Creatine

What?

Creatine monohydrate is a popular sports supplement used to maintain levels of high-energy phosphates during exercise. As a supplement, varying amounts are consumed per person corresponding to parameters such as body mass and level of training (i.e. maintenance versus loading doses). Numerous studies have reported beneficial effects including increased muscle mass during training and neural protection. However, negative reports have also been made of possible side effects, such as muscle cramping during exercise, and potential impurities.

Why?

During the 1990’s, and with the enactment of the Dietary Supplement Health and Education Act (DSHEA) studies on Creatine rapidly grew, coinciding with an increase in the oral consumption of Creatine. This was due, primarily, to a number of publications early in the 1990’s, which found Creatine to delay muscle fatigue. It was also reported that Creatine could enhance muscle energy recovery (Finn et al., 2001).

How?

Creatine is an amino acid formed from arginine and glycine via an A:G transferase enzyme. This produces ornithine and guanidinoacetate. Guanidinoacetate is then methylated via an S-adenosyl methionene. This forms creatine. In vivo, most of this is happening in the kidneys. The guanidinoacetate is then transferred to the liver where it is methylated to form creatine. After this, the creatine traverses to the skeletal muscle where it is transported across the cell membrane via a Na+ dependant transport system. The key feature of Creatine is that it can bind a high-energy phosphate. This is relevant because when ATP is depleted, such as during times of high-intensity workouts, the CrP can donate a high-energy phosphate and rephosphorylate ADP to ATP.

Creatine also acts as a temporal and spatial buffer. Creatine by itself, in its unphosphorylated state, is transported into the cell where it becomes phosphorylated by mitochondrial associated kinases. The Creatine-Phosphate can then move around the cell. In the cell, CrP can accumulated towards the synapse and assist with relatively high and stable synaptic potential energy.

Nervous tissue and the role of Cr supplementation is rapidly garnering more attention. There is mounting data in the literature supporting the use of Cr and Cr analogs in musculoskeletal disorders. Cr itself rapidly converts to creatinine, depending on the pH. At a pH greater than 6, the conversion is dramatically slowed. Cr normally converts to creatinine, which is not phosphorylatable, rapidly at acidic pH’s. In vivo, once that conversion happens, the creatinine (Crn) is excreted in the urine. Cr is essentially stable at neutral to basic pH’s.

Source: Creatine: are the benefits worth the risk? by: Mark a. Brudnak