WASHINGTON — The healthfulness of grain-based foods is manifest in a study comparing diverse population segments regularly consuming grain-based foods with individuals largely avoiding grains. That was the conclusion of research published in July in Food and Nutrition Sciences.
The 18-page study was written by Yanni Papanikolaou, Nutritional Strategies, Inc., Paris, Ont., and Victor L. Fulgoni III, of Nutrition Impact L.L.C., Battle Creek, Mich. It carries the title, “Certain Grain Food Patterns are Associated with Improved 2015 Dietary Guidelines Shortfall Nutrient Intakes, Diet Quality and Lower Body Weight in U.S. Adults: Results from the National Heath and Nutrition Examination Survey, 2005-2010.” The research was funded by the Grain Foods Foundation.
Based on the findings, the researchers suggested nutritionists in often lumping grain-based foods in just two broad categories — whole grains and refined grains — may be painting with too broad a brush.
“In many of the grain patterns examined, we see a better nutrient intake profile, which demonstrates the important dietary contributions made by different grain foods and emphasizes the importance of consuming whole grains and not eliminating refined grains,” the study says. “Indeed, while some of the grain food clusters contributed nutrients to limit in the diet as identified by the 2015 DGAC (2015-2020 Dietary Guidelines for Americans) report, including saturated fat, added sugars, and sodium, several of the grain food patterns were associated with lower intakes of these nutrients and improved shortfall nutrients and diet quality.
“Thus, it is conceivable to rationalize that Americans need more specific dietary guidance about grain consumption rather than simply having two broad categories of recommended intakes that revolve around refined and whole grains.”
Underpinning the study, the first to look at links between grain food pattern intake and nutrient profile, diet quality and health outcomes, is confusion that results when the healthfulness of grain-based foods are characterized in black and white terms, the researchers say.
“While certain grain food products are rich in nutrients to limit in the diet, including added sugar, total and saturated fat, grain foods can contribute positive nutrients to the diet, of which include dietary fiber, iron, magnesium, and B vitamins (thiamin, riboflavin, niacin and folate),” the study says.
The researchers note that of the top 10 sources of energy in the diet, 3 provide scant nutritional value. The rest — including milk, beef, poultry, cheese and baked foods — are significant contributors of nutrients of concern.
“Thus, eliminating these foods from food patterns could potentially have inadvertent effects on diet quality in the U.S. population,” the authors write.
While the Dietary Guidelines offer a number of healthy eating patterns and urge increased intake of whole grains and reduced intake of refined grains, the recommendations were offered in the absence of data associating different grain food patterns with nutrient and health outcomes in adults.
In conducting their study, the researchers hypothesized that 1) certain grain food patterns may significantly contribute positive nutrients, while concurrently lowering nutrients to limit in the diet; 2) certain grain food patterns would be associated with improved measures on health parameters, including body weight and overweight or obesity-related outcomes.
To test their hypotheses, the researchers used data that are the basis for what the government recommends as health eating patterns — What We Eat in America, the dietary intake component of NHANES (National Health and Nutrition Examination Survey), data gathered through the Centers for Disease Control and Prevention in collaboration with the U.S. Department of Agriculture.
The NHANES data were grouped by the researchers using cluster analysis, a statistical technique that analyzes large data sets to explore different patterns. Grain clusters were developed based on the percentage of calories consumed as the “centroid” of each cluster. Seven different clusters were compared with a no grains group.
The eight clusters were 1) no consumption of main grain groups, 2) crackers and salty snacks, 3) yeast breads and rolls, 4) cakes/cookies/pies, 5) cereals, 6) pasta/cooked cereal/rice 7) quick breads, and 8) mixed grains.
The clusters identify groups in which grains intake tend to be concentrated in a fairly narrow category of grain-based foods. For example, the cereals group captures data on 4.3% of the population who derive about 75% of their grains calories from cereal. The cakes/cookies/pies cluster, 4.6% of the population, consume 88% of their grains as cakes/cookies/pies. For the mixed grains group, 29.7% of the population, half of their grains intake is derived from yeast bread and rolls with significant percentages coming from cereal; cakes/cookies/pies; and crackers and salty snacks.
In their analysis, nutrient intake was adjusted for energy intake. The principal measure was comparing the different groups with the first — no grains group.
By one key measure, energy intake, the data did not favor the grain clusters. Daily caloric intake was higher in all seven grain clusters, 340 calories to 567 calories, per day than individuals in the no grains cluster. Still, this differential did not translate into higher rates of obesity or body mass index numbers.
Mean B.M.I. for the no grains cluster averaged 28.63, which was not statistically different than any of the clusters. Adults consuming past/cooked cereals/rice had lower body weights and waist circumference than those consuming no grains.
Similarly, by other important measures grains fared well. For instance, in terms of nutrients to limit, the grains patterns generally did as well as the non-grains group and in some cases did significantly better.
