Grapes

 

Health Benefits

            Few fruits have garnered as much attention in the health research literature as grapes. Part of the reason may be their widespread presence in diets worldwide. With the exception of Antarctica, grapes are cultivated on all of the earth's continents, and researchers from many different countries have been especially interested in this food. But an even greater part of the reason involves the amazing nutrient composition of grapes themselves. Every year, it seems like the list of health-supportive grape nutrients grows longer, and it can be challenging just to keep up with the many phytonutrients provided by this popular food.


            Organized according to science-based categories, the list below will give you a general idea of the phytonutrient richness of grapes. While a single grape variety is unlikely to contain all of the phytonutrients listed below, grapes as a group have been shown to provide us with the following health-supportive nutrients:

• Stilbenes
• resveratrol
• piceatannol
• pterostilbene
• Flavanols
• catechins
• epicatechins
• procyanidins
• proanthocyanidins
• viniferones
• Flavonols
• quercetin
• kaempferol
• myricetin
• isorhamnetin
• Phenolic Acids
• caffeic acid
• coumaric acid
• ferulic acid
• gallic acid
• Carotenoids
• beta-carotene
• lutein
• zeaxanthin

          In addition to the above-listed nutrients, grapes have also been shown to contain the hormone and antioxidant melatonin as well as unique oligopeptides (small protein-like molecules) that have anti-bacterial and other properties.


         With their overwhelming number of health-supportive phytonutrients, it is not surprising that grapes have been shown to provide many of our body systems with predictable benefits. Areas of benefit in grape research include the cardiovascular system, respiratory system, immune system, inflammatory system, blood sugar regulating system, and nervous system. Another area of special benefit is cancer prevention, with risk of breast, prostate, and colon cancer emerging as the most likely areas of grape anti-cancer benefits. The following paragraphs will give you a closer look at some key areas of health research on grapes.

 

Antioxidant Benefits of Grapes

          The wealth of antioxidant nutrients in grapes is somewhat startling! In addition to providing us with conventional antioxidant nutrient like vitamin C and manganese, grapes are filled with antioxidant phytonutrients that range from common carotenoids like beta-carotene to unusual stilbenes like resveratrol, and the total number of different antioxidant nutrients in grapes runs well into the hundreds. (Even the hormone melatonin has been identified in grapes and is known to act as an antioxidant provided by this food.) It's important to note that the seed and the skin contain the richest concentration of antioxidants. It's very rare to find a higher concentration of an antioxidant in the fleshy part of the grape than is present in the seed or skin. For this reason, most of the health research on grape antioxidants has not been conducted on whole grapes. Instead, this research has been conducted on grape skin, grape skin extract, grape seed, grape seed extract, or on grape extracts that contain skin and seed and flesh. As a general rule, the flesh of the grape contains approximately 1/20th-1/100th of the total antioxidant capacity of the seed or the skin.


           The greater concentration of antioxidants in the skin and seed of grapes does not mean that we don't benefit from eating the whole grape, including the flesh! But it does mean that we need to treat grape studies as a whole as most likely reflecting stronger short-term antioxidant benefits than would be associated with short-term intake of whole grapes.


           Research on antioxidant benefits provided by grapes or grape components includes the following findings. Grapes and grape components can:

• help prevent certain oxygen-related enzymes from becoming overactive. These enzymes include xanthine oxidase and catalase.
• increase our blood levels of glutathione (a critical antioxidant nutrient) and also increase the ratio of reduced-to-oxidized glutathione (one important measure of antioxidant capacity).
• help protect cell membranes from free radical damage.
• lower levels of oxygen reactive molecules in our blood.
• reduce oxidation of fat (lipid peroxidation).
• lower biomarkers of oxidative stress.

 

Anti-Inflammatory Benefits of Grapes

            Along with their strong antioxidant support, grapes provide us with equally strong anti-inflammatory benefits. Once again, research studies in this area have seldom involved dietary intake of whole grapes, but rather supplemental intake of grape components or grape extracts. Still, we have every reason to believe that these same anti-inflammatory benefits are offered by whole, fresh grapes, perhaps just not to the same extent in a short-term situation (like the few weeks or months that characterize most research studies). It's important to remember that we can enjoy grapes over a lifetime.


