WOLLONGONG, AUSTRALIA — Consuming up to 50% of all grain foods as refined grain foods without high levels of added fat, sugar or sodium was not associated with any increased disease risk in a review published on-line Jan. 3 in Nutrition Reviews.
The review also promoted whole grain consumption. It said most consumers, in order to meet target consumption of whole grain foods, will need to reduce their consumption of refined grains to no more than one-third to one-half of all grains. In the United States it is estimated less than 15% of total grain consumption is whole grain and only 6% to 8% of adults meet the target of three servings of whole grain per day.
The review identified 135 relevant articles from database searches of studies published between 2000 and 2010.
“The great majority found no associations between the intake of refined-grain foods and cardiovascular disease, diabetes, weight gain or overall mortality,” the review said. “A few studies found that very high intakes might be associated with some types of cancers, but at moderate levels of consumption the risks were not as significant.”
Go Grains Health & Nutrition Ltd., an Australian center for science-based evidence on the dietary health benefits of grain-based foods and legumes, commissioned the independent literature review. Peter G. Williams, a visiting principal fellow at the Smart Foods Centre at the University of Wollongong, was the review’s author. He acts as a paid scientific adviser for Go Grains Health & Nutrition.
The review whenever possible chose studies that reported results for core refined-grain foods, which were defined as foods based on refined grains without significant added fat, sugar or sodium. Examples included bread, breakfast cereal, pasta and rice. Refined cereal-based foods with large levels of added fat, sugar or sodium were excluded. Examples were cakes, pastries, cookies, donuts and pizza.
Sixteen of the studies showed an increase in health risk at the highest level of refined-grain consumption. In seven of those 16 studies, the definition of refined-grain foods included high-fat or sugar-added products like pizza or cakes, which made it impossible to draw conclusions from those results about the effect of core refined grains alone.
The review examined 18 cross-sectional studies that mostly reported on the risk of obesity or metabolic syndrome. Intake of refined grains at high levels was associated with higher visceral adipose tissue (VAT) in a Framingham Heart Study although the lowest VAT was recorded with two servings of refined grains and three servings of whole grains per day.
The review examined 13 case-control studies with 10 focusing on various cancers and three on ischemic heart disease.
“Overall, there is a lack of consistency in the case-control data about cancer that makes it difficult to draw clear conclusions,” the review said. “Some of the increased risks were only present at the very highest levels of intake, which is still consistent with safe intakes at lower levels. The few available case-control studies on the risk of ischemic heart disease do not suggest any significant risk is associated with moderate levels of refined-grain consumption.”
In examining other reviews and meta-analyses, the review found almost all the other reviews primarily were concerned with the health benefits of whole grains or of low-glycemic-index diets. None of the other reviews specifically examined how levels of refined-grain consumption may relate to health outcomes.
The review examined a systematic review by Glenn Gaesser, a professor and exercise and wellness program director for the Healthy Lifestyles Research Center at Arizona State University. He is also chairman of the scientific advisory board of the Grain Foods Foundation, Ridgway, Colo. Dr. Gaesser’s review concluded whole grain intake generally is associated inversely with body mass index (B.M.I), but refined-grain intake is not consistently linked to higher B.M.I.