Health Benefits of Grapes
Comparing diets among Western countries, researchers have
discovered that although the French tend to eat higher levels of animal fat, surprisingly
the incidence of heart disease remains low in France, a phenomenon named the French Paradox
and thought to occur from protective benefits of regularly consuming red wine. Apart from potential benefits of alcohol itself,
including reduced platelet aggregation and vasodilation, polyphenols (e.g., resveratrol) mainly in the grape skin provide
other suspected health benefits, such as:
of molecular mechanisms in blood vessels, reducing susceptibility to vascular damage
Decreased activity of angiotensin, a systemic hormone causing blood vessel constriction
that would elevate blood pressure
Increased production of the vasodilator hormone, nitric oxide (endothelium-derived
Although adoption of wine consumption is not recommended by some health authorities, a significant
volume of research indicates moderate consumption, such as one glass of red wine a day for women and two for men, may confer
health benefits. Emerging evidence is that wine polyphenols like resveratrol provide physiological benefit whereas alcohol
itself may have protective effects on the cardiovascular system.
Grape phytochemicals such as resveratrol (a polyphenol antioxidant), have been
positively linked to inhibiting any cancer, heart disease, degenerative nerve disease, viral infections and mechanisms of
of the genome through antioxidant actions may be a general function of resveratrol. In laboratory studies, resveratrol bears
a significant transcriptional overlap with the beneficial effects of calorie restriction
in heart, skeletal muscle and brain. Both dietary interventions inhibit gene expression
associated with heart and skeletal muscle aging, and prevent age-related heart failure.
Resveratrol is the subject of several human clinical trials,
among which the most advanced is a one year dietary regimen in a Phase III study of elderly patients with Alzheimer's disease.
Synthesized by many plants, resveratrol apparently serves
antifungal and other defensive properties. Dietary resveratrol has been shown to modulate the metabolism of lipids and to
inhibit oxidation of low-density lipoproteins and aggregation of platelets.
Resveratrol is found in wide amounts among grape varieties,
primarily in their skins and seeds which, in muscadine grapes, have about one hundred times higher concentration than pulp.
Fresh grape skin contains about 50 to 100 micrograms of resveratrol per gram.
Anthocyanins and other phenolics
tend to be the main polyphenolics in purple grapes whereas flavan-3-ols (e.g., catechins) are the more abundant phenolic
in white varieties. Total phenolic content, an index of dietary antioxidant strength, is higher in purple varieties due
almost entirely to anthocyanin density in purple grape skin compared to absence of anthocyanins in white grape skin. It
is these anthocyanins that are attracting the efforts of scientists to define their properties for human health. Phenolic
content of grape skin varies with cultivar, soil composition, climate, geographic origin, and cultivation practices or exposure
to diseases, such as fungal infections.
Red wine offers health benefits more so than white because many beneficial compounds are present in grape skin,
and only red wine is fermented with skins. The amount of fermentation time a wine spends in contact with grape skins is
an important determinant of its resveratrol content. Ordinary non-muscadine red wine contains between 0.2 and 5.8 mg/L,
depending on the grape variety, because it is fermented with the skins, allowing the wine to absorb the resveratrol. By contrast,
a white wine contains lower phenolic contents because it is fermented after removal of skins.
Wines produced from muscadine grapes may contain more than 40 mg/L, an exceptional
phenolic content. In muscadine skins, ellagic acid, myricetin, quercetin, kaempferol, and trans-resveratrol are major phenolics.
Contrary to previous results, ellagic acid and not resveratrol is the major phenolic in muscadine grapes.
The flavonols syringetin, syringetin 3-O-galactoside, laricitrin and laricitrin 3-O-galactoside are also found in
purple grape but absent in white grape.
Since the 1980s, biochemical and
medical studies have demonstrated significant antioxidant properties of grape seed oligomeric proanthocyanidins. Together
with tannins, polyphenols and polyunsaturated fatty acids, these seed constituents display
inhibitory activities against several experimental disease models, including cancer, heart failure and other disorders of
Grape seed oil from crushed seeds is used in cosmeceuticals and skincare products
for many perceived health benefits. Grape seed oil is notable for its high contents of tocopherols (vitamin E), phytosterols,
and polyunsaturated fatty acids such as linoleic acid, oleic acid and alpha-linolenic acid.
Concord grape juice Commercial juice products from Concord grapes have been applied in medical
research studies, showing potential benefits against the onset stage of cancer, platelet aggregation and other risk factors
of atherosclerosis, loss of physical performance and mental acuity during aging and hypertension in humans.