Adverse effects of vitamin E by induction of drug metabolism

Abstract

Observational studies with healthy persons demonstrated an inverse association of vitamin E with the risk of coronary heart disease or cancer, the outcome of large-scale clinical trials conducted to prove a benefit of vitamin E in the recurrence and/or progression of such disease, however, was disappointing. Vitamin E did not provide benefits to patients with cardiovascular diseases, cancer, diabetes or hypertension. Even harmful events and worsening of pre-existing diseases were reported, which are hard to explain. Since vitamin E is metabolized along the same routes as xenobiotics and induces drug-metabolizing enzymes in rodents, it is hypothesized that a supplementation with high dosages of vitamin E may also lead to an induction of the drug-metabolizing system in patients that depend on drug therapy. Compromising essential therapy might therefore outweigh any benefit of vitamin E in patients. It is recommended to work out at which threshold the drug-metabolizing system can be induced in humans before new trials with high dosages of vitamin E are started.

Intake of Medication and Vitamin Status in the Elderly

“…Vitamin E has been promoted as a strategy to prevent atheroscleosis, cardiovascular disease and cancer due to its properties such as inhibition of oxidation and inflammation, increasing release of prostacyclin, promoting blood vessel dilatation and reducing platelet aggregation [5,41]. There are, however, conflicting results on the benefit of vitamin E in the recurrences and/or progression of such diseases, and even worsening of pre-existing diseases, which is hypothesized to be due to interactions of vitamin E and the drug-metabolizing system, has been reported [42]. …”

Disruption of Vitamin E and Butylated Hydroxytoluene Antioxidant Function in Response to Paraquat-Induced Chromosomal Damage in Cultured Anuran Leukocytes

“…On the other hand, Brigelius-Floh [5] indicated that vitamin E does not always have beneficial effect on some of diseases such as cardiovascular diseases, cancer, diabetes and hypertension. Moreover, vitamin E in combination with the initiators azo compounds, Cu 2+ , was reported to enhance oxidation of human low density lipoproteins [1][2][3][4].…”

“…Moreover, vitamin E in combination with the initiators azo compounds, Cu 2+ , was reported to enhance oxidation of human low density lipoproteins [1][2][3][4]. These findings showed that the initiators are required for induction of vitamin E pro-oxidant activity [1][2][3][4][5].…”

Nutrigenómica: Revelando Los Aspectos Moleculares De Una Nutrición Personalizada

“…La activación de estos citocromos transforma al α-tocoferol en carboetil-1-hidroxicromano (CEHC), el que es conjugado con ácido glucurónico. El exceso de CEHC activa la expresión de enzimas que metabolizan drogas que se utilizan en la quimioterapia de pacientes cancerosos, con lo cual disminuye drásticamente la efectividad de dichas drogas (78).…”