The term French paradox was coined from the epidemiological observation that some French populations suffered
a relatively low incidence of coronary heart disease (CHD), despite a relatively high
dietary intake of saturated fatty acids. This phenomenon, first described by the Irish
physician Samuel Black in 1819, was later named the French paradox by Dr. Renaud,
a scientist from Bordeaux University in France in 1992.[1] In this controversial article, Renaud attributed this paradox to moderate red wine
consumption. Although it had been postulated that moderate alcohol intake would prevent
CHD by reducing atherosclerosis through beneficial effects on high-density lipoprotein-cholesterol
(HDL-C) levels, Renaud insisted that plasma HDL-C levels were not significantly higher
in the French population than in those of other Western countries, so that other mechanisms
should be advocated. After reevaluation of previously published studies, he concluded
that the reduction in CHD did not appear to be due to an increase in HDL-C levels
but rather to an improvement of the hemostatic balance, namely decreased platelet
aggregability.[1]
According to the Food and Agriculture Organization (FAO) of the United Nations,[2] the overall dietary fat consumption in France in 2003 (the last data available)
was approximately168 g/capita/day as compared with 155 g/capita/day in the United
States, 134 g/capita/day in the United Kingdom, and 126 g/capita/day in Sweden. The
consumption of animal fat was 47 g/capita/day in France, 16 in the United States,
19 in the United Kingdom, and 52 in Sweden. Although the overall consumption of alcoholic
beverages was ~255 g/capita/day in France, 269 in the United States, 340 in the United
Kingdom, and 211 in Sweden, that of wine was 145 g/capita/day in France, 19 in the
United States, 49 in the United Kingdom, and 47 in Sweden, so that wine consumption
represented ~57% of the overall consumption of alcoholic beverages in France, 7% in
the United States, 15% in the United Kingdom, and 22% in Sweden, respectively. However,
according to the atlas of global epidemic of heart disease and stroke issued by the
World Health Organization,[3] in 2002 the mortality rate for CHD in France (0.8%) was two to threefold lower than
in the United States (1.8%), United Kingdom (2.1%), and Sweden (2.3%). This is consistent
with the earlier findings of Criqui and Ringel, who reported that despite a diet enriched
in animal (saturated) fats and the highest wine intake worldwide, France had the second
lowest CHD mortality rate in 1994.[4] Now, nearly 20 years on from Renaud’s original article, several experimental and
epidemiological studies have investigated the fascinating association between red
wine consumption and cardiovascular mortality and morbidity. Notably, some health
researchers have questioned the validity of this relationship as explaining the paradox,
whereas others have provided reliable evidences of biological and clinical plausibility
to support the proposition.
WINE
WINE
In agreement with the observed relationship between moderate alcohol consumption and
reduced risk for CHD, it has been suggested that France's high red wine consumption
could be the primary factor influencing the positive relationship. According to the
2007 state of the vitiviniculture world report issued by the International Organization
of Wine and Vine, France is second only to Spain in terms of vineyards but is the
leading country in terms of hectoliters of wine produced per year (around 50 million,
which translates into 7 to 8 billion bottles per year).[5] All common styles of wine—red, rosé, white (dry, semisweet, and sweet), sparkling,
and fortified—are produced in France, and the country is the source of many grape
varieties such as Cabernet Sauvignon, Chardonnay, Pinot Noir, Sauvignon Blanc, Syrah
or Shiraz, Burgundy, and Bordeaux. In many respects, however, French wines have a
more regional than national identity, as attested by different grape varieties, production
methods, and classification systems in the various regions.
Although moderate alcohol intake from any type of alcoholic beverage appears to be
beneficial for the cardiovascular system,[6] several lines of evidence suggest that red wine might confer additional cardiovascular
benefits. The first support for a more pronounced cardioprotective effect for red
wine as compared with other alcoholic beverages emerged from the Copenhagen City Heart
Study, where 13,285 men and women 30 to 70 years of age were followed for ~12 years
and confirmed that the risk of cardiovascular mortality steadily decreased with increasing
intakes of red wine, from a relative risk (RR) of 1.00 for the subjects who never
drank wine to 0.51 (95% confidence interval [CI], 0.32 to 0.81) for those who drank
three to five glasses per day.[7] For spirits intake, however, the RR of dying increased from 1.00 for those who never
drank to 1.34 (95% CI, 1.05 to 1.71) for those with an intake of three to five drinks
per day. A nonsignificant trend in mortality risk was also observed in relation to
the subjects drinking beer compared with those who never drank beer.[7]
Although the primary ingredients of wine are water and alcohol, >500 compounds have
been identified in wine to date, 160 of which are esters (reviewed by Soleas et al).[8] Water, which represents from 80% to 85% of wine’s total mass, derives from grape
juice and it is thereby biologically pure. The alcohol content varies widely among
wines (from 10% to 17%) and is mainly attained by yeast-converting sugars. Besides
adding their own characteristic flavors and odors, alcohols are the main carriers
of aroma or bouquet. The most represented alcohol is ethanol; under standard fermentation
conditions, it can accumulate to nearly 14 to 15%, but generally ethanol concentrations
are in a range between 10% and 13%, depending on the sugar content of the grape, the
temperature, and the yeast strain. Methanol, which is predominantly generated from
the enzymatic breakdown of pectins, is a minor constituent of wine (0.1 to 0.2 g/L).
