Food dyes produce minimal effects on locomotor activity and vitamin B-6 levels in postweanling rats.

We investigated the effects of food dye consumption on locomotor activity, brain neurotransmitters, tissue vitamin B-6 levels, and hepatic cytochrome P-450 concentrations in postweanling rats. Animals were individually housed in stabilimeter-type activity cages for 4 1/2 weeks, and fed ad libitum a semipurified basal diet containing graded levels (4, 2, 1, 0.5 or 0%) of a blend of all seven Food, Drug and Cosmetic (FD & C) food dyes. Rats in the 4% dye group were significantly (P less than 0.001) less active during the first 3 weeks of dietary treatment, but no significant differences existed among groups during the final 10 days. Similarly, although dye ingestion depressed food intake (P less than 0.0025) and body weight (P less than 0.05) when averaged for all animals, the differences among groups disappeared by the last week of the experiment. Postmortem tissue analyses revealed no significant effect of dyes on brain tissue levels of serotonin, dopamine, norepinephrine, 5-hydroxyindoleacetic acid or homovanillic acid. Moreover, no significant differences were detected in either plasma and brain tissue levels of pyridoxal phosphate or in hepatic cytochrome P-450 concentrations. These results demonstrate that animals may adapt to the chronic consumption of food dyes and do so with minimal evidence of toxicity. Our data also suggest that previously reported behavioural abnormalities attributed to food dyes are probably unrelated to altered vitamin B-6 metabolism.