Everything you wanted to know about Creatine

Creatine is a metabolite that supplies energy to muscle and nerve cells and is present in vertebrates. In humans, about half of the daily creatine is synthesized by the amino acids arginine, glycine, and methionine. The rest comes mainly from fresh fish and meats. 95% of the concentration of creatine is found in the skeletal muscles (5). The average person has about 3.5-4 grams of creatine per kilogram of muscle stored in the body.

How does creatine work?

There are several theories regarding creatine’s effects in the human body. Much of the research focuses on two different ways methods.

 1. Provides energy for muscles by enhancing ATP Production

Your muscles use Adenosine Triphosphate (ATP) for energy when they contract. Although you get energy from other sources as well, such as carbohydrates and fats, it takes longer for this energy to be converted into a useable form. So, when you’re doing activities that require a quick burst of energy, such as weightlifting or sprinting, ATP provides a quick source of energy. Your muscles contain enough energy from ATP for about 10-15 seconds at maximum exertion. After this time, ATP is broken down into ADP and inorganic phosphate. ADP cannot be used as an energy source. Creatine stored in the muscles bond with phosphorus and convert ADP back into ATP. By taking creatine in supplement form, the body has more ATP to use, enabling you to exercise harder and longer while minimizing lactic acid production (4).

 2.Intramuscular water retention

Once creatine is stored in the muscle cell, it pulls water into the cell. This increases the size of the muscle. It is not clear though how much of an effect this has (4).

Several studies have found that elevated intramuscular creatine can enhance glycogen levels (3), which can allow for better “pumps” during your workout.

Researchers have also suggested that creatine may enhance protein synthesis, thereby making it easier to gain muscle. However, there have also been studies that have failed to find any effect on protein synthesis (1).

How much should you take?

Studies have shown that the human body can store up to 5 grams of creatine per kilogram (4). Many supplement manufacturers recommend taking a loading phase of 20 grams for 5 days, then 5-10 grams a day after the first five days. However, since the body can only store up to 5 grams per kilogram of body weight, the “loading’ phase is not really necessary. Most people can get good results taking 5 grams per day. Research has shown that taking 5 grams per day is safe (2). If you take it every day, you will eventually reach the upper limit, so may want to start taking it only on the days that you train once you’ve been using it for a few weeks. If you stop taking creatine, it takes about two weeks for your body’s creatine levels to go back to normal.

Are there any side effects?

The most common side effect is an increase in water weight. Some people may also experience gastrointestinal upset. Small-scale, longer-term studies have indicated that creatine supplementation is safe in healthy individuals (3).

References

1. Louis et al. (2003). No effect of creatine supplementation on human myofibrillar and sarcoplasmic protein synthesis after resistance exercise. Am J Physiol Endoncrinol Metab.; 285(5): E1089-94. Epub 2003 Jun 24.
2. Shao and Hathcock (2006). Risk assessment for creatine monohydrate. Regul Toxicol Pharmacol; 45(3):242-51. Epub 2006 Jun 30.
3. Volek and Rawson (2004). Scientific basis and practical aspects of creatine supplementation for athletes. Nutrition; 20(7-8):609-14.
4. Rivera, Hugo (2007). About.com: Bodybuilding. Available online from http://bodybuilding.about.com/od/supplementationbasics/a/creatine.htm [Cited Sept. 16, 2007].
5. Wikipedia.com. Entry on creatine. Available online from http://en.wikipedia.org/wiki/Creatine [Cited Sept.16, 2007].
6. Wikipedia.com. Entry on creatine supplements. Available online from http://en.wikipedia.org/wiki/Creatine_supplements [Cited Sept. 16, 2007].