(MensHealth) - In the 1970s, actor-turned-Paul-Masson-wine-pitchman Orson Welles admonished, “We shall sell no wine before its time.”

These days, Welles might say, “We shall sell no wine before it’s practically a distilled spirit.”

A new study from the University of California found that the alcohol content in the majority of wines, both white and red, sold in the world over the last decade is, on average, 0.42% higher than claimed on the label.

That number may seem small—who’s getting drunk on 0.42% extra alcohol?—but it is an example of the steady increase in wine’s alcohol content in recent years.

James T. Lapsley, Ph.D, a Professor of Viticulture at the University of California, Davis—who co-authored a 2011 paper on the subject for the Journal of Wine Economics, tellingly titled “Too Much of a Good Thing?”—claims that the grape sugar levels in wine have increased between 7 and 10 percent over the past few decades.

“A 10% increase in sugar concentration would result in 10 percent more alcohol,” says Lapsley. “I don’t think that has a huge health impact.”

As long as you drink moderately (a glass or two daily), that's likely true, though metabolizing ethanol in alcoholic beverages produces acetaldehyde, a toxic chemical thought to be a carcinogen in humans.

So what does sugar have to do with a wine’s alcohol level? During the process of fermentation, natural yeasts in the environment break down the sugars in the juice released by the grapes when crushed. 

The yeasts then convert the sugars into alcohol as well as carbon dioxide, which generally dissolves in the bottle.

Likewise, the longer a grape ripens, the more sugar it’s apt to develop. When there’s more sugar, the yeasts have more to convert, which results in more alcohol.

Don’t blame the grape, though, for the rise in alcohol. Instead, says Seattle-based certified sommelier Yashar Shayan, the rise can at least in part be attributed to the consumer.

“People like it,” he says. “They may claim they don't, but they do.”