Researchers looked into how just one drink a day can affect blood pressure. Here’s what they found

By Sandee LaMotte, CNN

(CNN) — As little as one alcoholic drink a day increased systolic blood pressure — the top number in a blood pressure reading — even in men and women with no existing hypertension, a new study found.

“We found no beneficial effects in adults who drank a low level of alcohol compared to those who did not drink alcohol,” said senior study author Dr. Marco Vinceti, a professor of epidemiology and public health at the University of Modena and Reggio Emilia in Italy, in a statement.

The negative impact of alcohol on systolic blood pressure continued to rise over the years, the study found, even in men and women who drank little each day. Small amounts of alcohol also raised the lower, or diastolic blood pressure reading, but only in men, according to the study, which was published Monday in the journal Hypertension.

“Both systolic and diastolic readings contribute to (cardiovascular) risk and go hand in hand, but of the two, systolic blood pressure is definitely the most important risk factor in adults,” said study coauthor Dr. Paul Whelton, chair in global public health at Tulane University’s School of Public Health and Tropical Medicine in New Orleans and president of the World Hypertension League.

Blood pressure and cardiovascular health

Blood pressure is measured in units of millimeters of mercury (abbreviated as mmHg), and written as two numbers, one above the other. The top or systolic reading, which represents the force of blood against artery walls when the heart contracts, is a “major risk factor for cardiovascular disease for people over 50,” according to the American Heart Association. The lower diastolic reading measures pressure in the arteries as the heart muscle rests between beats.

A normal systolic reading is typically 120 mm Hg or below but tends to rise as blood vessels weaken and narrow with age, the AHA said. A normal diastolic reading is below 80 mm Hg but begins to decline with age as arteries lose their elasticity and stiffen, at times leading to an increase in pulse rate.

“Alcohol is certainly not the sole driver of increases in blood pressure; however, our findings confirm it contributes in a meaningful way,” said Vinceti, also an adjunct professor in the department of epidemiology at Boston University’s School of Public Health. “Limiting alcohol intake is advised, and avoiding it is even better.”

The concept that too much alcohol raises blood pressure has been around for a long time, said Dr. Andrew Freeman, director of cardiovascular prevention and wellness at National Jewish Health in Denver.

“However, this review found relatively low levels of alcohol impacted blood pressure,” said Freeman, who was not involved with the research. “So, to me, this is yet another study showing there may not be any safe amount of alcohol.”

Risk rises with increasing alcohol levels

The review analyzed data from seven studies conducted in Japan, South Korea and the United States between 1997 and 2021. It followed more than 19,000 adults from age 20 to about 70 who had no prior diagnoses of alcoholism, binge drinking, cardiovascular disease, diabetes or liver disease over an average five-year span of time.

All participants were asked about their typical alcohol intake at the start of the studies, which was translated into grams of alcohol to avoid differences between countries on what constitutes a “standard drink.” The World Health Organization, for example, sets the standard at 10 grams of alcohol per drink, while the US defines it as 14 grams.

“In the US, you’re probably getting more than one standard drink per day,” Whelton said. “If you got a pour of wine with 14 grams of alcohol at a restaurant, you’ll want to say to your server, ‘You cheapskate, go back and pour a real glass of wine.’ We think we’re consuming one standard drink, but we’re not.”

Researchers then used statistics to plot how various amounts of alcohol affected blood pressure over time. Drinking an average of 12 grams of alcohol per day, or less than one US standard drink, produced a small rise in systolic pressure of 1.25 mm Hg over an average of five years.

“We were somewhat surprised to see that consuming an already-low level of alcohol was also linked to higher blood pressure changes over time compared to no consumption — although far less than the blood pressure increase seen in heavy drinkers,” Vinceti said.

In people who consumed an average of 48 grams of alcohol per day, or nearly 3.5 standard US drinks, systolic blood pressure rose nearly 5 mm Hg over the same time frame compared with nondrinkers.

“That would certainly move you from pre-hypertensive to hypertensive, just as eating an excessive amount of sodium, too few fruits and vegetables and not getting enough physical activity will push you in the wrong direction,” Tulane’s Whelton said.

Another finding: The impact of alcohol on blood pressure was even more significant if a person’s readings were already heading upward when the study began, Whelton said.

“This suggests that people with a trend towards increased blood pressure may benefit the most from low to no alcohol consumption,” he said.

Confusing messages about alcohol

How do the study results fit in with past research that has shown alcohol may be beneficial for the heart? For one, many of the older randomized clinical trials only compared light drinkers with heavy ones, and not to those who did not drink at all, Whelton said.

“What we generally have seen in the clinical trials are that drinkers are randomized to less alcohol, such as light beer, versus continuing to drink as normal. And of course, those who consumed low to moderate amounts of alcohol had better outcomes,” said Whelton, who coauthored a meta-analysis on such studies.

“From a blood pressure perspective, I think most people would agree that there’s no level in which alcohol is safe,” he added. “From a cardiovascular point of view, you may get mixed opinions.”

Studying alcohol use is difficult because it is associated with behaviors that can be both helpful and unhelpful, Freeman said.

“If you’re drinking in a smoke-filled bar at night with friends, (your exposure) to secondhand smoke and alcohol will certainly disrupt your sleep, and both are harmful to health,” he said. “But you’re also getting the positives of socialization.”

Research on “blue zones,” areas of the world where people typically live up to and past 100, has shown the diets in these locations often include small amounts of alcohol that are routinely consumed with dinner. Is it the alcohol that helps longevity, or the tight social networks?

“It can be hard to tease out these associations,” Freeman said, adding that he gives his patients the same guidance as the AHA and WHO.

“First, I don’t recommend people start drinking,” he said. “If they do drink, they should try to really minimize it and then do their best to maintain healthy behaviors that help the heart, such as exercise and stress reduction.

“Exercise is an amazingly effective way to lower blood pressure, both systolic and diastolic, as it helps the heart relax and maintain better efficiency.”

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