The promise and challenges of population strategies of prevention

In public health, we are concerned with improving the health of populations. When considering prevention strategies, we have to decide between a population strategy and a high-risk strategy. The population strategy aims to shift the distribution of a risk factor in the entire population whereas the high-risk strategy targets individuals in the population who are at highest risk of disease and might benefit most from prevention. A population-wide prevention strategy is often easier to implement as high-risk individuals do not have to be identified and targeted and may be more successful because it does not require behaviour modification and can be maintained indefinitely if appropriate. If a risk factor is well-established as causing disease, is difficult to control or modify on an individual level, and a shift of its distribution in the population does not move some people who are at low risk pre-intervention to a high risk post-intervention, a population strategy is the method of choice. The elimination of artificial trans fatty acids from the food supply is a perfect example of a population strategy—and long overdue. The detrimental effects of trans fat on human health are well established, avoidance of foods with trans fat is difficult for most individuals because few read and understand food labels and the hardened vegetable oils are hidden in many prepared dishes, and there is no known disadvantage to health from eliminating trans fats altogether. Trans fatty acids result from partial hydrogenation of vegetable oils and are popular among food manufacturers because they are inexpensive, increase shelf life time of processed foods and make fried and baked products such as French fries and cookies crispy. However, trans fatty acids increase low-density lipoprotein and lower high-density lipoprotein thereby promoting arteriosclerosis even at low levels of intake. The New York City Department of Public Health is exemplary in the United States in being proactive about banning the use of the artery-clogging fats in restaurants, as described in this issue of IJE. As of July 1, 2008, restaurants are required to clear artificial trans fat from all their menu items. A similar ban was announced on July 25, 2008, for the state of California when Governor Arnold Schwarzenegger signed a bill to phase out trans fats in restaurants and retail baked goods by 2011. The beauty of a ban of the bad oils is that the consumer does not have to worry about their intake, hence difficult to accomplish behavioural changes are not required. Of course, this only applies to meals consumed in restaurants, while foods sold in manufacturer-sealed packages are exempt. Optimally, the hardened fats should be eliminated from the entire food supply. Can this be accomplished? Denmark set the standard making it illegal for any food to have42% trans fat— offenders may face jail charges. The ban that went into effect in January 2004 has forced food manufacturers to be creative. A few years ago, McDonald’s claimed they could not reduce the excessively high trans fat content of their French fries without compromising their taste; but in Denmark—and now also in New York City—McDonald’s French fries are just as crispy with <0.5 g of fat per serving. There is no good reason to add an artificial diseasepromoting substance to our food supply. Manufacturers and food suppliers must realize that by adding partially hydrogenated oils or vegetable shortening to their products they promote premature disease and death among their customers—not an easy moral burden to carry. Governments may have to take action to protect people’s well-being if the quest for profit trumps responsibility on the suppliers’ side. But there is no free lunch. The required listing of trans fat contents on food labels has lead some manufacturers to replace them with naturally hard tropical oils, such as palm, palm kernel or coconut oil. Palm oil is one of the most widely produced edible oils. While these tropical oils do not contain artificial trans fatty acids, they are naturally very high in saturated E-mail: kmichels@rics.bwh.harvard.edu 1 Department of Obstetrics, Gynecology and Reproductive Biology, Obstetrics and Gynecology Epidemiology Center, Brigham and Women’s Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA. 2 Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA. Published by Oxford University Press on behalf of the International Epidemiological Association