Increased Whole Grain Consumption Does Not Affect Blood Biochemistry, Body Composition, or Gut Microbiology in Healthy, Low-Habitual Whole Grain Consumers

Abstract

A combination of dietary advice and provision of commercially available food items enabled subjects with a low-moderate habitual consumption of WG to substantially increase their WG intake, but there was little effect on blood biochemical markers, body composition, BP, fecal measurements, or gut microbiology. This trial was registered at www.controlled-trials.com as ISRCTN36521837.

Substituting whole grains for refined grains in a 6-wk randomized trial favorably affects energy-balance metrics in healthy men and postmenopausal women

“…Moreover, the magnitude of the effect was estimated to be greater than that attributed to the nondigestible energy content of the fiber itself. The between-group differences in fiber intake and stool weight equated to a difference of 4 g stool/g fiber, which was consistent with recent reports on the relation between stool weight and cereal fiber intake (10,46). Likewise, the increase in the stool energy content within the WG was consistent with multiple reports that have collectively shown that increasing dietary fiber intake reduces dietary energy digestibility (47,48).…”

“…To our knowledge, these results provide new mechanistic insights that support the consistent inverse associations between whole-grain intake and BMI and adiposity that have been documented in epidemiologic studies (3-9), but which have been largely unsubstantiated in previous clinical trials (4,(10)(11)(12)(13)(14)(15)(16)(17). As such, this study adds support for dietary guidance recommending the consumption of whole grains in place of refined grains.…”

“…After the run-in period, participants were randomly assigned by the study statistician with the use of a computer program. During the subsequent 6 wk, participants were provided with either a weight-maintaining whole grain-rich diet [whole grain-rich diet group (WG)] 10 or a weight-maintaining refined grain-based diet (weight-maintaining refined grainbased diet group (RG)] that did not contain any whole grains.…”

“…These recommendations are the result of accumulating evidence that has linked higher whole-grain intake to reduced risks of type 2 diabetes and cardiovascular disease (2)(3)(4)(5) and the consistent epidemiologic finding that individuals who consume recommended amounts of whole grains ($3 servings or 48 g/d), compared with individuals who consume few whole grains, have reduced BMI and adiposity and a lower prospective body weight gain (3)(4)(5)(6)(7)(8)(9). However, multiple randomized controlled trials (10)(11)(12)(13)(14)(15)(16)) and 2 recent meta-analyses of clinical trials (4,17) have largely been at odds with the epidemiologic data, collectively having failed to find evidence to support the favorable effects of whole grains on body weight. In addition, although 2 clinical trials have reported favorable effects of whole grains on adiposity (14,15), the collective evidence base has not been conclusive (10,13,17).…”

“…However, multiple randomized controlled trials (10)(11)(12)(13)(14)(15)(16)) and 2 recent meta-analyses of clinical trials (4,17) have largely been at odds with the epidemiologic data, collectively having failed to find evidence to support the favorable effects of whole grains on body weight. In addition, although 2 clinical trials have reported favorable effects of whole grains on adiposity (14,15), the collective evidence base has not been conclusive (10,13,17). Because of the many health sequleae that are associated with overweight and obesity, there has been substantial scientific interest in resolving these inconsistencies to clarify the role of whole grains in weight management and the prevention of obesity.…”