We examined plasma choline changes after ingestion of diets composed of common foodstuffs, with choline contents bracketing the average daily intake in the American diet, and ingestion of diets supplemented with exogenous purified lecithin. A diet with low choline content did not increase plasma choline concentrations; a diet with high choline content doubled plasma choline levels. A lecithin-supplemented (25 gm; 80% phosphatidylcholine) low-choline diet increased plasma choline levels 400%. These findings indicate that normal diets cause only small elevations in plasma choline; purified lecithin supplements are likely to have greater effects in treating neurologic diseases.