Wheat Bran, Whole Grain, and Food Synergy

This issue of Diabetes Care contains an article by Jenkins et al. (1) with a surprising, perhaps counter-intuitive result. The authors studied 23 type 2 diabetic volunteers in a randomized cross-over design with 3 months consumption of wheat bran contributing 19 g fiber per day, compared with 3 months consumption of refined grain with 4 g fiber per day. The wheat bran supplement had no discernible effect on body weight, fasting blood glucose, HbA_1c, serum lipids, apolipoproteins, blood pressure, serum uric acid, clotting factors, homocysteine, C-reactive protein, magnesium, calcium, iron, or ferritin. The only statistically significant finding was unanticipated: there was a small increase in LDL oxidation associated with wheat bran. The study was conducted meticulously by investigators well known for their important findings in the effect of foods on human metabolism. We applaud both the execution and the publication of this article.

Despite the applause, all studies have potential flaws, and limitations of this study deserve comment. One remarkable flaw is that 44 of the 67 people who began the study dropped out. There is no way to fully assess whether these dropouts might have biased the findings. In our experience, asking participants to stay with a study for two 3-month periods is very ambitious. According to Dr. Jenkins (personal communication, 14 June 2002), this difficult protocol was carried out without any payment to the participants. Our assumption is that the failure to provide any financial compensation to participants is telling and likely accounts for the high dropout rate. However, it is our opinion that desire to be compensated for research participation is largely unrelated to metabolic outcomes.

Another weakness in the study design is that the participants chose their own diets, except for …