Nurturing The Brain – Part 3, Red Wineby Sara Adaes, PhD | April 11, 2015
Have you ever heard of the “French paradox”? This concept originated in the 1980s and refers to the epidemiological observation that French people have a relatively low incidence of cardiovascular diseases despite having a diet rich in saturated fats.
Although it has been argued that the French paradox may be an illusion due to statistical distortions and the way health statistics are collected in France, it did promote a lot of research interest around what could be allowing the French to eat saturated fats and avoid cardiovascular disease. Soon, many possible explanations for the French paradox started to emerge. But the one that stuck (at least in pop culture) was that the low incidence of cardiovascular diseases in the French population could be due to their high per capita consumption of red wine.
Is there any scientific evidence of the beneficial effects of red wine?
Yes! Research has found that, when consumed in moderation, red wine can indeed be beneficial. There are different components of wine that may account for such effects, and one of them is alcohol itself. Alcohol has been shown to impair learning and memory formation, even in low doses, and heavy alcohol consumption is known to be associated with diabetes, hypertension and psychiatric conditions, for example. However, light to moderate consumption of alcohol seems to have some protective effects.
The beneficial effects of alcohol
A comprehensive systematic review and meta-analysis published in 2011 compared alcohol drinkers with non-drinkers for the outcomes of incidence and overall mortality from cardiovascular disease, coronary heart disease, and stroke; the study showed that moderate alcohol consumption (up to 1 drink a day) is consistently associated with a reduction in the risk of all outcomes. Larger amounts of alcohol, on the other hand, are associated with higher risks for stroke incidence and mortality.
A complementary meta-analysis also reviewed the effect of experimentally controlled alcohol consumption on the circulating concentrations of biological markers associated with coronary heart disease risk; it was found that moderate consumption of alcohol promotes a number of changes known to be cardioprotective, such as increased circulating levels of HDL cholesterol (the “good” one), apolipoprotein A1, and adiponectin and significantly decreased fibrinogen levels.
Although the cardiovascular effects of moderate alcohol consumption seemed fairly straightforward, the association of alcohol consumption with stroke was shown to be more complex and to differ by stroke subtype: light to moderate alcohol consumption is associated with a slightly reduced risk of ischemic stroke but higher risk of haemorrhagic stroke, while heavy alcohol consumption increases the risk of total, ischemic, and hemorrhagic stroke.
A possible explanation for these differential effects on ischemic vs haemorrhagic stroke lies on the anticoagulant effects of alcohol: on one hand these anticoagulant properties are beneficial for decreasing the risk of ischemic stroke, by reducing the formation of blood clots, but on the other hand, by inhibiting coagulation, alcohol increases the risk of hemorrhagic stroke. Furthermore, alcohol-induced hypertension may also contribute to the risk of hemorrhagic stroke, while the increase in HDL cholesterol associated with moderate alcohol consumption may have a protective role against ischemic stroke.
Clinical studies have also shown that alcohol may have neuroprotective effects in traumatic brain injury. Low to moderate blood alcohol content in traumatic brain injury patients has been associated with lower injury severity, reduced in-hospital mortality rates and increased 5-year survival rates compared to those with no or high blood alcohol concentration at the time of injury. Experimental animal studies have reinforced these findings and have also revealed that, besides these prophylactic effects, administration of a low to moderate dose of ethanol after stroke may also reduce brain infarction and improve functional outcome.
The effects of polyphenols
Wine contains a myriad of polyphenolic compounds known to have multiple beneficial health effects. Polyphenols are naturally occurring chemicals that have protective actions in plants. The polyphenolic content of wine varies greatly depending on the type of wine and the associated production methods, grape varieties and ageing processes. Some of the most abundant polyphenols in wine are tannins; an example of this type of molecules is the procyanidins present in grape seeds, grape skin and red wines (as well as in apples, green and black tea and in cocoa beans, where their concentration is highest).
Procyanidins have been emerging as one of the key factors in the French paradox: they are the principal vasoactive polyphenols in red wine and have been linked to a decreased risk of coronary heart disease and overall mortality. Interestingly, procyanidins are present at higher concentrations in wines from areas of southwestern France and Sardinia where longevity is higher and neurodegenerative disease incidence is lower.
Procyanidins have potent antioxidant properties. Oxidative stress is a well-known key factor in aging, neurodegeneration and in traumatic brain injury, as well as in cardiovascular diseases. Due to their strong antioxidant activity, procyanidins may therefore protect the brain against oxidative damage and age-associated changes. Indeed, recent evidence has demonstrated a protective role of wine polyphenols against Alzheimer’s disease, as well as a role in delaying age-related memory and cognitive decline. Experimental studies have also shown that procyanidins can counteract oxidative damage and behavioral dysfunction after traumatic brain injury.
Another component of red wine that has been linked to its beneficial effect is resveratrol. Resveratrol is a polyphenol found in the skin of red grapes, and in berries, for example. Resveratrol is quite a trend: it has been tested in numerous experimental contexts and is believed to be effective in protecting against cancer, cardiovascular diseases and neurodegenerative diseases, when administered in relatively high doses. The hype around resveratrol has led to a massive increase in its sale in the form of nutritional supplements, although clinical evidence of its effects is still scarce. However, the naturally occurring form of resveratrol actually has a low half-life in plasma and the amount of resveratrol present in red wine is probably too low to account for its beneficial effects.
The explanation for the French paradox is most likely multifactorial and associated with the quality of their overall diet. Nevertheless, it is likely that red wine may play a part. The key, as always, is moderation.
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