It's often assumed that, as muscles are made largely of protein, that athletes need a lot of protein in their diet. While it's true that, the more muscle mass one has, the more protein one needs, it's also true that Americans typically consume twice as much protein as they need. What happens to the excess? The body can't store excess protein as it can sugars or fats, so it is partly excreted and partly turned into fat.
There is one interesting exception to this waste, which occur in starvation and prolonged exercise. The body has need of some sugar to survive, so if one's reserves of glycogen are expended and one doesn't ingest any carbohydrates, the body can make sugar from proein through a process called gluconeogenesis. So, after hours of exercise, protein can become a fuel, but this only happens if one doesn't eat enough carbohydrates. There are a number of products for ultramarathoners that tout their protein content based on this fact. If one's running for 24 hours, one should get a typical day's amount of protein from some source, but nothing more is needed. Yiannos Kouros, multiple world record holder at ultra distances, gets almost all of his calories from carbohydrates when running.
Monica Scholz, who ran 23 hundred mile races in one year, does not eat carbohydrates when running, but dried meats. There's an idea behind this: after three days with insufficient sugar, one's brain starts using some ketone bodies (degradation products of protein) as fuel rather than sugar and, after 6 weeks, uses very little sugar. She doesn't have to worry about running out of glycogen... she doesn't use it! There are three drawbacks to this method. First, protein used as fuel creates ammonia, which has to be excreted in urine and increases the demand for water, which is at a premium when running. Second, the lack of glycogen reserves strictly limits how fast one can run. Third, one has to live on an Atkins-like diet, which is difficult to maintain.
Proteins are made of amino acids, nine of which have to be supplied by diet (the other 11 the body can make). Some of these amino acids play important roles outside of being building blocks for proteins; I've mentioned alanine's role in lactate metabolism and arginine is the precursor to creatine, which I also discussed. A number of amino acids are available as individual dietary supplements, each with health claims. As the half-life of most enzymes with which these interact is only 2-5 minutes, one would have to take them constantly to have any effect.
There is a special membrane transport system used to bring the branched-chain amino acids leucine, valine and isoleucine into muscle cells, so tese have been suggested as an ergogenic aid. The problem with this is that this sytem requirs insulin, which is only present when one has a large amount of sugar in one's blood and this doesn't occur during exercise. It would make sense, though, to include these when one eats a high carbohydrate (high glycemic load) meal; one doesn't need the supplement, however, as all proteins have large percentages of these. Just eat a balanced diet.
Trying to combine the two methods doesn't work. But, you may ask yourself: if I'm burning mostly fat during long runs, shouldn't I be eating fat? That's my next post.
5 hours ago