enhanced in 2010
Polyphenols in red wine
Only specific wines show health benefits. This article points at the wines with the highest health benefits. It also discusses in which wines to find specific chemical compounds such as polyphenols, resveratrol, procyanidins and OPCs.
The French paradoxThe French paradox refers to the observation that the French suffer a relatively low incidence of coronary heart disease, despite having a diet relatively rich in saturated fats. The phenomenon was first noted by Irish physician Samuel Black in 1819.
Oxidative stress is an attack on cells when a biological system cannot readily detoxify the redox reactive intermediates or easily repair the resulting damage.
Oxidative stress is involved in many diseases, such as atherosclerosis, Parkinson's disease, heart failure, myocardial infarction, Alzheimer's disease, fragile X syndrome and chronic fatigue syndrome, but short-term oxidative stress may also be important in prevention of aging by induction of a process named mitohormesis.
Free radical scavengers
Antioxidants are free radical scavengers: they slow or prevent the oxidation of other molecules by capturing free radicals. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Oxidation reactions can produce free radicals, which start chain reactions that damage cells. Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions by being oxidized themselves. As a result, antioxidants often are reducing agents such as thiols or polyphenols.
Polyphenols are a group of chemical substances found in plants. Flavonoids are the most abundant polyphenols in the diet. Tannins of the wine contain some flavonoid polyphenols. It is in the first years of the wine that some polyphenols help prevent cardiovascular diseases and some cancers, among other health benefits.
Other sources of flavonoids include all citrus fruits, berries, ginkgo biloba, onions, parsley, pulses, tea (especially white and green tea), seabuckthorn, and chocolate with a cocoa content of 70 percent or greater.
Resveratrol in red wines
Phytoalexins are antibiotics produced by plants when under attack by pathogens such as bacteria or fungi. Resveratrol is a phytoalexin produced naturally by several plants — including vines.
The health benefits of resveratrol on humans are unproven. In mouse and rat experiments, anti-cancer, anti-inflammatory, blood-sugar-lowering and other beneficial cardiovascular effects of resveratrol have been reported. Most of these results have yet to be replicated in humans.
Resveratrol is found in the skin of red grapes. Malbec has a thick skin and contains much resveratrol. Vine grapes grown in cooler climates have higher resveratrol levels than those from warmer climes (such as California and Spain). The varieties with most resveratrol in the wine include malbec, petite sirah, st. laurent and pinot noir.
Health benefits of procyanidin flavonoids
Proanthocyanidins are essentially polymer chains of flavonoids such as catechins. They are also known as OPCs, pycnogenol, leukocyanidin and leucoanthocyanin. They are found in many plants, and grape seeds and skin.
The effects of proanthocyanidins include neutralizing oxidants and free radicals, depressing blood fat, and inhibiting destruction of collagen, the most abundant protein in the body. These influences, along with other mechanisms, explain their benefit in venous and capillary disorders, including venous insufficiency, capillary fragility, diabetic retinopathy and macular degeneration. Some research indicates that the vascular benefits of red wine drinking depend on the presence of oligomeric proanthocyanidins.
Additionally, studies have shown that OPCs may prevent cardiovascular disease by mitigating the negative effects of high cholesterol on the heart and blood vessels.
OPCs depend on winemaking
OPCs are essentially polymer chains of flavonoids. These procyanidins are the most abundant flavonoid polyphenols in red wine — up to one gram per litre is found in some traditional style red wines. Repartition is discussed below.
Dr. Roger Corder is an author of many scientific papers detailing his research into the flavonoids of foods, but wine in particular. He summarized his findings in a 2007 book, The Red Wine Diet. Dr. Corder's compilation is a good discussion of flavonoids in foods and wines. Although it would have been more entertaining if peppered with more wit and humans interest, given the topic, its straightfoward, semi-academic telling of the story makes his points effectively.
Among the important observations Corder makes is that regions of the world with the greatest longevity also correspond to regions with the highest procyanidin flavonoids in their wines. Regarding the variable flavonoid content of various wines, he states:
"Although differences in the amount of procyanidins in red wine clearly occur because of the grape variety and the vineyard environment, the winemaker holds the key to what ends up in the bottle. The most important aspect of the winemaking process for ensuring high procyanidins in red wines is the contact time between the liquid and the grape seeds during fermentation when the alcohol concentration reaches about 6 percent. Depending on the fermentation temperature, it may be two to three days or more before this extraction process starts. Grape skins float and seeds sink, so the number of times they are pushed down and stirred into the fermenting wine also increases extraction of procyanidins. Even so, extraction is a slow process and, after fermentation is complete, many red wines are left to macerate with their seeds and skins for days or even weeks in order to extract all the color, flavor, and tannins. Wines that have a contact time of less than seven days will have a relatively low level of procyanidins. Wines with a contact time of 10 to 14 days have decent levels, and those with contact times of three weeks or more have the highest."
He points out that deeply-colored reds are more likely to be richer in procyanidins. Wines rich in procyanidins provide several-fold more, such that a single glass can provide the same purported health benefit as several glasses of a procyanidin-poor wine.
Varietals and OPC
So how do various wines stack up in procyanidin content? Here's an abbreviated list from Corder's book, The Red Wine Diet:
Australia — tend to be low, except for Australian Cabernet Sauvignon which is moderate.
Chile — only Cabernet Sauvignon stands out, then only moderate in content.
France — Where to start? The French, of course, are the perennial masters of wine, and prolonged contact with skins and seeds is usually taken for granted in many varieties of wine. French wines are better designated by region, rather than by variety of grape. Each wine region can vary widely in flavonoid content:
Bordeaux red wines rate moderately;
Burgundy red wines low to moderate;
Languedoc-Roussillon red wines moderate to high (and many great bargains);
Rhone red wines (Côtes du Rhône) moderate to high.
Malbec and tannat seem to be the varieties with the most OPC.
Italy — Much red Italian wine is made from the sangiovese grape and called variously Chianti, Valpolicella, and "super-Tuscan" when blended with other varietals. Corder rates the southern Italian wines from Sicily, Sardinia, and the mainland as high in procyanidins; most northern varieties are moderate.
Spain — Moderate in general.
United States — Cabernet Sauvignon is the standout for procyanidin content.
The wines with most health benefits
The wine with the highest procyanidin content is a wine grown in the Gers region of southwest France. The wines here are made with the tannat grape within the Madiran appellation; wines labeled "Madiran" must contain 40% or more tannat to be so labeled.
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