Other alcohols present in wine include the straight-chain alcohols, especially 1-propanol,
2-methyl-1-propanol, 2-methyl-1-butanol, and 3-methyl-1-butanol. Glycerol is also
present, and it usually adds a degree of sweetness. Acids (present from 0.4% to 1%)
give wine the sour or sharp aspect that enhances flavor when in balance with other
components. Of the three organic acids that originate in grapes, tartaric acid is
prevalent as the base measure of total acidity in wine, followed by malic and citric
acids. Three other acids—succinic, lactic, and acetic (source of volatile acidity)—are
also produced by fermentation. Although the grapes contain from 15% to 25% glucose
and fructose, these sugars are mainly converted to alcohol through fermentation. However,
traces of residual sugar (0.1%) can be found in dry wines, whereas sweet wines may
contain up to 10% sugars. Mineral salts (from 0.2% to 0.4%), comprising mainly potassium,
sodium, magnesium, calcium, and iron, are derived from mineral acids or organic acids.
Flavoring and coloring substances (from 0.01% to 0.5%) are mainly represented by polyphenolic
compounds, and these give wines color and account for differences in flavor between
reds and whites (their concentration is in fact much lower in white wines, 0.01% versus
0.2% in red wines). Phenols and related compounds can affect the appearance, taste,
mouth feel, fragrance, and antimicrobial properties of the beverage. They come from
the fruit (skins and seeds) and vine stems, with production by yeast metabolism, or
extraction from wood cooperage. The two primary phenol groups present in wine are
flavonoids and nonflavonoids. Again, these compounds are present in a larger amount
in red than in white wines. Whereas red wines contain up to 1060 gallic acid equivalent
(GAE) of flavonoids (namely catechins) and up to 235 GAE of nonflavonoids (namely
cinnamate derivatives), flavonoids and nonflavonoids are present at levels of 30 and
175 GAE, respectively, in white wines. Flavonols, namely tannins and anthocyanins,
are exclusively present in red wines, at a concentration of 450 and 20 GAE, respectively.
The concentration of phenolics in wine increases during skin fermentation but declines
as phenols bond and precipitate with proteins and yeast hulls, so that aging has a
dramatic effect on their final concentration. Traces of various chemical compounds
of a volatile nature account for certain odors in wine. These include alcohols, aldehydes,
esters, acids, and ketones. Sulfur derivatives are used to safeguard grapes and sterilize
and preserve wines. The presence of sulfites at 10 to 200 ppm (the upper limit for
Italian wines) is measured both in fixed sulfur dioxide, combined with other substances,
and free sulfur dioxide in the form of gas.[8]
Resveratrol (3, 4′, 5 trihydroxystilbene) is a naturally occurring phytoalexin released
by some spermatophytes such as grapevines in response to injury. Because it is mainly
present in grape berry skins but not in flesh, and a major factor influencing its
production is the fermentation time, white wine (which traditionally undergoes a shorter
maceration time) contains only low amounts of resveratrol as compared with red wine.[9] In rosé wines, the levels of resveratrol monomers are intermediate between those
of white and red wines. The concentrations of the trans-isomer of resveratrol, the
major isomer, vary widely in red wines originating from various countries, depending
mainly on grape cultivar, geographic origin, wine type, Botrytis infection, and oenological
practices. The highest concentrations of resveratrol are found in several red wines
from France (Beaujolais, Midi, Rhone, Bordeaux, Burgundy; concentrations from 3.7
to 7.1 g/L,), Spain (Pinot Noir, Merlot, Grenache; from 2.5 to 14 mg/L), and the United
States (Muscadine up to 32 g/L).[9]
THE FRENCH PARADOX: BIOLOGICAL AND EXPERIMENTAL EVIDENCE
THE FRENCH PARADOX: BIOLOGICAL AND EXPERIMENTAL EVIDENCE
Several experimental studies suggest that the polyphenolic compounds in red wine,
such as flavonoids and resveratrol, play an active role in preventing the development
and progression of cardiovascular disease (CVD), possibly through a kaleidoscope of
beneficial effects (Fig. [1]). Reliable evidence, however, attests that the most favorable biological activities
can be attributed to resveratrol and comprise inhibition of lipid peroxidation (lipoproteins,
membranes), chelation of copper, free-radical scavenging, alteration of eicosanoid
synthesis, inhibition of platelet aggregation, anti-inflammatory activity, improvement
of endothelial function, lowering of blood pressure, vaso-relaxing activity, modulation
of lipoprotein metabolism, activation of proteins that prevent cell senescence, and
anticancer and estrogenic activity.[10]
[11] Using microarray and quantitative real-time polymerase chain reaction methodologies,
Nicholson et al demonstrated that beside biochemical interactions with cells and plasma
components, treatment of human umbilical vein endothelial cells with resveratrol strongly
modulates gene expression, leading to significant (more than twofold) downregulation
of 363 genes and upregulation of 233 genes of the 10,000 genes present on the microarray.[12]
Figure 1 Favorable effects of wine components for counteracting the atherosclerotic process.
