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

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial aims to understand how eating whole grain versus refined grain rye bread affects digestion and heart health markers such as blood sugar and cholesterol. Participants will consume either type of bread and swallow a small device that tracks digestion while also providing a stool sample for gut health analysis. It is ideal for healthy individuals without digestive issues, diabetes, or grain allergies who are not on specific medications or supplements. As an unphased study, this trial offers a unique opportunity to contribute to scientific knowledge about diet and health.

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 prior data suggests that the Smartpill monitoring device is safe for use in this trial?

Research shows that whole grain rye bread is generally safe to eat. Studies have found that consuming whole grain rye can improve blood fat levels, such as cholesterol and triglycerides. This benefit is particularly helpful for individuals with metabolic syndrome, a condition that increases the risk of heart disease and diabetes.

Specific information on the safety of refined grain rye bread is lacking, but refined grains are a common part of many diets and are usually considered safe for most people.

Overall, whole grain rye is associated with positive health benefits, and studies have not reported any major safety concerns. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about using whole grain rye bread for metabolic health because it offers a natural, dietary approach to improving metabolism, unlike typical treatments that might involve medication or supplements. Whole grains are packed with fiber, which can help regulate blood sugar levels and improve digestive health, offering a potential new way to manage metabolic issues. Additionally, whole grain rye may impact gut health positively, which is increasingly recognized as crucial for overall metabolic function. This makes it an intriguing option for those seeking lifestyle-based interventions rather than pharmaceutical solutions.

What evidence suggests that this trial's treatments could be effective for metabolic health?

This trial will compare whole grain rye bread with refined grain rye bread for metabolic health. Research has shown that whole grain rye bread, which participants in this trial may receive, can benefit metabolism. Studies have found that consuming whole grain rye can improve blood fat levels, which are important for heart health. One study suggested that rye bread might lower insulin levels after meals without affecting blood sugar. Additionally, whole grain rye bread may help improve heart and metabolic health over several hours. While whole grains appear beneficial, they have only a small effect on gut bacteria in people with metabolic issues. ^{1 2 6 7 8}

Are You a Good Fit for This Trial?

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 for a Trial Participant

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

What Are the Treatments Tested in This Trial?

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.

How Is the Trial Designed?

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+

Published Research Related to This Trial

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]

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 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]

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]

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]

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]

Citations

1. sciencedirect.com sciencedirect.com/science/article/pii/S0022316622011907

Intake of Whole-Grain and Fiber-Rich Rye Bread Versus ... Our results indicate that the quality of grains has a minor effect on the intestinal microbiota composition in participants with metabolic syndrome.

2. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC11956258/

Effect of rye consumption on markers of glycemic control Overall, results of this meta-analysis suggest that rye consumption may reduce insulin postprandial AUC without affecting glucose markers.

3. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC4207773/

Whole Grain Rye Intake, Reflected by a Biomarker, Is ... Whole grain rye intake, reflected by a biomarker, is associated with favorable blood lipid outcomes in subjects with the metabolic syndrome – a randomized ...

4. sciencedirect.com sciencedirect.com/science/article/pii/S0002916522010747

Effects of whole-grain wheat, rye, and lignan ... Conclusions. WG rye, alone or with SDG supplementation, compared with WG wheat did not affect glucose metabolism but caused transient LDL-cholesterol reduction.

5. nutritionj.biomedcentral.com nutritionj.biomedcentral.com/articles/10.1186/s12937-017-0246-5

Effects of whole grain rye, with and without resistant starch ... Whole grain rye bread has the potential to improve cardiometabolic variables in an 11–14.5 h perspective in healthy humans.

6. journals.plos.org journals.plos.org/plosone/article?id=10.1371/journal.pone.0110827

Whole Grain Rye Intake, Reflected by a Biomarker, Is ... Whole Grain Rye Intake, Reflected by a Biomarker, Is Associated with Favorable Blood Lipid Outcomes in Subjects with the Metabolic Syndrome – A Randomized Study.

7. ajcn.nutrition.org ajcn.nutrition.org/article/S0002-9165(22)01074-7/fulltext

Effects of whole-grain wheat, rye, and lignan supplementation ... A whole-grain (WG)–rich diet has shown to have potential for both prevention and treatment of the metabolic syndrome (MetS), which is a cluster of risk ...

8. frontiersin.org frontiersin.org/journals/nutrition/articles/10.3389/fnut.2022.868938/full

The Effect of Rye-Based Foods on Postprandial Plasma ... Rye bread has been shown to induce lower insulin response in the postprandial phase, without affecting the glucose response.