Grapes for Gut and Heart Health

(CALGRAM Trial)

Overseen By Francene M Steinberg, PhD, RD

Age: 18+

Sex: Any

Trial Phase: Academic

Sponsor: University of California, Davis

Must not be taking: Antibiotics, Prebiotics, Insulin

Disqualifiers: Coronary artery disease, Hypertension, Stroke, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: 5

Duration: 3 weeks

40 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial examines how eating grapes affects gut and heart health in healthy, overweight adults. Researchers aim to determine if consuming freeze-dried grape powder can alter gut bacteria, improve gut barriers, and influence heart-related health markers like inflammation and blood vessel function. Participants will consume either grape powder or a placebo to compare health changes. This trial suits overweight men and women, aged 45-70, who manage type 2 diabetes or metabolic syndrome without using insulin. Participants must follow a specific diet and provide blood and stool samples. As an unphased trial, this study offers a unique opportunity to contribute to the scientific understanding of dietary impacts on health.

Do I have to stop taking my current medications for the trial?

The trial does not specify if you need to stop taking your current medications, but it mentions that participants should be on stable treatment for type 2 diabetes or metabolic syndrome. It's best to discuss your medications with the trial team.

Is there any evidence suggesting that this trial's treatments are likely to be safe?

Previous studies have shown that freeze-dried grape powder is safe for consumption. Research indicates that this grape powder can lower cholesterol levels and improve heart health. For example, one study found a 6.1% decrease in total cholesterol after consuming grape powder. Another study demonstrated that eating grape products can lower systolic blood pressure, the top number in a blood pressure reading.

Grapes are rich in nutrients and antioxidants like resveratrol and quercetin, which benefit the heart and immune system. Overall, evidence suggests that freeze-dried grape powder is well-tolerated, with no serious side effects reported in the studies. It appears to be a safe option for those looking to improve heart health and gut function. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about the freeze-dried grape powder treatment because it offers a natural and potentially beneficial approach to improving gut and heart health. Unlike traditional medications that may focus on specific chemical compounds or synthetic ingredients, this treatment uses a whole food derivative, which may provide a wide array of polyphenols and antioxidants naturally found in grapes. These compounds are thought to help reduce inflammation and improve cardiovascular function. Additionally, consuming this treatment in a simple powder form dissolved in water is a novel and user-friendly method, making it easy for participants to incorporate into their daily routines. This approach taps into the growing interest in dietary interventions for health improvement, which could offer a complementary or alternative option to standard pharmaceutical treatments.

What evidence suggests that this trial's treatments could be effective for gut and heart health?

Research shows that freeze-dried grape powder, which participants in this trial will consume, might benefit heart and gut health. Studies have found that consuming grape powder can lower total cholesterol by 6.1% and HDL cholesterol by 7.6%. Nutrients and antioxidants like resveratrol and quercetin in grapes seem to boost the immune system. Additionally, grape powder may help blood vessels relax and lower blood pressure, benefiting heart health. Evidence also suggests that grape powder can reduce inflammation, linked to various health problems. Overall, these findings indicate that grape powder could lower risks related to heart and metabolic health and improve gut health. ^{1 2 6 7 8}

Are You a Good Fit for This Trial?

This trial is for healthy overweight men and women aged 45-70 who want to explore the health benefits of grape powder on gut and heart health. Participants should not have major health issues but may have concerns like high blood pressure or arterial stiffness. They must be willing to consume a test product daily and follow their usual diet with some restrictions.

Inclusion Criteria

Overweight (BMI between 25-30 kg/m2)

Ability to understand the intervention concept and written consent to participate

I am willing to be randomly assigned to a treatment group, undergo tests, and provide stool and blood samples.

Exclusion Criteria

I do not have any serious medical conditions like heart disease, uncontrolled high blood pressure, diabetes, liver disease, or active cancer.

