While both glucose and fructose are “simple sugars” that provide 4 calories per gram, the body processes them differently. Glucose is metabolized by several organs (including the brain, liver, muscles, and fat tissue) and has a direct effect on blood sugar and insulin levels. Fructose is metabolized primarily by the liver, and though it does not have a significant effect on blood sugar or insulin levels, it can have a more immediate effect on triglycerides (fats in the blood). Both human and animal studies show that when fructose is consumed in excess it can lead not only to higher triglycerides but also to a fatty liver, decreased insulin sensitivity, and increased levels of uric acid (which causes gout).
The difference in how the body handles the two sugars has led to the belief that HFCS is much worse for you than regular sugar. However, several studies have clearly shown that HFCS and sucrose have indistinguishable metabolic effects and the same health consequences. That is, neither type of sugar is good for you.
The 2015–2020 U.S. Dietary Guidelines recommend that added sugars from any source, including HFCS, be limited to no more than 10 percent of calories a day. For someone consuming 2,000 calories a day, that's no more than 50 grams of added sugar. To put that into perspective, a 12-ounce Coca-Cola contains 39 grams of sugar (as HFCS in most formulations); a 16-ounce Coca-Cola has 52 grams, already above the recommended limit. Many other products, from bread to soup, also have added sugars, often as HFCS.
The best advice is to avoid sweetened sodas, which provide nothing more than empty calories (meaning the calories are not accompanied by any nutrients), and limit foods with any type of added sugars, which go by many names, including high-fructose corn syrup, sucrose, honey, turbinado sugar, dextrose, evaporated cane juice, and concentrated fruit juice. Total added sugars will be listed on the new Nutrition Facts label, which was supposed to go into effect for most foods by July 2018, but may now be delayed for several years under the Trump administration. In the meantime, check the ingredients list for them.
What about fruit? Don’t worry about the fructose in fruit, since it’s accompanied by healthful nutrients and antioxidants, as well as fiber, which slows absorption of fructose. Plus, you would have to eat several servings of fruit to get as much fructose as in a can of soda. But limit fruit juices to no more than a cup a day; some contain nearly as much fructose as soda.