High intake of refined grains was associated with higher risk of mortality and major cardiovascular disease (CVD) events, found a large 21-nation analysis.
No significant adverse health effects were found with consuming whole grains or white rice.
The Prospective Urban Rural Epidemiology (PURE) study has been examining diets from diverse populations in low-, middle- and high-income countries around the world. Over 16 years of analysis of 137,130 participants in 21 countries, including Canada, the researchers found the intake of refined grains and added sugars have greatly increased over the years.
Grains were categorised into three groups: refined grains, whole grains and white rice. Refined grains included goods made with refined (white) flour, including white bread, pasta/noodles, breakfast cereals, crackers, and bakery products/desserts containing refined grains. Whole grains included whole grain flours (buckwheat) and intact or cracked whole grains (steel cut oats).
The study found that having more than seven servings of refined grains per day was associated with a 27% greater risk for early death, 33% greater risk for heart disease and 47% greater risk for stroke.
"This study re-affirms previous work indicating a healthy diet includes limiting overly processed and refined foods," says Lear.
The study suggests eating whole grain foods like brown rice and barley, and having fewer cereal grains and refined wheat products. Reducing one's overall consumption of refined grains and having better quality carbohydrates is essential for optimal health outcomes.
Associations of cereal grains intake with cardiovascular disease and mortality across 21 countries in Prospective Urban and Rural Epidemiology study: prospective cohort study
Sumathi Swaminathan, Mahshid Dehghan, John Michael Raj, Tinku Thomas, Sumathy Rangarajan, David Jenkins, Prem Mony, Viswanathan Mohan, Scott A Lear, Alvaro Avezum, Patricio Lopez-Jaramillo, Annika Rosengren, Fernando Lanas, Khalid F AlHabib, Antonio Dans, Mirac Vural Keskinler, Thandi Puoane, Biju Soman, Li Wei, Katarzyna Zatonska, Rafael Diaz, Noorhassim Ismail, Jephat Chifamba, Roya Kelishadi, Afzalhussein Yusufali, Rasha Khatib, Liu Xiaoyun, Hu Bo, Romaina Iqbal, Rita Yusuf, Karen Yeates, Koon Teo, Salim Yusuf
Published in BMJ on 3 February 2021
To evaluate the association between intakes of refined grains, whole grains, and white rice with cardiovascular disease, total mortality, blood lipids, and blood pressure in the Prospective Urban and Rural Epidemiology (PURE) study.
Prospective cohort study.
PURE study in 21 countries.
148 858 participants with median follow-up of 9.5 years.
Country specific validated food frequency questionnaires were used to assess intakes of refined grains, whole grains, and white rice.
Main outcome measure
Composite of mortality or major cardiovascular events (defined as death from cardiovascular causes, non-fatal myocardial infarction, stroke, or heart failure). Hazard ratios were estimated for associations of grain intakes with mortality, major cardiovascular events, and their composite by using multivariable Cox frailty models with random intercepts to account for clustering by centre.
Analyses were based on 137 130 participants after exclusion of those with baseline cardiovascular disease. During follow-up, 9.2% (n=12 668) of these participants had a composite outcome event. The highest category of intake of refined grains (≥350 g/day or about 7 servings/day) was associated with higher risk of total mortality (hazard ratio 1.27, 95% confidence interval 1.11 to 1.46; P for trend=0.004), major cardiovascular disease events (1.33, 1.16 to 1.52; P for trend<0.001), and their composite (1.28, 1.15 to 1.42; P for trend<0.001) compared with the lowest category of intake (<50 g/day). Higher intakes of refined grains were associated with higher systolic blood pressure. No significant associations were found between intakes of whole grains or white rice and health outcomes.
High intake of refined grains was associated with higher risk of mortality and major cardiovascular disease events. Globally, lower consumption of refined grains should be considered.
BMJ study (Open access)