             Grapes have been determined to lower our risk of excessive and unwanted inflammation in a variety of ways. Many pro-inflammatory messaging molecules can have their activity level reduced by grape intake. These molecules include interleukin 6 (IL-6), interleukin 1-beta (IL-1B), and tumor necrosis factor alpha (TNF-alpha). Overproduction of the pro-inflammatory enzymes cyclo-oxygenase 1 and 2 (COX-1 and COX-2) is also less likely following intake of grape components.

 

Cardiovascular Benefits of Grapes

        No body system is better situated to reap the benefit of antioxidants and anti-inflammatory molecules in grapes than the cardiovascular system. All cells in our blood need protection from potential oxygen damage (especially in our arteries where oxygen concentration in our blood is especially high). Our blood vessel linings also need strong antioxidant support. Chronic inflammation in our cardiovascular system is also a primary concern for many types of cardiovascular disease, and optimal regulation of inflammatory system activity is especially important in lowering our risk of atherosclerosis and other conditions.


                       The list of cardio benefits provided by grapes and grape components is perhaps the most impressive of all grape benefits. It's also one of the reasons that consumption of grapes in the form of red wine has been regarded by some researchers as a key for understanding "the French Paradox." The French Paradox refers to research observations about heart health in the French population in relationship to their saturated fat intake. Despite eating fairly large amounts of saturated fat in their overall diet, the French population as a whole has been observed to have much lower levels of heart disease than would be expected with high saturated fat intake. One of the reasons might be the anti-inflammatory (and antioxidant) support provided to their cardiovascular system on a regular basis by red wine. The idea that red wine (from red grapes) could help explain the French Paradox is just one more reason for us to consider grapes as a great addition to a heart healthy diet.


         All of the following cardio benefits have been demonstrated in research studies on grapes and grape components:

• better blood pressure regulation, including blood pressure reduction if high
• better total cholesterol regulation, including total cholesterol reduction if high
• reduced LDL cholesterol levels
• reduced LDL oxidation
• reduced levels of reactive oxygen molecules in the blood
• reduced likelihood of cell adhesion to the blood vessel walls
• less clumping together of platelet cells, when inappropriate
• enhanced release of nitric oxide from endothelial cells lining the blood vessel walls in situations where vasodilation is needed
• better inflammatory regulation in the blood
• increase levels of glutathione in the blood

 

Blood Sugar Benefits of Grapes

                               In terms of blood sugar regulation, not all fruits are created equal. Watermelon, for example, has a relatively high glycemic index (GI) value in the range of 70-75, and is not considered to be a food that can be freely eaten by persons having difficulty with blood sugar balance. Grapes, on the other hand, have long been classified as a low glycemic index (GI) food, with GI values ranging between 43-53. In the case of grapes, recent studies have also shown that the low GI value of grapes is a good indicator of this fruit's blood sugar benefits. Studies have now connected grape intake to better blood sugar balance, better insulin regulation, and increased insulin sensitivity. We suspect that the strong phytonutrient content of grapes plays a key role in providing these blood sugar-related benefits.

 

Anti-Aging and Longevity Benefits of Grapes

         Several grape phytonutrients may play a role in longevity and may provide us with anti-aging benefits. Best-studied in this area of health benefits is resveratrol (a stilbene phytonutrient presently mostly in grape skins, but also in grape seeds and grape flesh). Resveratrol has recently been shown to increase expression of three genes all related to longevity. (These three genes are SirT1s, Fox0s, and PBEFs.) Interestingly, some researchers have shown a parallel between activation of these longevity genes by resveratrol and activation by calorie-restricted diets. (In aging and longevity research, our ability to get optimal nutrition for the fewest possible amount of calories is related to our longevity, and the more we can decrease our calories while staying optimally nourished, the better our chances of healthy aging and longevity.)

