Food Toxicology 2(2+0)

Lesson 8 : Factors That Influence Toxicity

Vitamins

1. Folate
   Folate is required in toxicant metabolism and chemical detoxification, particularly during induction of oxidases (protein synthesis). Folate deficiency leads to loss of drug metabolism, loss of enzyme induction, hyperchromic anemia, and teratogenic effects in offspring. Birth defects (neural tube) associated with folate deficiency have led to the increased recommendation of the vitamin by the medical community for women of childbearing age. In rats, folate is required for increased turnover of toxicant-metabolizing enzymes during chronic drug administration.

2. Thiamine (Vitamin B1)
   Increased cytochrome P450 activity, aminopyrine metabolism, and ethylmorphine metabolism are seen in dietary deficiency of thiamin. Thiamin deficiency is inversely related to increases in cytochrome P450 activity; increases in induction of ROS, lipid peroxidation, and which destroy cytochrome P450. Thiamin deficiency in humans and animals is characterized by anorexia, weight loss, cardiac involvement, and neurological involvement.

3. Vitamin E
   Tocopherols act to protect microsomal membranes against lipid peroxidation. A lack of tocopherols results in a loss of cytochrome P450 and loss in drug metabolism. Vitamin E protects against chronic liver damage induced by carbon tetrachloride and increases hepatic enzymes. Also, there is strong evidence that vitamin E, particularly with selenium, inhibits mammary tumors. Vitamin E deficiency has been shown to increase the susceptibility of laboratory animals to oxidative injury from a variety of air pollutants such as ozone and nitrogen dioxide. It is likely that the most important function of vitamin E is its ability to scavenge free radicals and prevent oxidative damage to crucial biomolecules.

4. Vitamin A
   Retinoids have a protective function against chemical carcinogens, probably by inhibiting the bioactivation of carcinogens or binding of foreign compounds to microsomal proteins. Retinols decrease the mutagenicity of cooked food heterocyclic amines by preventing their activation. Although carotenoids are previtamin A compounds, they have their own unique property of inhibiting mutagenicity of aflatoxin B1 independent of vitamin A.