Nearly a full year after the initial publication of the findings, UK newspaper, The Times Online, published a story covering a bit of research done at the University of California - Davis which was published by the American Journal of Clinical Nutrition in 2008, entitled Endocrine and metabolic effects of consuming beverages sweetened with fructose, glucose, sucrose, or high-fructose corn syrup. In the study, principal investigator Kimber L Stanhope performed a study where they fed two groups of people very similar diets, one group using glucose as their primary sweetener, the other using fructose.
And their findings, are really telling. The short version, is that there appears to be a very distinct difference in the metabolic processes that break down fructose compared to glucose. But the short version, isn't very interesting. If you're like me, and work on a College Campus which grants you access to a multitude of journals, or you can go to a nearby college to peruse their library, the article is written in fairly simple language, and is only a few pages long, so I do encourage you to read it if you can.
The research supports the hypothesis that consumption of fructose is a factor in the development of diabetes (specifically Diabetes mellitus), which can most simply be described as a selection of conditions where a person's insulin systems are broken in some way, either by not producing enough insulin, or responding abnormally to the presence of insulin. The studies show that the body produces less insulin and leptin, two hormones which are used as signals to the brain regarding energy balance. Essentially, with this system in place, our brains have trouble knowing how much energy we have derived from our food, leading us to eat more (to gain energy), and move less (to conserve what energy we have).
These figures were based on essentially a pair of one-day observations of the subjects, so some people are inclined to deny the findings out of hand, but while the logistics of doing a meaningful long-term study with all the variables controlled are basically impossible, it's still a telling result, and this lab, and others, appear to be moving forward with similiar research on other primates. On rhesus monkeys, they found, over the course of a year, that the monkey's fed on fructose as opposed to glucose tended to put on nearly 30% more weight, and (over the short term, at least) exhibited significantly less energy expenditure. The were lethargic. Now, after the 12 month mark, the glucose monkeys were almost as lethargic as the fructose ones, but these rhesus monkeys were getting over 40% of their daily calories in the form of sugar, and the dramatic reduction the 6 month and 12 month calculation in activity for the glucose monkeys (which took them from a ~.5% drop to a ~7.5% drop (where the fructose monkeys were at 6 months), does warrant further inquiry, that I've no doubt is being worked on. In the same period, the fructose monkeys went from ~7.5% drop in activity to a ~9% drop, significant, but not nearly as dramatic. It is most probably that gaining 40% of your diet from any sugar is going to be highly damaging, but at the very least, glucose seems to be less damaging in the short term, making it a better candidate for using in moderation.
More frightening was the findings regarding lipid metabolism. While both fructose and glucose encourage the production of fat, over a 10 week study, where each group recieved 25% of their energy requirements from sweetened beverages, the fructose group saw a dramatic increase in their levels of plasma triacylglcerol, a key component in most animal and vegetable fats. Further, the fatty deposits are consistent with medical evidence of the precursors of Atherosclerosis, or the buildup of fatty plaque on the inside of arteries, commonly believed to be a precursor to heart disease.
Incidentally, even though we talk about 'high-fructose corn syrup' (HFCS), HFCS is not actually pure fructose. The most common form is only about 55% fructose, the rest being made up of glucose. Up until the 1970s, the primary sweeteners used were about 50%-50% mixes of fructose and glucose, so while the evidence put forward by this research suggests we'd be better served by reducing the fructose level instead of the glucose level, as a sweetener goes, HFCS isn't the most chemically evil sweetener in the world.
The problem with HFCS, is that it's insidious. It's everywhere. Currently, the estimated mean consumption of added sweeteners by Americans is 15.8%. That number is based on a study published in 2000, which was based on data from the mid-1990s. Now, this number is well below the suggested maximum intake from added sugars of 25%, but the trend being seen among younger people is getting dangerously close to that (in my opinion frighteningly high) level anyway. More recent surveys of just beverage intake suggested that college students were getting ~25% of their daily caloric requirements from sugary beverages every day, and 13 year-olds were seeing at least 15%. And that is just from soft drinks, fruit drinks, and juices with added sugar. I'm frankly scared of what the figures would indicate when you start including the fact that even the most basically processed food you'll find at the grocery store or chain restaurant almost certainly has added sugar as well.
I'm looking forward to seeing what the results of more study on the rhesus monkeys are, since it appeared that the glucose monkeys lethargy were converging with that of the fructose monkeys (and giving the sharp uptick of the curve, had the potential to surpass it). At the end of the day, the study tells us little about the current dietary world. Yes, fructose is worse metabolically than glucose, but, chemically speaking, table sugar is not much different than HFCS anyway (I'd love to see a similar study comparing table sugar to HFCS-55, though I suspect the findings would show minimal difference). Ultimately, long term exposure to Glucose was starting to show effects similar to fructose as well. From a health perspective, the answer isn't to switch sugars, it's to reduce them. By how much? Well, without accurate data on sugar consumption, it would be pretty damn hard to gauge, but cutting out those sugar-added beverages would be a good start.
Credit: I first had my attention to this story raised by the Sustainable Food Blog at Change.org.