What is Creatine?  When we told our friends that we were writing information on creatine, some of them had quizzical responses. "You're writing on creating? Creating what?" "Is it a herb?" Creatine is a nutrient that is naturally found in our bodies. It is made from a combination of the three amino acids arginine, glycine and methionine. Creatine helps provide the energy our muscles need to move, particularly movements which are quick and explosive in nature. This includes the types of motion involved in most sports. Approximately 95 percent of the body's creatine supply is found in the skeletal muscles. The remaining five percent is scattered throughout the rest of the body, with the highest concentrations in the heart, brain and testes. (Sperm is chock-full of creatine!) The human body gets most of the creatine it needs from food or dietary supplements. Creatine is easily absorbed from the intestinal tract into the bloodstream. When dietary consumption is inadequate to meet the body's needs, a limited supply can be synthesized from the amino acids arginine, glycine and methionine. This creatine production occurs in the liver, pancreas and kidneys.  How Does Creatine Work?  Creatine is an essential player in one of the three primary energy systems used for muscle contraction. It exists in two different forms within the muscle fiber: as free (chemically-unbound) creatine and as creatine phosphate. This latter form of creatine makes up two-thirds of the total creatine supply. When your muscles contract, the initial fuel for this movement is a compound called ATP (adenosine triphosphate). ATP provides its energy by releasing one of its phosphate molecules. It then becomes a different compound called ADP (adenosine diphosphate). Unfortunately, there is only enough ATP to provide energy for about ten seconds, so for this energy system to continue, more ATP must be produced. Creatine phosphate comes to the rescue by giving up its phosphate molecule to ADP, recreating ATP. This ATP can then be "burned" again as fuel for more muscle contraction. (We'll discuss all this in greater detail in Chapter Six.) The bottom line is that your ability to regenerate ATP depends on your supply of creatine. The more creatine you have in your muscles, the more ATP you can remake. This allows you to train your muscles to their maximum potential. It's that simple. This greater ATP resynthesis also keeps your body from relying on another energy system called glycolysis, which has lactic acid as a byproduct. This lactic acid creates the burning sensation you feel during intense exercise. If the amount of acid becomes too great, muscle movement stops. But if you keep on regenerating ATP because of all the creatine you have, you can minimize the amount of lactic acid produced and actually exercise longer and harder. This helps you gain strength, power and muscle size; and you won't get fatigued as easily. Creatine has also been shown to enhance your body's ability to make proteins within the muscle fibers. Two of these proteins, actin and myosin, are essential to all muscle contraction. So when you build up your supply of these contractile proteins, you actually increase your muscle's ability to perform physical work. And the more work you do (whether it's lifting weights or running 100-meter dashes), the stronger you become over time. Athletes frequently divide their creatine use into two phases. The first phase, called the loading phase, fills up the muscle fiber's storage capacity for this nutrient. This phase usually lasts five to seven days. After that, athletes reduce their creatine consumption to a lower dosage level which continues for an extended period of time. This second phase is called the maintenance phase.  How Much Creatine Is In My Body?  The amount of creatine you have in your body depends mostly on the amount of muscle you have. (There is no creatine in body fat.) The average 70 kg (155 lb) person has a total of about 120 grams (4.2 ounces) of creatine in their body at any one time. Vegetarians by and large have lower creatine levels than meat-eaters. A study by Walker showed that the average sedentary person uses up about two grams of creatine per day. This creatine is broken down into a waste product called creatinine, which is collected by the kidneys and excreted in the urine. Athletes use up much more than two grams per day, with the exact amount depending on the type of sport, intensity level and muscle mass.  Can I Get Enough Creatine From My Diet?  The average person consumes about one gram of creatine per day. Creatine is found in moderate amounts in most meats and fish, which are, after all, skeletal muscle. Good sources of dietary creatine include tuna, cod, salmon, herring, beef and pork. Tiny amounts are found in milk and even cranberries. While it would seem logical that chicken and turkey have creatine as well, we were unable to find any published data to confirm this. Cooking destroys part of the creatine that exists in these foods. An important thing to remember is that meats and fish contain a lot more than creatine. All animal flesh contains relatively high amounts of cholesterol. Most meats, especially beef and pork, also contain high quantities of fat. One kilogram (2.2 pounds) of raw round steak contains only four grams of creatine, but 119 grams of fat. Porterhouse steak has a bit less creatine, but 325 grams of fat per kilo! Needless to say, you won't live to your 90s if you clog your arteries with the fat and cholesterol from all of the meat or even fish you'd have to eat to get the creatine you need to improve your strength and power. What you need is a nonfat, non-cholesterol supplement called creatine monohydrate.   Who Can Benefit From Creatine?  Although the research on creatine and exercise performance is relatively new, so far it appears that the greatest benefits occur in those sports which involve short, intense bursts of energy. That is because these sports rely most heavily on ATP as an energy source. Athletes in bodybuilding, powerlifting, martial arts, sprinting, and track and field events such as javelin and shot-put will greatly benefit due to greater strength. So would wrestlers, swimmers, football, hockey, basketball and tennis players. We doubt that creatine will be of any benefit for people who comfortably cruise on a cart around the golf course and occasionally get up to putt. Other sports where creatine is not likely to be of any significant benefit include bowling, skeet shooting and certainly billiards. It is still unclear whether athletes involved in endurance activities such as marathon running or long-distance bicycling will benefit from creatine supplementation. Stroud mentioned anecdotal reports that people in these sports may benefit, although other studies show that creatine either does not help or may actually be counterproductive. The difficulty in these situations appears to center on the increased muscle mass which creatine provides. While that's great if you're a bodybuilder or wrestler, it can be a detriment if you have to carry all that weight around during a marathon or triathlon. It becomes a tradeoff between the increased strength you get from creatine and the increased muscle mass. Further research will provide us with more definitive answers as to what role creatine can play in endurance-type sports.    Is Creatine Safe?  Experiments with the administration of creatine to humans have been going on for over a century. Dr. Paul Balsom of the Karolinska Institute in Stockholm, Sweden, is one of the world's leading experts on creatine. He states in a review article published in 1994 in Sports Medicine that "to the best of our knowledge, the only documented adverse effect that has been associated with creatine supplementation is an increase in body mass." We suspect that most athletes will gladly accept this "adverse effect." One caution we'd like to make is that the studies which used high dosages of creatine, such as 20 grams per day, were only a month or less in duration. As a result, we do not have controlled, scientific studies which indicate exactly what happens to athletes taking large amounts of creatine for many months or even years. The only long-term study on creatine to date provided one gram per day to patients with gyrate atrophy, an eye disorder. Sipila reported that creatine helped the condition. Therefore, we do not yet fully know the consequences of high dose, long-term supplementation. As part of our research for this book, we distributed a detailed survey to athletes in three states. Personal interviews with men and women who have used creatine for over a year did not reveal any long-term side effects which one should be concerned about. Nor is there a particular reason to think that there should be a problem, given the way in which creatine is synthesized and excreted by the body. The only short-term side effect mentioned was diarrhea, which some athletes said occurred when they took dosages greater than those recommended in this book. The diarrhea went away when the dosage was reduced.