Fructose and glucose are both simple sugars, also called monosaccharides. Glucose also is known by the name dextrose - that's the name we often see on those plastic bags of clear liquid beside hospital beds, with a tube dripping into the vein of a patient. Glucose is the sugar in corn syrup, and is produced by the breakdown of starch, a polymer made up of glucose molecules joined together. Fructose has the same atoms as in glucose(carbon, oxygen, and hydrogen), but when joined together we get sort of the mirror image of glucose - so think of glucose and fructose as left-handed and right-handed versions. Honey contains both glucose and fructose.

Sucrose is a disaccharide meaning there are two simple sugars joined together. It is the sugar found especially in sugar cane, sugar beet, maple syrup. For sucrose, the two sugars are glucose and fructose.

In the body, the glucose and fructose are absorbed as they are, although the absorption mechanisms differ. Sucrose, on the other hand, is broken down to the fructose and glucose by an enzyme of the small intestine. [Lactose and maltose are two other disaccharides, and the enzymes that break these and sucrose down are called, as a group, disaccharidases, and more specifically lactase, maltase and sucrase, respectively. You may already be aware of lactase since it has often been found "wanting" in HIV/AIDS resulting in gut cramps &/or diarrhea from dairy products.]

Once absorbed into the body, it is glucose that has special importance for the body. It is the central "fire wood" for our energy. Our body has a wonderful mechanism to make sure it gets an adequate, BUT CAREFULLY CONTROLLED, supply of glucose. Enzymes which break down starch to glucose are even in our saliva - since many of our foods are rich in starch, this seems to be one way Nature makes sure the starch digestion gets "on its way" early in the digestive process. If we don't have enough carbohydrate (carbohydrates include simple sugars and complex polymers such as starch that are sugars joined together), then our body has a complex system of chemical reactions that make it possible for glucose to be made from some parts of the protein in our food, or from some of the fat. There is also a series of reactions that enable fructose to supply some energy. This gets complicated, and I would want my biochemistry text in front of me to go further on this. The bottom line here, re the control, is that the body uses other signals to try to maintain a fairly constant level of glucose in the blood stream. Insulin is a hormone that participates in this regulation. When our body stops making enough insulin we have Insulin Dependent Diabetes Mellitus (IDDM), when our body doesn't use the insulin properly (insulin insensitivity) there may be higher than normal levels of it, and then we have what is called Non-Insulin Dependent Diabetes Mellitus (NIDDM).

There may be some negative effects from too high levels of fructose. At least in rats, high levels of fructose is sometimes used to cause hypertension. Neither glucose nor sucrose seem to do this. High levels of fructose may also be associated with too high levels of blood fat (serum triglycerides), which may already be too high in HIV. On this basis, high levels of fructose in our diet might be considered (more) undesirable (than either glucose or sucrose).

An issue that may be important here for people in whom we are seeing, sometimes strange, changes in body composition ("Crix belly" or "protease paunch", "Buffalo hump", a more general term "lipodystrophy", or whatever other names get used here) is that insulin insensitivity which is a characteristic of NIDDM seems to accompany this change in body composition. Thus the body tries to make more insulin to compensate for the its lower activity, that is insensitivity (just means the insulin doesn't do its job as well as it should). It's too early yet to decide on "cause and effect", but there are a bunch of things that may be problems. From some other studies of non-HIV related cases of NIDDM, it MIGHT be that high levels of fructose are not desirable. But there is also some evidence that HIGH levels of sucrose and glucose may also be undesirable. From this, then one might suggest that HIGH levels of either fructose, glucose or sucrose are undesirable. Keep in mind here, that I'm referring to HIGH levels. It is unrealistic to try to avoid all dietary sugars. But we can easily keep low those added sugars, and foods which have simple sugars as their main form of carbohydrate.

