The Addition of Whole Grains to the Diets of Adults: A Study of Digestive Health and Natural Defenses

The Addition of Whole Grains to the Diets of Adults: A Study of Digestive Health and Natural Defenses

The purpose of this study is to determine if substituting whole grains for refined grains in the diets of healthy adults over a period of 6 weeks alters the composition of the bacteria in the gut, and has beneficial effects on immune function, digestive health, cardiovascular health, regulation of body weight and composition, and vitamin K status.

The investigators hypothesize that whole grain consumption over a period of 6 weeks will alter the gut microflora toward a more beneficial bacterial profile, improve the immune response while reducing oxidative stress and inflammatory markers, have favorable effects on factors influencing the regulation of body weight and composition,increase bacterial vitamin K synthesis, and beneficially effect surrogate markers of cholesterol synthesis/absorption, vitamin D concentrations, and whole genome DNA methylation patterns. In statin users it is hypothesized that, consumption of whole grains will alter statin pharmacokinetics by decreasing rate of statin absorption, resulting in more sustained plasma concentrations.

This study is a randomized parallel-arm trial using a six-week dietary intervention following a 2 week run-in period. Healthy volunteers will be randomized to two groups (n=40/group), and consume either a diet rich in whole grains or a diet rich in refined grains provided at estimated energy requirements for 6 weeks. Outcomes will be measured during the run-in period and at week 6 of the intervention. To control for variation in microbiota an additional 10 volunteers will serve as "negative controls" and not undergo any diet intervention.

Subjects Inclusion Criteria

• Healthy male and female subjects aged 40-65 y (women must be > 1 year postmenopausal or had both ovaries removed, if premenopausal).

• Body mass index (BMI) 20-35 kg/m.2

• Pass screening blood and urine tests

  • Creatinine ≤ 1.5 mg/dL
  • glutamic oxaloacetic transaminase/serum glutamate pyruvate transaminase/total bilirubin ≤ twice the upper limit of normal range
  • Fasting glucose <125 mg/dL
  • hematocrit ≥ 32%
  • white blood cell count ≥ 1.8 x 103/mm3 (M)
  • PLT ≥ 100 x 103/mm3 (thou/µL)

• Must be willing to be randomized.

• Those randomized to either the WG or RG groups must be willing to consume only study foods and beverages provided.

Exclusion Criteria

• Self reported weight change >4kg within the past 3 months.
• Have participated in a weight loss program within the last 3-months; eligible if in weight reduction program to maintain body weight.
• Not willing to reduce habitual daily fiber intake (including prebiotics) within 2 wk prior to enrollment to < ~7g/1000kcal/d for men, or <~8g/1000kcal/d for women if currently consuming greater amounts.
• Not willing to stop consumption of probiotic or prebiotic supplements within 2 weeks prior to start of study if currently taking these, as well as during study participation.
• Vegetarian diet.
• Not willing to stop taking multivitamins, and supplements (with the exception of vitamin D and calcium), including fish oil or n-3 fatty acids and herbal supplements, for 30 days prior to or during study participation, if currently taking these.
• Regular use of laxatives, stool softeners, or anti-diarrheal medications, and medications influencing food intake and/or appetite.
• Not willing to undergo a 3-month washout period after colonoscopy prior to enrollment, and not willing to defer colonoscopy until after study completion.
• Eating disorder within the past 10 years.
• Disinhibited eating behavior as indicated by a score above 12 on the Three Factor Eating Questionnaire.
• Food allergies or aversions or other issues with foods that would preclude use of study diets, including gluten, milk, nuts, or eggs.
• Individuals identified during screening as having barriers expected to deter compliance with dietary requirements (e.g., stated dislike of study foods, inadequate resources to store and reheat meals, inability to adhere to food pick-up schedule).
• Alcohol consumption >2 drinks per day.
• Not willing to abstain from alcohol consumption during the study.
• Smoking or using nicotine containing products in the last 6 months.
• Use of aspirin, non-steroidal anti-inflammatory medications (NSAIDs) or antihistamine prescribed by a physician or clinician, or the inability to discontinue the use of these substances for 72 hrs before first day blood draw until 48 hrs after DTH implant (i.e. after second reading).
• Use of anabolic steroids, insulin, growth hormone or testosterone.
• Type I or type II diabetes.
• Uncontrolled major illnesses. (Will include if stable on drugs used to control cardiovascular, liver, and renal diseases, asthma, and dysphagia).
• Current use of proton pump inhibitors and H2 blockers to control acid-reflux/heart burn
• Use of medications which interfere with energy metabolism including oral glycemic agents and insulin.
• Uncontrolled hypertension as determined by study physician or nurse.
• Use of immunosuppressive drugs.
• Active cancer or current cancer diagnosis (except non-melanoma skin cancer).
• Active infection within 2 weeks of study enrollment, blood draws or skin tests; however, may participate if admission is postponed or study activity is rescheduled > 2 weeks after resolution of symptoms.
• Any antibiotic use within the past 3 months, except topical antibiotic use.
• History of dysphagia, malabsorptive disorders, inflammatory bowel disease or other gastrointestinal disorders such as ulcerative colitis, Crohn's disease, celiac disease , chronic diarrhea or constipation.
• Gastric bypass or other surgery for weight loss.
• Splenectomy or partial splenectomy.
• Autoimmune diseases such as rheumatoid arthritis and psoriasis. Autoimmune thyroid disease that has been treated and with stable replacement doses is not an exclusion.
• Taking warfarin or coumadin any time during the previous 6 months.
• Current diagnosis of or treatment for psychosis (i.e. schizophrenia, etc.). Include depression if has been stable on treatment regimen for > 6 months.
• Blindness or deafness not corrected with use of glasses and hearing aids.
• Does not speak English; due to insufficient funds to hire a translator and to get all study materials translated into another language to allow us to recruit non-English speaking participants non-English speakers will not be eligible to participate.