KANSAS CITY – It’s probable that no single scientific paper would convince a Dietary Guidelines Scientific Advisory Committee to meaningfully revise its guidance regarding the role of refined grains in the diet. Efforts spearheaded by the Grain Foods Foundation (GFF) to effect such a change should be viewed as a marathon, rather than a sprint. That said, a major mile marker in this marathon appears to have been crossed with the impending publication of an article looking into the connection between refined grains intake and increased risk of type 2 diabetes (T2D).
Funded by the GFF and published in the August issue of Mayo Clinic Proceedings, the commentary by Glenn A. Gaesser, PhD, a professor in the College of Health Solutions at the University of Arizona, Phoenix, and who leads the GFF’s Scientific Advisory Committee, shows scientific data fail to support the conclusion eating more refined grains raises the risk of T2D.
At issue is a warning in the 2020-2025 Dietary Guidelines for Americans that “dietary patterns characterized by higher intake of red and processed meats, sugar-sweetened foods and beverages, and refined grains are, in and of themselves, associated with detrimental health outcomes.”
The 2020-2025 Guidelines go on to say the findings “build on” research that generated a similar conclusion five years earlier in the 2015-2020 Dietary Guidelines.
“Building on” is an apt description for Dr. Gaesser’s latest commentary. It builds on numerous previous publications sponsored by the GFF and aimed at demonstrating the linkage between refined grains and poor health is not supported by science.
A brief review shows how this positive GFF work has steadily and meaningfully accumulated over the past six years, paper by paper. The conclusion in the Guidelines is based on measuring outcomes for cohorts based on “dietary patterns,” large groups of individuals whose eating patterns match one another — in this case consuming large amounts of meats, sweets and refined grains. In 2016, the GFF sponsored a study showing numerous dietary patterns, “cluster analysis,” that included heavy intake of refined grains was linked to better intake of shortfall nutrients.
More recently, Dr. Gaesser has criticized the dietary pattern guidance because it fails to parse the contributors to the poor health outcomes. Is it the red meat? The sweets? The refined grains? All of the above?
In 2019, Dr. Gaesser reviewed research that analyzed grain-based foods separately, and not as part of a so-called Western dietary pattern. After reviewing 11 meta-analyses of prospective cohort studies, he found refined grain intake was not associated with all-cause mortality, cardiovascular disease, T2D, coronary heart disease or obesity.
In the latest publication, Dr. Gaesser focuses specifically on the connection between grains and T2D. In the past, the Dietary Guidelines Advisory Committee has singled out diabetes and cardiovascular disease as linked to refined grains intake.
For his latest research, Dr. Gaesser reviewed ten publications looking at nearly 400,000 individuals followed through observational studies. Of 11 adult cohorts reviewed, nine showed no statistically significant association between higher intake of T2D and refined grains intake, one showed a higher risk and one showed a lower risk.
“These findings refute the commonly held belief that refined and non-whole grains can directly lead to T2D when consumed,” the GFF said. “Eating refined staple grain foods such as breads, cereals, and pasta was not associated with T2D risk.”
While a legitimate approach to scientific study, dietary pattern analysis is inferior to observational studies which, in turn, are inferior to randomized control trials. Reading Dr. Gaesser’s commentary, one concludes using dietary patterns for such an important recommendation as whether to avoid a staple food like grains is about as effective as performing surgery with a meat cleaver rather than a scalpel. The DGAC appears firmly committed to using dietary pattern analysis for its recommendations. The GFF should continue to build its case for why such an approach leads to flawed guidance when it comes to grains.