Tuesday, January 19, 2010
I Want Proof
There is a fad that's been circulating around the Internets for years now, and I'm sure is even older than that: the idea of so-called "negative calorie foods". The basic premise is that some foods require more calories to digest than they actually provide. For instance, a food that provides 5 calories, but requires 10 calories worth of energy for your body to process it, is considered to have negative calories.
It's an interesting concept, and it would be awesome if it were true. Unfortunately, I have been unable to find any concrete proof either way. We know how to determine a food's caloric content, but I wonder if we know how to determine how much energy it takes to process it? In trying to find answers online, I found several people who claimed to be knowledgeable, but who were obvious idiots, and/or didn't bother checking their facts. For instance, on this page, I found this comment:
"Celery has almost zero calories, it's so minuscule we round down to 0."
I've never heard of anyone making this claim. If we consult the USDA Standard Reference, we discover that an 8-inch stalk of celery contains about 6 calories. This is not a miniscule amount (unless compared to a Big Mac), and I certainly wouldn't round it down to 0.
I found several other references to celery containing anywhere from 5 to 20 calories per serving (though the serving size was never stated), and guesses that eating a single serving would burn anywhere from 5 to 20 calories. Even Snopes, which I lose more and more faith in every time I read anything there, claims the "negative calorie" concept is true, but offers absolutely no evidence or proof.
Can anyone tell me definitively how many calories are burned by eating a single serving (say, 40g, the approximate weight of an 8-inch stalk) of celery? I want a number, and I want to know how that number was obtained.
My next complaint involves cooking alcohol out of food. There are plenty of people that will tell you, "don't worry, the alcohol burns out". In my experience, these are people that either think you're silly for caring, or are reassuring themselves because they want it to be true. Other people will tell you that you can never burn it all out. The most outspoken of these that I've heard is Alton Brown, followed by his good buddy Ted Allen.
Both Alton and Ted have discussed this on their shows, Good Eats and Food Detectives, respectively. Food Detectives is kind of a culinary Myth Busters, but is far more scripted. They frequently perform experiments to prove or disprove myths, but in the case of the alcohol, they did a food demo that proved nothing, and then stated their "fact" as gospel.
Alton Brown has stated repeatedly that alcohol never cooks out completely, but has never offered proof. Some years ago I did some research and found a report on the USDA's website that seemed to imply that after 2 1/2 hours of oven roasting, the level of alcohol left in foods is 0% (which I'm guessing is actually < 0.5%). Unfortunately, in more recent visits, this report seems to have been removed. I have been unable to find it for years.
So, it begs the question: does alcohol really cook out, or not? Does anyone have any proof? Or can anyone at least point me to a report or study somewhere that even suggests something either way?
I'm not convinced on the negative calorie thing, or the alcohol thing. And I'm sick of people making claims with nothing to back them up. I want proof.
posted by Joseph at 1/19/2010 08:48:00 PM
4 Comments:
I've heard both those claims before, as well. I have never seen any evidence that would back up either claim. I suppose, for the negative calorie claim, a rather specific test would have to be set up, because just calculating the amount of energy an article may contain wouldn't solve the issue. I suspect different foods (with their varying degrees of fibre, sugar, etc.) would require the body to expend different amounts of energy to extract the energy from the food and process it to a state usable by the body. Also, there would be some minor energy lost in the conversion and some energy from the food that is not recovered by the body. I could see then how someone might claim that a 5 calorie stick of celery is a "negative calorie" food, if you make the assumption that it takes 3 calories to digest, one calorie is lost in translation and two are not recovered. After making those assuptions though, you're essentially back where you started with no real proof at all.
I think the alcohol cooking off is probably a relatively simple chemistry problem. Well, not so simple maybe. But if you knew the boiling point of each ingredient and the amount of heat applied and the time it was applied, I think you could probably calculate the points at which each of the ingredients would boil off. I guess it's a little more complicated than that, since you'd have to take into account outside pressures, affinities and a bunch of other variables, but theoretically, you could figure out when the alcohol is gone.
1/20/2010 8:43 AM
Have you consulted the nutrinomicon?
1/22/2010 9:19 AM
no, alcohol never gets completely cooked out unless it is under very exacting circumstances (i.e. a fractal still). this can easily be measured with a simple hydrometer, a cheap bottle of voka, and a thermometer. Ethanol will evaporate at 172F (http://www.ethanol-still.us/using_your_still_to_make_alcohol.htm), so bring the vodka up to the temperature and hold it there. Every thirty minutes take a sample, chill it to 70F, and measure with the hydrometer. you will certainly be loosing ethanol, but the whole thing will be evaporated completely before you hit zero alcohol.
Not that i'm actually advocating making your own mini-still :)
1/22/2010 11:21 AM
I saw an interesting article a while ago about calories that was kind of along those lines. (I looked for it again, but I couldn't find it.) The idea was that just going off calories doesn't work because our bodies don't incinerate food, they process it. Several studies are referenced about this. In one study they fed snakes whole meat, and then ground meat. They found that the snakes got more calories out of the ground meat because it was already processed. They also did studies with cooked vs raw and so forth. Others did studies where they found that hard food (like a granola type bar) took more calories to digest then softer food like cake. Therefore even though the cake might have a lower calorie count, in the end you get more calories from it. I suppose more research could be done along those lines to prove negative calorie foods.
On the other hand, I just remembered a problem I once had in physics. We had to mathematically test the idea of eating ice to lose weight. The idea was that ice has no calories, but when you eat it then you have to use energy to bring the temperature up to your body temperature. After we did the math we found that you'd have to eat an insane amount of ice to loose just one pound.
1/23/2010 10:07 PM
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