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. 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 were reports that creatine affected renal function. in a joint statement between the american college of sports medicine, academy of nutrition and dietetics, and dietitians in canada on performance enhancing nutrition strategies, creatine was included in their list of ergogenic aids and they do not list renal function as a concern for use. the most recent position stand on creatine from the journal of international society of sports nutrition states that creatine is safe to take in healthy populations from infants to the elderly to performance athletes. they also state that long term (5 years) use of creatine has been considered safe. it is important to mention that kidneys themselves, for normal physiological function, need phosphocreatine and creatine and indeed kidneys express significant amounts of creatine kinases (bb-ck and u-mtck isoenzymes). at the same time, the first of two steps for endogenous creatine synthesis takes place in the kidneys themselves. patients with kidney disease and those undergoing dialysis treatment generally show significantly lower levels of creatine in their organs, since the pathological kidneys are both hampered in creatine synthesis capability and are in back-resorption of creatine from the urine in the distal tubules. in addition, dialysis patients lose creatine due to wash out by the dialysis treatment itself and thus become chronically creatine depleted. this situation is exacerbated by the fact that dialysis patients generally consume less meat and fish, the alimentary sources of creatine. therefore, to alleviate chronic creatine depletion in these patients and allow organs to replenish their stores of creatine, it was recently proposed to supplement dialysis patients with extra creatine, preferably by intra-dialytic administration. such a supplementation with creatine in dialysis patients is expected to significantly improve the health and quality of the patients by improving muscle strength, coordination of movement, brain function and to alleviate depression and chronic fatigue that are common in these patients. safety contamination a 2011 survey of 33 supplements commercially available in italy found that over 50% of them exceeded the european food safety authority recommendations in at least one contaminant. the most prevalent of these contaminants was creatinine, a breakdown product of creatine also produced by the body. creatinine was present in higher concentrations than the european food safety authority recommendations in 44% of the samples. about 15% of the samples had detectable levels of dihydro-1,3,5-triazine or a high dicyandiamide concentration. heavy metals contamination was not found to be a concern, with only minor levels of mercury being detectable. two studies reviewed in 2007 found no impurities. interactions a national institutes of health study suggests that caffeine interacts with creatine to increase the rate of progression of parkinson's disease. food and cooking when creatine is mixed with protein and sugar at high temperatures (above 148 °c), the resulting reaction produces carcinogenic heterocyclic amines (hcas). such a reaction happens when grilling or pan-frying meat. creatine content (as a percentage of crude protein) can be used as an indicator of meat quality. dietary considerations creatine-monohydrate is suitable for vegetarians and vegans, as the raw materials used for the production of the supplement have no animal origin.