Vitamins are essential nutritive inorganic elements required by the body in small quantities to maintain good health; they are particularly useful for growth and reproduction. A meal is not considered as balanced without vitamins, which are regarded as the body’s boosters of the body’s defense mechanism. Vitamins have also been known to facilitate the intake of other essential body nutrients. Too much intake of vitamins has a toxic effect in the body (Edmunds & Mayhew, 2004).
When ingested in very large doses, Vitamin A and Vitamin D can easily cause vitamin toxicity. This therefore calls for caution when taking these two vitamins. On the other hand, Vitamin C, biotin, pantothenic acid and riboflavin have a very low likelihood of causing toxicity even when taken in large quantities. An overdose of these vitamins is therefore not considered as toxic as an overdose of vitamins A and D.
Small quantities of folic acid go a long way in reducing the chances of one developing neural tube defects and even cancer (Hayes, 2007). When vitamin D is used in this case, it would cause irreversible vitamin toxicity, where calcium crystals will be deposited in the soft body tissues. This usually damages the lungs, kidneys, the heart and a number of other organs.
Niacin usually comes in two main forms namely nicotinamide and nicotinic acid, with either of the two being capable of satisfying an adult’s vitamin needs.
However, nicotinic acid can lead to a number of conditions if taken in large quantities, including liver damage, diarrhea, nausea and skin rashes (Omaye, 2004).
Vitamin E toxicity is known to cause double vision, constant headaches, a feeling of tiredness, and diarrhea in human beings. In animals it interferes with the absorption of the other fat soluble vitamins. A megadose of vitamin K can cause anemia in adults and nerve damage among infants. It may also lead to the deposit of pigments in the infant’s brain, which may lead to fatalities (Hayes, 2007).
Vitamin B12 is very essential in treating pernicious anemia, which is very common among the elderly and in middle age. However, taking too much of it increases the chances of one damaging his or her nerves (Omaye, 2004). Vitamin B6 is toxic at doses of about 1000 times the RDA, but when one stops usage; complete recovery could be achieved after two years.
Bearing in mind the narrow therapeutic window of oncolytic drugs, complementary and alternative medicine use tends to increase the risk of interaction between the drug and the clinically relevant herb anticancers (Tracy & Kingston, 2007).
It is, on the other hand, estimated that complimentary and alternative medicines anticancer drug interactions are the ones responsible for the toxicity of chemotherapeutic drugs (Tracy & Kingston, 2007).
The induction of drug metabolizing enzymes as well as ATP binding cassette drug transporters could be one of the best possible mechanisms behind the complimentary and alternative medicines anticancer drug interactions (Edmunds & Mayhew, 2004).
In general, the drug interaction with herbal products has very severe effects especially to cancer patients, hence there is need to find ways to curb the problem (Aronson, 2009). The solution to this problem may as well lie in the regulation of vitamin intake to just the right levels. More research should therefore be done in this direction to solve the problem once and for all.
References
Aronson, K. J. (2009). Meyler’s side effects of herbal medicines. Mosby: Elsevier
Edmunds, M. W. & Mayhew, M. S. (2004). Pharmacology for the Primary Care Provider, 2nd Edition, Mosby: Elsevier Health Sciences
Hayes, W. A. (2007). Principles and methods of toxicology: 5th Edition. London: CRC Press
Tracy, S. T. & Kingston, R. L. (2007) Herbal products: toxicology and clinical pharmacology. 2nd Edition. New York: Humana Press
Omaye, S. T. (2004). Food and nutritional toxicology. London: CRC Press