Small clinical trial supports prior indications that whole grains aid weight control while reducing heart and diabetes risks
by Craig Weatherby
While not exactly startling, the results of a study from Pennsylvania State University resoundingly affirm the value of whole grains, versus the refined grains that dominate American diets.
The hypothesis that diets high in whole grains help reduce risk of obesity, heart disease and diabetes flows largely from epidemiological research. Such studies compare people's diets with their long-term health outcomes, and can only demonstrate associations, not cause and effect (McKeown NM et al. 2002).
And until recently, no controlled clinical trials directly tested the weight-loss and health-enhancing effects of diets high in whole, unrefined grain foods, versus diets high in refined grain foods such as white bread.
This data gap led researchers at Pennsylvania State University to conduct a controlled clinical trial in 25 obese women and 25 obese men (average age 46) diagnosed with metabolic syndrome (Katcher HI et al. 2008).
How the study worked
For the duration of the 12 week trial, all the participants ate a diet containing 500 calories less than normal, made up of five daily servings of fruits and vegetables, three servings of low-fat dairy products, and two servings of lean meat, fish or poultry.
All were encouraged to engage in moderate physical activity.
To test the effect of whole and refined grains, half were randomly assigned to eat only breads, pasta, and cereal made from whole grains, while the other half were told to avoid whole grain foods.
Participants in the whole grain group were directed to focus on foods that had whole grains as the first ingredient.
(The photo above portrays Paul Helton, one of the study participants, examining the whole-grain and refined foods used in the research.)
Results confirm wisdom of avoiding refined grains
Both groups enjoyed reductions in body weight—between 8 and 11 pounds on average—waist circumference, and the percentage of their weight occurring in the form of fat.
However, the whole-grain group experienced greater falls in the percentage of body fat located in the abdomen, compared to the refined-grain group.
This difference is critical, because the excess abdominal fat that yields an apple-shaped body is linked to a much greater risk of obesity, metabolic syndrome, heart disease, and diabetes (The risks of having a pear-shaped body, with excess fat around the hips and thighs, are much less).
The whole-grain group also enjoyed a big, 38 percent average drop in a key marker of inflammation called C-reactive protein or CRP, high blood levels of which raise people's risk for diabetes, hypertension and cardiovascular disease.
The researchers noted the large reduction in CRP levels was comparable to those achievable from the strong anti-inflammatory effects of statin drugs.
Their effect on CRP levels could be due to the surprisingly high antioxidant content of whole grains, which was overlooked until recently. Polyphenol antioxidants, like those in the outer layers of whole grains, can exert strong anti-inflammatory effects. See “Whole Grains: Under-Sung Antioxidant Aces.”
Blood levels of total, LDL, and HDL cholesterol decreased in both groups, while fiber and magnesium intakes increased only in the whole-grain group. Magnesium is very important to heart health, and both food factors may discourage or delay the onset of diabetes.
In a press release, renowned nutrition researcher Penny Kris-Etherton, Ph.D., recommended choosing grain foods in which at least 51 percent of the grain comes from whole grain, such as oatmeal, whole grain cereal, brown rice, whole-wheat pasta and snacks such as granola bars and whole-wheat crackers.
To her list we'd add wheat berries, barley, quinoa… and buckwheat, which is the antioxidant-rich fruit of a broadleaf plant and probably healthier than most “real” grains.
As Kris-Etherton said, “This is the first clinical study to prove that a diet rich in whole grains can lead to weight loss and reduce the risk of several chronic diseases.” (PSU 2008)
- Katcher HI, Legro RS, Kunselman AR, Gillies PJ, Demers LM, Bagshaw DM, Kris-Etherton PM. The effects of a whole grain-enriched hypocaloric diet on cardiovascular disease risk factors in men and women with metabolic syndrome. Am J Clin Nutr. 2008 Jan;87(1):79-90. PMID: 18175740
- McKeown NM, Meigs JB, Liu S, Wilson PW, Jacques PF. Whole-grain intake is favorably associated with metabolic risk factors for type 2 diabetes and cardiovascular disease in the Framingham Offspring Study. Am J Clin Nutr. 2002 Aug;76(2):390-8.
- Melanson KJ, Angelopoulos TJ, Nguyen VT, Martini M, Zukley L, Lowndes J, Dube TJ, Fiutem JJ, Yount BW, Rippe JM. Consumption of whole-grain cereals during weight loss: effects on dietary quality, dietary fiber, magnesium, vitamin B-6, and obesity. J Am Diet Assoc. 2006 Sep;106(9):1380-8; quiz 1389-90.
- Newby PK, Maras J, Bakun P, Muller D, Ferrucci L, Tucker KL. Intake of whole grains, refined grains, and cereal fiber measured with 7-d diet records and associations with risk factors for chronic disease. Am J Clin Nutr. 2007 Dec;86(6):1745-53.
- Pennsylvania State University (PSU). Whole grain diets lower risk of chronic disease. February 5, 2008. Accessed online March 2, 2008 at http://live.psu.edu/story/28577