How the Nurses’ Health Study Helped Americans Take the Trans Fat Out

In 2007, New York City (NYC) became the first US municipality to restrict trans fat use through a regulatory process in all foodservice establishments. After years of local policy change and accumulating evidence, in 2015, the US Food and Drug Administration (FDA) finalized its determination to remove the “generally recognized as safe” (GRAS) status for partially hydrogenated oils, the main dietary source of trans fat.¹ This action would remove virtually all nonnaturally occurring sources of trans fat from the US food supply. The Nurses’ Health Study (NHS) provided groundbreaking evidence that foods containing trans fat are particularly harmful, informing this dramatic nutrition policy change over the last decade.

FDA LABELING REGULATIONS

The NHS, a study of more than 120 000 women at the time of its initiation in 1976, added a food frequency questionnaire in 1980, including detailed questions to understand the types of fat consumed. This enhancement allowed researchers to assess levels of exposure to characteristics of the food supply (e.g., foods, nutrients) and associated health outcomes. Gathering information on women at a time when most health research involved men addressed a gaping research disparity, and provided information that would be critical to create well-informed, evidence-based public health initiatives.

The NHS was among the earliest long-term observational studies to examine the link between trans fat intake and risk of coronary heart disease (CHD). In 1993, utilizing data from more than 80 000 participants and four follow-up dietary assessments over eight years, Willett et al. described a 50% increase in CHD risk for women in the top quintile of trans fat intake compared with those in the lowest quintile of intake.² Hu et al. used NHS data to build on this finding in 1997 with research that landed a front page New York Times story and marked the beginning of a sea change in nutrition messaging: all fats are not the same, and trans fat is particularly damaging for cardiovascular health.³ In 2002, an Institute of Medicine report concluded that the consumption of any amount of trans fat increased risk of heart disease.⁴ Over time, research using NHS data highlighted the long-term impact of trans fat consumption, helping to maintain public attention to the problem. Analyses of the NHS became a critical component of the growing body of evidence that influenced local and national trans fat policy.

Copyright 2006, New York City Department of Health and Mental Hygiene. Reprinted with permission.

In 1993, the Center for Science in the Public Interest (CSPI), asked the FDA to require labels to describe the trans fat content of foods; CSPI followed this letter with a formal petition to the FDA. A decade later, the FDA proposed amending its labeling regulations to mandate that trans fat content be listed on the Nutrition Facts panel of packaged food, a change that took effect in 2006. The addition of trans fat content created an incentive for manufacturers to lower the trans fat content in foods, allowing motivated consumers to change purchasing patterns, and also provided crucial information that was needed for local policy action.

NEW YORK CITY HEALTH CODE AND BEYOND

The NYC Board of Health approved a Health Code amendment restricting restaurant trans fat use in December 2006, after a campaign to encourage voluntary reductions failed to demonstrate impact. By July 2008, all products used by NYC foodservice establishments were required to contain less than 0.5 gram of trans fat per serving, if any artificial trans fat was present. The restriction applied to all licensed foodservice establishments, including restaurants, school cafeterias, senior centers, and street-food vendors and was enforced by existing local Health Department restaurant inspectors. The percentage of restaurants using products with artificial trans fat for frying, baking, cooking, or in spreads dropped from 50% in 2005 to 1.6% in 2008 when the restriction took full effect.⁵ A study of 168 NYC restaurant locations, representative of 11 fast food chains, conducted in 2007 and 2009 found that average trans fat content in NYC fast food meals was substantially lower after the restriction.⁶ Purchases containing “0” grams trans fat almost doubled and the average trans fat content per purchase decreased by 2.4 grams to 0.5 gram.

Amending the Health Code to restrict trans fat in NYC restaurants was an innovative approach to address an important nutrition-related cardiovascular disease risk factor identified because of studies like the NHS. The Notice of Intention, proposing the trans fat restriction; the presentation to the NYC Board of Health members; and the Notice of Adoption,⁷ which the Board unanimously approved, referenced studies that used research based on NHS data, along with other trans fat research. Among the earliest studies that these sources relied on were the 1993 NHS findings by Willett et al. on trans fat intake and CHD among women.

Since NYC’s successful restriction of trans fat, more than 15 jurisdictions, including Philadelphia, Pennsylvania; Seattle, Washington; and the state of California, have used their authority to restrict trans fat in restaurant food. Local trans fat restrictions, along with changes in labeling and national media attention, made an impact: in 2012, the Centers for Disease Control and Prevention found that there was a 58% decline in blood levels of trans fatty acid between 2000 and 2009, using a national sample of White adults. However, local policy reliant on labeling information could only have limited impact because federal labeling requirements allow packaged foods with less than 0.5 gram trans fat to be labeled “0” grams trans fat. Federal regulation was needed to completely remove artificial trans fat from the food supply. In 2013, the FDA issued a tentative determination that partially hydrogenated oils were no longer GRAS, followed by a final determination in 2015.

In 2003, the World Health Organization recommended keeping trans fat intake very low in its expert consultation on diet, referencing research that relies on findings from the NHS. Prior to NYC action, Denmark had successfully regulated artificial trans fat, and the Canadian Trans Fat Task Force had issued a report recommending that trans fat content of foods be limited to specific levels.

INFORMING ACTION

NYC’s restriction of trans fat, along with other policy action described here, demonstrates public health advances informed by evidence drawn from the NHS on trans fat and CHD. Furthermore, the NHS is a unique contributor to the evidence base and to population-wide public health action because of its focus on women, a population that was not well represented in other studies at the time. Improving the nutritional content of food is an essential part of improving overall nutritional intake. Toward that end, the NHS has been, and we believe will continue to be, an important source of evidence to inform action.