Effects on Antioxidant Status, Oxidative Stress, and Lipoproteins
Several studies have shown that dietary antioxidant intake can prevent the development
and progression of CVD, paving the way to the hypothesis that dietary antioxidants
might be regarded as potential nonpharmacological agents because of the “oxidative
theory” of atherosclerosis.[13] Red wine contains a naturally rich source of antioxidants, which may protect the
body from oxidative stress, and most of these beneficial effects have been primarily
ascribed to resveratrol. Consumption of 400 mL/day of red wine for 2 weeks significantly
increased antioxidant status and decreased oxidative stress in young and older subjects,
as reflected by an increase in plasma total antioxidant status and significant decreases
in both plasma malondialdehyde and whole blood glutathione.[14] Likewise, plasma total phenolic concentrations increased significantly in healthy
volunteers consuming 375 mL red wine daily for 2 weeks. Trace levels of flavan-3-ol
metabolites, mainly glucuronides and methyl glucuronides of (+)-catechin and (-)-epicatechin,
were also detected in the plasma of the red wine group but not in plasma from the
control group. The maximum concentrations of conjugated dienes and thiobarbituric
acid-reactive substances in Cu-oxidized low-density lipoprotein-cholesterol (LDL-C)
were reduced, whereas plasma HDL-C concentrations increased after moderate red wine
consumption.[15] Resveratrol was reported to protect LDL-C against ferrimyoglobin, peroxynitrite,
copper, or 2 amidinopropane dihydrochloride-induced oxidation.[16]
[17] Berrougui et al showed that resveratrol inhibited copper- and irradiation-induced
LDL-C and HDL-C oxidation (as observed by a reduction in oxidation rate and an increase
in the lag phase), concomitantly enhancing cholesterol efflux.[18] Resveratrol also enhanced apolipoprotein A-1-mediated cholesterol efflux, by upregulating
ATP-binding cassette transporter 1 receptors, and reduced cholesterol influx or uptake
in macrophages. Incubation of macrophages with Fe/ascorbate ions attenuated apolipoprotein
A-1 and HDL-C mediated cholesterol efflux, whereas resveratrol (0 to 25 μM) significantly
redressed this attenuation in a dose-dependent manner.[18] Therefore, considering that lipoprotein oxidation, macrophage cholesterol accumulation,
and foam-cell formation are important steps in early atherogenesis, resveratrol may
be considered a natural antioxidant that enhances cholesterol efflux and could represent
a nonpharmacological option to prevent the development and progression of CVD. More
interestingly, resveratrol has also been proposed as a lifespan booster in several
organisms, in that it might be vaso-protective by counteracting endothelial cell senescence.
