WASHINGTON — Health risks associated with carbohydrate avoidance, confusion caused by the term “refined grains” and an impressive and growing body of scientific evidence demonstrating the value of grain consumption in preventing mortality and type 2 diabetes should stand as important considerations for the 2020 Dietary Guidelines Advisory Committee (D.G.A.C.), according to prominent grain industry groups.

Dubbed the “Grain Chain,” the groups submitted comments in a July 1 letter to the Center for Nutrition Policy and Promotion at the Food and Nutrition Service of the U.S. Department of Agriculture.

The advisory committee reviews scientific evidence about topics and questions related to dietary health and will provide a report on their findings. The report, along with public and agency comments, will lead to the drafting of the 2020-2025 Dietary Guidelines for Americans (D.G.A.), to be released by the Department of Health and Human Services and the U.S.D.A.

In the letter, the Grain Chain urged the D.G.A.C. to preserve recommendations that 45% to 65% of calories consumed come from carbohydrates and that six servings of grains should be consumed daily with at least half of all grain consumed as whole grains.

“Given that Americans continue to under-consume whole grains, we would also support increasing whole grain serving recommendations, while maintaining at least three servings daily of enriched grains,” the letter said. “The body of scientific evidence continues to support grain consumption because of its substantial nutritional contributions and its positive impact on health outcomes.”

The letter was accompanied by seven attachments, addressing specific items of concern for the D.G.A.C. In the first attachment, the Grain Chain emphasized the value of grains as forming a “nutritional foundation” for a variety of healthy dietary patterns.

“Recent changes to the Nutrition Facts panel based on shortfall nutrients provide a timely opportunity for the D.G.A.C. to highlight food sources of shortfall nutrients (e.g., enriched grain foods — folic acid, iron, potassium, dietary fiber, magnesium; whole grain foods — iron, dietary fiber, magnesium and potassium),” the group said.

Citing National Health and Nutrition Examination Survey data, the Grain Chain said grains account for 14% of caloric intake and 23% of dietary fiber, 34% of dietary folate, 30% of iron and 14% of magnesium — each of which was designated a “shortfall nutrient” in the most recent D.G.A.

Grains are versatile, the group explained, noting they fit into a wide range of dietary patterns, including plant-based diets.

“Not only are grain foods plants, they are convenient, affordable, versatile, good tasting and sustainable — all characteristics that make them desirable to consumers,” the group said.

The group described a trend of carbohydrate avoidance as a “grave concern” given the demonstrated health benefit associated with the enrichment and fortification of grains.

“Even more troubling is a new development, driven by consumer demand for so-called ‘clean’ labels: food manufacturers often consider foregoing enrichment and fortification of grain products, which, if widely adopted, could result in negative nutrition and health implications,” the group said.

Perhaps contributing to this trend has been a custom among researchers and others in nutrition and policy communities of categorizing enriched grains as “refined grains.”

The letter noted at least 95% of refined grains in the United States are enriched and fortified and are labeled accordingly.

“We encourage the 2020 D.G.A.C. to consider clarifying the terminology describing enriched grains in the Dietary Guidelines to more appropriately portray the non-whole grain portion of the grain category,” the Grain Chain said. “The 2015 Dietary Guidelines recommend limited consumption of ‘refined grains’ and do not distinguish between ‘nutrient-rich’ enriched grains versus unenriched refined grains. This dietary guidance does not sufficiently communicate the public health benefits of enriched grains: They are important sources of iron and folic acid essential for women of childbearing age.”

The expression “refined grains” is especially confusing since nutrition labels on food products at supermarkets read “enriched” or “whole grain.”

Particular emphasis in the letter is placed on the value of folic acid fortification. The group reminded the D.G.A.C. the number of babies born with neural tube defects has fallen by 35% in the United States since 1998, resulting in about 1,300 babies born healthy each year in the United States who might otherwise have been affected.

A third attachment focused on the role grain foods play in lowering the risk of chronic disease. A review this year of 11 meta-analyses showed refined grains were not associated with increased risk and premature death.

“The totality of evidence shows consumption of up to 50% of all grain foods as refined-grain foods (without high levels of added fats, sugar or sodium) is not associated with increased disease risk,” the letter said.

Maintaining a balanced diet is closely linked to the positive health outcomes, the group said.

“(The) findings show that when assessing total carbohydrate without regard to specific food source, diets with high (>70%) or low (<40%) percentage of energy from carbohydrates were associated with increased mortality, with minimal risk associated with 50% to 55%,” the Grain Chain said. “The data suggest a U-shaped relationship between life expectancy and overall carbohydrate intake, in which lifespan is greatest among people with 50% to 55% carbohydrate intake, a level that might be considered moderate in North America and Europe but low in other regions, such as Asia. These data provide further evidence that animal-based low-carbohydrate diets should be discouraged.”

Turning specifically to low-carbohydrate diets, the Grain Chain described research as inconclusive for key health endpoints, including management of type 2 diabetes and weight loss.

“Many of the studies used few subjects, are short in duration or lacked appropriate control groups,” the Grain Chain said. The group advocated additional research to better understand both potential benefits as well as health risks associated with following low-carbohydrate diets for periods greater than six months.

One particular challenge the group identified was finding uniformity in the term “low carbohydrate.”

“The terminology can be very confusing, and when a dietary pattern is described as ‘low’ carbohydrate, it can vary widely in actual carbohydrate levels,” the group said.

“Research using low or very low carbohydrate diets in the prevention or management of type 2 diabetes continues to accumulate,” the Grain Chain said. “However, the evidence remains inconclusive because studies often use few subjects and lack a control group, are short in duration and have variable retention rates. Adherence to lower carbohydrate eating plans has created problems because results from the intervention and control groups often converge by the end of the study.”

In a final supplement, the Grain Chain suggested pulses should not be folded into the grain category.

“There has been some discussion in past D.G.A.C. reviews about including pulses and legumes within the grain category,” the Grain Chain said. “We support the 2015-20 Dietary Guidelines placement of pulses and legumes within the protein as well as the vegetable groups as nutritionally similar foods.”

Signatories to the letter include the American Bakers Association, American Institute of Baking, the Grain Foods Foundation, the Independent Bakers Association, the National Pasta Association, the National Association of Wheat Growers, the North American Millers’ Association, the Retail Bakers of America, the Wheat Foods Council and USA Rice Federation.