Wholegrains and cardiovascular disease

Study finds blood pressure decrease in healthy participants

A brand new intervention study from the UK has found two serves of wholegrain foods a day can significantly lower cardiovascular disease risk in free-living, healthy middle-aged people, mainly by lowering blood pressure. Replacing white bread and refined breakfast cereal with just two slices of wholegrain bread and a cup of oats a day for twelve weeks was enough to reduce blood pressure and potentially reduce the risk of cardiovascular disease – one of Australia’s most costly and deadly diseases.

Two hundred and thirty three virtually healthy men and women aged between 40 and 65 were randomly sorted into one of three groups; refined grain group (control), wholegrain wheat, or wholegrain wheat + oats group. The authors designed this study to be practical and realistic for free-living individuals to achieve with little alteration to their usual lifestyle. Therefore, refined cereals and white bread where simply substituted for two slices of wholegrain bread and a cup of wholegrain breakfast cereal or a cup of oats and either two slices of wholegrain bread or a cup of breakfast cereal.

After only six weeks of the intervention, participants in both the wholegrain wheat and wholegrain wheat +oats group significantly decreased their systolic blood pressure by around 5mm Hg. This decrease is similar to the average reduction observed in twenty seven pharmacologic trials and could translate to a 15% decrease in the risk of coronary artery disease and 25% decrease of stroke. Using wholegrain foods to help maintain healthy normal blood pressure has worthwhile benefits, including a reduction in drug-related side effects of blood pressure lowering medication and significant cost savings for Australia’s healthcare system. The other great thing about this study is that the wholegrain products used are similar to those widely available from Australian supermarkets in contrast to supplements or specifically formulated foods.

The study did not show a favourable effect for cholesterol reduction or any other blood lipids, including inflammatory markers. These results are similar to that of the recently published sixteen week WHOLEheart study involving just over three hundred overweight adults. As suggested in the WHOLEheart study the findings of both these intervention trials do not question the efficacy of increasing wholegrain foods as a public health measure for disease risk reduction, but instead highlight some of the limitations associated with randomised controlled trials when investigating complex food synergies and nutrients, especially in otherwise healthy individuals. Lipid-lowering interventions commonly fail to show an effect in subjects with normal lipid levels, which was the case in this intervention and the WHOLEheart trial. Perhaps the results would have been even more favourable for all biomarkers of cardiovascular disease in an unhealthy population.

Although the exact mechanisms by which wholegrains can reduce blood pressure still remain unclear, the results of this study provide solid evidence for recommending the consumption of two serves of wholegrain foods a day to help reduce the risk of cardiovascular disease. Australian dietary guidelines recommend Australians eat 4+ serves of grain-based foods a day (including breads, breakfast cereals, rice and pasta). At least half of your serves should be wholegrain. Commonly available wholegrain foods include wholegrain bread and breakfast cereals, oats, brown rice, wholegrain pasta, popcorn, wholegrain crispbreads and rice cakes/crackers.

Sources:

Effect of increased consumption of wholegrain foods on blood pressure and other cardiovascular risk markers in healthy middle aged persons – a randomised controlled trial. Tighe P and Duthie G et al. Am J Clin Nutr. 2010. Published ahead of print.