Vegetarian/vegan

I have not used hormone replacement, antibiotics, or prebiotics in the last 3 months.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

1 week

1 visit (in-person)

Run-in

Participants limit intake of grapes and other polyphenol-rich foods while following their usual diet

1 week

Treatment

Participants consume 48 grams of freeze-dried grape powder or placebo dissolved in water twice daily

3 weeks

2 visits (in-person)

Washout

Participants undergo a washout period before crossover to the other intervention

3-4 weeks

Crossover Treatment

Participants switch to the alternate intervention (grape or placebo) for 3 weeks

3 weeks

2 visits (in-person)

Follow-up

Participants are monitored for safety and effectiveness after treatment

4 weeks

What Are the Treatments Tested in This Trial?

Interventions

• Freeze-dried grape powder
• Placebo powder

Trial Overview Researchers are testing if consuming freeze-dried grape powder can improve gut microbiome, intestinal permeability, inflammation levels, and vascular function compared to a placebo. The study involves taking the powder dissolved in water twice daily for four weeks while maintaining a normal diet with limited polyphenol-rich foods.

How Is the Trial Designed?

Group I: Placebo, Then Grape Experimental Treatment 2 Interventions

Participants consume 48 grams of placebo powder matching grape powder (dissolved into water) twice daily for 3 weeks. After a washout period of at least 3 weeks, participants then consume 48 grams of freeze-dried grape powder (dissolved into water) twice daily for 3 weeks.

Group II: Grape, Then Placebo Experimental Treatment 2 Interventions

Participants consume 48 grams of freeze-dried grape powder (dissolved into water) twice daily for 3 weeks. After a washout period of at least 3 weeks, participants then consume 48 grams of placebo powder matching grape powder (dissolved into water) twice daily for 3 weeks.

Who Is Running the Clinical Trial?

University of California, Davis

Lead Sponsor

Trials

958

Recruited

4,816,000+

California Table Grape Commission

Collaborator

Trials

8

Recruited

270+

Citations

1. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC8619073/

Effect of Grape Powder on Gut Microbiome: Pilot Study Grape powder consumption significantly decreased the total cholesterol by 6.1% and HDL cholesterol by 7.6%. There was also a trend of decreasing ...

2. clinicaltrials.gov clinicaltrials.gov/study/NCT07079982

Effects of Freeze-dried Grape Powder on Immune Profiles ... Grapes contain several nutrients and antioxidant polyphenols such as resveratrol, quercetin, vitamin K and fiber, which are known to promote heart and immune ...

3. cpp.edu cpp.edu/agri/agricultural-research-institute/showcase/abstracts_2025_bbw.pdf

The Effects of Freeze-Dried Whole Grape Powder on ... Major Conclusions: Grape consumption significantly increased fat-free mass, body mass index, and decreased TNF-α in healthy, normo- ...

4. onlinelibrary.wiley.com onlinelibrary.wiley.com/doi/full/10.1002/mnfr.202300224

Concentrated Grape Powder Consumption Modulates ... Four weeks' of concentrated grape powder (GP) consumption reduces circulating cholesterol in healthy free-living subjects consuming a low-fiber/low-polyphenol ...

5. researchgate.net researchgate.net/figure/effect-of-freeze-dried-grape-powder-on-cardiac-function-Abnormal-fractional_fig2_229074592

effect of freeze-dried grape powder on cardiac function.... demonstrated an improved arterial relaxation and a significant reduction in blood pressure and attenuated cardiac hypertrophy in spontaneously hypertensive rats ...

6. nature.com nature.com/articles/s41598-023-34813-5

Influence of grape consumption on the human microbiome A substantial body of information has accumulated suggesting dietary consumption of grapes may have a positive influence on human health.

7. sciencedirect.com sciencedirect.com/science/article/abs/pii/S0939475323001692

The effect of whole grape products on blood pressure and ... Whole grape products consumption significantly decreased systolic blood pressure. · Grape products did not have an effect on diastolic blood pressure, ...

8. liebertpub.com liebertpub.com/doi/10.1089/met.2018.0052

Effects of Freeze-Dried Grape Powder on High-Density ... Conclusions: Grape powder consumption did not impact HDL function in this cohort of adults with MetS. However, it was shown to improve fasting triglycerides, a ...