Whole grains and public health

Whole grains consist of the entire grain, and, unlike refined grains, they still contain bran, and germ, which are rich in dietary fibre and micronutrients. Whole grains were once neglected by researchers in favour of studies on dietary fibre, which found that cereal fibres were particularly healthy.As cereal fibres are found in whole grains together with micronutrients and phytochemicals, the focus of research shifted towards observational studies of whole grain intake. A large body of evidence on whole grains in relation to health outcomes has accumulated over the past 10 or 15 years. In a linked article, Aune and colleagues (doi:10.1136/bmj.i2716) report on their meta-analysis of 45 cohort studies, showing that a higher intake of whole grains is associated with a lower risk of cardiovascular disease and total cancer and all cause and disease specific mortality. Several mechanisms could explain the association between intake and a lower risk of major diseases and death. Whole grains have beneficial effects on glucose-insulin homeostasis, blood lipids, and gastrointestinal health. The new meta-analysis, however, has several weaknesses, including poor information on the assessment of whole grain intake in many of the included studies and few studies for some endpoints such as mortality from diabetes and infectious diseases. Future studies should improve the assessment of whole grain intake by reporting intakes in a similar way, using biomarkers to track compliance in randomised trials, and using validated assessment methods in observational studies. We still need more and better research on the biological mechanisms of health effects and the contribution to health of different grain types. For instance, studies suggest that whole grain oats and rye might be more beneficial than whole grain wheat in relation to cardiovascular disease. In most countries, cereals are a major energy source, and surprisingly little attention has been paid to the quality of cereals in dietary recommendations—that is, whether they are refined or “whole.” National guidance in Scandinavian countries recommends a whole grain intake of 75 g/day per 10 MJ. UK guidance is much less specific, with advice to choose “whole grain, brown or high fibre varieties whenever you can.” Currently, the whole grain intake in the UK is far below the intake recommended in Scandinavian countries (fig 1).