Whole Grains vs Refined Grains for Metabolic Health

Overseen By Brett R Loman, PhD, RD

Age: 18 - 65

Sex: Any

Trial Phase: Academic

Sponsor: University of Illinois at Urbana-Champaign

Must not be taking: Statins, Oral hypoglycemics, Antihistamines, others

Disqualifiers: Diabetes, IBS, IBD, others

Compensation: Varies

Number of Visits: 1

Duration: 1 day per crossover arm

50 Participants Needed

Trial Summary

Will I have to stop taking my current medications?

Yes, you will need to stop taking certain medications to participate in this trial. Specifically, you cannot be using statins, oral hypoglycemic agents, insulin, prescription fiber, cholesterol and bile acid absorption inhibitors, anti-histamines, proton pump inhibitors, or antacids.

What data supports the effectiveness of the treatment 'Whole Grains vs Refined Grains for Metabolic Health'?

Research shows that whole grain rye bread can help reduce cholesterol levels in men and improve insulin response, which may support better metabolic health compared to refined grains. ^{1 2 3 4 5}

Is rye bread safe for human consumption?

Rye bread, including whole grain and refined varieties, has been studied for its effects on glucose and insulin levels, cholesterol, and appetite. These studies suggest that rye bread is generally safe for human consumption and may even offer health benefits like reducing cholesterol and improving insulin response. ^{1 2 3 4 5}

How does the treatment of whole grain rye bread differ from other treatments for metabolic health?

Whole grain rye bread is unique because it can improve glucose metabolism and reduce insulin response after meals, which may help with metabolic health. Unlike refined grains, whole grains like rye are associated with a lower risk of metabolic syndrome, making them a healthier option for managing metabolic conditions. ^{1 2 4 6 7}

What is the purpose of this trial?

The goal of this randomized, crossover, clinical trial is to link: 1) gastrointestinal motility patterns induced by acute consumption of whole and refined grains, 2) enteric microbial production of bioactive metabolites, and 3) circulating postprandial appearance of metabolites important to cardiometabolic health including glucose, triglycerides, and cholesterol. Participants will be asked to consume a Smartpill monitoring device that records metrics of gastrointestinal motility in response to whole or refined grains, monitor cardiometabolic metabolties over an 8 hour postprandial window, and provide a fecal sample for microbiome-related analyses.

Eligibility Criteria

This trial is for individuals with cardiovascular or metabolic diseases, an imbalance of gut microbes, nutritional issues, or gastrointestinal dysfunction. Participants will need to be comfortable consuming different types of rye bread and using a Smartpill device to monitor their digestive system.

Inclusion Criteria

I am a healthy man or woman.

Exclusion Criteria

My doctor diagnosed me with stenosis.

I have been diagnosed with diabetes by a doctor.

I have been diagnosed with IBS by a doctor.

Timeline

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants consume a Smartpill monitoring device and either whole or refined grain rye bread, followed by monitoring of gastrointestinal motility and cardiometabolic metabolites over an 8-hour postprandial window.

1 day per crossover arm

1 visit (in-person) per arm

Follow-up

Participants provide a fecal sample for microbiome-related analyses and are monitored for any delayed effects.

1-2 days

Treatment Details

Interventions

• Refined grain rye bread
• Whole grain rye bread

Trial Overview The study tests how whole grain and refined grain rye bread affect the digestive system's movement patterns, the production of certain substances by gut microbes, and levels of blood sugar, fats like triglycerides and cholesterol after eating.

Participant Groups

Group I: Whole grain rye bread Experimental Treatment 1 Intervention

4.3 ounces of whole grain rye bread, consumed after an overnight fast (12+ hours)

Group II: Refined grain rye bread Placebo Group 1 Intervention

4.3 ounces of white rye bread, consumed after an overnight fast (12+ hours)

Who Is Running the Clinical Trial?

University of Illinois at Urbana-Champaign

Lead Sponsor

Trials

203

Recruited

40,600+

Findings from Research

Whole grain rye crisp bread (both unfermented and fermented) significantly increases feelings of fullness and reduces hunger compared to refined wheat crisp bread, with reported fullness 16% higher and hunger 11-12% lower after consumption.

Whole grain rye crisp bread also results in a lower postprandial insulin response, with unfermented rye crisp bread showing a 17% reduction in insulin response compared to refined wheat, suggesting that its dietary fiber content and microstructure contribute to these beneficial effects.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effects of unfermented and fermented whole grain rye crisp breads served as part of a standardized breakfast, on appetite and postprandial glucose and insulin responses: a randomized cross-over trial. Johansson, DP., Lee, I., Risérus, U., et al.[2018]

In a study involving 19 healthy postmenopausal women, rye breads resulted in significantly lower postprandial insulin and C-peptide responses compared to refined wheat bread, suggesting a beneficial effect on insulin metabolism.

