Sour keys are low-fat, sugar-laden, key-shaped candies with a strong sour flavor and a soft, yielding texture. They come in different sizes that determine their calorie content.
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Twenty calories are in a small sour key, according to The Allan Candy Company. A serving size is listed as 7 candies. Jumbo sour keys can have up to 90 calories per candy, according to MyFitnessPal.com, so carefully read package and serving size.
Ninety-six percent of the calories in sour keys come from carbohydrates. More than half of those carbs are simple sugars derived from glucose syrup, corn syrup, sugar or dextrose, common first ingredients in sour candies, according to the website of Bartek Ingredients, a manufacturer of the acidic chemicals that give sour keys their flavor.
The less sugar you eat, the better for your health. Not only does added dietary sugar increase the risk of diabetes, it also heightens heart disease risk factors and possible death, according to a study in the February 2014 issue of the "Journal of the American Heart Association: Internal Medicine." For this reason, the American Heart Association recommends that women eat no more than 100 calories per day from added sugar -- roughly 6 teaspoons -- and men, no more than 150 calories or 9 teaspoons.