Expressing dietary values for fat-soluble vitamins: changes in concepts and terminology.

The 9th ed. of the Recommended Dietary Allowances has abandoned the use of international units for expressing the food values for vitamins A, D, and E, and has set forth expressions based on absolute weights, including vitamin K. These changes will necessitate a revision in the manner in which both experimental and applied nutritionists deal with these vitamins. In this review, the background and rationale for these changes are presented in an effort to aid investigators in their transition to this new concept. Changes in the nomenclature of vitamin E are also explained.