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Food as Medicine Update: Grape (Vitis vinifera, Vitaceae)

Editor’s note: The Food as Medicine article series highlights a conventional food and briefly explores its history, traditional uses, nutritional profile, and modern medicinal research. We also feature a nutritious recipe for an easy-to-prepare dish with each article to encourage readers to experience the extensive benefits of these whole foods. With this series, we hope our readers will gain a new appreciation for the foods they see at the supermarket and frequently include in their diets.

The basic materials for this series were compiled by interns through the American Botanical Council’s (ABC’s) dietetic internship program. We would like to acknowledge ABC Chief Science Officer Stefan Gafner, PhD, for his contributions to this project. This is a revised version of an article that was first published in the December 2015 issue of HerbalEGram.

By Hannah Baumana and Mindy Greenb

a HerbalGram Associate Editor
b ABC Dietetics Intern (University of Texas at Austin, 2014)

Overview

The common grape (Vitis vinifera, Vitaceae) is a perennial climbing vine, which can be trained to grow along a fence, wall, or trellis.1 The vine A cluster of red grapes hangs on a vine surrounded by leaves turning yellow and goldproduces large, palmate leaves and clusters of small yellow flowers that mature to produce round, juicy berries that range in color from green to red to deep purple.2 Although the seeds are edible, many common grape varieties have been bred to grow without seed production, and vine grafting is a popular propagation strategy.3 The juice, pulp, skin, and seed of the grape can be used for various preparations.4 For the purposes of this article, “grapes” will refer to the fruit, and other plant parts will be differentiated by using the specific part (e.g., grape seed, grape leaf, grape vine, etc.).

Grape plants are native to an area that encompasses the Mediterranean, central Europe, and southwestern Asia. As one of the leading commercial fruit crops globally in terms of tons produced, grapes are cultivated all over the world in temperate regions. In 2018, the estimated total worldwide production of grapes was almost 80 million metric tons.5 China was the leading producer of grapes with almost 17% of the global market, followed by Italy, the United States, and Spain.

Historical and Commercial Uses

Grapes are generally sweet and are eaten raw or dried and processed into juice, jam, jelly, or wine.6,7 Depending on the variety, dried grapes are known commercially as raisins, sultanas (also known as golden raisins), or currants (not to be confused with the botanically distinct fruit from the genus Ribes [Grossulariaceae], also known as currants).8 Grape leaves are also a common ingredient in Mediterranean cuisines. Due to the leaves’ high tannin content, they often are used as an ingredient in preserving and pickling.

A botanical illustration of the grape plant and its many parts by Franz Eugen KöhlerGrapes have been consumed since prehistoric times and were one of the earliest domesticated fruit crops.2,6 According to Patrick McGovern, PhD, in Ancient Wine: The Search for the Origins of Viniculture (Princeton University Press, 2007), many Mediterranean cultures believed that “the vine sprang from the blood of humans who had fought against the gods.”9 But according to archaeological evidence, domestication had occurred by approximately 8000 BCE in the Transcaucasia area (which encompasses present-day Armenia, Azerbaijan, and Georgia and parts of both Iran and Turkey) and spread south to present-day Syria, Iraq, Jordan, and Egypt before moving toward Europe, where viticulture had been established in Spain by approximately 1000–800 BCE and France by ca. 600 BCE.10,11 Wine production followed soon after grape domestication, and the earliest known evidence of winemaking was discovered in the Republic of Georgia and dates to roughly 8000 BCE. The expansion of Christianity through Europe also brought with it the knowledge of winemaking, as monasteries spread and refined the winemaking process.11 Spanish missionaries and conquistadors introduced V. vinifera to the Americas.

Wine often has been used as a medium for producing herbal remedies, due to the solvent nature of the alcohol. The Ebers Papyrus, an Egyptian medical document that dates to 1500 BCE, called for the use of medicated wines for a variety of conditions, digestive issues, and jaundice.10 Both Chinese and Western traditions made use of medicated wines, though ancient recipes in China, which date to the Shang Dynasty (ca. 1600-1046 BCE), would have been made with rice (Oryza sativa, Poaceae) wine rather than grape wine.12 Many aperitifs and liqueurs originally were digestive aids made with wine and fortified with herbs such as wormwood (Artemisia absinthium, Asteraceae) herb and anise (Pimpinella anisum, Apiaceae) seed.13 Foundational Greek, Roman, and Persian medical documents all mentioned medicated wine, used either orally or topically (i.e., for dressing wounds).10

Phytochemicals and Constituents

Antioxidants neutralize highly reactive ions or molecules known as free radicals in the human body by donating electrons (which stabilizes free A green, palmate grape leafradicals) or modulating enzymes that metabolize free radicals. Free radicals are produced naturally through metabolism as part of normal physiological functions (e.g., as a defense mechanism against pathogens), but may be produced in excess, creating a situation where they adversely alter lipids, proteins, and DNA, and possibly trigger disease. Grape and grape products are good sources of beneficial antioxidant compounds.

