Perspective: Refined Grains and Health: Genuine Risk, or Guilt by Association?

Refined grain intake is widely assumed to be associated with adverse health outcomes, including increased risk for cardiovascular disease (CVD), type 2 diabetes (T2D), and obesity. The 2015 Dietary Guidelines Advisory Committee recommended that to improve dietary quality, the US population should replace most refined grains with whole grains. This recommendation was based largely on results from studies that examined dietary patterns, not separate food groups. A Western dietary pattern typically includes red and processed meat, sugar-sweetened foods and beverages, French fries, and high-fat dairy products, as well as refined grains, and has been linked to increased risk of many chronic diseases. However, when evaluated as a distinct food category, 11 meta-analyses of prospective cohort studies, which included a total of 32 publications with data from 24 distinct cohorts, demonstrated that refined grain intake was not associated with all-cause mortality, T2D, CVD, coronary heart disease (CHD), stroke, hypertension, or cancer. By contrast, consumption of red and processed meat was consistently associated with increased risk of these same health outcomes. Refined grain consumption up to 6-7 servings/d (1 serving = 30 g) was not associated with higher risk of CHD, T2D, hypertension, or all-cause mortality. Moreover, total grain intake was not associated with risk of CVD, CHD, stroke, or cancer, but was associated with lower risk of all-cause mortality. Consequently, the recommendation to reduce refined grain intake based on results from studies linking a Western dietary pattern to numerous adverse health outcomes is contrary to a substantial body of published scientific evidence. Future research needs to better define refined grain intake to distinguish between staple grain foods and indulgent grain foods, and to better design randomized controlled trials to resolve discrepancies between results from observational studies and such trials with regard to determining the benefits of whole grains compared with refined grains.