Saturated fat intake was lower in all grain patterns examined, except yeast breads and rolls, and crackers and salty snacks, when measured against those not consuming grain foods. Sodium intake was lower in adults in the cakes/cookies/pies and cereals. Total sugars were lower in many of the categories, but significantly higher (16.5 g/d) in adults predominantly consuming cakes/cookies/pies versus those not consuming grain foods.
Intake of micronutrients was fairly consistently higher in the grains clusters than the no grains group. Except for the cakes/cookies/pies group, iron intake was greater in adults in all grain cluster food pattern. Those consuming yeast breads and rolls; cereals; pasta/cooked cereals/rice and mixed grains had significantly higher intake of thiamin and riboflavin when compared with the no grains group. Folate was higher for all the groups, except the crackers and salty snacks and cakes/cookies/pies.
“Overall, the present data support several grain food patterns as part of a healthy dietary food pattern, that takes into consideration authoritative recommendations to reduce total fat, saturated fat and added sugar consumption, while concurrently increasing 2015-2020 Dietary Guidelines’ shortfall nutrients and/or nutrients of concern, including iron, magnesium, dietary fiber, vitamin D, potassium and B vitamins,” the researchers conclude.
The authors acknowledge the well-documented role of whole grains in the prevention of chronic diseases, including cardiovascular disease, type 2 diabetes, and with certain cancers. The Dietary Guidelines urge the consumption of at least half of all grains as whole grains and to increase whole grain consumption by replacing refined grains with whole grains.
Of concern, though, is the persistently small percentage of the population consuming large amounts of whole grains, the researchers say.
A recent NHANES analysis showed less than 8% of U.S. adults consumed at least three whole grain ounce equivalents per day, while about 50% of adults consumed between zero and three servings per day. Nearly 42% indicated consuming no whole grains each day, the study says.
The authors cite another study, “What We Eat in America 2007-2010,” showing that 95% of the population (children and adult) consume whole grains at levels lower than recommended.
“Coupled with the under consumption of whole grains, the 2015 DGAC concluded ‘several nutrients are under consumed relative to the Estimated Average Requirement or Adequate Intake levels set by the Institute of Medicine—these shortfall nutrients are vitamin A, vitamin D, vitamin E, vitamin C, folate, calcium, magnesium, fiber, and potassium,’” the study says. “The 2015 DGAC also identified iron to be a shortfall nutrient for adolescent and premenopausal females.”
The importance of iron and the risks of inadequate intake also are highlighted in the study. The authors note that grain foods represented the top four food sources for iron in the diets of U.S. children and adolescents, led by ready-to eat cereals, yeast breads, pizza, and cakes/cookies/pies, and crackers, popcorn, pretzels, and chips cumulatively contributing 0.1% of iron to the children and 48.7% to the adolescents.
Overall diet quality as measured by the U.S. Department of Agriculture Healthy Eating Index was lower for adults in the no grain pattern, 46.8, than for any of the other groups except the cakes/cookies/pies cluster, at 45.1. Cereals, at 54.7; pasta/cooked cereals/rice, 54.4; and mixed grains, at 49.5, were solidly higher than the no grains cluster.
In the discussion section of the study, the authors acknowledge limitations, most of which are problematic in all epidemiological studies — that recalled information upon which the figures are based may be inaccurate and biased from misreporting, memory challenges and other potential measurement errors experienced.
“In addition, the current evidence, being observational, cannot establish a causal link between the different grain foods patterns examined and improvements in diet quality, nutrient intakes and other health variables considered,” the study says. “However, a large strength of the current work stems from the use of NHANES, which is a large continuous survey that examines a nationally representative sample of about 5,000 individuals yearly by highly-trained medical personnel. Additionally we used numerous covariates to adjust data in an attempt to remove potential confounding; that said we acknowledge that residual confounding may still exist that could explain some of the results reported.”
The analysis conducted in the research generated some data that could be characterized as strange. For example, the no grains cluster consumed more refined grains (7.7 index figure) than any of the grains clusters (5.0 to 7.3 per day). Mr. Papanikolaou said mixed grains, such as pizza, were part of the no grains diet (though none of these items appeared in the top 10 of foods consumed by the no grains cluster). Sofaas calories (solid fats and added sugar) intake was higher for no grains (10.9 index) than the cakes/cookies/pies cluster.
Still, the researchers say the study cast a positive light on the role of grains in the diet.
They conclude, “Overall, while some grain food patterns were associated with elevated sodium and added sugar, the present data also support that several grain food patterns can serve as part of a healthy dietary food pattern, that accounts for 2015 Dietary Guidelines recommendations to reduce total fat, saturated fat and added sugar consumption, while concurrently increasing intake of shortfall nutrients and/or nutrients of concern, including iron, magnesium, dietary fiber, vitamin D, potassium and B vitamins.”