Grapes contain polyphenols, which are the most abundant source of dietary antioxidants and are associated with numerous health benefits.4,14 Phenolic compounds (e.g., flavonoids, stilbenes, and phenolic acids) are present in the skin of the fruit, as well as the flesh and seeds. Different grape varietals contain varying amounts of phenolic compounds, the levels of which tend to increase as the fruit ripens. Red wine and grapes are rich in flavonoids such as anthocyanins and catechins, stilbenes such as resveratrol, and phenolic acids such as caffeic acid and coumaric acid.

Anthocyanins are flavonoids that naturally occur in the plant kingdom and give many plants their red, purple, or blue pigmentation.4,15 Grapes also contain other flavonoids, including epicatechins and proanthocyanidins (PACs). Studying the benefits of individual phytochemicals in humans is difficult since phytochemicals are complex and often interact with other compounds to increase their overall benefits. Animal models have shown that anthocyanins protect against oxidative stress, which is present in the beginning stages of many chronic conditions, such as cardiovascular disease, diabetes, and cancer.16

Grape seeds are a particularly rich source of PACs. Also known as condensed tannins, PACs are polymers (naturally occurring large molecules consisting of the same or similar units) with flavan-3-ol monomers as building blocks. Grape seed extract (GSE), which is high in PACs, is a popular ingredient in nutritional supplements, and partially purified PACs have been used in phytomedicinal preparations in Europe for their purported ability to decrease the fragility and permeability of blood vessels.17,18

Grapes contain stilbenes, including resveratrol. Resveratrol, which is found in red wine and the skin and seeds of red grapes, is produced as part of the plant’s defense mechanism against environmental stressors.2,4,19,20 Resveratrol first gained attention as a possible explanation for the “French Paradox” — the observation that French people tend to have a low incidence of heart disease despite having a typically high-fat diet.2 The antioxidant activity of grapes is strongly correlated with the amount of resveratrol in the grape.19 Studies have found resveratrol to be anti-inflammatory, cardioprotective, and chemopreventive in animal models.20 In a human study in which healthy adults consumed resveratrol, it was determined that the compound was readily absorbed, but it metabolized quickly, leaving only trace amounts.21

In addition to their high resveratrol content, grapes are also an excellent source of vitamin K and provide moderate amounts of potassium, vitamin C, and B vitamins.

Table 1. Compounds Found in Grape18,22,23

Compound Type

Compounds

Plant Part

Activities

Anthocyanins

Malvidin-3-O-glucoside, malvidin-3-O-(6-O-acetyl)-glucoside, petunidin-3-O-glucoside

Fruit, leaf

Anti-inflammatory, antioxidant, cancer chemopreventive

Flavonols

Kaempferol-3-O-glucoside, taxifolin-3-O-glucoside

Skin, fruit, leaf

Anti-inflammatory, antimicrobial, cancer chemopreventive

Hydroxycinnamic acids

Coumaric acid, chlorogenic acid, caffeic acid

Leaf, fruit

Analgesic, anti-inflammatory, antimutagenic, antioxidant

Proanthocyanidins

Procyanidin B1, procyanidin B2

Seed, leaf, fruit

Anti-inflammatory, antioxidant, immune modulator, vasorelaxant

Stilbenes

Resveratrol (3,5,4'-trihydroxystilbene),

piceid

Skin, seed, fruit

Anti-diabetic, anti-inflammatory, antioxidant, cancer chemopreventive

 

Modern Research

A large cluster of red grapes on the vineGrapes have been the subject of numerous studies focused on many of their bioactive compounds, including flavonoids, stilbenes, and phenolic acids. Researchers have observed antioxidant, anti-tumor, immune-modulatory, antidiabetic, anti-atherogenic, anti-infectious, and neuroprotective properties of the fruit.20 However, more human studies are needed to support these purported benefits.

An in vitro study showed that antioxidants from a variety of grape extracts performed as well as or better than butylated hydroxytoluene (BHT), tocopherol, and trolox in radical scavenging activity, metal chelating activity, and inhibition of lipid peroxidation.15 Aqueous and ethanolic extracts of the seed had the highest amount of phenolic compounds of any of the extracts used in the study.

GSE, which has a growing body of research behind it, has gained attention for its possible use in lowering blood pressure and reducing the risk of heart disease, especially in pre-hypertensive populations.24 A standardized GSE made from white wine grapes was studied in human epithelial cells for its effects on gastrointestinal inflammation, and researchers reported potential anti-inflammatory benefits.25

Cardiovascular Disease

Polyphenols have been found to protect the human body from inflammation, which is common in people with heart disease.20 In a 2013 meta-analysis of clinical trials, the acute effects of polyphenols on the endothelium (inner lining of the blood vessels) were investigated. The analysis found that blood vessel function significantly improved in healthy adults in the initial two hours after consuming grape polyphenols.26 Another analysis found that the polyphenols in every part of the grape — fruit, skin, and seed — had cardioprotective effects.27 In animal, in vitro, and limited human trials, grapes showed beneficial actions against oxidative stress, atherosclerosis (plaque build-up in arteries), high blood pressure, and ventricular arrhythmia (irregular heartbeat).

