Les interactions entre les vitamines A, D, E et K : synergie et/ou compétition

Abstract

Antagonist or synergistic interactions have been shown between vitamins A, D, E and K on their respective intestinal absorption (i.e. for vitamins A and E), metabolism (i.e. for vitamins E and K) and biological effects (i.e. for vitamins A and D). Studies have variously indicated antagonistic, additive or synergistic effects of vitamin A in combination with vitamin D, occurring during hormonal ligand binding to their respective nuclear receptors and at multiple steps in cell. In vitro experimental studies have demonstrated that vitamins C and E, the main dietary antioxidants, can interact positively, and this has been confirmed as occurring in vivo. The putative interaction may be direct, via vitamin C ‘‘sparing’’ of vitamin E. However, the antioxidant effects of these two vitamins may operate within the context of an integrating system relying on many other vitamins and nutrients such as b-carotene, lipoic acid and ubiquinol. Any alteration, therefore, in the status of a single vitamin or nutrient could affect the status of other vitamin(s). It also appears that randomized trials aimed to investigate the protective effects of these nutrients by using supplements could not take in account the complexity of these interactions. Vitamin E interacts negatively with vitamin K. The mechanisms by which vitamin E interferes with vitamin K activity, especially blood clotting, are not known. The interference may involve metabolic pathways. Vitamin E may compete for the yet undiscovered enzyme involved in the conversion of phylloquinone (K1) to menaquinone 4 (MK-4, the most potent extrahepatic tissue vitamin K). Vitamin E competes with K1 for the hypothetical cytochrome P450 enzyme that v-hydroxylates the K1 side chain, thereby preventing its b-oxidation and its removal for MK-4 formation. Finally, vitamin E increases xenobiotic pathways that increase hepatic metabolism and excretion of all vitamin K forms.

Keywords

• vitamin A
• vitamin D
• vitamin E
• vitamin K
• antagonistic effects
• additive effects
• synergistic effects