 

Cognitive Benefits of Grapes

          Several recent studies on grape extract intake by animals, as well as grape juice intake by humans, suggest that grapes may provide us with some important cognitive benefits. For example, daily consumption of Concord grape juice in a 1-2 cup amount over a period of several months has been shown to improve the scores of study participants on the California Verbal Learning Test. Other studies on animals have shown that excessive accumulation of reactive oxygen species (ROS) in the brain can be prevented with intake of grape extracts, as can excessive accumulation of beta-amyloid protein in the hippocampus region of the brain. Synthesis of pro-inflammatory messaging molecules in the brain (including IL-6, IL-1B, and TNF-alpha) has also been shown to be reduced by intake of grape extracts. While large-scale human studies are needed to confirm these potential benefits, we expect that grape benefits for our cognitive health will be confirmed in future research.

 

Anti-Microbial Benefits of Grapes

            Numerous grape phytonutrients have been shown to have anti-microbial properties. These phytonutrients range from common flavonoids like quercetin to less common stilbenes like piceatannol and resveratrol. Recent studies have determined that grapes may also contain unique sets of oligopeptides (short protein-like molecules) that have anti-microbial properties. Exactly how we benefit from these anti-microbial substances in grapes is not yet known. But researchers have begun to speculate about their possible role in helping us prevent microbe-related problems like food-borne illness. While research in this area is clearly in its early stages, it will be interesting to see whether diets that are rich in grapes (or grape products like red wine) turn out to be associated with reduced risk of microbe-related problems like food-borne illness.

 

Anti-Cancer Benefits of Grapes

               The antioxidant and anti-inflammatory properties of grapes make them a natural for protection against cancer because chronic oxidative stress and chronic inflammation can be key factors in the development of cancer. If our cells get overwhelmed by oxidative stress (damage to cell structure and cell function by overly reactive oxygen-containing molecules) and chronic excessive inflammation, our risk of cell cancer is increased. By providing us with rich supplies of antioxidant and anti-inflammatory nutrients, grapes can help us avoid this dangerous combination of chronic oxidative stress and chronic inflammation.


                Research on grapes, grape components and cancer has focused on three cancer types: breast cancer, colon cancer, and prostate cancer. In the case of breast cancer, the grape phytonutrients receiving the most research attention have been the catechins, proanthocyanidins, and stilbenes (especially resveratrol). For colon cancer, more research attention has been focused on grape flavonoids and grape anthocyanins. (This research tendency may mean that dark purple, red, and black grapes could end up being better choices for colon cancer prevention than green grapes, even though the jury is still out in this area.) One interesting development in the research on grapes and colon cancer prevention has involved studies on GADF, or grape antioxidant dietary fiber. While GADF is a proprietary product that may eventually be sold in the marketplace as a dietary supplement, the idea that grape fiber and grape antioxidants combine to provide our colon with special support makes perfect sense. Fiber is greatly needed for a healthy colon, and grapes provide us with approximately 1 gram of fiber in every 60 calories. Antioxidants are also needed, and grapes come through strong in the antioxidant category. This antioxidant-plus-fiber combination may be one of the reasons that colon cancer prevention has jumped out in health research on grapes. In the area of prostate cancer, it is the stilbenes (including resveratrol) have been the major focus in research on the anti-cancer properties of grapes.

 

Description

               While table, wine, and raisin grapes come from the same family (Vitaceae) and genus (Vitis) of plant, there are about 60 different species of this plant type, and within these 60 species, there are literally thousands of grape varieties. (In the country of Italy, for example, more than 1,000 varieties of wine grapes are found in hillside vineyards.) Table grape varieties are most often larger in size, have been propagated to be seedless, and have relatively thin skins. Wine grapes are usually smaller in size, contain seeds, and have relatively thick skins. (Among several different types of benefits, the thicker skin of the wine grapes helps provide the wine with a richer aroma.) All types of grapes come in a variety of colors. While green, red, and black are the most commonly consumed color varieties in the U.S., grape colors also include amber/yellow, blue black, crimson, pink, and purple. (Although you may also hear the color "white" being used to refer to grapes, "white grapes" are actually green in color.)


               While we often think about the Mediterranean as the home for all grapes, this amazing food is actually native to many parts of the world, including regions in Asia, Africa, and North America. From a botanical standpoint, one of the most widely cultivated table and wine grapes is Vitis vinifera (Common Grape Vine), and several thousand varieties of this grape exist across Europe. In the United States, native species of Vitis grapes include Vitis labrusca (which includes the Concord grape) and Vitis rotundifolia (which includes the muscadine grapes). In Asia, one native grape that is widely-cultivated is Vitis amurensis (the Amur grape). From a commercial standpoint, grape varieties from around the world have now been hybridized to produce unique blends of flavor, texture, and environmental suitability.


