Short answers, pulled from the story.
Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847. The name "fructose" was coined a decade later in 1857 by English chemist William Allen Miller, combining the Latin fructus (fruit) with the chemical suffix -ose.
Fructose is the sweetest naturally occurring carbohydrate, with a relative sweetness measured at 1.2 to 1.8 times that of sucrose. The six-membered ring form of fructose is responsible for this heightened sweetness; the five-membered ring form tastes roughly the same as table sugar. Because warming shifts the balance toward the five-membered ring, fructose tastes less sweet in hot beverages than in cold ones.
High-fructose corn syrup (HFCS) is produced by hydrolyzing cornstarch to glucose and then using the enzyme glucose isomerase to convert that glucose to fructose. The two most common grades are HFCS-55, containing 55% fructose and used mainly in soft drinks, and HFCS-42, containing 42% fructose, used in processed foods, breakfast cereals, and bakery products.
Fructose is absorbed in the small intestine primarily via GLUT5 transport proteins rather than the mechanisms used by glucose. Absorption capacity per serving ranges from less than 5 g to 50 g and increases significantly when glucose is present simultaneously. After crossing the intestinal wall, fructose travels directly to the liver via the hepatic portal vein, where it is almost entirely captured and metabolized.
In 2022, the European Food Safety Authority found fructose and other added free sugars are associated with a moderate increased risk of obesity and dyslipidemia (more than 50%) and a lower increased risk of non-alcoholic fatty liver disease, type 2 diabetes, and hypertension (15% to 50%). Excessive fructose intake can also drive triglyceride synthesis in the liver, contributing to metabolic syndrome.
Fructose that is not absorbed in the small intestine passes into the large intestine, where colonic bacteria ferment it, producing hydrogen, carbon dioxide, short-chain fatty acids, and other gases. This fermentation causes bloating, flatulence, diarrhea, and gastrointestinal pain. Apple and pear juices are of particular concern for children because of their high concentrations of free fructose relative to glucose.