The differences in insulin response were not solely due to fiber content, but rather structural differences in the rye breads, indicating that the physical properties of the bread may play a key role in glucose and insulin regulation.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Structural differences between rye and wheat breads but not total fiber content may explain the lower postprandial insulin response to rye bread. Juntunen, KS., Laaksonen, DE., Autio, K., et al.[2022]

In a study involving 121 type 2 diabetic patients, whole wheat, wheat bran, and rye breads did not significantly differ in their effects on blood glucose and insulin levels compared to white wheat bread.

All four types of bread led to similar increases in blood glucose levels, indicating that these alternative breads may not be effective substitutes for white bread in managing diabetes.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dietary breads: myth or reality? Mesci, B., Oguz, A., Sagun, HG., et al.[2017]

Sourdough wholegrain rye bread (WGR) significantly improved glucose metabolism and increased plasma levels of beneficial short-chain fatty acids (SCFAs) compared to white wheat bread (WW), with lower postprandial insulin levels and improved insulin secretion after consumption.

Rye bran-enriched white wheat bread (BRB+WW) also showed beneficial effects on glucose metabolism and SCFA production, but these effects were less pronounced than those observed with WGR, indicating that while BRB+WW is beneficial, WGR may be the superior option.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Postprandial glucose metabolism and SCFA after consuming wholegrain rye bread and wheat bread enriched with bioprocessed rye bran in individuals with mild gastrointestinal symptoms. Lappi, J., Mykkänen, H., Bach Knudsen, KE., et al.[2018]

In a study involving 40 healthy participants (18 men and 22 women), consuming whole meal rye bread significantly reduced total cholesterol by 8% in men, while no significant changes were observed in women or during the wheat bread period.

The reduction in cholesterol levels was dependent on the amount of rye bread consumed, indicating that incorporating rye bread into the diet can be an effective and practical way for men with elevated cholesterol to lower their serum cholesterol levels.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Rye bread decreases serum total and LDL cholesterol in men with moderately elevated serum cholesterol. Leinonen, KS., Poutanen, KS., Mykkänen, HM.[2018]

Whole grain consumption is associated with a lower risk of metabolic syndrome (MetS), with a relative risk of 0.80, indicating that higher whole grain intake may help reduce the likelihood of developing MetS.

In contrast, refined grain consumption is linked to a higher risk of MetS, with a relative risk of 1.37, suggesting that diets high in refined grains may increase the chances of developing this condition.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Associations of Whole Grain and Refined Grain Consumption With Metabolic Syndrome. A Meta-Analysis of Observational Studies. Guo, H., Ding, J., Liang, J., et al.[2021]

A review of 135 studies published between 2000 and 2010 found that moderate consumption of refined grains (up to 50% of total grain intake) is not linked to increased risks of cardiovascular disease, diabetes, weight gain, or overall mortality.

While very high intakes of refined grains may be associated with certain cancers, the evidence suggests that moderate consumption does not pose significant health risks, but it is still recommended to prioritize whole-grain foods for better health.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Evaluation of the evidence between consumption of refined grains and health outcomes. Williams, PG.[2015]

References

1. United States pubmed.ncbi.nlm.nih.gov

Effects of unfermented and fermented whole grain rye crisp breads served as part of a standardized breakfast, on appetite and postprandial glucose and insulin responses: a randomized cross-over trial. [2018]

2. United States pubmed.ncbi.nlm.nih.gov

Structural differences between rye and wheat breads but not total fiber content may explain the lower postprandial insulin response to rye bread. [2022]

3. Ireland pubmed.ncbi.nlm.nih.gov

Dietary breads: myth or reality? [2017]

4. England pubmed.ncbi.nlm.nih.gov

Postprandial glucose metabolism and SCFA after consuming wholegrain rye bread and wheat bread enriched with bioprocessed rye bran in individuals with mild gastrointestinal symptoms. [2018]

5. United States pubmed.ncbi.nlm.nih.gov

Rye bread decreases serum total and LDL cholesterol in men with moderately elevated serum cholesterol. [2018]

6. Switzerland pubmed.ncbi.nlm.nih.gov

Associations of Whole Grain and Refined Grain Consumption With Metabolic Syndrome. A Meta-Analysis of Observational Studies. [2021]

7. United States pubmed.ncbi.nlm.nih.gov

Evaluation of the evidence between consumption of refined grains and health outcomes. [2015]