Editor's note: This popular story from the Daily Briefing's archives was republished on Sept. 30, 2020.

We all know that consuming too much sugar is unhealthy—but just how dangerous is it to have a sweet tooth? Here's what the research shows, Jane Brody writes for the New York Times' "Well."

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What are 'free sugars'?

The health risks of sugar, Brody reports, are generally linked to so-called "free sugars"—a term that includes both sugars added to foods, such as in candies, pastries, and sodas, as well as those sugars that are naturally present in honey, syrups, and fruit juice.

"Free sugars" do not, however, include sugars naturally present in whole foods such as fruits, whole grains, and milk, Brody writes.

The health risks of overconsuming free sugars

Numerous studies show that the regular consumption of free sugars, particularly in sweetened drinks, can increase the risk of obesity, diabetes, heart disease, and premature death, Brody writes.

For instance, one study published in Circulation found cardiovascular morality was 31% higher among adults who had no prior heart disease diagnosis and consumed two or more sugar-sweetened beverages a day compared with adults who rarely drank them. The total death rate was 28% higher among adults who consumed at least two sugar-sweetened drinks per day.

Another long-term study published in JAMA found that regular consumption of sugar-sweetened drinks and naturally sweetened fruit juices increased the risk of early death by up to 44%.

Further, research by Kimber Stanhope, a nutritional biology researcher at the University of California, has tied consumption of high-fructose corn syrup, which is found in sodas and energy drinks, to an increased risk of heart disease and kidney stones.

While glucose, a different form of sugar, is metabolized in cells throughout the body, fructose is metabolized solely in the liver, which causes fat production and can increase the risk of heart and fatty-liver disease, Brody writes.

But "it turns out serious health risks are not limited to liquid sources of sugar," Brody writes. The added sugars in solid processed foods can also cause negative health effects, especially if they're overconsumed.

Brody cites the documentary "That Sugar Film," which follows a filmmaker who ate seemingly "healthy" processed foods that contained 40 teaspoons of sugar per day and developed health problems. Brody notes that Americans on average consume 42.5 teaspoons of sugar per day.

Why do Americans consume so much sugar?

According to Stanhope, the peculiar way the body handles fructose may be a driving factor behind America's "sweet tooth."

"[F]ructose doesn't stimulate the satiety-promoting substance leptin," which would otherwise prompt people to stop eating, Stanhope explained. In fact, brain studies show that people responded positively to pictures of high-fructose foods, such as cookies, candy, and ice cream, even after already consuming fructose.

Another factor behind America's high consumption of sugar could be industry-funded studies—supported by many of the same companies that produce sugary foods and beverages—that may "see[m] to exonerate sugar consumption as a health hazard," Brody writes. "To a layperson unfamiliar with subtle nutritional influences, these and similar findings may appear convincing, but they rarely survive independent scientific scrutiny."

While Stanhope acknowledges that more research is needed to resolve conflicting findings from these studies, she advises that, for now, consumers should follow the American Heart Association's recommendation to reduce their daily added sugar intake from 15% of their average daily calories to 5% (Brody, "Well," New York Times, 7/22).