This is a question addressed in the latest (June 2010) issue of the American Journal of Clinical Nutrition (AJCN).
For many years now the key nutritional advice, particularly for those at high risk of cardiovascular disease, has been to reduce saturated fatty acids (SFA) and replace these with complex carbohydrates. As a result, reports Frank Hu in his recent AJCN editorial, a substantial decline in energy intake from total and saturated fatty acids has occurred in the United States. At the same time, this has spurred an increase in consumption of refined carbohydrates and added sugars.
Is this dietary shift contributing to the twin epidemics of diabetes and obesity?
The answer to this question may be ‘yes’! In a paper published in the June 2010 issue of the AJCN, by Jakobsen et al, the authors used substitution models to investigate the risk of myocardial infarction (MI) associated with a higher intake of carbohydrate and a lower intake of saturated fatty acids. Carbohydrate values with a different glycaemic index (GI) were also investigated. This large Danish cohort study suggests that replacing SFA with carbohydrate with a low GI is associated with a lower risk of MI, but replacing SFA with a high GI food is associated with a higher risk of MI. This study is notable for its size (involving 53,664 men and women) and long duration of follow-up (12 years). This is the first epidemiological study to investigate specifically the effects of substituting SFA with carbohydrate foods of different GI and provides direct evidence that substituting high GI carbohydrate for SFA actually increases risk of IHD.
So, it seems the answer to the question — what’s worse, sugar or fat, is that sugar is actually worse. It seems we should be focussing our attention more on reducing our intake of sugary and high GI foods (such as white bread and potatoes), as well as fat and SFA, and replacing these foods with low GI alternatives.
We also need to recognise that the term ‘complex carbohydrate’ is not a useful one any more in terms of characterising carbohydrates. It is much more useful to look at the type of fibre present, the amount of processing, the GI and the GL (glycaemic load). Our focus should be on reducing our intake of highly processed carbohydrates such as white bread and having, instead, more wholegrains, pulses and nuts.