Some more information on the carbohydrates is in a monograph about Liquid Food Supplements, and is available at website www.catie.ca, by looking under the sections for monographs, and then find my name. But this information was written before the issues came up with lipodystrophy. I'll be doing a more lengthy article on this, likely to be published in a newsletter in the Fall. For now, we can speculate a lot, but with little information as to what is really going on. There were some good reviews by Dr Donald Kotler from the recent Geneva International AIDS conference - hopefully you were able to access these - I got them from website , but I suspect there are other of the commmunity-based sites that also have these available.

One issue that I've not addressed here, is that the different enzymes to dowith metabolism of fructose and glucose may have different dependences on certain minerals. In general, magnesium is important for many enzymes that deal with the glucose. It runs in my mind that manganese may be involved in an enzyme to do with fructose, but I need to look this up. Generally, chromium, zinc, magnesium, and manganese are all involved. Of these, zinc and magnesium have been commonly observed to be low in HIV/AIDS in the absence of supplementation. Both should be monitored, although it is difficult to interpret serum zinc levels. Serum magnesium should be monitored every 3-6 months. Mixed nuts and some tofus are good dietary sources. Bananas, leafy greens, avocados are some other reasonable sources. A 250 mg magnesium citrate supplement is used by many. I'm not aware of chromium having been observed to be low in HIV/AIDS, but there are studies of NIDDM where 500-1000 MICROgrams were found to help make the insulin more active (that is the insulin INsensitivity was lowered).

I hope this is of help for you. It may be possible to provide more information if you have more specific issues that you're dealing with. But to be frank, it will not be easy to provide much more definitive information, but the subject (as you can tell from my answer) is quite complex, and there is not always agreement by experts. I hate the expression!!, but it is true, "we need more research".

1) Sugar is sugar, no matter what the name. It can turn to fat easily, and if you are worried about fat-accumulation, then you might have to take it easy on sugar in your diet. A can of soda contains essentially 9 tsp. of sugar, an equal amount of orange or grapefruit juice has almost as much. That's a lot of sugar in one dose for someone worried about fat accumulation, or just big fluxes in their blood sugar that might change mood levels.

2) Consuming alot of sugar can cause a small amount of dampening of the immune system. How much is hard to judge. Test tube studies say one thing, finding a measure for human quantification is more difficult.

No studies show the effect of dietary or other sugar doses on HIV growth or on viral load, or on CD8 cell killing of HIV-infected cells.

The science answer is all the speculation that Chester mentions above... Fructose metabolism has a life of its own. It does not need insulin to process it as much as other dietary sugars do. At the same time, in the gut cell layer, there is something called the "dissacharide effect" where fructose gets more quickly converted to fat (triglyceride) than other sugars. Net result, all sugars can be fat-provoking, it's just that insulin is not always the mediator.

If this question is a result of a person's trying to "have their cake and eat it too", i.e., trying to manipulate diet between various sugar sources to squeeze out some extra sweet tolerance, I don't think the strategy will pay off.

Basically, you need to eat 3 or 4 fruit items a day . Gut flora need the fruit pulp to live on. The flora represent a very important "immune organ" that cannot be allowed to starve. The fructose (fruit-sugar) contained in the fruit should not represent trouble to even an insulin-resistant person. If it is, there are medicines and supplements to take to restore some sugar-handling capacity, starting with Alpha Lipoic Acid.

Bottom line, a person on a healthy diet, might choose to generally avoid most sodas, eat solid fruit more than consume large amounts of fruit juice. The person may also have small servings of cookies and dessert pastries (200 calories each) as a prudent limit. Meals would be a balance of protein-starch-vegetable (chicken-potato-spinach) rather than and a large plate of just pasta and sauce, or rice and a few beans (starchy protein).

Hope this helps.

Diana Peabody, RD responds:

One more comment on fructose. Absorption of fructose can be saturated in a similar manner to lactose causing diarrhea in susceptible individuals. Young children are at increased risk. We often see young children who drink a lot of fruit juice (even the pure unsweetened stuff) with chronic diarrhea that resolves when the juice is stopped. There appears to be a similar effect in HIV infection for some.