Risk evaluation of increased intake of vitamin C and E

B. Gassmann, Nuthetal

The ‚classical‘ toxicological procedure of fixing safe intakes or Tolerable Upper Intake Levels is based on the mathematical model of a ‚risk assessment and food safety‘ concept. Accordingly, identified undesirable effects on humans health are related the nutrient dose ingested (hazard characterization).

Uls are derived from the dose-effect curves thus obtained, combined with toxicological characteristic values (LOAEL, NOAEL) and factors of uncertainty (UL). Although data of animal experiments may also be included, the results of the classical toxicological procedure often are unsatisfactory because of insufficient data for many nutrients.

Besides toxicological characteristic data, this applies to the bioavailability of nutrient quantities ingested with the daily diet, with enriched food and with food supplements and the dependence of these on physiological conditions and to interactions with other nutrients or food components. Insufficient knowledge of toxicological characteristic data and of hazard potentials as well as uncertainties regarding the mode of derivation have led to different levels of prolonged safe intakes in USA and Europe: vitamin C 2000 and 1000 mg/day, vitamin E 1000 and 540 and 300 mg all-rac tocopheryl acetate resp. or 200 mg alpha-tocopherol equivalents/day.

Recently tolerable upper intake levels are also calculated from epidemiological studies and disseminated to the non-technical press: e.g. 300 mg/day for vitamin C supplements and postmenopausal diabetics, or 400 I.U. vitamin E (264 mg RRR-a- or 364 mg all-rac tocopheryl acetate) to prevent an increase in general mortality. A justifiable derivation of Uls in this way is doomed to failure because it is impossible for reasons of organization and financing to conduct long-term intervention studies in large random samples of different population groups with graduated nutrient doses to determine dose-effect relationships using clinical key and endpoints or biomarker profiles for checks.

Keywords: Vitamin C / vitamin E / increased intake / risk evaluation

Sie finden den Artikel in deutscher Sprache in Ernährungs-Umschau 02/05 ab Seite 52.