Tuesday, April 21, 2009

Fructose vs. Glucose Showdown

As you've probably noticed, I believe sugar is one of the primary players in the diseases of civilization. It's one of the "big three" that I focus on: sugar, industrial vegetable oil and white flour. It's becoming increasingly clear that fructose, which constitutes half of table sugar and typically 55% of high-fructose corn syrup, is the problem. A reader pointed me to a brand new study (free full text!), published in the Journal of Clinical Investigation, comparing the effect of ingesting glucose vs. fructose.

The investigators divided 32 overweight men and women into two groups, and instructed each group to drink a sweetened beverage three times per day. They were told not to eat any other sugar. The drinks were designed to provide 25% of the participants' caloric intake. That might sound like a lot, but the average American actually gets about 25% of her calories from sugar! That's the average, so there are people who get a third or more of their calories from sugar. In one group, the drinks were sweetened with glucose, while in the other group they were sweetened with fructose.

After ten weeks, both groups had gained about three pounds. But they didn't gain it in the same place. The fructose group gained a disproportionate amount of visceral fat, which increased by 14%! Visceral fat is the most dangerous type; it's associated with and contributes to chronic disease, particularly metabolic syndrome, the quintessential modern metabolic disorder (see the end of the post for more information and references). You can bet their livers were fattening up too.

The good news doesn't end there. The fructose group saw a worsening of blood glucose control and insulin sensitivity. They also saw an increase in small, dense LDL particles and oxidized LDL, both factors that associate strongly with the risk of heart attack and may in fact contribute to it. Liver synthesis of fat after meals increased by 75%. If you look at table 4, it's clear that the fructose group experienced a major metabolic shift, and the glucose group didn't. Practically every parameter they measured in the fructose group changed significantly over the course of the 9 weeks. It's incredible.

25% of calories from fructose is a lot. The average American gets about 13%. But plenty of people exceed that, perhaps going up to 20% or more. Furthermore, the intervention was only 10 weeks. What would a lower intake of fructose, say 10% of calories, do to a person over a lifetime? Nothing good, in my opinion. Avoiding refined sugar is one of the best things you can do for your health.

U.S. Fructose Consumption Trends
Peripheral vs. Ectopic Fat
Visceral Fat
Visceral Fat and Dementia
How to Give a Rat Metabolic Syndrome
How to Fatten Your Liver

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