Whole grains retain the bran, germ, and endosperm that are removed in milling to produce white flour and white rice. The bran contains fibre, B vitamins, and polyphenols. The germ contains vitamin E, essential fats, and additional polyphenols. The endosperm, which is all that refined grains retain, contains primarily starch and some protein. Refining a grain removes approximately 80 percent of its nutritional value while retaining the majority of its calories.
The Evidence for Whole Grain Consumption
- Cardiovascular disease: meta-analyses of prospective cohort studies consistently find 20 to 30 percent reductions in cardiovascular disease risk in the highest versus lowest whole grain consumers
- Type 2 diabetes: each additional daily serving of whole grains is associated with a 5 to 10 percent reduction in type 2 diabetes risk in prospective studies
- Colorectal cancer: whole grain fibre is associated with a 17 percent reduction in colorectal cancer risk per 90g per day increase in consumption
- All-cause mortality: a meta-analysis of 45 studies found a dose-dependent reduction in all-cause mortality with increasing whole grain intake, with approximately 5 percent lower risk per serving
- Body weight regulation: whole grain consumption is associated with lower body weight and slower weight gain over time in prospective studies despite similar caloric content
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