6Table 3: Biochemical Function of <strong>Vitamin</strong>s<strong>Vitamin</strong> Classical Role More Recent Role<strong>Vitamin</strong> C Hydroxylation Reaction In Vivo AntioxidantBeta-carotene Provitamin A Antioxidant, Immune Function<strong>Vitamin</strong> K Clotting Factors Calcium Metabolism<strong>Vitamin</strong> D Calcium Absorption, Differentiation and Growth,Mineralisation of BoneImmune Function<strong>Vitamin</strong> B 6 Coenzyme Steroid RegulationNiacin Coenzyme Lipid LoweringFolic Acid Production and Maintenance Protection Against Neural Tubeof New CellsBirth DefectsFolic Acid, B 6 and B 12 Energy Metabolism May Lower Risk of Heart Disease andStroke*Antioxidant vitaminsProtection against Cancer and HeartDisease**Research ongoingDietary ReferenceIntakesFrom 1941 until 1989, RDAs(Recommended Dietary Allowances)were established and used to evaluateand plan menus to meet thenutrient requirements of certaingroups. They were also used inother applications such as interpretingfood consumption records ofpopulations, establishing standardsfor food assistance programs,establishing guidelines for nutritionlabelling, etc.The primary goal of RDAs was toprevent diseases caused by nutrientdeficiencies.In the early 1990s, the Food andNutrition Board (FNB), the Instituteof Medicine, the National Academyof Sciences (USA), with the involvementof Health Canada, undertookthe task of revising the RDAs, and anew family of nutrient reference valueswas born – the DietaryReference Intakes (DRIs).The primary goal of having thesenew dietary reference values wasnot only to prevent nutrient deficiencies,but also to reduce the risk ofchronic diseases such as osteoporosis,cancer, and cardiovasculardisease.The first report, Dietary ReferenceIntakes for Calcium, Phosphorus,Magnesium, <strong>Vitamin</strong> D and Fluoride,was published in 1997. Since then,three additional vitamin relatedreports have been released,addressing folate and other B vitamins,dietary antioxidants (vitaminsC, E, selenium and the carotenoids),and the micronutrients (vitamins A,K, and trace elements such as iron,iodine, etc). The DRIs are a comprehensivescientific source primarily fornutrition scientists (see References).They are used by health authoritiesin many countries as a basis fordecisions regarding nutritional informationon micronutrients.There are four types of DRI referencevalues: the Estimated AverageRequirement (EAR), the RecommendedDietary Allowance (RDA), theAdequate Intake (AI) and the TolerableUpper Intake Level (UL).• Estimated Average Requirement(EAR) – the amount of a nutrientthat is estimated to meet therequirement of half of all healthyindividuals in a given age andgender group. This value is basedon a thorough review of the scientificliterature.• Recommended Dietary Allowance(RDA) – the average daily dietaryintake of a nutrient that is sufficientto meet the requirement of nearlyall (97-98%) healthy persons. Thisis the number to be used as a goalfor individuals. It is calculated fromthe EAR.• Adequate Intake (AI) – only establishedwhen an EAR (and thus anRDA) cannot be determinedbecause the data are not clear-cutenough; a nutrient has either anRDA or an AI. The AI is based onexperimental data or determinedby estimating the amount of anutrient eaten by a group ofhealthy people and assuming thatthe amount they consume is adequateto promote health.