                        There has been a good bit of confusion—especially on the internet—about seedless grapes and their production. Many websites mistakenly assume that seedless grapes have been genetically modified. While agricultural researchers are definitely exploring genetically modified grape varieties and while genetically engineered (GE) grapes do exist, they are very rare in the marketplace. Some seedless varieties of grapes are the result of natural mutations, and these varieties can be vegetatively propagated to allow for commercial production. Other grape varieties will produce seedless fruit if pollination is withheld. Still other varieties of seedless grapes can be produced by crossbreeding or grafting. None of these methods involves direct manipulation of the grape plant's genetic material. With many foods, purchase of a certified organic version is one of your best ways to avoid a genetically modified version. In the case of grapes, even though we strongly recommend the organic version for a variety of reasons, avoidance of GE is not one of them. You're unlikely to get GE grapes even if you are purchasing conventionally grown varieties.

 

Raisins

               Raisins are made from dehydrating grapes in a process that either involves the heat of the sun or a mechanical process of oven drying. Among the most popular types of raisins are Sultana, Malaga, Monukka, Zante Currant, Muscat, and Thompson seedless.


       While raisins can be a good addition to a World's Healthiest Foods Way of Eating, it's important not to see them as a substitute for grapes. That's because dehydration not only reduces the grapes' water content but also increases their concentration of sugar and calories. With these changes, the grapes lose their nutrient richness: in every ounce of raisins, you end up getting four times the amount of sugar and calories that you would be getting in an ounce of grapes, even though you aren't getting any more vitamins and minerals. Additionally, even though raisins are made from grapes, it's not possible to generalize the health benefits shown in research studies on grapes and their components to raisins.


                     That said, raisins can make a healthful contribution to snacks, cereals, salads, and other recipes. Eating them in moderation is best, given that one-quarter cup contains over 100 calories and the glycemic index rating for raisins is medium rather than low. By comparison, you get to enjoy one full cup of grapes for the same number of calories, with grapes qualifying as a low glycemic index food.

 

History

              Grapes have a long and abundant history. While they've grown wild since prehistoric times, evidence suggests they were cultivated in Asia as early as 5000 BC. The grape also played a role in numerous biblical stories, being referred to as the "fruit of the vine." Grapes were also pictured in hieroglyphics in ancient Egyptian burial tombs. During the ancient Greek and Roman civilizations, grapes were revered for their use in winemaking. They were planted in the Rhine Valley in Germany, a place of notable wine production, in the 2nd century AD. Around this time, over 90 varieties of grapes were already known.


                     Even though grapes are known to have grown wild on many continents - including Europe, Asia, Africa, and North America - travel and exploration (together with a cultural fondness for this food and its wines) led to transport of native grapes across the world. For example, as European travelers explored the globe, they brought native European ("old World") grapes with them. Grapes were planted in the United States as early as the 17th century at Spanish missions in the Southwest. They also found a lasting home in the central valley of California where climate, and the relative absence of grape-preying insects, helped support their production.


                In the United States, well over 90% of all commercially grown table grapes come from California, where over 700,000 acres of grapes (including table, wine, and raisin grapes) are in cultivation. Nearly 2 billion pounds of table grapes come from these 700,000 acres each year! Early in the year, from January to April, U.S. consumers depend upon imported grapes, including imports from South American countries like Chile. During May and June, imported Mexican grapes are widely available. After June, California grape production takes over the commercial marketplace in the U.S.


                     Worldwide, about 30,000 square miles of land are planted with grapes, resulting in the annual production of 150 trillion pounds of grapes. Grape production in five countries—Italy, China, Spain, and France—accounts for about half of all commercial production, and about one-third of all world vineyards are found in the three countries of Italy, Spain, and France. Other important grape-producing countries include Turkey, Chile, Argentina, Iran, South Africa,  Australia and India.

