Normal Healthy Human Studies:

Nutrition and Intelligence in Children

by Ward Dean, M.D. and John Morgenthaler

In the studies presented here, simple nutritional supplementation produced significant increases in intelligence and academic performance in school children.

The latest study, conducted by Stephen Shoenthaler and colleagues, tested 615 schoolchildren from Stanislaus County, California. The children were randomly assigned to one of four different groups receiving various vitamin-mineral supplements on a triple-blind basis (the students, testers and scientists did not know which group each student had been assigned to). The study lasted 12 weeks and was designed to examine whether the intelligence increases seen in earlier studies of children were due to a general effect on most children, or whether it was due primarily to effects on a smaller subset of children suffering from sub-clinical nutritional deficiencies.

The first test group received only a placebo. The second group received a 50% RDA supplement (designed to bring nutritional status up to minimal RDA levels). The third group were given a 100% RDA supplement, and the fourth a 200% supplement (of most, not all, vitamins and minerals—see table).

Analysis of the test results revealed a 3.7 point relative increase in the non-verbal I.Q. scores with the 100% RDA group. The 50% and 200% groups experienced smaller but significant relative increases of 1.2 and 1.5 points respectively. Verbal I.Q. scores were unchanged and may have actually decreased slightly.

These result suggest that vitamins may have an inverted-U-shaped dose-response curve like many other cognitive drugs. This study suggests that optimum intake in adolescents is between one and two times the RDA. The study also suggests that a significant proportion of “normal, healthy” children are in fact sub-clinically nutritionally deficient, even though they show no overt signs of physiological pathology. This study confirms the earlier work of Sandstead [1986] and Cherkin [1987] which suggest that mental dysfunction is one of the first manifestations of nutritional deficiency. Current definitions of nutrition deficiency are based on physiological observations.

Previous Research

The connection between nutrition and mental performance has been investigated for decades. Children who were malnourished as infants perform more poorly on mental performance tests than children who were adequately nourished as infants [Cravioto and Delicardie, 1970]. Even infants themselves exhibit enhanced mental performance [eye contact with figures on a screen] when adequately nourished [Rush, et al., 1980]. Intelligence (or mental impairment) has been associated with nutrient supplements, skipping breakfast, sugar, food additives, toxic metals, and malnutrition. Schoenthaler’s book, Improve Your Child's I.Q. and Behavior provides excellent recommendations based on this research.

In 1988, Drs. David Benton and Gwilym Roberts published a 9-month study of 90 English schoolchildren (50% boys and 50% girls), 60 of whom took either a placebo or a vitamin supplement, and 30 of whom took no tablets. According to 3-day dietary questionaires, most children were receiving close to the recommended daily allowance through their normal diet. About 10% of the children consumed less than 25% of the RDA.

Between the start of the experiment (September) and the end (June), verbal intelligence had increased 7 points in the supplemented group and 6 points in the control group. The non-verbal intelligence, however, had increased 8 points in the supplemented group and only one point in the control group.

Conclusion

Verbal intelligence tests are thought to reflect “crystallized” abilities which are strongly influenced by increased vocabulary skills. Non-verbal intelligence tests are thought to reflect “fluid” mental abilities which are not so skill oriented. It is these non-verbal mental abilities which respond to supplementation.

As far as the old controversy about cognitive effects of dietary supplementation is concerned, Schoenthaler and colleagues say “there are such effects, they act in a predictable manner, and they occur in children who would normally be considered as receiving a sufficient diet” [1991]. This is in full agreement with Benton and Roberts conclusion that children with a “typical” British diet respond to supplementation with “an increase in their non-verbal intelligence.”

Both the short-term study of Schoenthaler, et al., and the short-term study of Benton and Roberts indicate that vitamin and mineral supplementation causes significant improvement in children's intelligence and academic performance. The official supposition that normal school diets provide fully sufficient nutritional support for children is incorrect. Supplementation is a convenient and cost-effective means to ensure above-RDA-level nutrition and enhance the quality of our educational system. Benton and Roberts are convinced that, in our present educational environment, “dietary deficiencies are hampering neural function [of unsupplemented] children.”

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References

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