I received a packet of glossy brochures and a small booklet the other day from the Corn Refiners Association, along with a Dear Doctor cover letter. The purpose of the mailing was to explain to me, the doctor, that much of the negative press surrounding high-fructose corn syrup (HFCS) lacks scientific merit, and that this “versatile sweetener” is pretty much the same as sucrose.

The cover letter started off comically enough: "Because you are a trusted source of information about nutrition...," like nobody knows that medical doctors are considered so uniformed and so biased regarding nutrition that nearly three-quarters of patients won’t even tell their doctor what nutrients and herbs they are taking. But, flattery is like a foot in the door, so I read on. The letter was signed by the president of the Corn Refiner’s Association and also by a cardiologist/professor with a university affiliation. The letter did not disclose the cardiologist’s conflicts of interest, but a Medline Search revealed that he has received research funding and consulting fees from PepsiCo, one of the biggest users of HFCS in the world.

The main point of the information packet was that HFCS is nutritionally the same as sucrose (table sugar). Emphasizing that point was considered so important that it was stated at least 17 different times in the mailing. As discussed below, HCFS and sucrose are not the same, which might be why so much effort was made to convince doctors otherwise. As a corollary to the main point, the packet sought to dispel the “myth” that “sugar is healthier than HFCS.”  The use of the word “healthier” is particularly amusing, since almost no one on the planet considers sugar to be a health food. A more appropriate framing of the argument would have been to claim that HFCS is no more likely to give you diabetes, make you fat, raise your triglyceride and uric acid levels, cause nonalcoholic fatty liver disease, or give you stomach aches and diarrhea than sucrose is. While there is a great deal of research that contradicts such claims (as discussed, for example, in my review article on the adverse effects of dietary fructose), at least those would have been claims that could have been debated honestly.

The Corn Refiner’s Association argues that HFCS and sucrose are pretty much the same, because they both consist of about 50% fructose and 50% glucose. In actuality, HFCS consists of 55% fructose and 42% glucose, while sucrose consists of 100% sucrose (which can be hydrolyzed by intestinal enzymes to 50% fructose and 50% glucose). The difference in the relative proportions of fructose and glucose in these two sweeteners (1.31:1 versus 1:1) may not be insignificant. Fructose malabsorption is a common cause of gastrointestinal symptoms that mimic irritable bowel syndrome. Fructose malabsorption tends to occur primarily when the fructose concentration of a meal exceeds that of glucose, because glucose enhances the intestinal absorption of fructose. HFCS, which contains fructose in excess of glucose, is much more likely to cause gastrointestinal symptoms than is sucrose, which is hydrolyzed to equal parts fructose and glucose.

The fact that HFCS consists mainly of two monosaccharides, while sucrose is a disaccharide, may also not be insignificant. In order to be absorbed as its constituent monosaccharides, sucrose must first be hydrolyzed by intestinal mucosal disaccharidases. Thus, the absorption of fructose from sucrose might be considerably slower than the absorption of the free fructose present in HFCS. That possibility is supported by studies in which serum fructose concentrations increased to a greater extent after feeding free fructose than after feeding the same amount of fructose in the form of sucrose.

Fructose is the most powerful reducing sugar of all of the edible sugars. Reducing sugars promote the glycosylation of tissue proteins, which is a factor both in the complications of diabetes and in the aging process. The human body has elaborate mechanisms to prevent serum fructose concentrations from rising to any great extent, but these mechanisms can be overwhelmed by feeding large quantities of free fructose. Exposure to the large amounts of free fructose that are currently being consumed is unprecedented in human evolution, and there is no reason to believe that humans are equipped to handle this new stressor. There are still significant gaps in our knowledge regarding the consequences of consuming large amounts of free fructose. According to my reading of the scientific literature, the effects of HFCS are somewhere between slightly worse than the effects of sucrose and seriously horrible.