March 20, 2014 -- Saturated fats have long been called ''bad fats'' for their effect on the heart. But a new analysis calls into question whether they're really that bad after all.
The findings, published in the Annals of Internal Medicine, have sparked renewed debate about fats and heart health.
The new study should trigger a review of current diet guidelines for heart health, according to the researchers who did the analysis. Other experts, including one from the American Heart Association, disagree.
There is some common ground. All agree that dietary fat is just one factor that drives heart disease risk. Paying attention to the other factors is also important.
WebMD asked a study co-author, a cardiologist, a nutrition expert, and the American Heart Association to elaborate.
Researchers looked at 72 published studies on fats and heart disease. The studies involved more than 600,000 people from 18 countries. Some people already had heart disease, while others did not. The researchers reanalyzed the results, an approach called a meta-analysis.
They looked at whether different fats helped or hurt your heart. The different fats included:
Saturated fats (found in meats, whole-fat dairy products, and baked goods)
Polyunsaturated fats, such as omega-3 and omega-6 (found in fish, nuts, seeds, and vegetable oils)
Monounsaturated fats (found in olive and canola oils)
Trans fats (found in fried foods and baked goods, and being phased out of the food supply)
The surprise? Saturated fats, long thought to raise heart disease risks, had no effect. Neither did monounsaturated fats, which are thought to help the heart, says study researcher Dariush Mozaffarian, MD, at the Harvard School of Public Health.
Which fats did have an effect? Trans fats, known to raise bad cholesterol and lower good cholesterol, were linked with a higher risk of heart disease, as expected. Omega-3s from food helped. Omega-6s appeared to help.
What do the researchers say about the findings?
Nutritional guidelines on fats and heart health by such organizations as the American Heart Association may deserve another look, the study authors say.
The focus should move beyond just the fat content of food, Mozaffarian says. "We can't judge the healthfulness of a food [only] by how many grams of saturated fat it has. We really should be moving toward a food-based analysis.
"It's not just the fat grams, and the type of food, but the way the food is processed," he says. For instance, the analysis found that a type of saturated fat linked with milk and dairy products reduced heart disease risk.
Based on the analysis, Mozaffarian and his colleagues say, the current heart health guidelines that promote eating more foods with omega-3s and omega-6s and less of those with saturated fats are not needed.