Resistant Starch Wheat for Improved Metabolic Health

Resistant starch (RS) is a type of dietary fiber that provides fermentable carbohydrate (FC)
in the lower bowel yielding positive effects on postprandial glycemia and weight management
as well as digestive tract health. RS is defined as the portion of starch resistant to
digestion by amylases, allowing it to reach the distal intestine where it can be fermented by
the resident intestinal microbiota. A limited number of human studies using RS from high
amylose corn have demonstrated that RS increases synthesis of gut peptides that improve
glucose homeostasis and insulin secretion. Based on these studies, the FDA has recently
approved the following health claims for resistant starch derived from corn (RS2): lowering
of blood glucose, blood cholesterol, and blood pressure; increased mineral absorption;
improved laxation; and reduced energy intake. The purpose in the proposed "proof of concept"
study here is to show that RS provided in the form of wheat flour products has similar
beneficial effects. The investigators aim to further explore the effect of RS on the gut
microbiota. The intestinal microbiome is comprised of over one trillion bacterial cells
comprised of approximately one thousand species that perform diverse functions ranging from
energy harvest, angiogenesis, immunomodulation, and regulation of mood and behavior. Some of
the major products of bacterial metabolism include acetate, propionate, and butyrate, the
major short chain fatty acids (SCFA). These bioactive fermentation products have been
associated with improved glucose homeostasis, attributed, in part, by their interactions with
receptors on intestinal cells to augment secretion of glucagon-like peptide-1 (GLP-1), an
incretin hormone known to stimulate insulin secretion.

This study is a randomized, cross-over design consisting of two 1-week dietary intervention
periods as well as a 2-week washout period in between. Subjects will be randomly assigned to
receive either RS wheat first or regular wheat first, then will be crossed over to the
opposite treatment following a 2-week washout period. Wheat products made from RS wheat and
regular wheat will be provided and the volunteers will be instructed to incorporate the
products into their usual diet for 7 days. This study will probe the associations between the
gut microbiota profiles, fermentation of RS wheat, microbial-mediated alterations in bile
acids, and glycemia. The investigators will measure these effects in healthy, middle-aged
humans using an interdisciplinary approach that integrates nutrition, microbiology,
intestinal physiology, and analytical chemistry.

Inclusion Criteria:

- Healthy adults. Healthy means that the candidate reports that s/he feels well and can
perform normal activities.

Exclusion Criteria:

- BMI <18.5 and >39.9 kg/m2

- Presence of of untreated or uncontrolled metabolic diseases

- Presence of gastrointestinal disorders that could interfere with the study outcome
(i.e. Crohn's disease, Irritable bowel syndrome, Colitis)

- Use of oral antibiotics within the past 3 months

- Presence of cancer or other serious chronic disease by self report

- Current use of prescribed or over the counter weight loss medications

- Pregnant

- Lactating

- Current use of tobacco

- Dietary restrictions that would interfere with consuming the intervention foods