Friday, August 8, 2008
1) Carnitine: Carnitine (or l-carnitine, if you care to be that specific) is a fatty acid transporter. It basically helps fat move from one side of a mitochondria to the other, where it can be broken down, like a crossing guard helping kids across the street. Because fat yields 9 kcal/g of energy (as opposed to the 4 kcal/g in proteins and carbohydrates) it stands to reason that having plenty of carnitine should allow you to burn lots of fat, and either lose weight faster or, for athletes, get more energy--for the first 30 seconds of sustained physical effort, the muscles go through the glycogen that they've stored. For the next 4-6 minutes, they go through the sugar that's already in the blood. After that, they begin to utilize fat as an energy source as well as the sugar that the liver releases--hence, carnitine.
But does it work? First, let's consider the following: the kind of athlete who would most benefit from carnitine would be an endurance athlete, since they have taxed their muscles to the point where they would need fatty acids. So why, in most of the trials where they've studied carnitine, do they use "resistance-trained" subjects (resistance training referring to weights)?. And if carnitine does, in fact, help with weight training, does the condition of the athlete prior to the study matter? Given the current lack of evidence and a good study to look at, I'd have to venture NO on this one.
2) Carbohydrate loading This was first cooked up in 1957, by Gunthar Alvorg. The premise goes like this: you deplete your glycogen stores completely for about three days, going on long runs and not eating a single carbohydrate. Then, for three days, you replenish your glycogen stores by eating lots and lots of carbohydrates. And on the big day, you run forever, because your body has somehow "soaked up" the glycogen.
It's a very nice theory. And there is some merit to it--after all, endurance athletes go through carbohydrates like a chainsaw through butter. This article gives an extremely detailed account of how carbohydrate loading is supposed to work, but the science shows otherwise. In study after study, they've shown no significant between performance or glycogen storage capacity between those who were carb-loading and those who were not.
So the verdict on carb-loading is, again a NO. However, given that it is, for the most part, harmless and doesn't require spending a fortune on sugar pills, and that many of us feel better for it, go ahead and enjoy that pasta dinner before your marathon.
3) What are the protein requirements of athletes? Protein is what makes a body a body--amino acids are the molecular building blocks for the impressive biceps of gymnasts and the massive thighs of a cyclist. Muscles are constantly being broken down and rebuilt, and it is this sped-up cycle of break-down-build-up that makes the protein requirements of athletes higher than those of us ordinary mortals. Given that ordinary, relatively sedentary people require only 50-70 grams of protein a day, or about 10 ounces of meat a day (meat is mostly water, and only 10-20% protein), it is surprising, really, how little protein athletes really need: 90 g for a male triathlete is plenty. Obviously, if you're growing, or trying to grow muscle, you'll need to eat relatively more protein But again, like carbohydrate loading, this is more a question of personal opinion. I never paid much attention to how much protein I was eating, because I assumed that eating a varied vegetarian diet would suffice. And it did, for the most part. But others have to watch their protein intake carefully.