Fructose: Is natural healthy?
Fructose, commonly called fruit sugar, has a reputation as a 'health' food that I am not sure it deserves. Fructose is a monosaccharide. Other monosaccharides are glucose and galactose. When fructose is chemically bound with a molecule of glucose it becomes sucrose, common white table sugar.
While all monosaccharides taste sweet, fructose tastes very sweet. If sucrose is rated at 100, fructose scores a relative 173 in sweetness. Honey tastes sweet because the bees spit in an enzyme which cleaves apart the sucrose in flower nectar into two sugar molecules, one fructose and one glucose. Honey has twice as many sugar molecules in it to taste sweet compared to white sugar and more than half of the sugars are very sweet fructose molecules. Tupelo honey, which has more fructose than any other honey, is the sweetest tasting honey. When you hear the song refrain, "She's as sweet as tupelo honey....," we are talking sweet.
Fructose has a reputation of being "healthy." It is referred to as fruit sugar to imply naturalness. Fruit is about the only natural source of fructose but fructose is not the predominant sugar in it. The vast majority is still sucrose. The great health advantageā of fructose is that it doesn't cause sudden fluctuations in blood sugar. For people who have glycemic problems, where sugar ingestion sends them on a roller coaster of hypoglycemic episodes, fructose is a relatively safe sweetener. It has a low glycemic index, 26 compared to whole wheat flour at 100.
Fructose may be a natural sugar but it is not a natural component of the human diet in the amounts many people now eat. Fructose is not extracted from fruit but is made enzymatically from the starch in corn. Food manufacturers, especially beverage makers, love fructose. Fructose tastes sweeter and is cheaper than either cane or beet sugar. Baked goods brown easier and stay fresh longer when made with fructose. Fructose consumption has gone from almost none per year to a WHOLE LOT (find out how much sometime).
Is fructose safe? The knee jerk explanation that it's from fruit isn't adequate. In the late 1970's when the first mountains of fructose reached the public we were already concerned about the way fructose caused hyperlipidemia. Research suggested that it raised blood fats, especially triglycerides. Since fructose doesn't raise blood sugars the way sucrose does, diabetics like it. But since most diabetics die of heart disease, raising triglycerides, a major risk factor for heart disease, may cancel the advantage. Fructose is a reducing sugar and when heated in food combines with certain amino acids, causing the food to brown. This process called a Maillard Browning Reaction has some curious implications. First increasing fructose in our bodies may increase Maillard Reactions in our bodies. Amino acids are bound and tied up into dark stiff sugar-protein complexes. This sort of browning in the human body is generally known as aging. Brown spots in the tissue, inflexible membranes, these are browning reactions and not particularly desirable. Will increasing body fructose loads speed aging?
Maillard Reactions bind up specific amino acids. This can theoretically cause specific nutrient deficiencies. Three amino acids, lysine, arginine and tryptophan, are of special concern; these amino acids are often used as supplements for their therapeutic effects. Lysine is often used to reduce herpes infection outbreaks. Arginine may play a role in reducing heart disease occurrence. Tryptophan has a long history of use in treating insomnia and depression. All three amino acids are tied up in Maillard Browning Reactions with fructose. We need to have more of these amino acids available not less.
Fructose is difficult for some people to digest. If throughout all recorded history, prehistory and evolutionary history people never ate concentrated fructose, what makes us expect that people will have the necessary enzymatic mechanisms to digest and metabolize large amounts now? It turns out hereditary fructose intolerance is a fairly common genetic disorder, usually diagnosed in infancy. However, it's difficult to diagnose and often these individuals grow up unaware of their true condition and simply have a natural aversion to fruit. They suffer from GI symptoms because of small amounts that enter the diet and are typically labeled as IBS patients.
Fructose intolerance is the underlying cause in most patients with unexplained GI symptoms. The majority of these patient's (130 of 159) met the ROME criteria for IBS. (66th Annual Scientific Meeting of the American College of Gastroenterology, October 2001) Another study looked at patients with celiac disease and found that after gluten elimination all patients improved and the majority were symptom free, but 17% remained with significant symptoms. After fructose elimination, those remaining patient's symptoms completely resolved (Gastroenterology 1997 Jun;112(6):1830-8).
In the last few months I have started doing elimination/challenge routines with fructose in much the same way weāve experimented with milk to rule out lactose intolerance, to see if it isn't causing indigestion. The human body was not designed to digest or metabolize large amounts of fructose. Fructose appears in small to modest amounts in nature, but the large quantities added to the food supply are not natural.There are a number of areas of theoretical and clinical concern with eating large quantities of fructose. My advice is not to eat more than you have to and certainly donāt go out of your way to eat it because it is "good for you."