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Archive November 2007
Saturday 3 November 2007
So, recently I've been thinking I would like to perform an experiment comparing the effects of High Fructose Corn Syrup (the sweetening agent in most soft drinks nowadays, also known as Glucose-Fructose Syrup) and Sugar (aka sucrose, pretty much, once it's as refined as it is in a soft drink) on the human body. It is often alleged that the increasing prevalence of HFCS is a significant contributor to obesity, and, by its defenders, it is often argued that it has pretty much the same ratio of glucose and fructose as sucrose breaks down into so it can't be different.

Now, I personally agree that it does have pretty much the same ratio of glucose and fructose, but what I'm not sure about is: 1. whether sucrose breaks down entirely into D-fructose and D-glucose, the sort that the body absorbs, or if some part of it will break down into the L- forms, and 2. whether the fact that sucrose has to break down into glucose and fructose will reduce the impact on the body because the glucose and fructose will be introduced more slowly as a result.

So, I was thinking what experiment would I perform, and I think pretty much the simplest and most effective experiment would be to have a blood monitoring device watch levels of glucose, leptin and insulin in the subject's blood at small intervals for a time after the subject chugs a half pint of solution (glucose or HFCS). Then a week later, with the subject having fasted into the same initial state, do the same with the other solution. Repeat four or five times alternating to make sure previous experiments are not effecting later experiments (or if they are, to make it so you have enough results that you can compensate for the effect - ideally use two or more subjects drinking the opposite solutions.)

And then I was thinking "well, that monitoring hardware is pretty expensive even just for a glucose monitor, is there some way you can make money from this sort of study if you're not being sponsored to come up with a specific result?" And the only way I could think of that you might is to sell the result to whoever it favours (ie. HFCS people would buy your study if it shows they are not responsible for obesity, sugar people would buy it if it says HFCS is for lardasses.) So I went looking to see who the people are who would buy a study, and I found something. Oh yes, I found something.

I found the sort of studies that "The Corn Refiners Association" might buy (actually it was Pepsi that paid for this one). They are studies which say "These short-term results suggest that when fructose is consumed in the form of high fructose corn syrup, there are no differences in the metabolic effects compared to sucrose." And when I say the studies say that, I mean just that. They say it. They don't show it. On the contrary, the experiment results, despite being fudged into oblivion, say that HFCS is quite sharply different. Here is the PDF file of the study. (Pages 103-112 of something.)

First point of interest - on page 107, see the most legible graph of "no difference". The left two thirds of the graph are almost illegible like all the other graphs, obscured by a mass of error-margin bars, but you can just about follow the lines back from the legible part to see this "no difference". It's a "no difference" of a consistent 10-20% higher leptin level in the HFCS line. Consistent. The error margins might say "but it could be equal, honest", but that's for each individual measurement - there are 20 or so measurements there, and they all are 10-20% higher. That's no margin of error.

Second point of interest - in the experimental conditions the subjects are not consuming only the products in question. They are consuming 30% test product, and 70% "a normal diet". So one might infer from this that a 10-20% difference might be more like a 30-60% difference if we were comparing apples to oranges rather than comparing an apple and two bananas to an orange and two bananas. And you know what you really can't do with a 30-60% difference? Fudge it with error bars.

Point of interest 3 - the laughable table of data on page 108. The area under the curve. Just like the lines, the numbers (reflecting glucose, insulin and leptin) are all 10-20% higher with HFCS than with sucrose. But look at the numbers. HFCS area under the glucose curve = 144.83 ± 116.62. An error margin of 80%. Sucrose area under the glucose curve = 121.33 ± 135.67. An error margin of a staggering 112%. They're claiming they can't even tell whether the subject had reduced glucose from consuming sugars. Why? Because you need a huge margin of error to claim your correlation is not significant.

The actual experiment design is pretty good, but the "LA LA LA THE RESULTS SAY NOTHING" conclusion is just comical. Anyway, my personal conclusion is that I now don't feel the need to perform the experiment for myself, seeing as an experiment showing the results it was trying to avoid is usually a pretty reliable indicator of how things are. [00:29] [9 comments]

Wednesday 31 October 2007
This post is about physics. You may want to not bother.

So, I've been arguing in the comments of someone else's livejournal. The dispute is me saying that a car at 110mph colliding head-on with a stationary car is an equivalent impact to a car at 55mph colliding head-on with another car going the opposite way at 55mph. The other person is arguing that a car going at 55mph has 313kJ of kinetic energy, and a car going 110mph has 1252kJ of kinetic energy, so the collision at 110mph must be more severe. (1252 > 313+313)

I was frankly surprised that he would believe this because it's self-evident to me that he is wrong, from two or three distinct physics approaches that all agree - but he's not a stupid guy, and I couldn't immediately explain why he is wrong, only why I am right. His math is right, and kinetic energy is proportional to velocity squared. After a little research I found the answer, and after a bit of argument also found why he was so fixated on the wrong answer - because it has been argued a lot with a slightly different situation, in which he would be right. A 55mph car colliding head-on with another 55mph car is not equivalent to a 110mph car hitting a wall. It is, in fact, equivalent (for the car's occupants) to a 55mph car hitting a wall. But it is also equivalent to a 110mph car hitting a stationary identical car.

But how and why is he wrong about the kinetic energy? I'll explain it in comments later if anyone is interested and nobody else has explained it. [16:17] [4 comments]