Whether you're an accomplished athlete or you've just started an exercise program, you need to know about creatine. Many supplements touted over the years as performance enhancers have come and gone, but creatine is here to stay. I predict that it will be one of the most popular muscle-building nutrients ever made available to you. Why? Because it works. Yes, it really works to increase muscle mass.

Note: Over the past two months I have had reports from three individuals (or family members) who have noted increased aggressiveness and irritability from creatine. A study published in the Nov 29 issue of JAMA reports that some creatine products may have been contaminated with small amounts of androstenedione or other anabolic steriods. Could this account for the irritability and aggressiveness? I don't know for sure at this time.

Q. What is Creatine?
A. When we told our friends that we were writing a book on creatine, some of them had quizzical responses. You're writing on creating? Creating what? Is it an herb?

Creatine is not an herb, mineral, vitamin, hormone, or steroid. Creatine is a natural nutrient found in our bodies and the bodies of most animals. Approximately 95% of the body's creatine supply is found in the skeletal muscles. The remaining 5% is scattered throughout the rest of the body, with the highest concentrations in the heart, brain and testes.

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.

Q. How Does Creatine Work?
A. Creatine is an essential player in the primary energy source used for muscle contraction. It exists in two different forms within the muscle fiber: as free (chemically-unbound) creatine and as creatine phosphate. This later 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. ATP provides its energy by releasing one of its phosphate molecules. It then becomes a different compound called ADP. Unfortunately, there is only enough ATP to provide energy for about 10 seconds, so for muscle contraction 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.

The bottom line is that your ability to regenerate ATP depends on your supply of creatine. More creatine, more ATP remade, and more ability to train your muscles to their maximum potential. It's that simple. This greater ATP synthesis 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 using 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, especially the 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. Creatine can also absorb intracellular water, thus resulting in a higher muscle volume. This could lead to the "pumped up" feeling and look. An additional way creatine increases muscle size is thought to be its fluid retention abilities within muscle tissue.

Q. Who Can Benefit From Creatine?
A. Although the research on creatine and exercise performance is relatively new, so far it appears that the greatest benefits occur in those who wish to put on muscle mass. Athletes in bodybuilding, powerlifting, martial arts, and track and field events such as javelin and shot-put may benefit due to greater strength. So could wrestlers and football 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 skeet shooting, and certainly billiards. Body builders and anyone who wishes to have more muscle build will find creatine extremely helpful.

It is still unclear whether athletes involved in endurance activities such as marathon running or long-distance bicycling will benefit from creatine supplementation. There have been anecdotal reports that people in these sports may benefit (Stroud, 1994), although other studies show that creatine either does not help or may actually hurt. 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 supplementation can play in endurance-type sports.