The priority now being urged for specific programmes to prevent deficiencies of iodine, iron, and vitamin A comes from, first, the increasing understanding of their extent and far-reaching consequences. (Certain other micronutrient deficiencies e.g. those of vitamin D, zinc, fluoride and folic acid may be important problems in certain areas for certain population groups, but are not discussed here.) Mental retardation caused by iodine deficiency; the contribution of iron deficiency to anaemia, hence debilitation and excess mortality particularly in childbirth; and the effect of vitamin A deficiency in causing blindness, and on increased incidence and severity of infection, and possibly mortality - all these have led to a view that the modern world should not tolerate the persistence of these deficiency diseases.
At the same time, the existence of proven and low-cost methods27 for preventing these deficiencies adds powerfully to the case for controlling them widely and without delay. These options are briefly outlined below.
In the long run, iodine deficiency can be prevented (and has been for many years in most industrialized countries) by fortification of salt with iodine. This normally requires legislation, a centralized salt supply, and the necessary equipment, funding, and distribution systems. This method is being adopted in a number of developing countries, and requires sustained support and trouble-shooting technical problems.
In the interim, vulnerable individuals can be protected using iodized oil, administered by injection or orally. Single injections of iodized oil prevent deficiency for up to 5 years. Administration by mouth probably gives around 12 months' protection. Programmes to provide immediate cover are important while fortification is established, particularly in remote areas - and iodine deficiency often is concentrated in these - with particular emphasis on reproductive-age women to prevent mental retardation at birth, in its extreme form causing cretinism.
Preventing iron deficiency requires increasing the daily intake and absorption of this micronutrient, in contrast to iodine and vitamin A where periodic supplementation can work. Fortification is a long-term option, again adopted in many industrialized countries, for example using bread or sugar. Dietary change to increase iron intake and - crucial in this case - absorption, can be promoted by various means including public education, and will often gradually occur with economic development, but only slowly. Increased consumption of animal products and sources of vitamin C (to increase absorption) are needed, as well as lowering intakes of absorption inhibitors such as in certain cereal products, which is more difficult.
Distribution of daily supplements of iron tablets (usually ferrous sulphate) is therefore widely necessary to reduce the extent of anaemia, which is immensely prevalent and damaging, particularly in women in poor countries, where prevalences of 50% or more are commonly observed. The success of such programmes on the scale needed depends on a number of factors, many in common with other aspects of health (especially ante-natal) care and distribution of essential drugs. Constraints are common in supply and logistics, access to health posts or other distribution points, training of staff and communicating to recipients, adherence to the daily regime, anaemia diagnosis and treatment, and so on. Overcoming these requires sustained support. But the point is that there are no insuperable problems, the supplement itself is cheap and potentially highly cost-effective, and determined efforts to control iron deficiency can be expected to succeed, with enormous benefits especially for poor women.
Deficiency of vitamin A can be tackled by periodic distribution of large doses (e.g. as capsules every six months), by fortification, and by changing dietary patterns. Here again, both short- and long-term measures may be indicated, depending on circumstances. The benefits include reducing sickness, preventing blindness, and increasing child survival.
For young children in areas of vitamin A deficiency -particularly those at risk of measles - periodic distribution of oral vitamin A doses generally through the health (including immunization) or social services may be an important option. The doses are inexpensive and straightforward to administer. Here again, what is required is the decision to tackle the problem, supplies and distribution, training, public information, and monitoring.
Fortification is technically feasible - of sugar, for instance - although yet to be widely adopted in developing countries (in industrialized countries there is generally enough vitamin A available in the diet and fortification is unnecessary). Nonetheless, this is an option to be considered.
In many countries the overall food supply is adequate in vitamin A and its precursors (in many plant products). The issues are to do with feeding patterns, notably of young children, and absorption; the latter improves with increased intakes of fats and oils.
Increased income is associated with better vitamin A nutrition. In the interim success has been achieved through interventions such as nutrition education and promoting vegetable production through home gardens. These constitute useful options especially in areas where the deficiency is particularly common.
As results accumulate of studies currently under way on the effects of vitamin A supplementation on child survival - most so far showing a significant response -it can be expected that even greater attention will be directed to preventing this deficiency. The means exist, and need to be implemented.