fat-soluble vitamins: Vitamins that dissolve in fat. It is possible to overdose on such vitamins since they are stored in body fat.

fatty acid: A chain of carbon atoms with hydrogen atoms attached and a carbon-oxygen-oxygen-hydrogen group (the unit that makes it an acid) at one end.

fluoride: Many cities in the United States add fluoride to the municipal water supply to prevent tooth decay, and many toothpastes contain it as an additive; but this use is somewhat controversial. The mineral does have toxicity concerns and is associated with increased cancer risk.

folate; folic acid: An essential nutrient for human beings and other vertebrates.

Food and Drug Administration; FDA: Federal Agency tasked with determining the safety of foods and drugs marketed in the United States.

free radicals : Molecular fragments that can bond and possibly cause cancer.