Wednesday, February 15, 2012

Fructose: A Sucker Punch To Your Liver

The review of three papers that follows is taken from Gary Taubes' blog.  The papers are fascinating. 

The BLUF:  high intake of fructose or mixed fructose/glucose (table sugar or HFCS) makes you sick way out of proportion to the amount consumed.  The caveat to that is that these animals were drinking 25% of their daily intake a fructose or the mixed sugars - that's equivalent over 100g/day for most of us.  That's quite a lot (but the US Govt says that much is OK) and there's no way to know where the safe/unsafe level of consumption of these food products is for each of us, because we're all in different stages of metabolic health/illness. 

This site has some interesting comparisons on sugar content:, the big takeaway being that the idea that juices are heathy is questionable at best.  This site,, shows a similar number.  Of the ~3.4g of sugar per ounce, this soft drink will have a roughly 50/50 mix of glucose and fructose.  In short, the test subjects were eating something like 40 ounces (~500 kcal of sugar) of sugary drinks/day, of varying amounts of fructose and glucose.  As you'll read, the more fructose they consumed the worse off they became, even with control of caloric intake.  Interestingly, there was also an observation that as they substituted fructose for non-sugar calories, their energy expenditure decreased.

A recommendation to consider would be to remove sugars (you can't eat sugar without getting fructose unless you go to superhuman lengths) until you have achieved glycemic control, the majority of the fat loss you want, and can see the improvements in your blood lipids (especially triglycerides).  At that point, you could safely reintroduce some amount of sugar without fear of injury.  If you are trying to regain glycemic control and stuffing a bunch of fruit and sugars down the hatch, the results are likely to be mixed at best.  If you are wedded to the idea of "fruit" as necessary for health, try substituting frozen organic (COSTCO baby!) or fresh berries instead.

Lastly, the measurement of the effects of these drinks on metabolic outcomes was very rapid - just as it is for non-alcoholic fatty liver disorder, which when treated with low carb/no fructose shows a measurable (via electronic imaging) reduction in less than one week.

Paper number one describes an experiment in which rhesus monkeys were fed their usual monkey chow diet supplemented by a daily 300-calorie ration of fructose-sweetened water. After a year, every last one of the 29 monkeys had developed “insulin resistance and many features of metabolic syndrome, including central obesity, dyslipidemia and inflammation.” Four of the monkeys progressed to type 2 diabetes.
Worth noting is that the monkeys apparently drank all the fructose-sweetened drinks they were given, but they adjusted for the 300 additional calories by cutting back significantly on the chow. All in all, they averaged only 26 calories per day more with the fructose than they did without it. This suggests that the negative sequelae observed over the course of the year were indeed caused by the fructose itself and not an increased intake of total calories (unless we’re willing to accept that increasing calories by just a couple a dozen a day is sufficient to do some very bad things to monkeys and do them relatively quickly.)
The second and third papers, both published in October, were randomized controlled trials in humans — rather than primates or rodents — which is  always a nice attraction in nutrition research since there’s no guarantee any animal model really reflects the physiological situation in, well, us.
The second paper reported that overweight and obese older adults (40 to 72 years-old) getting a quarter of their calories from fructose-sweetened beverages used less fat for fuel and actually expended less energy than did the same subjects when they were getting the equivalent calories from glucose drinks. So the calories were the same; the metabolic effects were different. For the fructose, the effects were what we’d expect (okay, what I’d expect) if the fructose beverages were causing or exacerbating insulin resistance, an observation that Havel et al had published earlier. The more insulin resistant these people became, the less fat they used for fuel—hence, we can assume, the more fat they stored—and the lower their basal metabolic rate. (The rhesus monkeys, too, had decreased their energy expenditure in response to drinking fructose.)
The third study was a trial in younger subjects (18 to 40-year-olds), some lean, some not. These subjects were given three beverages to drink every day, constituting again about a quarter of their day’s ration of calories. The beverages were sweetened either with fructose, glucose or high fructose corn syrup. For the HFCS group, this 25 percent of calories was compatible with what the U.S. Dietary Guidelines considers a safe upper limit for sugar consumption. Still, after only 12 days—less than two weeks—subjects in both the HFCS and fructose groups, but not the glucose group, saw a significant increase in heart disease risk. Triglycerides went up; LDL cholesterol went up, and ApoB concentrations, a measure of the number of LDL particles, increased.

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