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In to recent trials on rural school boys, we tested two schedules of B-complex vitamin supplements: a) therapeutic does for one month, b) low does (close to RDA) for one year (Table 3). Appropriate placebo groups were also included. Through in both trials, the supplemented children showed significant biochemical improvement, more than 50 percent continued to be in the deficient range for riboflavin and pyridoxine status as judged by enzymatic tests and guidelines reported in literature (3, 4)(Table 3). Thiamin deficiency was not a problem to start with, probably because of the low caloric intake in these children. The scatter in biochemical values was wide before and after supplementation and hence the data could not be utilized for deriving the interpretative guidelines for biochemical tests.     The reasons for persistent deficiency are obscure. Two possibilities need to be investigated : a) the utilization of vitamins was poor, either due to associated protein and calorie deficiency, or some other non-nutritional constraints such as metabolic losses due to infection, and b) inherent inter individual variation  due to genetic or other factors. Preliminary evidence on urinary excretion of riboflavin and morbidity, points to the first possibility.

Clinical impact of supplementation as assessed by prevention or cure of oral lesions was seen in the first trial where higher doses of vitamins were given for 1 month, but not in the second trial where RDA levels were given for one year.

In the second study, psychomotor testing was done. The supplemented children had superior performance in one of the psychomotor tests viz. Hand steadiness test. Thus, even in the absence of clear-cut clinical impact, some other functional impact may be seen. A weak correlation existed between the hand steadiness test and riboflavin status as judged by the EGR-AC. However, the data could not be used for deriving discriminatory guideline for EGR-AC on the basis of functional performance.

In a recent study from Gambia, Bates et al. (11) also could not normalize the EGR-AC values of rural pregnant and lactating women by meeting their riboflavin requirement. They conclude that the requirement of this community may be higher than hitherto recommended.

In conclusion, it can be said that though it may not be possible to develop ideal biochemical tests and clear-cut correlations between biochemical and clinical deficiency may not be always apparent, the value of such tests in detecting subclinical deficiency and establishing clinical diagnosis is indisputable.