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Dietary risk factor modification : Make it tasty!

Comment by Nicolle Kraenkel, EACPR Exercise, Basic and Translational Research Section


Diet affects a large part of lifestyle-related cardiovascular risk. While previous studies have addressed individual components, such as unsaturated fatty acid intake, or carbohydrate content, a better control of cardiovascular risk factors might be achieved by combining several such strategies.

The recent study by Jenkins et al. analysed the effects of complex dietary intervention, comparing a test group aiming for low-glycaemic load achieved by increased intake of canola oil, which is rich in alpha linoleic acid (ALA) as well as monounsaturated fatty acids (MUFA) with a control group, whose diet featured an increased wheat fibre-content. The study included 141 well controlled and –medicated participants, of which 119 completed the study.

Both dietary interventions achieved significant improvements of HbA1C, lipid parameters (total cholesterol, LDL-C, triglycerides, and total cholesterol HDL as well as LDL:HDL ratios) and vascular reactivity, with a significantly greater effect in the test group, following a diet enriched in ALA and MUFA with the aim to displace a part of the dietary carbohydrates and thus achieving a lower glycaemic load than in the control group focusing only on enhanced intake of wheat fibres. As a consequence, cardiovascular risk as given by the Framingham risk score, was reduced in both groups, but significantly more in the test group than in the control group.

While in pre-clinical, and to some degree also in clinical studies we can try to investigate single diet components, in daily practice, our dietary behaviour is extremely complex, especially over the long time courses which need to be addressed for effective cardiovascular prevention. This aspect might have huge potential for population-wide prevention, as several metabolic principles can be addressed, but it may also affect long term adherence in daily life.

As complex as the metabolic changes are also the mechanisms potentially involved in the lowering of cardiovascular risk by the various dietary strategies. In the test group, lipid parameters, HbA1C, as well as vascular reactivity improved as compared to baseline, and to a greater extent than in the control group ingesting only a high-wheat fibre diet without definition of ALA or MUFA intake. Those observations are in agreement with multiple previous studies describing the beneficial effects of ALA and MUFA, along with in vitro and in vivo investigation of responsible mechanisms.

While fibres from many cereals, such as oats or barley reduce cholesterol and post-prandial glycaemia, this effect could not be shown for wheat fibres. An earlier study, however, could show an improvement in insulin resistance (1). The authors therefore speculate that improved insulin together with the improved endothelial function they were able to demonstrate, contribute to the lowering of cardiovascular risk in people adhering to the high wheat-fibre diet.

As shown previously for other treatments, the benefit of the dietary intervention on HbA1C improvement was significantly greater in those participants with BP>130mmHg, as compared to those with lower BP. However, even in the well-treated participants, with BP, HbA1C and LDL levels close to target, the interventions were successful.

Thus, complex dietary interventions covering the intake of omega 3 fatty acids and unsaturated fatty acids together with a lowering of glycaemic load can indeed yield an additional favourable effect on cardiovascular risk on top of pharmacological intervention.

If this can be achieved by palatable dietary supplements as well as in combination with dietary education, it might even improve adherence rates in the general population.

(1) Effect of whole grains on insulin sensitivity in over- weight hyperinsulinemic adults.
Pereira MA et al.
Am J Clin Nutr 2002;75:848–855