Dr. Kumar’s Take:
This is not a study of what individual people ate. It is a natural experiment in New York State, where 11 highly urban counties restricted trans-fatty acids between 2007 and 2011, and researchers compared hospital admissions for heart attack and stroke in those counties against 25 similarly urban counties without restrictions from 2002 to 2013. Three or more years after the restrictions took effect, the restriction counties had a 6.2% larger decline in combined heart attack and stroke admissions than the comparison counties, beyond the downward trend both groups already shared. I find that persuasive because the effect showed up at the level of whole populations, in hard admission data, after a policy change rather than after a survey about diet. Trans fats are not a fat you need to balance in your diet. They are a fat worth removing.
Note:
This study was published in JAMA Cardiology in 2017. It is observational, so it cannot prove that the restrictions themselves caused the drop in admissions. What it can show is that the counties with trans-fatty acid restrictions saw cardiovascular admissions fall further than similar counties without them.
Key Takeaways:
✔ Three or more years after implementation, restriction counties had an additional 6.2% decline in combined heart attack and stroke admissions (95% CI, -9.2% to -3.2%; P < .001).
✔ Heart attack admissions drove the result, with an additional 7.8% decline (95% CI, -12.7% to -2.8%; P = .002).
✔ The decline in stroke admissions, at 3.6%, did not reach statistical significance (95% CI, -7.6% to 0.4%; P = .08).
✔ The benefit took time. The decline only reached significance 3 or more years after restrictions were implemented.
Actionable Tip:
My advice is to treat trans fats as something to eliminate rather than moderate: read labels, skip anything listing partially hydrogenated oils, and be aware that food prepared in places without such restrictions may still contain them.
Brief Summary:
Researchers ran a retrospective pre-post study of New York State residents hospitalized for heart attack or stroke from 2002 to 2013, using the state health department’s Statewide Planning and Research Cooperative System along with census population estimates. Trans-fatty acid restrictions were adopted in 11 counties between 2007 and 2011, all of them highly urban. Counties of similar urbanicity without restrictions served as the comparison group. In 2006, the year before the first restrictions took effect, there were 8.4 million adults (53.6% female) in the restriction counties and 3.3 million adults (52.3% female) in the 25 comparison counties. Three or more years after implementation, the restriction populations had significantly fewer heart attack and stroke admissions than temporal trends alone would predict.
Study Design:
- Type: Retrospective observational pre-post study, analyzed as a natural experiment with difference-in-differences regression
- Population: Residents of 11 New York State counties with trans-fatty acid restrictions and 25 comparison counties without them, men and women, hospitalized for heart attack or stroke
- Period: 2002 to 2013, with restrictions implemented between 2007 and 2011
- Data Collection: New York State Department of Health Statewide Planning and Research Cooperative System and census population estimates
- Outcome Measured: Composite of heart attack and stroke events based on primary discharge diagnostic codes, with admission rates calculated by year, age, sex, and county of residence
- Adjustments: Fixed effects by county and year, linear time trends by county, plus adjustment for age, sex, and commuting between restriction and nonrestriction counties. Comparison counties were matched on urbanicity using US Department of Agriculture Economic Research Service urban influence codes.
- Analysis Period: December 2014 through July 2016
Results:
- Combined heart attack and stroke admissions fell an additional 6.2% in restriction counties 3 or more years after implementation, beyond temporal trends (95% CI, -9.2% to -3.2%; P < .001).
- Heart attack admissions fell an additional 7.8% (95% CI, -12.7% to -2.8%; P = .002).
- Stroke admissions fell 3.6%, which did not reach statistical significance (95% CI, -7.6% to 0.4%; P = .08).
- The decline reached statistical significance only 3 or more years after restrictions were implemented.
- The populations compared were large: 8.4 million adults in restriction counties and 3.3 million adults in comparison counties as of 2006.
How Trans Fats Harm the Heart
Trans fats are created when vegetable oils are turned into solid fats through a process called partial hydrogenation, and they have deleterious cardiovascular effects. The value of this study is that it moves the question from the laboratory to the population level: when a group of counties restricted these fats, hospital admissions for cardiovascular events in those counties fell further than in comparable counties that did not. The US Food and Drug Administration planned a nationwide restriction in 2018, and the New York experience is one of the clearest signals available on what that kind of policy does to real admissions.
Related Studies and Research
L-Carnitine and Heart Health: Investigates how L-carnitine may influence cardiovascular risk through effects on fatty acid metabolism.
CoQ10 and Cardiovascular Health: Highlights CoQ10’s role in supporting heart function and mitochondrial health.
Linoleic Acid and Heart Disease: Examines the cardiovascular effects of polyunsaturated fats as a contrast to trans fats.
PURE Study: Dietary Fats, Carbs, and Heart Health: Discusses findings on various fats and carbohydrates in relation to heart disease.
Frequently Asked Questions
What are trans fats?
Trans fats are a type of fat made by adding hydrogen to liquid oils to make them solid, a process called partial hydrogenation. They have deleterious cardiovascular effects, which is why counties and countries have moved to restrict them.
What did this study actually measure?
It measured hospital admissions for heart attack and stroke, not what anyone ate. The exposure was living in a county where trans fats were restricted, and the comparison was living in a similarly urban county where they were not.
Why did the effect take years to appear?
The decline reached statistical significance only 3 or more years after restrictions were implemented. Cardiovascular risk accumulates over years, so a change in the food supply would not be expected to show up in admission counts right away.
Does this prove trans fat restrictions save lives?
No. This is an observational study, so it shows association rather than causation. It does show that populations with restrictions experienced fewer cardiovascular events than populations without them, beyond the temporal trends both groups shared.
Conclusion
Restricting trans fats was followed by a measurable drop in hospital admissions for heart attack and stroke across millions of people. That is about as close to a real-world test of this policy as you are likely to see. In your own kitchen, the takeaway is simple: read labels, avoid partially hydrogenated oils, and choose whole, fresh options whenever possible.
