Hydration is considered to be an important aspect of nutritional health. Unfortunately, many water sources are low in beneficial magnesium and calcium and high in cancer causing arsenic and chlorination by-products. Current research indicates that bolstering the magnesium and calcium content in both bottled and tap water may reduce the risks of acute myocardial infarction and certain cancers. Also, eliminating arsenic and chlorination by-products could reduce the rate of colon, bladder, lung, and skin cancers. As long as water does not meet the research-backed standards of dissolved constituents, it is not clear whether drinking water is actually good for one's health.