A complete ban on trans fat within the human diet may decrease the number of heart attacks and strokes in the American population, a recent Yale-led study has found.

Eric Brandt, a clinical fellow at the Yale School of Medicine, led the research, which observed changes in hospital admissions for myocardial infarction and strokes in New York counties that restricted trans fat in eateries prior to 2012. The results indicated that since the restrictions, combined admissions for MI and stroke declined by a statistically significant 6.2 percent while admissions for MI alone declined by 7.8 percent.

This significance goes beyond the secular trend of decreasing MI and stroke cases observed in counties that did not have such trans-fat restrictions. The study, published on April 12 in the Journal of the American Medical Association Cardiology, substantiates the claim that policies restricting trans fat are effective on a population level, supporting the 2015 decision by the U.S. Food and Drug Administration to introduce a near-complete nationwide ban on foods containing trans fat.

“In this study’s context, the restrictions on trans fat led to a decline in heart attacks and strokes,” Brandt said. “So, we can look forward at more national bars and expect that there will be a similar, if not greater, decline when this policy goes national because the regulations going into next year will be more broad than the ones that were implemented in New York.”

Trans fat, or trans-fatty acids, still compose a significant part of people’s diets and has been proven to be associated with cardiovascular disease, according to Rebecca Myerson, a professor of health economics at the University of Southern California and a co-author of the study.

Myerson added that trans fat, often made by modifying unsaturated fats with trans double bonds, was used by many food companies to increase shelf life and even improve the texture of some food items.

In 2006, the FDA required trans fats to be included in nutrition labels, and after many published studies indicating the danger of trans fats, the federal agency announced in 2013 that it will take action regarding the artery-clogging artificial fatty acids.

However, as the FDA revoked its “Generally Recognized As Safe” classification for partially hydrogenated oils containing trans fat in 2015, companies are now nearing the end of their three-year compliance period. Brandt said that the large amount of clinical evidence of individual-level harm done by trans fat led to this call by the FDA. Even so, there was initially some opposition to this public policy, with New York being called the “nanny state.”

This retrospective observational study compared New York counties in which trans fat is banned to counties in which it is not, controlling for urbanicity and traffic data. It used data from New York State Department of Health’s Statewide Planning and Research Cooperative System, according to the study paper.

“One of the issues with these studies is that you have to wait several years until you have the data. Since New York was the first state to impose such restrictions, it gave us the necessary data without lagging the research,” said Marcelo Perraillon, a professor at the Colorado School of Public Health and a co-author of the study.

He explained that although a randomized clinical trial was impossible for this study, the control group — the counties similar to the population “exposed” to the county-level trans-fat ban — were used to give relatively accurate data of the secular trend involving the decline in MI and stroke rates across the country.

“In this case we know this is a public policy that was well-implemented with a very high level of compliance,” Brandt said. “And this helps to show that when a public policy is well-implemented and well-thought-out, it can have a measurable and good effect on the population.”

He also noted that he hopes this research can help decrease any obstruction to the implementation of the national ban in 2018, “given we know what a great effect it can have on the whole United States.”

Perraillon agreed on the potential benefits of the new national policy, although he qualified the implications of this research due to the study’s observational nature.

He said that although it is clear trans fats are not good for human health, many consumers are not aware of the trans-fat contents of foods they purchase. Perraillon added that for this reason, avoiding such “blind spots” by banning trans fat was a favorable policy.

Myerson noted, however, that because the study was observational, she doubted whether it alone could support the introduction of trans-fat bans everywhere.

“Unless you have randomized data and the randomization works great, you always have concerns about the data. And I think that that’s one of the dangers of relying too much on one study,” Myerson said.

Use of partially hydrogenated oils will only be permitted under FDA approval after June 18, 2018.