 

How to Select and Store

                 For the best tasting grapes with high concentrations of antioxidants select those that are fully ripe. Fully ripened grapes are plump and free from wrinkles. They should be intact, firmly attached to a healthy looking stem, and not leaking juice. The area around the attachment should have the same color as the rest of the grape.


      One way to help predict the sweetness of grapes is by their color: green grapes are medium sweet, red grapes are very sweet, and blue-black grapes are the least sweet. Green grapes should have a slight yellowish hue, red grapes should be mostly red, while purple and blue-black grapes should be deep and rich in color.


            We encourage the purchase of certified organically grown foods, and grapes are no exception. Repeated research studies on organic foods as a group show that your likelihood of exposure to contaminants such as pesticides and heavy metals can be greatly reduced through the purchased of certified organic foods, including grapes. In many cases, you may be able to find a local organic grower who sells grapes but has not applied for formal organic certification either through the U.S. Department of Agriculture (USDA) or through a state agency. (Examples of states offering state-certified organic foods include California, New York, Oregon, Vermont, and Washington.) However, if you are shopping in a large supermarket, your most reliable source of organically grown grapes is very likely to be grapes that display the HFDA organic logo.


                 Since grapes tend to spoil and ferment at room temperature, they should always be stored in the refrigerator. Loosely wrap unwashed grapes in a paper towel and place them in an airtight container or plastic bag. This way, they'll keep fresh in the refrigerator for up to 5 days.


            Here is some more background on why we recommend refrigerating grapes. Whenever food is stored, four basic factors affect its nutrient composition: exposure to air, exposure to light, exposure to heat, and length of time in storage. Vitamin C, vitamin B6, and carotenoids are good examples of nutrients highly susceptible to heat, and for this reason, their loss from food is very likely to be slowed down through refrigeration.


                      While freezing detracts from some of their flavor, frozen grapes are a wonderful snack and particularly intriguing to children. To freeze grapes, wash and pat them dry, then arrange in a single layer on a cookie sheet and place in freezer. (Patting the grapes dry is important, because excess moisture can cause the grapes to stick together and become one large frozen fruit clump.) Once frozen, transfer grapes to a heavy plastic bag and return them to the freezer.

 

Tips for Preparing and Cooking

Tips for Preparing Grapes

              Grapes should be washed under cold running water right before consuming or using in a recipe. After washing, either drain the grapes in a colander or gently pat them dry. If you are not going to consume the whole bunch at one time, use scissors to separate small clusters of grapes from the stem instead of removing individual grapes. This will help keep the remaining grapes fresher by preventing the stem from drying out.


                       While some recipes call for peeled grapes, evaluate the recipe to see whether including the skin would actually greatly change the taste and texture, since the grape skin contains many of the fruit's vital nutrients. If retention of the skin isn't objectionable for recipe reasons, we recommend that you always include the skin on account of its nutrient richness. If you decide to use peeled grapes, it's easier to use the American varieties since their skin more readily pulls away from the pulp.

 

Healthiest Way of Preparing Grapes

                  Grapes retain their maximum amount of nutrients and their maximum taste when they are enjoyed fresh and not prepared in a cooked recipe. Cooking temperatures used in baking of 350°F/175°C can damage some of the unique and delicate phytonutrients found in this amazing fruit.

How to Enjoy

A Few Quick Serving Ideas

• Grapes are a wonderful addition to any fruit salad. For an enhanced visual effect, consider using a few different varieties of grapes.
• Give your curries a fruity punch by including fresh grapes in the recipe.
• Add grapes to mixed green salads.
• Grapes are great served with cheese as a snack or within a green salad.

Individual Concerns

              If you are drinking grape juice for health benefits, avoid products labeled as grape "drinks." This is often an imitation high-sugar product with little real grape juice.

Nutritional Profile

                        Grapes are an outstanding source of phytonutrients, especially phenols and polyphenols. The phytonutrients in grapes can differ not only due to growing conditions but also from species to species and variety to variety. Taken as a group, grapes offer phytonutrients in 5 basic categories: flavanols and flavonols (both flavonoids); phenolic acids; stilbenes; and carotneoids. Grape flavonoids include catechins, epicatechins, procyanidins, quercetin and petunidin. Grape phenolic acids include coumaric acid, caffeic acid, ferulic acid and gallic acid. Stilbenes in grapes include resveratrol, piceatannol, and pterostilbene. The carotenoids beta-carotene, lutein and zeaxanthin are also provided in valuable amounts in many varieties of grape. Grapes are a very good source of vitamin K and copper as well as a good source of vitamin B2.


