Creatine a naturally- occurring supplement, has a key role in body energy production. As Creatine can be made in the liver, kidney and pancreas, it is not an essential nutrient.
Creatine is vastly used in some sports such as body building and weight lifting as performance enhancement supplement, though still there is not enough evidence for its impacts. The claim to this popularity is that it may increase lean muscle mass and improves the performance of athletes, most specifically when they perform high-intense activities during a short period.
Some other clinical studies also advocate the ability of creatine in the increase of muscle mass. They claim that enhancement in muscle mass can decrease the weakness of muscles at the time of certain illnesses. According to these studies, the conditions such as heart failure, muscular dystrophy, COPD and similar conditions can be improved by Creatine. However, to prove the role of creatine in disease control, more investigations in this area has to be done.
Introduction
Creatine, which is a natural substance has a significant effect in your body. However, it is not considered an essential supplement nutrient, because your body can provide it from the amino acids L-arginine, glycine, and L-methionine in the liver, kidneys, and pancreas.
Creatine breaks down into creatine phosphate or phosphocreatine which will be stored in the muscles. Phosphocreatine breaks down into ATP, a major source of energy when body performs high-intensity, short-duration exercises.
The purpose of this review was to assess the literature evaluating some creatine medical implications and safety issues.
Uses
Athletic performance
Creatine is proved to increase the energy by assisting adenosine triphosphate (ATP) production in skeletal muscles when performing anaerobic training, and particularly enhances the performance of short duration, high intensity exercises such as weight lifting or sprinting (1, 2).
However, no studies suggest that creatine improves performance in endurance sports like running, or in exercises that is not repeated, although study results are mixed (2).
In a meta-analysis of seven trials on young men (<36years old), creatine combined with resistance training increased the maximal lifting weight for bench press and squat (3). Subsequent randomized trials have confirmed that creatine improves maximum power output (4, 5).
Nonetheless, we cannot claim that all human studies prove the role of creatine in improving the performance of athletes. Each person tends to respond to creatine supplements differently. Previous Researches have already done don'''t clearly explain how creatine supplementation can improve the performance. It seems that this supplementation facilitates the use of fuel for body during exercise and subsequently increases the production of muscles. There is again the need for more research.
Neuromuscular disorders
Lack of creatine in muscle cells is thought to result in muscular dystrophy in some people which may contribute to muscle weakness. Based on high quality evidence form RCTs, muscle strength was increased in muscular dystrophies with short- and medium-term creatine treatment. Evidence also show that creatine improves functional performance in idiopathic inflammatory myopathy and muscular dystrophy; Creatine is well tolerated in these people. Muscle strength in metabolic myopathies is not proven by high quality but limited evidence from RCTs, to show significant improvement. High-dose creatine treatment affected the daily activities and caused pain in muscles in McArdle disease (6).
A considerable body of literature, has confirmed the neuroprotective effects of creatine, both in vitro and in vivo. Enough studies are done on the neuroprotective effects of creatine in transgenic mouse models of some neurodegenerative diseases, such as amyotrophic lateral sclerosis, Huntington'''s disease and Parkinson'''s disease. Investigations suggest that creatin can protect against excitotoxicity as well as against ''-amyloid toxicity in vitro. Some studies reveal that creatin can protect body against lesions produced by the toxins malonate and 3-nitropropionic acid (3-NP), inhibitors of succinate dehydrogenase (7).
Creatine supplements can contradict the loss of muscle strength which happens in immobilized limbs following surgery or injury, for example (8, 9).
Muscular fitness is low in people with Parkinson's disease. The decrease in muscular fitness includes decreased muscle mass, muscle strength, and increased fatigue. The result of one study showed that giving creatine to people with Parkinson's disease improved their ability in exercise and their endurance. Another study proved that creatine supplements boosted the mood of participants and reduced their need for medication, when compared those who didn't take creatine (10, 11).
Heart disease
Creatine supplements may help lower the levels of triglyceride according to initial studies done on this subject matter. Based on a 56-day, double-blind, placebo-controlled study on 34 men and women, creatine supplementation can reduce levels of triglycerides in the blood by about 25%. Other blood lipids such as total cholesterol didn'''t show to be affected significantly. (12).
The use of creatine supplementation is supported by some researchers in people with chronic heart failure. Easily getting fatigued is an unpleasant experience in people with congestive heart failure. Some research has shown a positive result in reducing this symptom by giving creatine supplementation as a treatment. A study on 20 people with heart failure revealed that short-term creatine supplementation on top of standard medication helped to increase body weight and improved muscle strength. Other studies, however, showed no improvement (13, 14).
