although the evidence is difficult to interpret systematically and the appropriate dosing is unknown. The greatest effects appears to be in individuals who are stressed (due, for instance, to sleep deprivation) or cognitively impaired. Muscular disease A meta-analysis found that creatine treatment increased muscle strength in muscular dystrophies, and potentially improved functional performance. Creatine treatment does not appear to improve muscle strength in people who have metabolic myopathies. High doses of creatine lead to increased muscle pain and an impairment in activities of daily living when taken by people who have McArdle disease. According to a clinical study focusing on people with various muscular dystrophies, using a pure form of creatine monohydrate can be beneficial in rehabilitation after injuries and immobilization. Mitochondrial diseases Parkinson's disease Creatine's impact on mitochondrial function has led to research on its efficacy and safety for slowing Parkinson's disease. As of 2014, the evidence did not provide a reliable foundation for treatment decisions, due to risk of bias, small sample sizes, and the short duration of trials. Huntington's disease Several primary studies have been completed but no systematic review on Huntington's disease has been completed yet. ALS It is ineffective as a treatment for amyotrophic lateral sclerosis. Adverse effects Side effects include: Weight gain due to extra water retention to the muscle Potential muscle cramps / strains / pulls Upset stomach Diarrhea Dizziness One well-documented effect of creatine supplementation is weight gain within the first week of the supplement schedule, likely attributable to greater water retention due to the increased muscle creatine concentrations by means of osmosis. A 2009 systematic review discredited concerns that creatine supplementation could affect hydration status and heat tolerance and lead to muscle cramping and diarrhea. Renal function A 2019 systematic review published by the National Kidney Foundation investigated whether creatine supplementation had adverse effects on renal function. They identified 15 studies from 1997–2013 that looked at standard creatine loading and maintenance protocols of 4–20 g/day of creatine versus placebo. They utilized serum creatinine, creatinine clearance, and serum urea levels as a measure of renal damage. While in general creatine supplementation resulted in slightly elevated creatinine levels that remained within normal limits, supplementation did not induce renal damage (P value< 0.001). Special populations included in the 2019 Systematic review included type 2 diabetic patients and post-menopausal women, bodybuilders, athletes, and resistance trained populations. The study also discussed 3 case studies where there