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Perspectives from Micronutrient Malnutrition Elimination/Eradication Programmes
Micronutrient malnutrition cannot be eradicated, but the elimination and control of iron, vitamin A and iodine deficiencies and their health-related consequences as public health problems are currently the targets of global programmes. Remarkable progress is occurring in the control of goitre and xerophthalmia, but iron-deficiency anaemia (IDA) has been less responsive to prevention and control efforts. Subclinical consequences of micronutrient deficiencies, i.e. "hidden hunger", include compromised immune functions that increase the risk of morbidity and mortality, impaired cognitive development and growth, and reduced reproductive and work capacity and performance. The implications are obvious for human health and national and global economic and social development. Mixes of affordable interventions are available which, when appropriately adapted to resource availability and context, are proven to be effective. These include both food-based interventions, particularly fortification programmes, such as salt iodization, and use of concentrated micronutrient supplements. A mix of accompanying programmes for infection control, community participation, including education, communication and information exchange, and private sector involvement are lessons learned for overcoming deterrents and sustaining progress towards elimination.
Micronutrients are essential vitamins and minerals that are needed in small amounts for various physiological functions, but which cannot be made in sufficient quantities in the body. Although several nutrients meet this definition, only three -- iron, vitamin A and iodine -- are currently major targets for public health programmes to control the deficiency and prevent any health-related consequences. Other micronutrient deficiencies, e.g. zinc, folate, and possibly vitamin B12, could become of public health concern as more is learned about their prevalence and health consequences. Because the body cannot be stimulated to produce essential micronutrients or be made less dependent on them, they must be provided regularly in the food or through supplements. The need for some micronutrients, however, can be lessened by correcting any factors that decrease efficient absorption, utilization and conservation, e.g. by menu adjustments to improve bioavailability and control of infectious disease.
From a global perspective, micronutrient malnutrition cannot be eradicated and is unlikely to be eliminated, as defined by zero incidences, even if control measures are continued. But the problem can be reduced to an acceptable public health level by deliberate efforts, which will need to continue for the foreseeable future. Using this definition of elimination, i.e. elimination as a problem of public health significance, iodine-deficiency disease (IDD) is on the horizon for elimination, followed by vitamin A deficiency (VAD) and iron deficiency (ID). A range of possible interventions exist for the elimination of these three deficiencies, some of which could be linked to other public health efforts, e.g. immunization programmes that include distribution of supplements to vulnerable groups, parasite elimination programmes aiming to improve efficiency of iron metabolism, and diarrhoea control programmes that enhance vitamin A conservation. Depending on the mix of control strategies, the effort applied to each, and the prevailing social and economic levels of development, the elimination of other micronutrient deficiencies could also be addressed.
Magnitude of Micronutrient Malnutrition
It is fallacious to estimate the magnitude of a health problem due to micronutrient malnutrition using extant signs of deficiency. This approach was characteristic of pre-1990 thinking and did not excite political concern or broad-based interventions. While relatively few persons are clinically affected, subclinical deficits -- "hidden hunger" -- are more pervasive, and include consequences that potentially compromise immune functions (morbidity and mortality, cognitive development (school performance and mental achievement) and growth, reproductive and work capacity, and performances (achieving potentials and productivity). The consequences of micronutrient malnutrition therefore extend beyond individuals and families to whole communities and nations. The magnitude of the problem is reasonably firm when estimates are based on clinical signs but less firm when based on those whose health is compromised by subclinical effects. Early in the 1990s, WHO estimated that deficiencies of iron, iodine, and vitamin A influenced the health of 2000 million, 1500 million, and 250 million persons, respectively; often these deficiencies overlapped in the population groups affected (1).