However, to counterbalance this hypothesis, Schilder et al showed that exposure of
primary human endothelial cells to resveratrol was associated with increased levels
of reactive oxygen species (ROS), which were causally linked to an accumulation of
cells in the S phase of the cell cycle. Using a siRNA approach, two nicotinamide adenine
dinucleotide phosphate (NADPH) oxidases were identified (Nox1 and Nox4) as major targets
of resveratrol and primary sources of ROS that act upstream of the observed S-phase
accumulation. In synthesis, chronic exposure to resveratrol was associated to prooxidant
effects, by activating NADPH oxidases and inducing a premature senescent growth cell
arrest in primary human endothelial cells, which possibly feeds back into ROS increase.[19] Viniferin, catechin, and resveratrol isolated from grape skin strongly inhibit various
isoforms of the cyclooxygenase enzyme, which plays an important role in inflammatory
disorders, including atherosclerosis.[20] Recently, resveratrol was shown to extend the lifespan in yeast through the activation
of longevity gene SirT1, which is also responsible for the longevity mediated by calorie restriction.[21]
Effects on Endothelial Function
Endothelial dysfunction is an early marker of atherosclerosis and vessel damage, and
it is a prognostic factor for CVD risk. In vitro studies have consistently demonstrated
a variety of beneficial effects of red wine components on endothelial function. Directly
acting on vascular smooth muscle cells, red wine components produce coronary vasodilation,
attenuate oxidative stress in the heart (under different pathological conditions),
and improve cardiac function in the ischemic myocardium through the protection of
endothelial function, the expression of several cardioprotective oxidative stress-inducible
proteins, and the activation of adenosine receptors and nitrous oxide synthase mechanisms.[22] In a single blind crossover study, Whelan et al reported that the consumption of
4 mL/kg of either red or white wine with a light meal acutely improved brachial flow-mediated
dilatation after 6 hours, whereas blood-alcohol levels had returned to baseline values
by this time; the magnitude of this effect on endothelial function was substantially
similar after both red and white wines.[23] Karatzi et al also observed that brachial flow-mediated dilatation was higher following
the acute consumption of 250 mL of dealcoholized red wine than that following the
acute consumption of red wine.[24]
Regarding the biological mechanisms linking endothelial function to moderate wine
intake, it has been reported that alcohol per se can induce a marked increase in both
basal and stimulated nitric oxide (NO) synthesis by primary cultures of bovine aortic
endothelial cells and human umbilical endothelial cells, sustained by a rapid increase
of endothelial NO synthase protein and mRNA expression levels. In particular, both
endothelial NO synthase protein and mRNA increase by nearly twofold within 3 hours
and gradually decline after 0.1% ethanol ingestion, but the increased levels of mRNA
persist up to 24 hours.[25] A 20-hour treatment of human umbilical vein endothelial cells and of a human umbilical
vein endothelial cells-derived cell line with an alcohol-free red wine polyphenol
extract also led to a concentration-dependent increase (up to threefold) in NO release,
associated with an up to twofold increased human endothelial NO synthase promotor
activity. Remarkably, although polyphenol extracts from wines of specific origin and
grape cultivars vary strongly in their individual activity, when averaged, the activity
cannot be attributed to a specific grape cultivar or growing area.[26] Resveratrol (0.1 μmol/L) also decreased the gene expression of the potent vasoconstrictor
endothelin-1.[27]
Although the long-term beneficial effects of moderate red wine consumption on endothelial
function are well established, currently there is still controversy about its acute
(postprandial) effects, and not all wines seem to be equally effective. As such, a
recent analysis of all available data about the acute effect of red wine constituents
on endothelial function yielded inconclusive results, so that further larger studies
are necessary to elucidate this matter.[28]
Effects on Primary Hemostasis
Consumption for a 4-week period of 30 g/day of alcohol either from red wine or other
alcoholic beverages resulted in similar decreases in collagen-induced platelet aggregation
and plasma fibrinogen levels. However, adenosine diphosphate (ADP)-induced platelet
aggregation was not affected by any treatment, and no significant differences were
detected comparing platelet function at the end of red wine or dealcoholized treatments
with findings at the end of alcohol treatment and abstinence, so that the beneficial
effects of moderate red wine consumption on primary hemostasis appeared to be primarily
due to the alcohol and not to the nonalcoholic fractions present in red wine.[29] In a similar study by the same authors, consumption for a period of 4 weeks of nonalcoholic
components either from 320 mL of red wine or from dealcoholized red wine resulted
in similar increases in polyunsaturated fatty acids in all phospholipid fractions
of platelets, with the exception of sphingomyelin. Thus the observed increase of polyunsaturated
fatty acids in platelet phospholipids due to the nonalcoholic components of red wine
suggests an antioxidant effect that could be relevant in explaining the beneficial
effects of red wine reported in epidemiological studies.[29]
Collagen-induced platelet aggregation has been reported to be significantly reduced
in subjects consuming two to four drinks per day of red wine (23 to 46 g of alcohol
per day).[30] Polagruto et al reported that a flavonol-rich grapeseed extract decreased significantly
ADP-stimulated platelet reactivity at 1, 2, and 6 hours. Similarly, this extract decreased
epinephrine-stimulated platelet reactivity 2 hours following consumption.[31] Acute alcohol intake significantly increased platelet aggregation in suspension
when stimulated with low concentrations of ADP (0.1 and 0.5 ug/mL). However, this
effect was not observed when consuming the same amount of the alcohol contained in
red wine. Conversely, adhesion to fibrinogen was inhibited by alcohol but not red
wine at high shear rate after six drinks. This inhibition was accompanied by a reduction
in aggregate size at 90 and 180 minutes after the start of the experiment. Adhesion
to collagen was not altered by either alcohol or red wine intake.[32]
Although platelets are anuclear cellular elements, they might undergo apoptotic events
as well. Lin et al showed that resveratrol (5 to 25 μM/L) completely inhibits platelet
aggregation stimulated by collagen, but it also stimulated in a time- and concentration-dependent
manner the dissipation of the mitochondrial membrane potential (DeltaPsim), activation
of caspases-9, -3, and -8, gelsolin and actin cleavage, Bid cleavage into truncated
Bid, Bax translocation, cytochrome c release, and phosphatidylserine exposure in human
platelets, which are well-known events leading to platelet apoptosis.[33] Fehr et al showed that that, compared with water, an acute exposure to alcohol has
only modest effects on hemorheological parameters and platelet aggregation in vivo
and no effect in vitro, which suggests that other factors must be involved in both
beneficial and harmful effects of wine consumption.[34] As such, the evidence that resveratrol might simultaneously inhibit platelet aggregation
and stimulate platelet apoptosis could represent an additional potential therapeutic
option for preventing pathological outcomes in patients suffering from thrombotic
conditions or thrombocytosis.
