How a glass of wine a day affects your heart, according to doctors

Many people toast the end of the day with a five‑ounce glass of wine, hoping that ritual keeps heart trouble at bay. Two new analyses suggest the habit might offer real – if limited – protection for adults already at higher risk of cardiovascular disease.

The latest evidence comes from a Spanish arm of the long‑running PREDIMED trial. The study tracked 1,232 older adults following a Mediterranean diet and found that those who averaged roughly half to one glass per day had significantly lower heart risks.

After five years, their risk of heart attack, stroke, or cardiac death dropped by nearly half.

Researchers verified intake by measuring wine‑derived tartaric acid in urine instead of relying on memory, a switch that turned vague drink logs into hard numbers.

The work was led by Professor Ramon Estruch of the University of Barcelona and Hospital Clinic Barcelona.

Chemical reveals true wine intake

Questionnaires often miss what people actually pour, so scientists struggle to pin down alcohol’s true effects. Using the grape‑exclusive metabolite tartaric acid makes it possible to see how much wine someone enjoyed over the previous week without asking them to confess.

“By measuring tartaric acid in the urine, alongside food and drink questionnaires, we have been able to make a more accurate measurement of wine consumption,” said Estruch.

The study linked tartaric acid levels to self-reported wine intake, confirming it as a reliable consumption marker.

Wine’s effects in Mediterranean diets

Adopting such objective tools may help resolve decades of conflicting findings that swing from “red wine is medicine” to “no amount is safe.”

The investigators also adjusted for smoking, exercise, and other lifestyle habits, so the reduced risk cannot be written off as a simple marker of healthier living.

Importantly, tartaric acid only captures wine, not beer or spirits, letting researchers isolate how fermented grape products behave inside a diet already rich in extra‑virgin olive oil, fish, and vegetables.

That context matters because many of wine’s plant compounds appear to interact with the broader Mediterranean plate, enhancing their antioxidant reach.

Benefits tied to small servings

Participants who logged between three and thirty‑five five‑ounce glasses a month, roughly half to one serving a day, saw their risk of a major cardiac event fall by 50 percent. Light users who stayed below half a glass a day gained a 38 percent cut.

Once intake climbed above one glass each day, the advantage disappeared and, in some analyses, reversed.

That pattern mirrors American Heart Association guidance, which caps daily wine at one five‑ounce serving for women and two for men.

Men, who made up just under half the study group, appeared to draw a stronger benefit. However, statisticians caution that the sex difference may fade in larger samples.

Even within the favorable range, nurses warned that pouring size matters because many home glasses hold eight or nine ounces, inadvertently nudging people past the safer ceiling.

What makes wine different

Wine carries a mix of polyphenols such as resveratrol, quercetin, and catechins that seem to boost the lining of blood vessels.

Clinical reviews report that supplemental resveratrol can improve endothelial function, a key factor in healthy blood pressure and clot prevention.

Red wine has more antioxidants due to skin fermentation, though white wine still provides some. That biochemical cocktail may partly explain why studies often find beer or spirits lack the same signal.

Moderate alcohol itself can raise high-density lipoprotein (HDL), the so‑called “good” cholesterol, yet ethanol also raises triglycerides and blood pressure at larger doses. Polyphenols may tilt the equation back toward benefit, but only within a narrow window.

Too much wine harms the heart

A 2023 systematic review that pooled data from 4.8 million people found no reduction in all‑cause mortality among moderate drinkers once misclassified former drinkers were excluded.

The authors warned that earlier optimism probably stemmed from comparing social drinkers with people who quit because of illness.

Heavy pouring is indisputably harmful. Even one extra daily drink can raise systolic blood pressure by two to four millimeters of mercury, a change large enough to push many people into hypertension. Elevated pressure strains arteries, sets the stage for arrhythmias, and accelerates heart failure.

Professor Giovanni de Gaetano noted that the biomarker approach “provides robust evidence that moderate wine consumption is associated with lower CVD risk. He cautioned that the same data “remind us of the risks associated with higher levels of consumption.”

Alcohol also carries addictive potential, and the Centers for Disease Control and Prevention (CDC) estimates that roughly one in ten deaths among working‑age adults is tied to excessive drinking.

That sobering statistic explains why public health agencies repeat that zero is the only completely risk‑free dose.

Wine, humans, and heart health

For adults older than about 35 who already follow a Mediterranean diet, a small glass of wine with supper may fit comfortably into a heart‑conscious lifestyle.

People who are pregnant, taking interacting medications, or battling addiction should not take the PREDIMED results as a green light.

Nutrients that give wine its appeal, including resveratrol, also reside in grapes, blueberries, nuts, and olive oil. Anyone who chooses to skip alcohol can still obtain similar antioxidant support without ethanol’s downsides.

Clinicians emphasize that no one should start drinking for health reasons. Instead, the sensible takeaway is that very modest wine, enjoyed with meals and within established limits, is unlikely to harm. It might even help certain high‑risk adults when paired with vegetables, fish, and extra‑virgin olive oil.

The study is published in the European Heart Journal.

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