Grape Science Center

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Cardiovascular (Heart) Health

Cardiovascular Health

We invite you to discover the emerging science behind Concord grapes. While more research is needed to confirm Concord grapes’ link to health, in this section you will find the very latest information on grape science.

Please note: The following research overviews are based on a thorough assessment of the studies, but they are intended to be summaries only. Please refer to publications in each section for further details. As always, please keep study designs and limitations in mind when assessing how this research may or may not relate to your health or the health of your clients.


In addition to a produce-rich diet and active lifestyle, Concord grapes may be one important ingredient in maintaining a healthy cardiovascular system by supporting healthy arteries, which helps promote healthy blood flow and blood pressure.1,2

Concord grapes may help support flexible arteries to promote healthy blood flow.3-8

  • A study by Freedman et al. in 2001 (Circulation) investigated 20 healthy adults who drank Welch’s Purple Grape Juice (7 mL/kg/d) for 14 days. Compared to baseline, after two weeks of juice consumption, platelet aggregation (clotting) was inhibited and superoxide (a free radical) release was decreased. In addition, drinking grape juice stimulated the production of nitric oxide by platelets – which promotes arterial relaxation and allows them to support healthy blood flow. While there was no significant change in the level of certain antioxidants within the plasma, an ORAC assay showed a significant increase in total plasma antioxidant capacity.6 See below for more on Concord grape juice’s impact on antioxidant activity and platelet aggregation.
  • Concord grape juice consumption appears to help widen arteries when necessary, specifically in individuals with coronary artery disease (CAD). In 1999, Stein et al. studied 15 participants with CAD who consumed Concord grape juice for two weeks (4 mL/kg/d twice daily) and saw increases in flow mediated dilation of the brachial artery.7 Chou and colleagues performed a similar study over a longer time period. These researchers found that in two groups of 11 adults with CAD, supplemented with different levels of Concord grape juice (4 mL/kg/d and 8 mL/kg/d respectively), there were equivalent and significant increases in brachial dilation compared to baseline findings after 28 days.4
  • In contrast, a study on grape juice and blood pressure of 64 subjects with pre-hypertension or stage 1 hypertension found that after eight weeks of consuming 100% Concord grape juice and a placebo beverage, there was no benefit of the grape juice on arterial stiffness and endothelial function. The authors suggest that no change was seen perhaps because the subjects were generally healthy and had only modestly elevated blood pressure.9
  • Early research shows that Concord grape juice may work in a similar fashion to red wine to promote healthy, flexible arteries—but without the confounding effects of alcohol. For example, findings from a 2007 Cardiovascular Research study found that Concord grape juice was shown to stimulate the production of nitric oxide in cells that line the arteries, promoting arterial relaxation. In this laboratory study, Anselm and colleagues examined animal coronary arteries ex vivo to determine arterial endothelium production of nitric oxide following treatment with Concord grape juice. The researchers found nitric oxide production was stimulated more than the control not treated with Concord grape juice.3 Additional research has also illustrated that Concord grape juice produces this relaxation effect by stimulating the same reactions in the arteries that are activated by red wine.
  • In a laboratory study by Schini-Kerth et al, the authors found that treating endothelial cells with Concord grape juice increased nitric oxide levels by 50%. And, for the first time, researchers showed that Concord grape juice boosted the levels of endothelial nitric oxide synthase (the protein that makes nitric oxide) for up to a full day. Specifically, Concord grape juice turned on proteins that signal the cell to make more endothelial nitric oxide synthase.8

Concord grapes may help promote healthy, clear arteries.7, 10-13

  • Although there is no evidence from human studies to suggest that Concord grape juice will lower total cholesterol levels, it may help manage the effects of LDL, or “bad,” cholesterol to help keep arteries free and clear of excess plaque build-up.7, 10-13 If LDL particles are oxidized while in the arterial wall, this can initiate a cascade of events that can eventually lead to arterial blockage. Some,7,10 but not all14 research has shown that Concord grape juice is linked to an increase in serum antioxidant capacity as determined by ORAC. And studies have linked Concord grape juice to slowing of LDL oxidation, alone or with the addition of vitamin E.4, 7, 10-13
  • A 2002 study by O’Byrne et al., published in the American Journal of Clinical Nutrition, investigated the differences between Concord grape juice and vitamin E (alpha-tocopherol) on oxidative stress in healthy adults. Seventeen participants were randomized to a vitamin E (400 IU, alpha-tocopherol) group and 15 to a Concord grape juice (10 mL/kg/d) group. Both groups experienced significant increases in serum antioxidant capacity and decreased LDL oxidation rate.10 Positive results on LDL-oxidation were also seen by Stein et al. (study also noted above), where CAD patients drinking Concord grape juice for two weeks experienced slowed LDL oxidation time versus baseline (117 v. 87 minutes).7 While these findings are promising, Chou and colleagues found that consuming Concord grape juice had no beneficial effect on LDL oxidation rate in CAD patients studied over a 28 day period.4 Additionally, in a recent study in healthy adults, Hollis and colleagues failed to find a significant increase in serum antioxidant capacity with chronic Concord grape juice consumption.14