Causes and Consequences
Signs of micronutrient deficiencies have been noted in ancient art and literature, and efforts to treat and control the problems are recorded in medical lore that long preceded an understanding of their basis (2). Through the ages, but particularly during the twentieth century and especially the last quarter of this century, scientific discoveries have elucidated the causes and broad-ranging consequences of deficiencies of iron, vitamin A, and iodine. Epidemiological studies have identified vulnerable groups and factors associated with prevalence, and have provided reasonable global prevalence estimates. National and community intervention trials have demonstrated effective, affordable, population-based solutions. None the less, micronutrient malnutrition has not been eliminated as a global problem. The most notable barriers to elimination are not the lack of scientific understanding but operational deterrents, including absence of political resolve at all levels (not just at the top), ineffective use of financial and human resources, and lack of intervention strategies packaged in a mix of validated effective programmes with appropriate effort given to each intervention. The deterrents can be overcome by deliberate global and local efforts. This conference is an important global effort to generate resolve, resources, and a framework for developing, implementing and monitoring appropriate strategies for universal sustained disease elimination. However, it is unlikely that a "one-size-fits-all" global solution will be found at national and local levels. The exception may be iodine-deficiency disorders, which are showing a remarkable response to universal salt iodization (USI). For vitamin A and iron deficiencies, however, successful elimination will be sustainable only when people are able to procure and are willing to consume diets, including fortified foods, that contain micronutrients in adequate quantity and quality, or to procure supplements during periods of increased physiological need or other difficult nutrition situations.
Progress Towards Control
Global programme initiatives taken in the last decade are making an impact. Recent monitoring shows progress in control of clinical and subclinical forms of micronutrient malnutrition, particularly of iodine and vitamin A deficiencies (2,3). Goitre and xerophthalmia rates -- markers of clinical deficiency -- are declining, and shifts in urinary iodine concentrations and serum retinol distribution levels -- markers of subclinical deficiencies -- are shifting towards adequate levels, especially for iodine. Unfortunately, there is less evidence of global progress in controlling iron deficiency and iron deficiency anaemia (IDA). However, the true magnitude of global progress during the 1990s has been inadequately evaluated because there are a limited number of post-intervention, repeat biological assessment surveys, particularly for vitamin A and iron (4). For iodine, post-intervention surveys, especially in Latin America, show that IDD has been eliminated in several countries, e.g. Bolivia, Ecuador and Peru, and that the global prevalence has been reduced from about 30% early in the decade to 14% in 1997.
Corroboration of progress comes from process indicators (usually easier to monitor than biological indicators), which show growing programme-coverage achievements for both iodine and vitamin A (4). Control programmes for IDD in developing countries began with the use of iodine concentrate (initially by injection, and later orally), through one-to-one delivery programmes with slow and costly progress. More recently, accelerated and cost-effective progress has been achieved through USI in places where this programme has been mandated, monitored, and enforced, even at the level of community managed enterprises in hard-to-reach areas. Iodized salt is now reaching remote areas in developing countries, where only in isolated situations and emergencies is there a need for injection or oral delivery of concentrates. Sustained control, however, depends on institutionalizing salt iodization, product quality assurance, and continued effective surveillance.
Progress towards control of xerophthalmia is not easily attributed to a single intervention approach. Periodic universal or targeted distribution of high-dose supplements is the single most used intervention approach and coverage has increased and undoubtedly contributed towards control. Although the cost of the supplement is small (US$ 0.02-0.03), the human resource cost to achieve and sustain high coverage on a repetitive basis is considerable and competes with other health service needs. The recent linking of vitamin A distribution to national immunization days (NIDs) focused on poliomyelitis eradication or to measles immunieation, supplemented by a mid-year campaign (micronutrient days), has achieved high coverage (4). However, the sustainability of a campaign approach is in question because special immunization days are expected to be phased out, and because campaigns to support single health issues that must be repeated biannually are costly in money and manpower. Even in Indonesia, where vitamin A supplements have dominated national control efforts since 1974 and xerophthalmia, i.e. clinical deficiency, was declared to be under control in 1994, low serum retinol levels have persisted among over 50% of preschool-aged children. Thus, to rid a country of all the consequences of VAD, i.e. to eliminate it as a public health problem, requires a more diversified strategy, including control of infectious disease and improvement of the diet (5).
There is little evidence of global progress in controlling ID -- or even IDA -- in developing countries where prevalence rates are high. Lack of compliance with daily supplementation regimens, and inhibitors to bioavailability from local foods and fortified products have been major, but potentially surmountable, constraints. In some countries, such as Venezuela, iron fortification of wheat and corn flour has effectively halted a trend towards increased prevalence of deficiency due to inadequate food consumption as a result of a declining economy (6). However, the general level of bioavailability of iron from Venezuelan diets is considerably greater than that in, for example, South Asia, where fortification alone is unlikely to control the problem. Indeed, the wide range in the bioavailability of non-haem iron from diets typical of different cultures where anaemia is prevalent again argues for broad-based interventions, which in many situations would require attacking the contributing causes such as hookworm, schistosomiasis and malaria infections.
