Search

Ten healthy volunteers were used in two studies investigating the effect of short-term Brassica consumption on caffeine metabolism. In the first study volunteers were given three Brassica-containing meals, the last one 3 h prior to caffeine administration. In the second study volunteers were given two Brassica-containing meals and then fasted overnight before caffeine administration. In both studies the mean plasma half-life of caffeine was reduced by approximately 20% following a Brassica diet, suggesting that Brassica vegetables stimulate caffeine metabolism. When caffeine was given 3 h after the last meal, plasma caffeine concentrations over 6 h, were increased by up to 27% on the Brassica diet compared to controls. This may be due to a transient increased permeability of the intestine to caffeine, immediately following Brassica consumption. This effect was not seen in the second study where there was a 12-h period between the last meal and caffeine administration. There was large interindividual variation in the effect of the Brassica diet on caffeine metabolism.

The toxic and carcinogenic effects of many compounds depend on their activation to reactive molecules in the cytochrome P-450 system of the endoplasmic reticulum of cells. Changes in dietary input alter P-450 levels in different tissues and so alter toxicity. In this way, low protein diets protect against carbon tetrachloride poisoning. Fats, proteins, and nonnutrients such as flavones, antioxidants, and contaminants like DDT all affect P-450 levels. The activated molecules may be diverted from their target sites by inactivation processes, such as epoxide hydratase or glutathione trappin. This is also under nutritional control. Low protein diets render animals sensitive to acetaminophen by reducing glutathione levels. In the sequence of events leading from initial contact of toxin with organism to eventual cell injury or neoplasm, nutritional factors are of import at every stage. Assessments of the toxicity of chemicals that do not take into account the nutritional variable in man are likely to be incorrect.