Whole grains are cereal grains that contain the original material found in whole unprocessed plants. This includes all the fibre, vitamins and minerals. In contrast, refined grains are processed during manufacture and some of the germ and most of the bran layer is removed. This causes a substantial loss of the fibre and the vitamins and mineral content of the cereal grain, although the starch levels remain similar between pre- and post-processing. Evidence shows that consumption of whole grains confers significant health benefits compared to refined grains. The exact reason for this is not fully clear, but evidence suggests it is mainly as a result of the higher fibre content of the whole grains. In particular, whole grains may cause improvement in blood chemistry relating to weight gain and cardiovascular disease and this may relate to the favourable metabolic action of fibre to control blood sugar levels and improve glycaemic control. However, there is some variability between different cereal grains in this respect.
Of all the whole grain cereals, oats appear to have the most beneficial effects on blood cholesterol. This may relate to the high levels of soluble fibre in oats which contains a substance called beta-glucan.
On one study, a group of researchers analysed the previous research that had been performed on whole grain cereals in a meta-analysis. This involved analysing all the previous studies that had compared the metabolic outcome of whole grain versus refined grain consumption on changes in blood cholesterol levels. A total of 24 studies were included in the meta-analysis. The results of the analysis showed that whole grain cereal consumption significantly decreased low density lipoprotein (LDL) cholesterol and total cholesterol in healthy adults, but did not lower high density lipoprotein (HDL) cholesterol or triglycerides. Of the cereal grains investigated, whole grain oats had the most beneficial effects. That these effects were seen in otherwise healthy adults suggests that the changes may be even more pronounced in those with elevated levels of cholesterol. Whole grain oats are an effective way to lower cholesterol levels and may have significant health effects when incorporated into a high quality diet.
While oats may have the most beneficial effects on blood cholesterol of all the cereals grains, they are a poor source of alkylresorcinols. Alkylresorcinols are antioxidants in whole grains and may provide significant health effects by reducing free radical damage. Eating a range of different whole grains is therefore recommended in order to take advantage of the various health effects in different cereal grains.
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