Refined grain consumption associated with increased risk for mortality, CVD events
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Refined grain consumption was associated with an increased risk for mortality and major CVD events, according to new data from the PURE study published in The BMJ.
“Previous studies have been conducted mostly in North America and Europe, with limited information from other parts of the world where the amount and types of carbohydrates consumed in the diet vary, as do their contributions to overall calories,” Sumathi Swaminathan, MD, associate professor in the division of nutrition at St. John’s Research Institute in Bangalore, India, and colleagues wrote. “The PURE study has the distinct advantage of examining diets from diverse populations in low-, middle- and high-income countries in multiple regions across the world.”
The prospective cohort study included 137,130 participants (mean age, 50 years; 42% men) from 21 countries who were followed for a median of 9.5 years. Participants completed a country-specific food frequency questionnaire to evaluate consumption of refined grains, whole grains and white rice.
The primary outcome was the composite of mortality or major CVD events such as death from CV causes, nonfatal MI, stroke or HF. Participants were stratified by refined grain consumption: less than 50 g per day, 50 g to less than 150 g per day, 150 g to less than 250 g per day, 250 g to less than 350 g per day, and at least 350 g per day.
According to the researchers, 9.2% of participants experienced a composite outcome event during follow-up.
The highest level of refined grain intake (> 350 g per day) was associated with elevated risk for total mortality (HR = 1.27; 95% CI, 1.11-1.46; P for trend = .004), major CVD events (HR = 1.33; 95% CI, 1.16-1.52; P for trend < .001) and mortality or major CV events (HR = 1.28; 95% CI, 1.15-1.42; P for trend < .001) compared with the lowest level of refined grain intake (< 50 g per day). There was also an association between higher refined grain consumption and higher systolic BP.
There were no significant associations found between whole grain consumption or white rice consumption and adverse health outcomes.
“Our study from 21 countries showed that higher intake of refined grains was associated with higher risk of total mortality and major cardiovascular events,” the researchers wrote. “Reduction in quantity and improvement in quality of carbohydrate is essential for better health outcomes.”
Perspective
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Monica Aggarwal, MD, FACC
The original PURE data suggests that the carbohydrate is the enemy. In our editorial regarding PURE in the American Journal of Medicine (Gianos E, et al. Am J Med. 2017;doi:10.1016/j.amjmed.2017.11.024), we wrote that the likely problem is the type of carbohydrate.
This study looks at the carbohydrate more closely and breaks down the type of carbohydrates that were ingested in the large multi-country PURE trial; namely, whether the carbohydrates ingested were whole grain or refined carbohydrates. Not surprisingly, there was a clear difference in mortality between the types of carbohydrates ingested. With ingestion of refined grains, there was a higher risk for mortality and CV events, and this was not seen with intake of whole grains. Refined grains have a low glycemic index and increase sugar levels quickly, do not make you feel full and have minimal fiber, unlike the whole grains. Many cultures have shifted to easier eats that are more refined and highly processed and have shifted away from whole and minimally processed grains. With that, we see higher rates of diabetes, obesity and CVD.
It reminds us that there are so much data that saturated fats are not good for CV mortality but if you replace the saturated fats with refined carbohydrates, we make the situation worse. If we replace the saturated fats with complex carbohydrates, we make people do better. The focus of cardiology clinics should be to emphasize whole foods: fruits and vegetables, complex carbohydrates including beans and lentils, lean fish or plant-based proteins, nuts, seeds and spices. If we get people eating this way and moving more, it would be a game changer. The enemy is not the carbohydrate, it is the refined carbohydrate.
What is interesting about this study is that white rice did not have an association with clinical outcomes. That certainly deserves further study.
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