Drugs may act in various ways to impair proper nutrition: by hastening excretion of certain nutrients, or by interfering with the body’s ability to convert nutrients into usable forms. Nutrient depletion of the body occurs gradually, but for those taking drugs over long periods of time, these interactions can lead to deficiencies of certain vitamins and minerals, especially in children, the elderly, those with poor diets, and the chronically ill.
Some drugs inhibit nutrient absorption by their effect on the bowel wall. Among these are colchicine, a drug prescribed for gout, and mineral oil, an ingredient used in some over-the-counter laxatives.
A number of drugs affect specific vitamins and minerals. The antihypertension drug hydralazine and the antituberculosis drug INH can deplete the body’s supply of vitamin B6 by inhibiting production of the enzyme necessary to convert the vitamin into a form the body can use, or by combining with the vitamin to form a compound that is excreted.
Similarly, anticonvulsant drugs that are used to control epilepsy can lead to deficiencies of vitamin D and folic acid because they increase the turnover rate of these vitamins in the body.