ROCHESTER, MINNIE. — Contrary to the conclusions reached by the Dietary Guidelines Advisory Committees in both 2015 and 2020, the scientific data does not suggest an association between a higher intake of refined grains and an increased risk of type 2 diabetes (T2D), Glenn said A. Gaesser, a professor in the College of Health Solutions at the University of Arizona, Phoenix.
The findings, which challenge Dietary Guidelines recommendations to reduce consumption of refined grains, will be published in a commentary in the August issue of Mayo Clinic Procedures.
Dr. Gaesser, who is on the scientific advisory committee of the Grain Foods Foundation, based his conclusions on data from 10 publications that looked at 11 adult cohorts that included a total of 398,994 people: 268,419 women and 130,575 men. Of the 11 cohorts, 9 showed no statistically significant association between higher T2D intake and refined grain intake, 1 showed higher risk, and 1 showed lower risk. The only study that showed an increased risk was the smallest cohort in the collection, which represented 0.3% of study participants.
“These findings refute the common belief that refined and non-whole grains can directly lead to T2D when consumed,” GFF said. “Eating refined staple grain foods such as breads, cereals, and pastas was not associated with T2D risk, and total grain intake was consistently associated with a lower T2D risk. Even in studies that included indulgent grain foods such as cakes, cookies, sweet rolls and muffins in the refined grain food category, no association was seen with Type 2 diabetes risk.”
In a YouTube video of Dr. Gaesser’s comment, he concluded: “The take-home message here is that people should be eating more whole grains, that’s for sure, and the studies back it up pretty strongly, but it also suggests that We should probably relax our recommendations on reducing refined grain intake, because there is no convincing evidence to suggest that a reduction in refined grain intake will lead to a lower risk of diabetes.”
The results weren’t just for staple grain foods like bread, pasta, cereal or rice.
“Whether refined grains were defined to include only staple grain foods or a mix of staple and indulgent grain foods did not appear to influence the results,” he said.
By way of background, Dr. Gaesser said that the last two Dietary Guidelines Advisory Committees (DGACs) had based recommendations to reduce consumption of refined grains on “moderate” evidence suggesting that such reductions were associated with a lower risk of DT2. Moderate evidence was generated by investigating dietary patterns.
“’Healthy’ dietary patterns are characterized by increased consumption of fruits, vegetables, whole grains, low-fat or fat-free dairy products, seafood, legumes, and nuts,” said Dr. Gaesser. “In contrast, ‘unhealthy’ (Western) dietary patterns are characterized by increased consumption of red and processed meat, sugary foods and beverages, potato chips, high-fat dairy products, and refined grains. A substantial body of research shows that a healthy dietary pattern is associated with a lower risk of T2D and that an unhealthy dietary pattern is associated with a higher risk of T2D.”
Because dietary pattern research groups many foods together, Dr. Gaesser said the risk identified by the DGCA may not be “attributable to refined grains per se, but to the other foods within the unhealthy dietary pattern.” In fact, he noted that T2D risk has been independently associated with intake of red and processed meats and sugar-sweetened beverages.
To conclude that refined grain intake is associated with T2D, studies in which refined grains are considered as a separate food category, independent of a dietary pattern, should be considered. It was to that end that Dr. Gaesser reviewed studies that looked at refined grains as a distinct food category.
Ideally, when it comes to assessing the risk of grain intake and T2D, Dr. Gaesser said more distinctions should be made between so-called staple grain foods like bread, cereal, pasta and rice and indulgent grain foods like cookies and cakes. Such distinctions were not made in the 10 studies he analyzed, making the lack of association between refined grains and T2D surprising, Dr. Gaesser said.
The studies it evaluated included in the categories of refined grains cakes, cookies, sweets and desserts, sweet rolls, pancakes, waffles, muffins and pizza.
“These foods generally contain high amounts of sugar and fat and low amounts of fiber,” said Dr. Gaesser. “None of the cohort studies examined separate associations between type 2 diabetes risk and intake of basic or indulgent refined grain foods or provided information on the percentage contributions of different refined grain foods to total refined grain intake. “.
He continued: “Even with the inclusion of indulgent grain-based foods, none of the studies showed an elevated risk of T2D associated with higher refined grain intake, and none of the meta-analyses indicated an association between refined grain intake and DT2. ”
Relying on dietary patterns to establish an association with T2D likely led the DGAC to its conclusions about refined grains, conclusions that now appear suspect.
“The increased risk of T2D associated with the unhealthy (Western) dietary pattern is likely due to the consumption of red and processed meats and sugar-sweetened beverages rather than refined grain foods themselves,” said Dr. Gaesser.
The DGAC has always recommended consuming at least three servings of whole grains per day, but Dr. Gaesser said that less than 7 percent of the US population consumes the recommended minimum of three servings per day of whole grains, and more 70% of Americans eat less than one serving a day of whole grains. He cited data indicating that refined grain consumption is five times greater than whole grain consumption (for wheat flour, USDA data actually suggests refined grain consumption is about 20 times greater than whole grain consumption). of whole grains).
“Although research strongly supports the recommendation to increase whole grain intake to reduce T2D risk, the optimal amount of whole grain intake is not entirely clear,” said Dr. Gaesser. “The risk appears to be significantly reduced up to about three daily servings of whole grains. Americans currently consume less than one serving per day.”
In the Women’s Health Initiative Observational Study, one of the larger studies discussed in Dr. Gaesser’s commentary, the lower risk of diabetes for higher intake of refined grains was similar to that for higher intake of whole grains .
Dr. Gaesser said there is evidence that as total grain intake increases, the risk of T2D decreases nonlinearly up to 10 servings per day.
“This may be particularly relevant to US dietary recommendations, as this level of total grain consumption exceeds current grain intake among Americans,” said Dr. Gaesser.