Human clinical trials have found that GSE supplementation was associated with significantly lowered systolic blood pressure (SBP) and heart rate with no significant effects on diastolic blood pressure (DBP), C-reactive protein, or serum lipid levels. In addition, GSE supplementation has been shown to decrease SBP in healthy subjects and populations at risk for cardiovascular disease, including those with hypertension and metabolic syndrome and those experiencing menopause.18

Cancer Chemopreventive Effects

The causes of and treatments for cancer are complex and multifaceted, and researchers have investigated the cancer chemopreventive effects of polyphenols. These antioxidants demonstrate the ability to protect the body from cancer-causing substances and to prevent tumor cell growth by protecting DNA and regulating natural cell death.16,20,28 In an in vitro study, grape extracts from two varieties of fruit exhibited inhibitory activity against human colon cancer cells. GSE also has shown the ability to induce apoptosis (normal, pre-programmed cell death) in pancreatic cancer cells and inhibit growth of pancreatic cancer cells.29 These outcomes are thought to be the result of the anti-inflammatory and antioxidant activities of PACs. Additionally, in vitro and animal studies have shown that resveratrol’s cancer chemopreventive activities affect all stages of tumorigenesis.30

Diabetes

In a randomized, double-blind controlled clinical study, healthy overweight or obese subjects with a family history of type 2 diabetes were given grape polyphenols to counteract a high-fructose diet. After nine weeks of supplementation, grape polyphenols protected against fructose-induced insulin resistance in all subjects.31 In another study, diabetic patients who consumed a dealcoholized Muscadine grape wine had reduced fasting insulin levels.32 GSE and grape juice supplementation have both been associated with reduced blood sugar levels in patients with type 2 diabetes in clinical trials.33

Nutrient Profile
Per 150 g (approx. 1 cup) grapes34

Macronutrients:

104 calories
1.1 g protein
27.3 g carbohydrates
0.2 g fat

Secondary Metabolites:

Excellent source of:

Vitamin K: 22 mcg (27.5% DV)

Good source of:

Potassium: 288 mg (8.2% DV)
Vitamin C: 4.8 mg (8% DV)
Thiamin: 0.1 mg (6.7% DV)
Riboflavin: 0.1 mg (5.9% DV)
Dietary Fiber: 1.4 g (5.6% DV)
Manganese: 0.1 mg (5.5% DV)
Vitamin B6: 0.1 mg (5% DV)

Also provides:

Phosphorus: 30 mg (3% DV)
Magnesium: 11 mg (2.8% DV)
Iron: 0.5 mg (2.8% DV)
Vitamin A: 100 IU (2% DV)
Niacin: 0.3 mg (1.5% DV)
Vitamin E: 0.3 mg (1.5% DV)

DV = Daily Value as established by the US Food and Drug Administration, based on a 2,000-calorie diet.

 

Recipe: Pickled Chai Grapes
Courtesy of Edward Lee35

Ingredients:

  • 3 pounds red seedless grapes, stemmed, washed, dried
  • 1 cinnamon stick
  • 2 cups champagne vinegar
  • 1 cup water
  • 2 cups sugar
  • 1 teaspoon salt
  • 3 chai tea bags

Directions:

  1. Slice each grape in half and transfer, along with the cinnamon stick, to a large, clean jar.
  2. Combine vinegar, water, sugar, and salt in a large saucepan and bring to a boil, stirring to dissolve the sugar and salt.
  3. Pour hot pickling liquid over the grapes and add the tea bags. Refrigerate.
  4. After two days, remove the tea bags. Let the grapes pickle for four more days before consuming and they will keep up to a month.

 

Image Credits (top to bottom):

Vitis vinifera. Photo courtesy of Eflon.
Botanical illustration by Franz Eugen Köhler from Köhler’s Medizinal-Pflanzen (1897).
Vitis vinifera leaf. Photo courtesy of Stefan.lefnaer.
Vitis vinifera. Photo courtesy of Luis Fernández García.

References

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  2. Murray MT, Pizzorno J, Pizzorno L. The Encyclopedia of Healing Foods. New York, NY: Atria Books; 2005.
  3. Vitis vinifera. North Carolina Extension Gardener Plant Toolbox. Available at: https://plants.ces.ncsu.edu/plants/vitis-vinifera/. Accessed January 28, 2022.
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  16. Lila MA. Anthocyanins and human health: An in vitro investigative approach. J Biomed Biotechnol. 2004;2004(5):306-313.
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  24. Park E, Edirisinghe I, Choy YY, Waterhouse A, Burton-Freeman B. Effects of grape seed extract beverage on blood pressure and metabolic indices in individuals with pre-hypertension: A randomised, double-blinded, two-arm, parallel, placebo-controlled trial. Br J Nutr. 2015;16:1-13.
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  35. Lee E. Smoke and Pickles: Recipes and Stories from a New Southern Kitchen. New York, NY: Artisan; 2013.
References