Saturated fats and cardiovascular health: what to believe?

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The Annals of Internal Medicine recently published a study summarizing the evidence about associations between fatty acids and coronary disease which sparked lots of debate and discussions among the nutrition scientific community. The meta-analysis conducted by R. Chowdhury & Al. indeed concluded on a lack of significant association between the major types of fatty acids, in particular saturated fatty acids, and coronary heart disease (CHD), with the exception of an adverse link with trans fatty acids. This conclusion, widely covered in the media, openly challenged the long-term dietary advice to limit saturated fats in the diet and obviously led to expected and legitimate questions by consumers. So how much saturated fat is acceptable and what food should one consume?

The effects of saturated fats on health have been largely debated over the past years by scientists and there is a consensus to moderate their consumption while recognizing that a bit of saturated fats belong to a healthy and balanced diet. The recommended maximum intake of saturated fat in most dietary guidelines is maximally 10% of total daily energy intake whereas intake of polyunsaturated fatty acids (both omega 6 and 3) is advised at 6-11% of daily energy.  In most countries however, people eat too much saturated fats and too little polyunsaturated fats. Dietary advice from the past has put much emphasis on the need to lower saturated fat intake and total fat intake as such. Now we know that what replaces saturated fat in the diet could be more important than just reducing it. Drs. Walter Willett, Francks and Meir Stampfer from Harvard University emphasize this fact when they openly reply to the recent study: “A central issue is what replaces saturated fat if someone reduces the amount of saturated fat in their diet.

If it is replaced with refined starch or sugar, which are the largest sources of calories in the U.S. diet, then the risk of heart disease remains the same. However, if saturated fat is replaced with polyunsaturated fat or monounsaturated fat in the form of olive oil, nuts and probably other plant oils, we have much evidence that risk will be reduced.” The Chowdhury study eludes the question of what to replace saturated fats with and relies on incomplete evidence which should therefore be interpreted with caution.

Alice H. Lichtenstein, a nutritional biochemist at Tufts University, said that “it would be unfortunate if these results were interpreted to suggest that people can go back to eating butter and cheese with abandon,” citing evidence that replacing saturated fat with foods that are high in polyunsaturated fats – instead of simply eating more carbohydrates – reduces cardiovascular risk.

This appeal to caution regarding changing our dietary habits was echoed by one of the co-authors of the study, Emanuele Di Angelantonio of the University of Cambridge, who said: “We are not saying the guidelines are wrong and people can eat as much saturated fat as they want. We are saying that there is no strong support for the guidelines and we need more good trials.” He added that the main problem is that the paper was “wrongly interpreted by the media.

Most nutrition experts and health associations, such as the European Heart Network, issued statements stressing that “this new study does not warrant a change in guidelines with respect to reducing the intake of saturated fats and replacing them with poly-unsaturated fats, ideally with more omega-3 polyunsaturated fats.” (EHN) International scientific nutrition recommendations still recommend to moderate our intake of saturated fats and to increase our consumption of poly-unsaturated fats (see for example World Health Organisation, the European Food Safety Authority, Nordic Nutrition Recommendations, German Nutrition Recommendations, British Recommendations from NHSDutch Nutrition Recommendations, French Nutrition Recommendations)

Regarding giving clearer and unbiased advice to consumers about food products, we agree with Prof Tom Sanders of King’s College London when he says: “It really is time that we moved away from focusing on individual components of diet like saturated fat, salt and sugar and moved into better describing diets that we know are associated with a lower risk of heart disease such a Mediterranean dietary pattern or a vegetarian dietary pattern. Studies like this just cause a lot of confusion and undermine sensible dietary advice given in the UK which has had some degree of success in reducing heart disease in the UK. Indeed, death rates from cardiovascular disease have fallen by 55 per cent since 1997 despite the increase in obesity so we must be getting something right.”

It takes many studies and much evidence to reach new scientific conclusion as to what food and how much to consume. In diets, as in the rest, the key principle to keep in mind is that of moderation and balance. The margarine sector welcomes new scientific insights and has proved in the past its flexibility and willingness to embrace innovation to make healthier products but we also agree with the heart associations, dieticians and experts overall that more intervention studies are needed before drawing clear conclusions and changing our nutrition habits.

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