however, come with a caveat common to many of the other studies on high-protein, low-carb diets. In short, don't go crazy on the red meat.
"This study doesn't mean that you should load your plate with steak and bacon," said the study's senior author Frank Hu, associate professor of nutrition and epidemiology at Harvard School of Public Health.
"The quality of fat and carbohydrate is more important than quantity. A heart-healthy diet should embrace healthy types of fat and carbohydrates," Hu said.
Some experts remain skeptical of the study.
"This is an observational study, not a randomized trial," said Dr. Neal D. Barnard, president of the Physicians Committee for Responsible Medicine in Washington, D.C.
"We already have randomized trials of low-carb diets, and they clearly show that approximately one in three low-carb diets has a significant increase in LDL [bad] cholesterol. Such findings are far more relevant than observational studies to the question of what effects do low-carb diets have," Barnard said.
Adding to the skepticism of some experts are the limitations of the study -- specifically, that it only looked at female nurses, and that the self-reporting method used could be considered unreliable.