Banning trans fats in New York prevented thousands of heart attacks, study finds

Trans fats, or partially hydrogenated oils, have long been tied to heart disease risk. And starting next summer, the Food and Drug Administration will prohibit food manufacturers from adding trans fats to foods like cookies, crackers, and microwave popcorn. If New York is any guide, a new analysis finds, that move could prevent tens of thousands of heart attacks and strokes in upcoming years.

Trans fats occur in vegetable oils to which hydrogen has been added to make them more solid. That process is why, for example, oil-based margarine can come in stick form like butter.

And New York state provided a natural laboratory to study the effects of abolishing these fats. Between 2007 and 2011, 11 counties in the state — most of them in the greater New York City area — banned restaurants from preparing food with partially hydrogenated oils. Using population estimates and state department of health data, a research team looked at the number of hospitalizations for heart attack or stroke in counties that implemented these laws compared to counties that didn’t.

What they found was that those hospitalizations declined across the board, but they declined more quickly in the counties that cracked down on trans fats. Those counties had a 6.2 percent lower rate of heart attacks and strokes combined a few years out from the laws’ beginning than did the counties that didn’t enact trans fat bans. The team published its findings Wednesday in JAMA Cardiology.

The researchers are careful to point out that the counties differed in some important ways — including lifestyle factors, demographics, and other public health measures on the books — but after controlling for those factors, the difference still remained.

For heart attacks alone, the decline was 7.8 percent, along with a 3.6 percent decline in stroke events alone.

The results show that trans fat restrictions are beneficial to public health, especially when people don’t always have enough information to make healthier choices themselves, said Rebecca Myerson, one of the study’s authors at the University of Southern California’s Schaeffer Center for Health Policy and Economics.

“Although there is already plenty of information out there about the [trans fat] content of packaged foods, at restaurants people didn’t know,” she said. “And now they don’t have to.”

Yasmin Mossavar-Rahmani, a professor of epidemiology and population health at Albert Einstein College of Medicine, was not involved with the study, but she finds the conclusions “heartening.”

Trans fat restrictions are “a low-cost ways of changing people’s habits,” she said.

But Mossavar-Rahmani also suggested that the findings might look different if the study were more representative of New York’s population.

“They weren’t able to look at the potential effect of racial and ethnic differences,” she said. “There could be differences in the rate of decline that might be genetic. I hope they can get a better handle on that.”

“Race was not well-measured in our data,” agreed Myerson, who handled the research team’s data analysis. “Our results line up well with the predictions,” she said. “I’m confident that within the bounds of the methods we used, the results would not change if we had included race in our model.

“But if there are differences between racial groups,” she added, “it would be interesting to see whether a national [trans fat] restriction could narrow that gap.”