There is evidence that plain old hamburgers reduce your susceptibility to skin and stomach cancer. The actual effective ingredient is an oil in ground beef called linoleic acid. However, the rest of the stuff in hamburgers may be bad for your health. When cooking oil is heated to over 400 degrees Fahrenheit (204 degrees Celsius) and reused for a long time, the chemicals in it change. Research indicates that the oil used by many fast-food establishments for frying hamburgers and other foods such as French fries is often carcinogenic.