The therapeutic benefits of grapes
Grapes are a delicious food that also have wide healing capacities.
Grapes (Vitis vinifera) are a type of fruit, actually berries, that grow in clusters of 15 to 300 and can be red, black, dark blue, yellow, green, orange or pink. White grapes are actually green and are derived from the purple grape, whereby the production of anthocyanins are genetically turned off.
Table grapes are often thin-skinned and seedless and contain about 15 per cent sugars; wine grapes are valued for the aroma from their thicker skins and seeds and contain 24 per cent sugars, much higher than table grapes.
Grapes, grape juice, grape seeds, grapeseed oil and wine are consumed as foods and medicines, and grapevine leaves are also used as an edible food wrapping in many cultures. Dried grapes are called raisins generically, with sultanas originally being a raisin from the sultana grapes of Turkey, and currants were originally dried black Corinth grapes.
Grapes are one of the oldest fruit crops domesticated by humans. Cultivated for 6000 to 8000 years that archaeologists are aware of, grapes originated in Central Asia and travelled to the Mediterranean. Grapes and wine have grown alongside the development of human cultures.
Yeasts are one of the earliest domesticated microorganisms, which occur naturally on the grape skins, leading to the discovery of alcoholic drinks like wine. The earliest archaeological evidence for a substantial wine-making industry dates from 8000 years ago in Georgia. The wine industry developed alongside pottery so the wine could be stored. Archaeologists have even found a tree resin in ancient wine jars that acted as an antibacterial preservative so the wine could be stored for longer periods.
Raw grapes are 81 per cent water, 18 per cent carbohydrates and 1 per cent protein with negligible fat. They are one of the richest sources of polyphenols in fruits.
Polyphenols (anthocyanins) levels are higher in the darker coloured grapes (as are the flavonols syringetin and laricitrin), and catechins are higher in the white varieties. Other phenolics are ellagic acid, quercetin, kaempferol and resveratrol. Phenolic level depends on the grape variety and cultivation practices, and are found mainly in the grape seeds and skins, as are the tannins.
One hundred grams of fresh grapes contain 70–182 mg phenolics of which 65 to 76 per cent are flavonoids, mainly in the skins and seeds. The antioxidant power of the polyphenols in grape seeds has been shown to be 20 times greater than vitamin E and 50 times greater than vitamin C. Eating seedless grapes loses some of the potential health benefits provided by these phytochemicals.
There is extensive research on the therapeutic properties of grapes, with the polyphenols being the most studied components. These have been shown to have antioxidant, anti-inflammatory, anticancer, antimicrobial, antiviral, cardioprotective and neuroprotective properties amongst others. Resveratrol (mainly from red grapes) has been studied extensively and has been shown to have multiple health benefits in humans.
Antioxidant and anti-inflammatory
The polyphenols in grape skins and seeds are strong free radical scavengers and chelators of reactive oxygen species (ROS). Grape polyphenols inhibit multiple pathways of inflammation including the COX-2 and prostaglandin pathways. Chronic inflammation through these pathways is a key factor in the development of chronic disease, such as cardiovascular disease, cancer, diabetes, arthritis, respiratory disease and autoimmune diseases. The activity of grape polyphenols in decreasing inflammation, and oxidative ROS species can be highly beneficial in preventing these common illnesses.
Grape flavonoids target multiple pathways to overcome chronic inflammation and have been compared with the synthetic mono-targeted anti-inflammatory drugs such as the NSAIDS. These studies have demonstrated that grape flavonoids have higher anti-inflammatory activity (and are therefore more effective), without the potential side effects. One study demonstrated this effectively when comparing grapes and indomethacin.
The consumption of grapes and grape products is associated with measurably decreased risk factors for cardiovascular disease. Grape polyphenols have been shown to reduce the development of atherosclerosis by a number of mechanisms — including reducing the oxidation of the LDL cholesterol fraction (a primary initiating event in atherosclerosis), improving endothelial function, lowering blood pressure, reducing inflammation and inhibiting platelet aggregation (stickiness).
A clinical trial on 66 subjects with type-2 diabetes over 45 days of resveratrol supplementation showed that resveratrol significantly improved fasting blood glucose, haemoglobin A1C, insulin and insulin resistance and lipid profiles while also lowering blood pressure.
Oestrogen regulation and osteoporosis
Resveratrol has been shown to be a phytoestrogen that can modify oestrogen receptor pathways. It has been shown to be effective in the management of osteoporosis in postmenopausal women without an increase in the risk of breast cancer, and can be supplemented to regulate oestrogen in breast cancer.
Grape flavonoids have been shown to prevent neurodegenerative activity in the brain and central nervous system by inhibiting inflammation and by reducing oxidative stress. Clinical studies have shown that grape juice improved cognitive function and reduced memory decline in older adults.
For excellent health, grapes are a beneficial food to consume regularly, particularly red grapes. For maximum benefit, ensure that the seeds and skins are also eaten.