The Skeptic's Guide to Sports Science: Confronting Myths of the Health and Fitness Industry by Tiller Nicholas B

Author:Tiller, Nicholas B.
Language: eng
Format: epub
Publisher: Routledge
Published: 2020-02-15T00:00:00+00:00

6.7 Fruit, Vegetables, and the Myths of Dietary Fructose

Fructose has been marginalized in recent years for its harmful effects, but this is mostly unjustified. That’s not to say fructose is healthful; it’s still a sugar, after all, and overconsumption can lead to weight-gain and insulin resistance. But the negative stigma surrounding fructose is also perhaps due to a common misconception in the public domain in which fructose is confused with high-fructose corn syrup (HFCS). The latter is a food additive, liquid at room temperature, comprising both fructose and glucose. These two single-molecule sugars aren’t bound as in table sugar (sucrose), but exist in adjustable proportions depending on the desired sweetness of the food. Fructose sweetens the additive and is added to confectionary in high quantities. HFCS is used in a wide range of products including soft-drinks, cereals, biscuits, cakes, ice-cream, and table sauces like Ketchup (i.e., all the good stuff). Despite the controversy, however, there’s nothing inherently evil about HFCS relative to, say, table sugar. Indeed, when the latter is consumed and meets saliva in the mouth, the chemical bond between glucose and fructose is broken by the amylase enzyme; thenceforth, it’s chemically identical to HFCS. Both sucrose and HFCS are energy-dense and nutritionally meager, and one should abstain for the most part.

By contrast, fructose alone is a single-molecule, naturally occurring fruit sugar, contained in much of the fruit and vegetables we eat; the greatest amounts are found in apples, pears, grapes, watermelon, and various dried fruit (i.e., that which are most sweet). The fact that fructose is naturally occurring is inconsequential; arsenic is also naturally occurring, as are snakes. But the concerns around fructose – to the extent where some will advocate eliminating fruit from the diets of healthy people – are centered on the fact that fructose and glucose are both monosaccharides, simple sugars/single molecules. These differ from polysaccharides, like starch and fiber, which are many molecules long and, therefore, slower to digest in the gut. Our society is particularly wary of dietary sugar, and rightfully so. But the assumption that the digestive system treats both simple sugars in the same way is a false one.

So, how does your body differentially deal with glucose and fructose? Glucose is the end-product of carbohydrate breakdown. This means that, regardless of the carbohydrate ingested (be it fruit, pasta, or candy), the glucose is liberated to appear in the blood and get oxidized or stored. The various carbohydrate types differ in the rate at which glucose is released from food and enters the blood. Glucose is absorbed rapidly through the small intestine via a transporter, the name of which isn’t important, but the transporter has a high-affinity for glucose and evokes a sharp rise in blood sugar and insulin concentrations. It’s for this reason that glucose is designated the highest glycemic index rating of 100 and, indeed, all other foods are referenced against it. When you’re contesting an endurance sport like marathon or triathlon, glucose is a valid means of augmenting performance

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