Effects on Secondary Hemostasis and Fibrinolysis
A meta-analysis of experimental studies assessing the effects of moderate alcohol
intake on plasma HDL-C, apolipoprotein A-I, fibrinogen, triglycerides, and other cardiovascular
risk biomarkers showed that a dose of 30 g of alcohol per day significantly increased
the concentrations of plasma HDL-C by 8%, apolipoprotein A-I by 7%, plasminogen by
6%, and tissue plasminogen activator (tPA) by 20%. A nonsignificant trend toward lower
levels of lipoprotein(a), fibrinogen, and von Willebrand factor (VWF) was also observed.
Therefore, on the basis of published associations between these biomarkers and risk
of CHD, it was estimated that 30 g of alcohol/day would lead to a reduction of nearly
25% in overall CHD risk.[35] Meaningful data about the relationship between alcohol consumption and secondary
hemostasis were also provided by the Framingham Offspring Study. Levels of fibrinogen,
plasma viscosity, VWF, factor VII, plasminogen activator inhibitor-1 (PAI-1), and
tPA were measured in a cross-sectional analysis of 3223 U.S. adults free of CVD. Light-to-moderate
alcohol consumption was associated with lower levels of fibrinogen, plasma viscosity,
VWF, and factor VII. The association was most pronounced for consumers of 3 to 7 drinks
weekly for viscosity, and 7 to 21 drinks weekly for other plasma hemostatic factors.
Alcohol intake of 7 to 21 drinks weekly or more was also associated with impaired
fibrinolytic activity, reflected by higher levels of tPA. Moreover, moderate wine
drinkers had lower PAI-1 levels than other drinkers, particularly at 3 to 21 drinks
weekly.[36] In a further large epidemiological study, including 3158 men age 60 to 79 years,
daily alcohol consumption showed a positive dose-response relationship with HDL-C,
coagulation factor IX and tPA, and a negative dose-response relationship with fibrinogen
and VWF after adjustment for potential confounders. Moreover, alcohol consumption
showed a borderline negative association with D-dimer and no significant association with factors VII or VIII or C-reactive protein.[37] Van Golde et al evaluated the acute changes in a large array of plasma hemostatic
parameters 5 and 15 hours after the consumption of four (62.5 g of alcohol) and eight
(125 g of alcohol) glasses of red wine, concluding that both doses of wine had no
acute effects on activated cephalin time, thrombin-antithrombin complexes, factors
VII and VIII, and VWF levels.[38] In a further small experimental study, the same authors investigated the short-term
effects of three glasses of red wine daily during two periods of a week, with a week
of abstinence from alcohol, in healthy male volunteers. Although some slight shifts
in the various plasma hemostatic parameters could be noticed during these drinking
periods, all favoring impairment rather than stimulation, no significant effects of
moderate alcohol intake could be observed on fibrinolysis.[39] With regard to lipoprotein(a), a highly atherogenic and antifibrinolytic lipoprotein
particle,[40] Sharpe et al demonstrated that 200 mL of red wine per day for 10 days are effective
in lowering its plasma concentration by up to 12%.[41] Surprisingly, this reduction was also observed with vodka but not with white wine,
raising the issue of potential differences between various alcoholic drinks.[42] Accordingly, it was also observed that serum lipoprotein(a) is inversely and dose-dependently
related with alcohol intake in patients with hypertension, and this relationship was
independent of the size distribution of apolipoprotein(a) isoforms.[43] Therefore, it seems reasonable to conclude that reduction of lipoprotein(a) concentrations
by regular consumption of alcohol might favorably affect the atherosclerotic risk
profile and thereby decrease cardiovascular morbidity.
An interesting study evaluating the acute effects of different alcoholic beverages
on secondary hemostasis was performed by Tousoulis et al. Eighty-three healthy subjects
were randomized into five groups to receive an equivalent dose of alcohol contained
in four different alcoholic beverages (264 mL red wine, 264 mL white wine, 633 mL
beer, and 79 mL whiskey) and 250 mL water.[44] Although no acute effect was observed in plasma lipid parameters in all study groups,
VWF was significantly reduced by 9% and 14% 4 hours after ingestion of red wine and
beer, respectively. Conversely, the PAI-1-to-tPA ratio was increased by 64%, 85%,
and 79% after ingestion of white wine, beer, and whisky, respectively. No significant
acute changes were observed in plasma fibrinogen and acute-phase reactants (i.e.,
C-reactive protein, interleukin 6, and tumor necrosis factor α). The short-term effects
(5 to 24 hours) of a low (two glasses, 250 mL, 20 g alcohol) and a high (six glasses,
750 mL, 60 g alcohol) intake of red wine were also investigated in male volunteers.