Lessons from ongoing programmes
The major factors noted above for progress, or lack thereof, in elimination of micronutrient malnutrition argue for holistic strategies. Such strategies usually require a mix of direct and indirect interventions based on modifications in the quantity and quality of diets, including use of fortified food products, supplementation, and public health measures, as well as education and awareness campaigns (5). On the surface the case for control of IDD would appear to be an exception, i.e. a single mandated fortification programme applied in underdeveloped countries appears to have worked. And, based on experience in industrialized countries, such as the USA, Switzerland, and Austria, where salt iodization has controlled IDD for over half a century, the success will be sustainable as long as the control measure continues. The tenuous political and economic circumstances existing in many developing countries, however, and current experience in some of them, confirm that legislation alone may be inadequate unless coupled with demand creation and change in human behaviour. Information, education, and communication (IEC) are important at political and consumer levels to sustain support for enforcement, quality control, and surveillance.
Are there other lessons from the remarkable success in moving towards IDD elimination that are applicable to other micronutrients? To consider this question, it is prudent to compare briefly the epidemiology of the micronutrient deficiencies as relevant to selection of intervention measures. In addition to fortified food products, increasing the quantity or variety of food grown locally in endemically deficient areas can contribute to elimination of both vitamin A and iron deficiencies, but not iodine. Controlling infectious diseases will have a minor influence on the prevalence of IDD or its severity because ingested iodine is readily absorbed and assimilated even in the presence of illness, and virtually irrespective of other food items. In contrast, disease control and food selection and preparation will significantly influence absorption and utilization of both vitamin A and iron. For all three micronutrients, past failures have led to an awareness of the importance of IEC strategies to accompany all interventions, even those of mandated fortification. Where consumers have a choice they must be convinced that the fortified products bring benefits to them, and where they do not have a choice, i.e. mandated universal fortification, politicians must continually be reminded of the benefits -- political, economic and health -- of effective programmes and their continuation even when national financial difficulties occur. A very recent example comes from the mandated, universal vitamin A sugar fortification legislation in Guatemala, which was temporarily rescinded in early January 1998 for political rather than health reasons. Previously, sugar fortification had also been stopped for economic reasons and it took several years to reinstate the programme. Fortunately the recent stoppage was temporary because a public and international outcry resulted in a quick reversal of the decision that came forth from an informed group of advocates and consumers. Hence, I argue that IEC is a crucial part of strategies for sustainability.
Because the etiology of vitamin A and iron deficiencies are more complex than for iodine, it is less realistic on a global basis to hope for similar success from fortification alone for the control of vitamin A and iron malnutrition, or to rely only on repetitive distribution of high-dose nutrient supplements. Both approaches are likely to be needed in the elimination battle. Solutions based on food production and dietary diversification and modification, which also have proven effective in some circumstances, have received least support as interventions partly because they are difficult to monitor and evaluate, require more resource inputs, take longer to implement, and are slower to demonstrate improvement in micronutrient status. None the less, recent studies demonstrate feasible means to speed the process of dietary diversification through well-designed intensive social marketing and education techniques that include building support structures to reinforce behavioural changes. The studies showed improved micronutrient status sustained after the intensive intervention had terminated. A key element to success has been community participation.
This analysis would suggest that the lessons from IDD control that are transferable to other micronutrients apply primarily to fortification process issues, including forming lasting government-private sector partnerships which respect the need for incentives and corporate benefit, in addition to creating a sense of social responsibility involving IEC. In contrast, more limited information from food-based programmes indicated that people participation and ownership are key elements if changed behaviours are desired outcomes.
I challenge programme planners and implementers to analyse the problem of elimination of micronutrient malnutrition based on the broadly accepted premises and global facts shown below.
Control of some micronutrient deficiencies has been a by-product of economic, social, and ecological development, or the equitable distribution of social and economic resources, but these development processes are often slow to evolve in the developing world. It is unacceptable, however, to allow the consequences of micronutrient malnutrition to continue where development is slow because affordable solutions are available. Therefore, although elimination of micronutrient malnutrition should be seen as a development issue, it can be facilitated through deliberate intervention efforts, including -- but not limited to -- the use of vitamin and mineral supplements. The challenge is to select the correct mix for every situation.
* Food and Nutrition Board, Institute of Medicine, National Academy of Sciences, Washington, DC 20418, USA.
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