A sugar-laden diet may raise your risk of dying of heart disease even if you aren’t overweight. So says a major study published in JAMA Internal Medicine.

Added sugars make up at least 10% of the calories the average American eats in a day. But about one in 10 people get a whopping one-quarter or more of their calories from added sugar.

Over the course of the 15-year study on added sugar and heart disease, participants who took in 25% or more of their daily calories as sugar were more than twice as likely to die from heart disease as those whose diets included less than 10% added sugar. Overall, the odds of dying from heart disease rose in tandem with the percentage of sugar in the diet—and that was true regardless of a person’s age, sex, physical activity level, and body-mass index (a measure of weight).

Sugar-sweetened beverages such as sodas, energy drinks, and sports drinks are by far the biggest sources of added sugar in the average American’s diet. They account for more than one-third of the added sugar we consume as a nation. Other important sources include cookies, cakes, pastries, and similar treats; fruit drinks; ice cream, frozen yogurt and the like; candy; and ready-to-eat cereals.

Nutritionists frown on added sugar for two reasons. One is its well-known links to weight gain and cavities. The other is that sugar delivers “empty calories” — calories unaccompanied by fiber, vitamins, minerals, and other nutrients. Too much added sugar can crowd healthier foods from a person’s diet.

Could it be possible that sugar isn’t the true bad guy boosting heart disease risk, but that it’s the lack of heart-healthy foods like fruits and veggies? Apparently not. In this study, the researchers measured the participants’ Healthy Eating Index. This shows how well their diets match up to federal dietary guidelines. Regardless of their Healthy Eating Index scores, people who ate more sugar still had higher cardiovascular mortality.

Exactly how excess sugar might harm the heart isn’t clear. Earlier research has shown that drinking sugar-sweetened beverages can raise blood pressure. A high-sugar diet may also stimulate the liver to dump more harmful fats into the bloodstream. Both factors are known to boost heart disease risk.

Federal guidelines offer specific limits for the amount of salt and fat we eat. But there’s no similar upper limit for added sugar. According to the American Heart Association’s recommendation, women should consume less than 100 calories of added sugar per day (about 6 teaspoons) and men should consume less than 150 per day (about 9 teaspoons).

To put that in perspective, a 12-ounce can of regular soda contains about 9 teaspoons of sugar, so quaffing even one a day would put all women and most men over the daily limit.

If you’re going to have something sweet, have a fruit-based dessert. That way, at least you’re getting something good out of it. Of course, plain fruit with no added sugar is ideal. If you’re trying to curb a soda habit, mix a little fruit juice with seltzer water as a replacement.