After the acute intake of two glasses of red wine, no clinically significant disturbances
of plasma fibrinolysis were observed. However, 5 hours after the consumption of six
glasses of red wine, a continued inhibition of fibrinolysis was evident, as mirrored
by a dramatic 5- to 13-fold increase of PAI-1 activity and PAI-1 antigen. Although
a modest rise of tPA antigen was also observed, tPA activity fell, as did plasmin-antiplasmin.[45]
Several in vitro studies also support the hypothesis that moderate red wine consumption
may exert beneficial effects on fibrinolysis. Cultured human umbilical endothelial
cells preincubated for 1 hour in the presence of ethanol (0.025 to 0.2%) showed a
two- to fourfold increase of urokinase plasminogen activator receptor mRNA and antigen
levels, associated with a 36% increase of urokinase plasminogen activator (uPA) binding
activity to endothelial cells.[46] Low concentrations of ethanol (0.025 to 0.2%) also induced a short-term versus long-term
increase in surface-localized fibrinolytic activity in cultured human umbilical endothelial
cells via different mechanisms. Short-term effects were primarily mediated by alcohol-induced
membrane conformational changes that simultaneously facilitate increased surface-localized
plasminogen receptor availability and fibrinolytic protein/receptor interactions,
resulting in increased tPA affinity for Glu-plasminogen and accelerated activation.
The long-term effects were instead attributed primarily to the alcohol-induced increased
availability of both newly synthesized tPA and plasminogen receptor and, hence, accelerated
activation of Glu-plasminogen.[47] Cultured human umbilical endothelial cells preincubated in the presence of varying
concentrations of flavonoids such as catechin, epicatechin, quercetin, and resveratrol
(0.001 to 10 μM/L) also showed upregulation of both tPA and uPA gene transcription,
resulting in the sustained increased expression of surface-localized fibrinolytic
activity by each of these phenolic compunds.[47] These combined results are consistent with the hypothesis that low to moderate alcohol
intake may induce a favorable genetic modulation of fibrinolytic proteins, ultimately
increasing surface-localized endothelial cell fibrinolysis.
Effects on Blood Pressure and Insulin Sensitivity
Many observational studies have consistently shown a strong positive relationship
between chronic heavy alcohol consumption (more than three drinks per day) and hypertension,
thus supporting the current recommendations that daily alcohol reduction should represent
an important component of lifestyle modification for the prevention and treatment
of hypertension among heavy drinkers.[48] Xin et al conducted a meta-analysis of randomized controlled trials to assess the
effects of alcohol reduction on blood pressure.[49] They included 15 randomized controlled trials (total of 2234 participants) in which
alcohol reduction was the only intervention difference between active and control
treatment groups. Overall, alcohol reduction was associated with a significant reduction
in mean systolic and diastolic blood pressures of –3 mm Hg and –2 mm Hg, respectively.
The effect of alcohol reduction on blood pressure was consistent across subgroups,
including those defined by presence or absence of hypertension. Furthermore, a dose-response
relationship was observed between mean reduction in reported consumption of alcohol
and net change in both systolic and diastolic blood pressure. However, because the
participants included in these 15 clinical trials were fairly heavy alcohol drinkers
(more than three drinks/day), this meta-analysis was unable to examine the long-term
effect of moderate alcohol consumption on blood pressure, which at present remains
not fully understood. A linear, J-shaped, or threshold association between alcohol
consumption and blood pressure has been reported in some observational epidemiological
studies.[50]
[51]
[52] However, in controlled clinical studies that directly tested the effects of alcohol
intake on blood pressure, findings are inconsistent, perhaps because of differences
in duration of alcohol use and the timing of blood pressure measurements. In this
setting, McFadden et al recently performed a systematic review of trials that measured
blood pressure after a period of sustained alcohol intake (defined as daily intake
of at least one alcoholic drink daily) in one group and that also included a control
group of individuals who consumed no alcohol.[53] Nine studies met the entrance criteria. This review demonstrated a significant rise
in systolic blood pressure and diastolic blood pressure of 2.7 mm Hg and 1.4 mm Hg,
respectively, after alcohol intake. An early effect of alcohol leading to a reduction
in blood pressure (in the hours after exposure) and a later effect (next day) of raising
blood pressure led to smaller differences in the net effect of alcohol on blood pressure
when ambulatory blood pressure monitoring measurements were compared with casual office-
or clinic-based measurements. All of these findings indicate that the timing of blood
pressure measurements after alcohol intake has a substantial effect on the magnitude
and perhaps even the direction of blood pressure changes identified within any study.
