Fructose is a controversial sugar, and many writers have blamed it for the obesity epidemic because it is even sweeter than regular table sugar (sucrose) and it doesn’t send the same fullness signal to the brain, as compared to glucose, so may promote greater cravings for food. These writers point out it has become more prevalent in our diet at the same time as the growing obesity epidemic and has been associated with poor insulin function.
However, so has glucose, and this is where most writers have got this topic wrong! You see, very few products use pure fructose; they almost always use sucrose or (more so these days) high fructose corn syrup (HFCS), and the content of fructose in these two sugars is almost identical. Despite the name ‘High Fructose Corn Syrup’, it only contains slightly more fructose that regular sugar (sucrose)—sucrose is 50% glucose and 50% fructose, whereas HFCS is 45% glucose and 55% fructose).
So the confusion and misinformation has been created by the fact that writers have assumed that HFCS is substantially higher in fructose, and they are using research done on fructose to implicate HFCS.
To muddy the waters even more, many authors are comparing the negative effects of pure fructose to pure glucose—glucose (a.k.a. dextrose) is rarely used as a food ingredient either, so such comparisons are virtually irrelevant.
So what is the research on HFCS? Well, most recent studies have shown that high-fructose corn syrup (HFCS) has virtually the same effects on the body as sugar. Of course, this shouldn’t be surprising because, as we mentioned above, they are almost identical in composition.
So what’s the bottom line here?
HFCS is sweeter than table sugar, so it could possibly promote increased intake of the various foods it’s contained in. It is certainly a fact that we now consume more sugar than we used to, especially in fizzy drinks. However, the newer research shows fairly convincingly that HFCS has similar effects on blood sugar, insulin, and other aspects of the metabolism as compared to regular sugar, so unless someone can show good evidence otherwise, the case against HFCS is not strong.
However, if you are interested in the effects of pure fructose, you should know that it replenishes sugar in the liver (in the form of glycogen) more so than the muscles, as compared to normal sugar or glucose. This has two implications:
1) when the liver senses that it is full, further sugar intake is more likely to be converted to fat (although this only happens to a limited degree);
2) and HFCS would be less effective at boosting muscle glycogen.
So if you are trying to gain muscle, get good pumps, and maximise performance, you would be better off using glucose (dextrose), maltodextrin or a high-GI waxy-maize-type product. One last note, some exercise drinks contain some fructose to ‘top off’ glycogen storage in the liver, which is fine but only necessary for endurance sportsmen.