Human Vitamin and Mineral Requirements Report of a joint FAO/WHO expert consultation Bangkok, Thailand Food and Agriculture Organization of the United Nations World Health Organization Food and Nutrition Division FAO Rome The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concern- ing the delimitation of its frontiers or boundaries. All rights reserved. Reproduction and dissemination of material in this information product for educational or other non-commercial purposes are authorized without any prior written permission from the copyright holders provided the source is fully acknowledged. Reproduction of material in this information product for resale or other commercial purposes is prohibited without written permission of the copyright holders. Applications for such permission should be addressed to the Chief, Publishing and Multimedia Service, Information Division, FAO, Viale delle Terme di Caracalla, 00100 Rome, Italy or by e-mail to [email protected] © FAO 2001 FAO/WHO expert consultation on human vitamin and mineral requirements iii Foreword he report of this joint FAO/WHO expert consultation on human vitamin and mineral requirements has been long in coming. The consultation was held in Bangkok in TSeptember 1998, and much of the delay in the publication of the report has been due to controversy related to final agreement about the recommendations for some of the micronutrients. A priori one would not anticipate that an evidence based process and a topic such as this is likely to be controversial. But the reality is that there is surprisingly little data on specific health status indicators on which to draw conclusions, whereas there is more information in relation to overt deficiency disease conditions. The recommended intakes are therefore largely based on the interpretation of the best available scientific information, and this leaves the door open for differences in interpretation. A fundamental point is that when we look at recommended nutrient intakes (RNIs) in industrialized countries over the last 25 years, the levels for some of the micronutrients have been gradually increasing. The question is whether this comes from better scientific knowledge and understanding of the biochemical role of the nutrients, or whether the criteria for setting the levels of the requirements have changed. Even if the scientific knowledge base has expanded, it appears that the basic criteria for deciding on levels to recommend may bear more of the responsibility. Whereas RNIs for vitamins and minerals were initially established on the understanding that they are meant to meet the basic nutritional needs of over 97 percent of the population, a fundamental criterion in industrialized countries has become one of presumptive role these nutrients may play in the “prevention” against an increasing range of disease conditions that characterise these populations. The latter approach implies the notion of “optimal nutrition”, and this may be insidiously pushing requirements to higher levels time and again. This shift in the goal for setting RNIs is not without reason. The populations that are targeted for prevention through “optimal nutrition” are characterised by sedentary lifestyles and longer life expectations. The populations of developed countries are ageing, and the concern for the health of the ageing has become prominent. By contrast the micronutrient needs of developing countries as a whole have not really changed, and are more appropriately described as those that will satisfy basic needs of younger populations that are physically active. This, nevertheless, is not to deny the double burden of malnutrition, which is rapidly rising in many developing countries, and one needs to also bear that in mind. The concern raised about possible differences in micronutrient needs of populations with different lifestyles is for a very practical reason. The logic behind the establishment of micronutrient needs of industrialized nations has come about at the same time that there is a large and growing demand for a variety of supplements of all kinds, and manufacturers have responded quickly to meet this market. This phenomenon could be skewing our strategy for nutritional development, with a tendency to want to resolve micronutrient deficiency problems of developing countries through the use of supplements and fortification strategies, rather than through increasing the consumption of an adequate and varied diet. Higher levels of RNIs in developed countries can easily be supported because they can be met with supplementation in addition to food. But when it becomes difficult to meet some of the micronutrient needs of developing countries by consuming locally available food, there is a problem. iv FAO/WHO expert consultation on human vitamin and mineral requirements The nutrients of concern currently are, first, calcium, for which the RNI may be difficult to meet without dairy products. The recently revised US/Canada Dietary Reference Intakes (DRIs) only propose an Acceptable Intake (AI) for calcium, instead of a Recommended Daily Allowance (RDA), in recognition of the fact that intake data is out of step with the relatively high intake requirements observed with experimentally derived values. Another is iron, particularly during pregnancy, where supplementation appears to be essential during the second half of pregnancy. Folic acid requirements are doubled for women of child-bearing age to prevent the incidence of neural tube defects in the foetus. Conversion factors for carotenoids are under review, with the looming conclusion that servings of green leafy vegetables needed to meet vitamin A requirements would probably need to be at least doubled. In view of this uncertainty, we have only provided for “recommended safe intakes” rather than RNIs. Selenium is undergoing growing interest because of its properties as an antioxidant. The RNIs recommended from the FAO/WHO process for this micronutrient are in a lower range than that provided by the US/Canada process because the latter is calculated on a cellular basis, whereas the former are based on the more traditional whole body estimates. Are these “developments” or “new understandings” appropriate and applicable for developing countries? There is no clear answer based on our current knowledge, but the time may be coming when RNIs will need to be seen differently for developing countries, and based on developing country data. There may be a need to identify some biomarkers that are specific to developing country conditions. There is therefore an urgent need for research to be carried out in developing countries about their nutrient needs. The current situation also implies that the RNIs for the micronutrients of concern discussed above will need to be re-evaluated as soon as significant additional data becomes available. Guy Nantel FAO Coordinator for the expert consultation Food and Nutrition Division Kraisid Tontisirin Director Food and Nutrition Division FAO/WHO expert consultation on human vitamin and mineral requirements v CONTENTS Foreword i Participating experts xiiiii Background paper contributors xvii Background paper reviewers xix Consultants xxi Secretariat xxii Chapter 1 Introduction 1 Background 1 Terms of reference and process 1 Definitions of terms used 2 Report of the consultation 4 References 6 Chapter 2 Food-based approaches to meeting vitamin and mineral needs 7 Dietary diversification when consuming cereal and tuber-based diets 9 How to accomplish dietary diversity in practice 10 Practices which will enhance the success of food-based approaches 11 Delineating the role of supplementation and food fortification for nutrients which cannot be supplied by regular foods 12 Recommendations for the future 15 Future research 16 References 25 Chapter 3 Thiamin, riboflavin, niacin, vitamin B6, pantothenic acid and biotin 27 Thiamin 28 Riboflavin 31 Niacin 33 Vitamin B6 36 Pantothenate 38 Biotin 40 General considerations for B-complex vitamins 42 References 44 Chapter 4 Folate and folic acid 53 Role of folate and folic acid in human metabolic processes 53 Definition of populations at risk for folate deficiency 57 Delineation of dietary sources 57 Evidence on which to base a recommended intake 57 Differences in bio-availability of folic acid and food folate 59 Neural tube defects 59 Cardiovascular disease 60 Colorectal cancer 60 Upper limit 60 Future research 60 References 62 vi FAO/WHO expert consultation on human vitamin and mineral requirements Chapter 5 Vitamin B12 65 Role of vitamin B12 in human metabolic processes 65 Dietary sources and availability 65 Absorption 65 Populations at risk for and consequences of vitamin B12 deficiency 66 Vitamin B12 interaction with folate or folic acid 67 Assessment of vitamin B12 status 68 Evidence on which to base a recommended intake 68 Future research 70 References 71 Chapter 6 Vitamin C 73 Role in human metabolic processes 73 Overview of significant scientific information 74 Definition of population at risk 75 Dietary sources of vitamin C and limitations to vitamin C 76 Information used to derive dietary requirement of vitamin C 77 Future research 80 References 81 Chapter 7 Vitamin A 87 Role of vitamin A in human metabolic processes 87 Population at risk and consequences of vitamin A deficiency