Removing industrial trans fat from foods
(Published 15 April 2010)
Cite this as: BMJ 2010;340:c1826
- Dariush Mozaffarian, assistant professor of medicine and epidemiology,
- Meir J Stampfer, professor of medicine and epidemiology
As part of a 12 step manifesto to better public health, the UK Faculty of Public Health and Royal Society for Public Health proposed that consumption of trans fatty acids (TFAs) should be virtually eliminated in the United Kingdom by next year.1 They noted that, “it has been proven that industrially-produced TFA can damage health,” “there is no known safe level of consumption,” and “banning TFA from foods is a relatively easy way to help protect the public.”1 Are these arguments sound?
TFAs are created when vegetable oils are partially hydrogenated to convert large numbers (typically 30-60%) of naturally occurring cis unsaturated double bonds into trans unsaturated double bonds. A high TFA content provides physical and chemical properties that are attractive to food manufacturers, including the creation of relatively inexpensive (compared with animal derived fats) solid or semi-solid fat. The process also destroys labile omega-3 acids (α-linolenic acid), and this reduces the propensity for fats to become rancid, increases shelf life, and optimises deep frying applications. Use of partially hydrogenated vegetable oils has increased since the 1950s because of these commercial advantages and since the 1960s because of public health recommendations to replace saturated fats (such as butter and lard) with alternatives.
Because mammals and most edible plants synthesise only cis double bonds, TFAs are rare in the natural human diet. Ruminant TFAs, found in meat and milk from cows, sheep, and goats and formed by the animal’s gut flora, are the main natural source. Compared with industrial TFAs, ruminant TFAs contain some different isomers and are generally consumed in lower amounts (about 0.5% of total energy intake). At the low levels consumed, ruminant TFAs have no apparent major adverse health effects.2 3 For these reasons, the 12 step manifesto sensibly focuses on eliminating industrially produced TFAs.
Total and industrial TFA consumption adversely affects several cardiovascular risk factors. In randomised trials, TFA consumption lowers high density lipoprotein cholesterol and raises low density lipoprotein cholesterol, triglycerides, the total cholesterol to high density lipoprotein cholesterol ratio, the apolipoprotein B to apolipoprotein A1 ratio, and Lp(a) lipoprotein.2 3 4 TFAs may also promote systemic inflammation, endothelial dysfunction, insulin resistance, visceral adiposity, arrhythmias, and the development of diabetes.2 3 4 Not surprisingly, TFA consumption is associated with a substantial risk of heart disease events, including myocardial infarction and death from coronary disease. This risk is far higher per calorie consumed than for any other dietary macronutrient, including saturated fat.4
Risk occurs even at low consumption. In developed nations, the average population consumption of TFAs is often 2-4% of total energy intake.5 Major sources of industrial TFAs include baked goods, deep fried foods, packaged snacks, margarines, and shortening.2 Paradoxically, consumption in developing nations may be even higher from cooking fat used at home or by street vendors, especially in lower income populations, because partially hydrogenated fats are often cheaper or even government subsidised in many regions.6 7 Notably, average TFA consumption in any nation or region masks important subgroups of the population who are eating much more than the average, including people eating as much as 6-8% of total energy intake as TFAs.
Public campaigns, food labelling, and legislative policies may reduce TFA consumption. It recently became mandatory to include the TFA content on food labels in the United States and Canada, and this led some manufacturers to reduce or eliminate TFAs in some products.8 However, many foods still contain industrial TFAs, especially in restaurants, schools, cafeterias, coffee shops, and bakeries, where food labels are not mandatory. Comprehensive education to encourage such businesses in New York City to voluntarily reduce the use of partially hydrogenated fats was unsuccessful.9 Legislative strategies have been more successful than labelling or education. In both Denmark and New York City, legislation has effectively eliminated industrial TFAs; for example, in New York restaurants the prevalence of use of industrial TFAs has declined from 50% to less than 2%.9 10
What are the potential downsides to legislation? Concerns have been raised that such approaches might increase the use of saturated fats as a replacement; fail because of insufficient supply of appropriate replacement fats and oils; or reduce food availability, taste, or affordability. None of these concerns have been realised in Denmark or New York City. Reformulations that replace industrial TFAs with cis unsaturated fats would maximise health benefits; nevertheless, any reformulation removing partially hydrogenated fats—even if they were replaced with animal fats or tropical oils—would produce health benefits.4 Furthermore, in practice, manufacturers and restaurants generally remove TFAs from foods without corresponding increases in saturated fat.8 9 Thus, we have no evidence that such legislation leads to harm from increased saturated fat. In addition, the experiences in Denmark and New York City show that adequate replacement fats and oils are available.9 10 Seed developers, farmers, and oil processors seem to be responsive to changing demand. As demand for healthier fats and oils continues to increase, global supply and quality will probably continue to rise, while at the same time the partial hydrogenation of oils decreases. Finally, evidence suggests that mandated TFA reformulations do not appreciably alter prices, sales, taste, or availability of foods.9 11 Indeed, the change is essentially invisible to consumers.
Because industrial TFAs are not part of our natural food supply, their regulation does not alter individual consumer choice, being similar to regulations that prohibit adulterated foods. With increasing supplies of alternatives, the commercial and cost advantages of partially hydrogenated oils are now small. Thus, removing industrial TFAs is one of the most straightforward public health strategies for rapid improvements in health. On the basis of current disease rates,12 a strategy to reduce consumption of industrial TFAs by even 1% of total energy intake would be predicted to prevent 11 000 heart attacks and 7000 deaths annually in England alone.2 A national, rather than regional, policy would also reduce the burden on manufacturers and restaurants and, importantly, protect all susceptible populations including children and socioeconomically disadvantaged subgroups. Action by the UK might also produce larger benefits by inspiring other developed and developing countries to take similar measures to protect their citizens’ health.
Cite this as: BMJ 2010;340:c1826
Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare that: (1) DM and MJS have no support from any company for the submitted work; (2) DM has served as a consultant for Nutrition Impact, which might have an interest in the submitted work; (3) their spouses, partners, or children have no financial relationships that may be relevant to the submitted work; and (4) they have no non-financial interests that may be relevant to the submitted work.
Provenance and peer review: Commissioned; not externally peer reviewed.