The truth about fatty acids

Saturated fatty acids are widely considered a villain in heart-related diseases because they have long been blamed for raising bad cholesterol levels. Early studies have even suggested a link between saturated fatty acid intake and ischemic heart disease, which causes reduced blood supply to the heart and kills more than seven million people worldwide each year.

Yvonne van der Schouw at the Julius Center for Health Sciences and Primary Care in the Netherlands and co-workers¹ have now put this long-held belief under scrutiny. They assessed the lifestyle, diet and physical status of 35,597 Dutch people from the European Prospective Investigation into Cancer and Nutrition study; one of the largest cohort studies ever conducted on the relationships between diet, cancer and other chronic diseases. The information for the study was obtained through general questionnaires, food-frequency questionnaires and physical examination. The team then tracked the fate of these people, with special attention paid to the number of ischemic heart disease cases, over the course of 12 years.

In total, Schouw and her team discovered 1,807 cases of ischemic heart disease over the study period, of which 158 (8.7%) were fatal. After adjustment for age, gender, body mass index, education level, physical activity, smoking/alcohol consumption patterns and a host of other potentially important factors, they found that a higher intake of saturated fatty acids resulted in a 17% reduction of ischemic heart disease risk. In contrast, the substitution of saturated fatty acids with total carbohydrates or animal proteins led to higher ischemic heart disease risks. In particular, high-glycaemic-index carbohydrates (those that raise blood glucose levels higher than others) appeared to have the largest impact.

The researchers also examined how saturated fatty acids of different chain lengths and from different food sources might affect ischemic heart disease risk. They observed slightly lower ischemic heart disease risks in people who consumed more short-to-medium-chain saturated fatty acids and whose sources of saturated fatty acid intake were from butter, cheese, milk and dairy products.

Schouw and her team are uncertain why the results from their study are so different to those from other studies. One possibility is that their study only considered a limited range of saturated fatty acids. Perhaps, in populations that consume a wider range of saturated fatty acids, the relationships found are opposite.

The researchers believe there remains much to be learned from the data. Their findings on the associations between ischemic heart disease risk and saturated fatty acids of different carbon chain lengths will open avenues for further research.

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