This report reassess the dietary advice to consumers on foods and supplements containing Vitamin A (retinol), given evidence from the National Diet and Nutrition Survey that the dietary intake for some adults might exceed the safety guidance level set by the Expert Group on Vitamins and Minerals (EVM) in 2003. Liver and dietary supplements (including fish liver oils) are the main sources of retinol. The report concludes that there is insufficient evidence on the association between high intakes of retinol and poor bone health to justify a change in dietary advice for all consumers, but as a precaution for those who are regular consumers of liver (once a week or more) it may be advisable to avoid supplements containing retinol. People at risk of osteoporosis (such as postmenopausal women and older people) are also advised to limit their retinol intakes. Further research is needed on the relationship between retinol intake and bone fracture risk.

Reviews the recent breakthroughs in vitamin A research. Discusses the metabolism of vitamin A; the mechanism of action of vitamin A and the provitamin A carotenoids; the role of retinoids in embryonic development, skin and epithelial cells, blood cells, vision, and reproduction; vitamin A deficiency and teratogenicity; and the anticancer role of vitamin A from an epidemiological point of view. Intended as a source of information for scientists engaged in research in the field of vitamin A.

This volume is the newest release in the authoritative series issued by the National Academy of Sciences on dietary reference intakes (DRIs). This series provides recommended intakes, such as Recommended Dietary Allowances (RDAs), for use in planning nutritionally adequate diets for individuals based on age and gender. In addition, a new reference intake, the Tolerable Upper Intake Level (UL), has also been established to assist an individual in knowing how much is "too much" of a nutrient. Based on the Institute of Medicine's review of the scientific literature regarding dietary micronutrients, recommendations have been formulated regarding vitamins A and K, iron, iodine, chromium, copper, manganese, molybdenum, zinc, and other potentially beneficial trace elements such as boron to determine the roles, if any, they play in health. The book also: Reviews selected components of food that may influence the bioavailability of these compounds. Develops estimates of dietary intake of these compounds that are compatible with good nutrition throughout the life span and that may decrease risk of chronic disease where data indicate they play a role. Determines Tolerable Upper Intake levels for each nutrient reviewed where adequate scientific data are available in specific population subgroups. Identifies research needed to improve knowledge of the role of these micronutrients in human health. This book will be important to professionals in nutrition research and education.