Concord grapes have been shown to have an anti-clotting effect6,11,15 similar to red wine.16

  • Red wine has been shown to have an effect on inhibiting platelet aggregation.16
  • A crossover study by Keevil et al. compared the effects of consuming about two cups/day of either purple grape, orange or grapefruit juice in 10 healthy adults. 100% grape juice was the only juice to show anti-clotting effects through its ability to inhibit platelet aggregation.15 Freedman et al. published similar benefits of Concord grape juice on decreasing platelet aggregation in a study of 20 healthy, adults consuming 7 mL/kg/d for 2 weeks.6 Both authors attribute the anti-clotting effects to Concord grape juice’s high content of proanthocyanins and other flavonoid polyphenols. While these clinical results are exciting, these outcomes were not replicated by Albers and colleagues who found Concord grape juice to have no beneficial effect on platelet aggregation in those who were already on aspirin therapy.17
  • An animal study by Shanmuganayagam et al., published in Atherosclerosis, also supports the anti-clotting effects of Concord grape juice. Twenty animal subjects were fed the same high cholesterol diet for the first 48 days. For the second 48 days, half of the group received Concord grape juice and the other half of the group received a sugar water control. The animals drinking Concord grape juice experienced significantly reduced platelet aggregation by day 96.11

In certain populations, Concord grapes may play a role in healthy blood pressure.9,18,19

  • A double-blinded, placebo controlled study by Park et al., (Biofactors, 2004) of 40 adult Korean men with elevated blood pressure, found that daily consumption of Concord grape juice for 8 weeks (5.5 mL/kg/d) resulted in lower systolic and diastolic blood pressure versus baseline.18
  • Another study by Mark and Maki found that after 12 weeks of daily consumption of 12 oz. of Concord grape juice, both systolic and diastolic blood pressure responses were significantly decreased in men with a high baseline systolic blood pressure.19
  • It is healthy and normal for blood pressure to drop at night—giving the heart a rest. People who do not experience these nighttime (nocturnal) dips in blood pressure may be at increased risk for heart-related health issues over time.20,21 A recent double-blind, cross-over study, published in the American Journal of Clinical Nutrition by Dohadwala et al., of 64 adult men and women with pre-hypertension or stage 1 hypertension, found that drinking Concord grape juice helped lower nocturnal blood pressure and had a beneficial effect on blood glucose levels compared to a placebo-matched control. This study also found that Concord grape juice consumption did not impact body weight. No significant decrease in 24-hour ambulatory blood pressure was found, so these findings should not be taken to mean that Concord grape juice treats high blood pressure.9

Bottom Line

Based on published research to-date, Concord grapes and grape-based products appear to play a positive role in promoting heart-health in certain population groups. With that said, findings from animal, both in vivo and ex vivo, and in vitro models need to be replicated in larger human studies in order to better understand the biomedical benefits of grapes and grape products in a more diverse population.