Several epidemiological and intervention studies have examined the relationship between
daily alcohol consumption and insulin sensitivity in individuals both with and without
diabetes. For example, in a randomized crossover trial of 63 nondiabetic postmenopausal
women, consumption of 30 g/day of alcohol (two drinks per day) significantly improved
insulin sensitivity and decreased plasma insulin and triglyceride concentrations after
8 weeks of intervention when compared with placebo.[54] In a multicenter randomized clinical intervention trial of subjects with type 2
diabetes who had previously abstained from alcohol, daily consumption of one alcoholic
drink resulted in a reduction of fasting glucose after 30 days of intervention, and
this relationship was stronger in subjects with higher hemoglobin A1c.[55] Several other investigators have reported beneficial effects of moderate drinking
on insulin sensitivity and glucose metabolism.[56]
[57]
[58]
[59] Interestingly, the potentially beneficial changes in insulin sensitivity with moderate
alcohol intake might help explain the results from several prospective observational
studies showing a strong inverse association between moderate alcohol drinking and
the risk of incident type 2 diabetes.[60]
[61]
[62]
THE FRENCH PARADOX: CLINICAL AND EPIDEMIOLOGICAL EVIDENCE
THE FRENCH PARADOX: CLINICAL AND EPIDEMIOLOGICAL EVIDENCE
Although excessive amounts of red wine as well as other alcoholic beverages remain
a definite risk for health, mild-to-moderate amounts of red wine may provide a net
beneficial effect. Interest in the cardiovascular benefits of regular wine consumption
has increased considerably over the past 30 years.[63] In 1979, St Leger and colleagues drew attention to the cardioprotective properties
of wine when they described a strong inverse relationship between wine consumption
and risk of death from CVD in various countries from Europe, North America, and Australasia.[64] Since then, several epidemiological studies in different developed countries have
analyzed the beneficial effects of regular wine consumption on the risk of CHD morbidity
and mortality.[1]
[7]
[65]
[66]
[67]
[68]
[69]
[70]
[71] A study conducted by Grønbaek and colleagues in 24,623 Danish subjects over 10 years
investigated the chronic effect of one to three glasses of alcoholic beverage (beer
or wine) per day on cardiovascular mortality.[7] A beneficial effect of wine intake emerged from this study as subjects with low-to-moderate
wine intake had half the risk (RR, 0.51; 95% CI, 0.32 to 0.81) of dying from cardiovascular
causes as those who never drank wine, whereas beer and spirit drinkers did not experience
this advantage. These results were reinforced when the same group of investigators
performed a systematic review of large population-based cohort studies in which the
type of alcohol consumed, smoking status, educational level, physical activity, and
obesity were assessed at baseline. Compared with nondrinkers, light-to-moderate drinkers
who avoided wine had a RR of death from all causes of 0.90, whereas those who drank
wine had a RR of 0.66. The authors concluded that moderate wine intake may have a
beneficial effect on all-cause mortality that is additive to the protection afforded
by alcohol per se.[69] Similar results emerged from a study conducted by Renaud and colleagues in 36,250
French middle-aged men where moderate red wine consumption but not of other alcoholic
beverages reduced all-cause mortality over 18 years.[72] Klatsky and colleagues followed up 128,934 adults in Northern California for up
to 20 years[71] and showed that light-to-moderate drinkers were at lower risk from CHD mortality
(RR for 1 to 2 drinks per day = 0.7; 95% CI, 0.6 to 0.9). A preference for red wine
consumption resulted in a lower RR for CHD mortality compared with liquor and beer.
