Determination of vitamin K in foods: a review.

Vitamin K receives less dietary attention and fewer assays in foods than other fat-soluble vitamins. It is widely distributed in foods, usually at low concentrations. The human requirement is small. Intestinal bacteria synthesize vitamin K, which presumably helps provide the metabolic requirements for vitamin K. An RDA for vitamin K has not been published, but infants fed milk-substitute formulas risk vitamin K deficiency and it is recommended that those formulas contain supplemental vitamin K. Vitamin K in foods includes phylloquinone (K1) found in plants and several menaquinones (K2) found in animals and synthesized by microorganisms. Many vitamin K methods were developed primarily to identify forms present and determine their relative bioactivities. Until recently bioassays with chicks were the only practical methods to determine vitamin K content of foods. Various physicochemical methods have been developed to determine vitamins K in pure solutions, concentrates, and pharmaceuticals. Because of low concentrations of vitamin K in foods and the extensive purifications of extracts required, there has been only limited use of physicochemical methods, such as column chromatography, thin-layer chromatography, and high-performance liquid chromatography, with foods; the latter method perhaps offers the greatest possibilities for further development.