The results of an experiment on the effects of creatine on a total of 1,226 patients with heart problems did show that creatine may improve shortness of breath in these patients. However, the researchers concluded that more factors like the dose and duration of treatment as well as larger studies have to be determined before drawing a firm conclusion on the benefits of creatine for congestive heart failure (15). A randomized controlled trial showed that creatine supplementation did not significantly improve functional capacity that assesses by use of peak VO2 and 6MWT (13).
On the other hand, homocysteine which is associated with heart diseases, including heart attack and also stroke, is reported to be lowered by using creatine. (16).
Chronic Obstructive Pulmonary Disease (COPD)
Creatine may become a new ergogenic treatment in COPD. The result of a study on people with COPD who took creatine proved that this study group increased muscle mass, strength and endurance, and improved their health status compared to those who took placebo. They did not increase their exercise capacity, though. More research is needed (17).
Another study in COPD patients with chronic respiratory failure showed that the nutritional diet combined with Co-Q10 and creatine, prompted the increase in lean body mass and exercise tolerance, dyspnea reduction, improve in the quality of life and exacerbations (18).
Diabetes mellitus type 2
The study in regard to the impacts of creatine on type 2 diabetes which was performed on 28 diabetic patients, verified that creatine supplementation does not harm kidney function in these patients who underwent exercise training (19).
Researchers also have pointed out the therapeutic role of creatine on insulin resistance. This therapeutic impact includes enhancements in insulin sensitivity, glucose tolerance and protein GLUT-4 expression, which could obviously bene'''t diabetic patients (19, 20).
These patients however, are mostly susceptible to developing chronic kidney disease. The studies which prove the safety of creatine on human, have been performed on only healthy and young individuals. In this context, researchers provide the evidence that 3 months of creatine supplementation in older individuals may not affect the function of kidney. This safe period encompasses even patients with chronic kidney disease and insulin resistance. Also, it supports the development of further studies focused on the therapeutic role of creatine for this population (21, 22).
Elderly
Aging results in reduced physical activity and consequent decrease in muscle creatine, muscle mass, bone density, and strength. Creatine ingestion however, has proven that can reverse these changes, and subsequently improve daily life activities.
Similar to the young, concurrent creatine supplementation along with resistance training in older adults has proven an increase in lean body mass, enhancement of fatigue resistance, increase in muscle strength, and improvement in the performance of activities of daily living to a greater extent, compared to doing resistance training alone. Additionally, creatine supplementation plus resistance training results in a greater increase in bone mineral density in comparison to performing resistance training alone.
The bene'''ts of creatine ingestion for older adults are considerable. It can improve their quality of life and eventually may reduce the disease burden associated with sarcopenia and cognitive dysfunction (23).
Saftey issues:
No investigation have been performed on the long-term risks and benefits of creatine.
In previous studies, there was a report of two cases of renal dysfunction following creatine intake. However, studies from some laboratory did not find any harmful health effects on kidney function in healthy humans who took supplementation of oral exogenous creatine for short, medium, and long-term (24, 25).
Despite some claims on the adverse effect of creatine on kidney function, the limited published evidence and wide experience with this supplement proves the safety of this supplementation in patients with normal baseline renal function (26, 27).
According to a review article, creatine supplementation slightly impacts creatine concentrations and renal function in young healthy adults. Creatine concentrations may increase after long periods of creatine supplementation, however, the increase is extremely limited and unlikely to affect estimates of creatine clearance and subsequent dosage adjustments. There is need for more studies in elderly and patients with renal insufficiency (26).
The other concern entails the fact that creatine is metabolized in the body to the toxic substance formaldehyde. Anyhow, it is not proven if the amount of formaldehyde produced in this trend will cause any harm. Although three deaths were reported in individuals who took creatine, other causes were most likely responsible (28).
Conclusion
Several high-quality studies have proven the benefits of creatine in the performance of high-intensity, short-duration exercises. However, it is not useful in endurance sports. Creatine supplementations have shown an increase in lean body mass, strength, and total work, based on the available evidence.
Preliminary clinical studies also suggest that the ability of creatine in increasing muscle mass and strength may help to fight muscle weakness, associated with illnesses such as heart failure, muscular dystrophy, COPD etc.
Creatine consumers need to evaluate all the information supporting the use of creatine as well as the known and theoretical risks of using the product including possible renal dysfunction.
More experiment has to be done in this area to prove the efficacy of creatine in disease management. Individual differences such as fitness levels, sex, and age, should be considered in future studies to provide more reliable and precise results.