Biological Properties of B Vitamins, Part 1: Vitamins B1, B2, B3, and B5

This review summarizes current knowledge about essential vitamins B1, B2, B3, and B5. Except for vitamin B3, these B vitamins must be obtained from the diet; vitamin B3 can also be synthesized from the amino acid tryptophan. All these vitamins are water-soluble, which determines their main characteristics: they migrate into water, so they are partially lost when food is washed or boiled; they require membrane transporters to penetrate into cells; and their safety, because any excess vitamins are rapidly excreted through the kidneys. The therapeutic uses of B vitamins are mainly limited to vitamin deficiency diseases or similar conditions, but since they are generally very safe, they have also been studied in other pathological situations. Niacin (a form of vitamin B3) is the only exception because it has known lipid-lowering effects at gram doses.