Heavy drinkers (six or more drinks per day) had a higher risk of noncardiovascular
mortality than those who did not drink (RR = 1.6; 95% CI, 1.3 to 2.0). In a large
prospective study, Thun et al examined the long-term effect of alcohol consumption
on mortality among middle-aged and elderly US adults.[73] Of 490,000 men and women who reported their alcohol and tobacco use, 46,000 died
during 9 years of follow-up. The authors compared the rates of all-cause and cause-specific
mortality across categories of baseline alcohol consumption and adjusted for other
prognostic risk factors. The cardiovascular mortality rates were 30% to 40% lower
in men (RR, 0.7; 95% CI, 0.7 to 0.8) and women (RR, 0.6; 95% CI, 0.6 to 0.7) reporting
at least one drink daily than those in nondrinkers. Moreover, the all-cause mortality
rate was also lower among men and women reporting approximately one drink daily. Very
recently, Djoussé et al examined the association between alcohol consumption and risk
of CVD and death in 26,399 female participants from the Women’s Health Study.[74] They confirmed there was a J-shaped relation between alcohol consumption and incident
CVD and total and CVD deaths in a multivariable model. Compared with abstainers, alcohol
intake of 5 to 15 g/day was associated with 26%, 35%, and 51% lower risk of CVD, total
death, and CVD death, respectively. For CVD risk reduction, plasma lipids made the
largest contribution to the lower risk of CVD, followed by hemoglobin A1c/diabetes,
inflammatory/hemostatic factors, and blood pressure factors. Overall, therefore, mounting
evidence strongly supports the cardiovascular benefits of moderate alcohol consumption
in most populations, with a dose-response relationship traditionally depicted as a
“J-shaped” curve, being a moderate alcohol intake (10 to 30 g/day) beneficial and
either no intake or an excessive intake (>30 g/day) harmful.[75] A J-shaped relationship also emerged from a meta-analysis published in 2002 by Di
Castelnuovo and colleagues.[65] In this meta-analysis including 26 prospective studies with >200,000 persons, the
RR for CHD of wine drinkers in respect to nondrinkers was 0.68 (95% CI, 0.59 to 0.77),
whereas the benefit associated with beer drinking was 10% lower (RR 0.78; 95% CI,
0.70 to 0.86). The same authors more recently published a comprehensive meta-analysis
of alcohol consumption and all-cause mortality in 34 prospective studies totaling
more than a million subjects.[76] Again, they confirmed a strong J-shaped relationship between all-cause mortality
and alcohol intake, showing that light-to-moderate amounts of wine (one to two drinks
per day in women and two to three drinks per day in men) are inversely associated
with total mortality in both men and women (maximum protection was 18% in women and
17% in men).
Although several clinical studies have to date investigated the role of wine intake
on cardiovascular health, only a few controlled trials have directly compared red
wine with other alcoholic beverages.[77]
[78]
[79]
[80]
[81] The type of alcohol-containing beverage consumed does not appear to make a difference
on the risk for CHD in a cohort of 38,077 U.S. male health professionals over 12 years
of follow-up.[70] Similar mortality risk reductions were also found to be associated with red wine,
white wine, other types of wine, and combinations of wine types in the cohort study
conducted by Klatsky and colleagues.[71] In a recent review on this topic, it was concluded that the CVD risk appeared to
be more strongly related to the drinking pattern than to the type of alcoholic drinks
consumed.[82] Overall, therefore, the current evidence is not conclusive, and a clear and definite
answer to the hypothesized superiority of red wine to other alcoholic beverages could
only arise from future large well-designed prospective randomized trials.
However, there does exist some important evidence in favor of a potentially cardioprotective
effect of red wine not related to alcohol, and these come from experimental studies
evaluating the acute intake of dealcoholized red wine. Karatzi and colleagues investigated
the acute intake of 250 mL dealcoholized red wine on endothelial function in 15 men
with angiographically documented CHD,[83] and they found that it decreased arterial stiffness and improved the augmentation
index, as derived from arterial wave reflection patterns. The same group of investigators
observed that a similar dose of alcohol-free red wine decreased adverse postsmoking
arterial wave reflections and lessened the rise in systolic blood pressure.[84] Other experimental studies found that brachial artery flow-mediated vasodilation
was improved by the acute intake of 250 to 500 mL of dealcoholized red wine.[85]
[86]
CONCLUSIONS
CONCLUSIONS
Wine has been part of human culture for >3000 years, serving dietary and socioreligious
functions. Its production takes place on every continent, and its chemical composition
is profoundly influenced by oenological techniques, the grape cultivar from which
it originates, and climatic factors.[8] Several prospective studies have consistently demonstrated that light-to-moderate
red wine consumption (one to two drinks per day; 10 to 30 g alcohol) is strongly associated
with a lower incidence of CVD events compared with abstinence or occasional alcohol
consumption. Most studies have reported a J-shaped association, with no consumption
or chronic heavy consumption of wine (three or more drinks per day) and other alcoholic
beverages associated with increased CVD risk compared with moderate consumption. Globally,
the cardiovascular benefits of wine are likely due to combined, additive, or perhaps
synergistic effects of alcohol and other wine components (mainly resveratrol and other
polyphenolic compounds) on atherogenesis, coagulation, and fibrinolysis.
Although there is now also growing evidence that suggests moderate red wine intake
might represent a promising “therapeutic” option to prevent and perhaps even treat
CVD, some doubts still remain. First, it is still unclear whether the beneficial effects
of red wine intake can be attributed to any specific type of grape(s), and therefore
any single wine source cannot be considered better than any other. Second, it remains
to be determined whether the reported beneficial benefits of alcoholic beverages in
general, and of red wine in particular, are biased by one or more socioeconomic confounders.
Accordingly, the beneficial effects of red wine intake in human health should be better
defined, and additional research is required before any firm recommendation can be
made to abstainers to initiate a light to moderate consumption of red wine.