Bibliography

  1. Vislocky LM and Fernandez MLF. Biomedical Effects of Grape Products. Nutrition Reviews. 2010. 68(11): 656-670. onlinelibrary.wiley.com/doi/10.1111/j.1753-4887.2010.00335.x/abstract
  2. Vislocky LM and Fernandez ML. Grapes and Grape Products: Their Role in Health. Nutr Today. 2013. 48(1):47-51. delivery.sheridan.com/downloads/original/196284_Vislocky_44393S_Marybeth.exe
  3. Anselm E, Chataigneau M, Ndiaye M, Chataigneau T and Schini-Kerth VB. Grape juice causes endothelium-dependent relaxation via a redox-sensitive Src- and Akt-dependent activation of eNOS. Cardiovasc Res. 2007. 73(2):404-413. www.ncbi.nlm.nih.gov/pubmed/16962569
  4. Chou EJ, Keevil JG, Aeschlimann S, Wiebe DA, Folts JD and Stein JH. Effect of ingestion of purple grape juice on endothelial function in patients with coronary heart disease. Am J Cardiol. 2001. 88(5):553-555. www.ncbi.nlm.nih.gov/pubmed/11524068
  5. Fitzpatrick DF, Hirschfield SL and Coffey RG. Endothelium-dependent vasorelaxing activity of wine and other grape products. Am J Physiol. 1993. 265(2 Pt 2):H774-778. www.ncbi.nlm.nih.gov/pubmed/8396352
  6. Freedman JE, Parker C, 3rd, Li L, Perlman JA, Frei B, Ivanov V, Deak LR, Iafrati MD and Folts JD. Select flavonoids and whole juice from purple grapes inhibit platelet function and enhance nitric oxide release. Circulation. 2001. 103(23):2792-2798. www.ncbi.nlm.nih.gov/pubmed/11401934
  7. Stein JH, Keevil JG, Wiebe DA, Aeschlimann S and Folts JD. Purple grape juice improves endothelial function and reduces the susceptibility of LDL cholesterol to oxidation in patients with coronary artery disease. Circulation. 1999. 100(10):1050-1055. www.ncbi.nlm.nih.gov/pubmed/10477529
  8. Alhosin M, Anselm E, Rashid S, Kim JH, Madeira SVF, Bronner C and Schini-Kerth VB. Redox-sensitive up-regulation of eNOS by purple grape juice in endothelial cells: role of PI3-kinase/Akt, p38 MAPK, JNK, FoxO1 and FoxO3a. PLoS ONE. 2013. 8(3):e57883. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0057883
  9. Dohadwala MM, Hamburg NM, Holbrook M, Kim BH, Duess M, Levit A, Titas M, Chung WB, Vincent FB, Caiano T, Frame AA, Keaney Jr JF, and Vita JA. Effects of Concord grape juice on ambulatory blood pressure in prehypertension and stage 1 hypertension. Am J Clin Nutr. 2010. 92(5):1052-1059. www.ncbi.nlm.nih.gov/pubmed/20844075
  10. O'Byrne DJ, Devaraj S, Grundy SM and Jialal I. Comparison of the antioxidant effects of Concord grape juice flavonoids alpha-tocopherol on markers of oxidative stress in healthy adults. Am J Clin Nutr. 2002. 76(6):1367-1374. www.ncbi.nlm.nih.gov/pubmed/12450905
  11. Shanmuganayagam D, Warner TF, Krueger CG, Reed JD and Folts JD. Concord grape juice attenuates platelet aggregation, serum cholesterol and development of atheroma in hypercholesterolemic rabbits. Atherosclerosis. 2007.190(1):135-142. www.ncbi.nlm.nih.gov/pubmed/16780846
  12. Vinson JA, Teufel K and Wu N. Red wine, dealcoholized red wine, and especially grape juice, inhibit atherosclerosis in a hamster model. Atherosclerosis. 2001. 156(1):67-72. www.ncbi.nlm.nih.gov/pubmed/11368998
  13. Vinson JA, Yang J, Proch J and Liang X. Grape juice, but not orange juice, has in vitro, ex vivo, and in vivo antioxidant properties. J Med Food. 2000. 3(4):167-171. www.ncbi.nlm.nih.gov/pubmed/19236173
  14. Hollis JH, Houchins JA, Blumberg JB and Mattes RD. Effects of Concord Grape Juice on Appetite, Diet, Body Weight, Lipid Profile, and Antioxidant Status of Adults. J Am Coll Nutr. 2009. 28(5):574-582. www.ncbi.nlm.nih.gov/pubmed/20439553
  15. Keevil JG, Osman HE, Reed JD and Folts JD. Grape juice, but not orange juice or grapefruit juice, inhibits human platelet aggregation. J Nutr. 2000. 130(1):53-56. www.ncbi.nlm.nih.gov/pubmed/10613766
  16. Folts JD. Antithrombotic potential of grape juice and red wine for preventing heart attacks. Pharmaceutical Biology. 1998. 36(Suppl. 1):21-27. www.ingentaconnect.com/content/tandf/phbi/1998/00000036/A00100s1/art00005
  17. Albers AR, Varghese S, Vitseva O, Vita JA and Freedman JE. The antiinflammatory effects of purple grape juice consumption in subjects with stable coronary artery disease. Arterioscler Thromb Vasc Biol. 2004. 24(11):e179-180. www.ncbi.nlm.nih.gov/pubmed/155284833
  18. Park YK, Kim JS and Kang MH. Concord grape juice supplementation reduces blood pressure in Korean hypertensive men: double-blind, placebo controlled intervention trial. Biofactors. 2004. 22(1-4):145-147. www.ncbi.nlm.nih.gov/pubmed/15630270
  19. Mark D and Maki K. Concord grape juice reduces blood pressure in men with high systolic blood pressure. Presented at Experimental Biology. San Diego, CA. April 11-15, 2003.
  20. Ben Dov IZ, Kark, JD, Ben Ishay D, Mekler J, Ben Arie L and Bursztyn M. Predictors of all-cause mortality in clinical ambulatory monitoring: unique aspects of blood pressure during sleep. Hypertension. 2007. 49(6):1235-1241. www.ncbi.nlm.nih.gov/pubmed/17389258
  21. Sayk F, Becker, C, Teckentrup C, Fehm HL, Struk J, Wellhoener JP and Dodt C. To dip or not to dip: on the physiology of blood pressure decrease during nocturnal sleep in healthy humans. Hypertension. 2007. 49(5):1070-1076. www.ncbi.nlm.nih.gov/pubmed/17353512
Eating a balanced diet rich in a variety of fruits and vegetables is important for maintaining overall health. Delicious Concord grapes and 100% grape juice are part of a nutritious diet, but they should not be used to treat health problems. If you are worried about your health or are faced with a medical concern, be sure to consult with your doctor.

