The detrimental effect of trans isomers from dietary unsaturated fatty acids on coronary heart disease has been based on observational studies and theoretic models. Oomen and colleagues used the observed decline in dietary consumption of trans fatty acids in the Netherlands to demonstrate the strong link between these dietary components and the risk of heart disease.
During the 1980s, the consumption of trans fatty acids in the Netherlands declined significantly, mainly because of the reduction of these compounds in margarines. The trans fatty acid content of margarines decreased from a maximum of 50 percent to the current 1 to 2 percent as “soft” products took the place of traditional hard margarines. During this time, 878 men from a Dutch town became involved in the Seven Countries Study of coronary heart disease in men who were born between 1900 and 1919. In 1985, the 367 survivors plus 711 other men of the same age living in the same town were asked to participate in the study. Men with angina pectoris or previous myocardial infarction were excluded from the study. Extensive medical and dietary information was collected from the remaining 667 men in 1990 and 1995. Blood samples were taken for cholesterol and high-density lipoprotein measurements, and blood pressure, cigarette smoking status, diabetes status and cardiac risk profile were established. Through national records, all participants were monitored for death from coronary heart disease or occurrence of nonfatal myocardial infarction. Only three participants were lost to follow-up during the 10-year study. All reported events were verified by hospital records and interviews with relatives.
The mean daily intake of trans fatty acids fell from 10.9 g in 1985 to 4.4 g in 1995. Men with high intake also tended to have high total fat and cholesterol intake and to be smokers. High intake of trans fatty acids was inversely associated with the daily intake of carbohydrates, protein, alcohol and use of vitamin supplements. During the 10 years of follow-up, 49 cardiac deaths and 49 other significant coronary events were documented (affecting 15 percent of the baseline population). After adjusting for age, body mass index, smoking and dietary covariates, trans fatty acid intake was positively associated with increased risk of coronary heart disease events.
The authors calculate that the risk of dying from a coronary event increased by about one third for each 2 percent of dietary energy from trans fatty acid intake. They estimate that the observed decrease of 2.4 percent in trans fatty acid intake may have contributed to a 23 percent decline in coronary deaths (about 4,600 men per year) in the Netherlands during the study.