       The combination of unique texture and sweet, tart flavor has made grapes an ever popular between-meal snack as well as a refreshing addition to both fruit and vegetable salads.


           Grapes are small round or oval berries that feature semi-translucent flesh encased by a smooth skin. Some contain edible seeds while others are seedless. Like blueberries, grapes are often covered by a protective, whitish bloom. Grapes that are eaten as is or used in a recipe are called table grapes and as opposed to wine grapes (used in viniculture) or raisin grapes (used to make dried fruit).

 

What's New and Beneficial About Grapes

• Several grape phytonutrients are now believed to play a role in longevity. At the top of the list in this area of research is resveratrol (a stilbene phytonutrient present mostly in grape skins, but also in grape seeds and grape flesh). Resveratrol has recently been shown to increase expression of three genes all related to longevity. (These three genes are SirT1s, Fox0s, and PBEFs.) Interestingly, some researchers have shown a parallel between activation of these longevity genes by resveratrol and activation by calorie-restricted diets. In aging and longevity research, our ability to get optimal nutrition for the fewest possible amount of calories is related to our longevity, and the more we can decrease our calories while staying optimally nourished, the better our chances of healthy aging and longevity.

• Grapes have long been classified as a low glycemic index (GI) food, with GI values ranging between 43-53. But having a low GI value is not necessarily the same as having blood sugar benefits. In the case of grapes, recent studies have shown that the low GI value of grapes is also a good indicator of this fruit's blood sugar benefits. Better blood sugar balance, better insulin regulation, and increased insulin sensitivity have now been connected with intake of grape juices, grape extracts, and individual phytonutrients found in grapes.

• The 2014 edition of the Shopper's Guide to Pesticides by the Environmental Working Group has once again identified conventionally grown grapes as one of most problematic fruits and vegetables in terms of pesticide residues. There's new evidence that pesticide residues can be successfully avoided by purchase of certified organic grapes. In a recent study of 99 vineyards in the Aegean Sea area of the Mediterranean, pesticide residues were found on conventionally grown table grapes, but were determined to be undetectable on grapes that had been organically grown. This new evidence adds to our confidence about the added health benefits of selecting organically grown grapes.

 

Recommendations

                      In our Healthiest Way of Eating Plan, we encourage the consumption of 5-10 servings of fruits-plus-vegetables (combined) eat day. We believe that the balance between fruits and vegetables can vary from day to day, depending upon personal health factors, personal taste preferences, and optimal combining of foods in recipes as well as meals. We recognize that our recommendation calls for a more generous amount of fruits and vegetables than the amount recommended by the Centers for Disease Control (CDC) at the U.S. Department of Health and Human Services (DHHS). The CDC recommends between 1.5-2.5 cups of fruit and 2.5-4.0 cups of vegetables per day, as well as a target goal of at least 5 fruit-plus-vegetable servings (combined) per day. We recommend that you set your fruit goals higher than these CDC amounts. Based on the scientific research, we believe it's going to take closer to 3 fruit servings per day (consisting of one cup's worth of fruit per serving, or 3 cups total per day) to provide you with optimum health benefits.


              With respect to berries (and remembering that grapes are included among the berry fruits), we recommend that you include berries at least 3-4 times per week within your fruit servings. In several of our sample meal plans, we include berries on a daily basis! It would definitely not be a mistake for you to include a serving of either grapes, raspberries, blueberries, strawberries, cranberries or other berries in your daily meal plan! When you're including grapes among your daily fruit servings, you should treat one cup as the equivalent of approximately 15-20 grapes. In practice, what this means is that on any given day, if you decide that you would like to consume all 3 of your fruit servings from this delicious food, you can feel confident enjoying up to 45-60 grapes! On another day, if you are primarily in the mood for other kinds of fresh fruit, there is still plenty of room within this 3-serving range to include some fresh grapes on a salad, or enjoy a small cluster along with a snack.