Are refined grain foods associated with heart disease?
Nowadays, many food guides and other nutritional guidelines recommend switching out refined grains for whole-grain, less refined options. Foods labeled “whole grain”, including brown rice, oatmeal, and whole-grain breads, contain all parts of the original harvested grain; these parts are called the germ, the bran, and the endosperm.
The bran and the germ are typically removed during the processing of refined grains, so refined grains such as white flour, white bread, and many baked goods, generally do not contain these parts of the grain.
The germ and the bran of whole grains are very nutritious; they are rich in fibre, B vitamins, and trace amounts of minerals such as magnesium and zinc. Increasing intake of whole-grain foods may help people obtain these nutrients. Whole grain foods also often have a lower glycemic index (GI) than their refined counterparts; this means that they release glucose at a slower rate than foods with a higher GI.
Many studies have linked regular consumption of whole grains to a lower risk of cardiovascular disease, and this could potentially be attributed to the increased levels of beneficial nutrients in whole grains. However, it is unknown whether increased consumption of refined grains is associated with an increased risk of cardiovascular disease.
To investigate this, researchers at Simon Fraser University conducted a large population-level study called the Prospective Urban Rural Epidemiology (PURE) study, and the results were published in the British Medical Journal. The study followed 137,130 participants from 21 different countries for an average of nine years to determine any potential correlations between dietary intakes of refined grains and cardiovascular disease.
Researchers tracked participants’ intake of three different types of grains: refined grains, whole grains, and white rice. Refined grains included any wheat products that had the bran and germ removed through processing methods. Whole grains consisted of whole grain flours and intact whole grains, such as oats, bulgur, barley, and whole corn. White rice included both parboiled and regular white rice as well as any pre-prepared breakfast foods made from white rice. Since white rice is a staple food for many communities in a variety of places, this type of grain was examined separately.
Refined grains associated with cardiovascular risk
In the study group, higher intakes of refined grains were associated with a higher risk of cardiovascular disease and its complications, including stroke and early mortality. No significant association was found between the intakes of white rice and whole grains and cardiovascular disease risk and mortality.
The results of the study suggest that higher intakes of refined grain foods could potentially be associated with an increased risk of cardiovascular disease; however, more research is needed to confirm this. These results are consistent with previous studies and recommendations suggesting that focusing carbohydrate intake on whole-grain sources could be beneficial.
References
Anderson, J.W. (2003). Whole grains protect against atherosclerotic cardiovascular disease. Proc Nutr Soc 62(1): 135-142. Doi: 10.1079/PNS2002222.
EurekAlert! (2021 February 19). American Association for the Advancement of Science (AAAS). Retrieved 2021 February 22 from https://www.eurekalert.org/pub_releases/2021-02/sfu-emr021921.php
Health Canada (2019 September 5). Government of Canada. Retrieved 2021 February 22 from https://www.canada.ca/en/health-canada/services/canada-food-guide/resources/healthy-eating-recommendations/eat-a-variety/whole-grain/get-facts.html
Swaminathan, S., Dehghan, M., Raj, J.M. (2021). Associations of cereal grains intake with cardiovascular disease and mortality across 21 countries in Prospective Urban and Rural Epidemiology study: prospective cohort study. BMJ 2021(372). Doi: 10.1136/bmj.m4948
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