Guide to Navigating Research Studies

The definition of scientific research is performing a methodical study in order to prove a theory or answer a question. The following is a brief overview of different types of research used in health and nutrition exploration 1:

Case-Control Study
Clinical Study
Cohort Study
Cross-Sectional Study
Observational Study
Pilot Study
Preclinical or Laboratory Studies
Randomized Controlled Trials

Reference:

1. Hulley SB, Cummings SR, Browner WS, Grady D, Hearst N, Newman TB. Designing Clinical Research: An Epidemiologic Approach. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.


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An observational study, usually a retrospective study (a study that looks backward in time) that compares two groups of people: 1) those with the specific condition (e.g., disease) being studied (cases) and, 2) a similar group of people without that condition (controls). Researchers compare these two groups of people and important characteristics, such as certain lifestyle choices, to determine what factors may be associated with the condition under investigation.

A type of study that often includes patients with specific health conditions who could benefit from receiving a new treatment. These studies can also be performed in healthy subjects. The end goal of a clinical study (also called clinical research or clinical trial) is to determine effectiveness and safety of a health intervention in humans.

An observational study, usually prospective (looking forward), that follows a group of similar people over time. The goal is to determine which factors and exposures affect the development of a specific outcome or health condition (e.g., disease) during the study’s time period.

A type of observational study, often given as a survey, that examines a group of subjects during a single occasion, or over a very short period of time. This type of study aims to describe the relationship between health-related conditions (e.g., metabolic syndrome, hypertension) and other factors that exist in the general population (e.g., dietary intake, physical activity levels), during a particular time period.

A type of study in which researchers simply observe subjects and measure the associations between certain characteristics (e.g., fruit/vegetable intake) and specific outcomes (e.g., obesity). Examples of observational studies include case-control studies, cross-sectional studies, and cohort studies. While these studies gather important information, they cannot prove that a specific treatment or factor affects health.

A small scale, preliminary study that is conducted to determine the potential for a larger study.

A stage of research that often occurs prior to trials involving humans. This type of research can help determine mechanisms of action of a treatment, or how the treatment is causing the effect, as well as help ensure the safety of treatment in subsequent human trials.

In vitro
Testing performed in a controlled environment, such as a test tube or a Petri dish, instead of living organisms. In vitro literally means "within the glass" in Latin.

Ex vivo
These experiments are performed on tissue (e.g., animal or human cells) taking place outside of the organism, such as in a laboratory setting. In Latin, this means "out of the living."

In vivo
These tests are done on whole, living organisms. Technically, animal and human testing are two forms of in vivo research, which means "within the living." These experiments may be performed outside of a laboratory setting.

A study designed to provide the most credible information about the cause and effects of treatment. These types of studies are recognized as unbiased because they involve the random assignment of treatments to subjects being studied.

Bias
The tendency throughout any stage of research to generate findings that may not reflect "true values." In clinical trials, researchers try to avoid many kinds of bias, including selection by randomizing subjects, measurement by creating placebos and performing blind trials, and confounding by carefully designing the study and analyzing the findings.

Blind
Study in which subjects do not know whether they receive the treatment or the placebo, which assists in prevention of bias. Double-blinded studies are a higher level of scientific rigor because neither the participants nor the investigators know who is receiving the treatment or the placebo. A double-blind crossover study means each participant undergoes both the treatment and control scenario, typically with a wash-out period in between.

Placebo-controlled
Study that allows researchers to isolate the effect size of the treatment by comparing a group given a simulated treatment (e.g., grape flavored drink) to those with the real treatment (e.g., Concord grape juice), which reduces measurement bias. The placebo should match as closely as possible to the treatment without containing the active ingredients.

Randomized
Study involving participants who are randomly assigned to either the treatment or the placebo group, reducing selection bias.