Vitamins, iron, and physical work.

Combined marginal deficiencies of iron, vitamin C, and B-group vitamins are widespread in developing countries. An understanding of the functional implications poses a continuing challenge, both for the development of new techniques of investigation and for the design of effective intervention programmes. Practical intervention in developing countries also needs to take account of the interactions of micronutrient status and disease susceptibility. It is becoming clear that combined deficiencies of certain vitamins, or of iron and vitamins, although less severe than those causing the lesions of classic clinical deficiency, can seriously reduce work performance. Riboflavin, particularly, has a special relation with iron economy.