Birth-control pills are currently being used by an estimated 100 million women throughout the world, not just as a way to prevent conception, but also as a treatment for a variety of disorders from osteoporosis to endometriosis. Despite "The Pill's" widespread use, or perhaps because of it, debate continues over its potential side effects, including the possibility that it changes a woman's requirements for some vitamins and minerals.
Folic acid, Vitamin A, Vitamin B-12, Vitamin C, copper, iron and zinc have all been mentioned as being affected by the hormones in oral contraceptive agents. But either the evidence is fragmentary or the alteration is not considered to be of clinical significance.
The nutrient that perhaps has been studied the most extensively in connection with birth-control pills, however, is Vitamin B-6. In the late 1960s, a few years after the pill was introduced to the general public, investigators began to report that some oral contraceptive users were deficient in B-6. However, further research seemed to contradict this finding. That left women in doubt as to whether they should be taking B-6 supplements while on the pill. Recent studies, which examined the different methods used in obtaining these results, help explain the apparently contradictory findings.
Many of the tests for nutritional status are indirect. That is, they are not a direct measurement of a vitamin's concentration in the blood or urine. Instead, they measure the ability of whatever amount of vitamin is present in the body to perform that vitamin's special function.
One such procedure is a "load test." The person is given a large amount of a compound whose metabolism involves, in this case, a step that is dependent on Vitamin B-6. If she is deficient, a less than normal amount of that compound is metabolized, or broken down. Obviously, then, fewer breakdown products will find their way into the urine.
Two amino acids, both of which require a Vitamin B-6 dependent enzyme for their metabolism, traditionally have been used in load tests to measure Vitamin B-6 status. One is methionine and the other is tryptophan. Only the tryptophan load test really indicates B-6 deficiency, even when other measures of B-6 status (such as blood and urine levels of the vitamin and its metabolites) are within normal limits. Recent evidence suggests that the explanation for the discrepancy lies in the fact that while both amino acids require B-6 for their metabolism, the estrogens in the pill seem to lower the activity only of that B-6 dependent enzyme necessary to metabolize tryptophan.
So where does all this leave the birth-control pill user? Technically speaking, she is probably not at risk of developing a Vitamin B-6 deficiency. But it is thought that some of the pill's side effects, such as mental depression and fatigue, may be the result of altered tryptophan utilization in the body. In addition, some of our requirement for niacin, which is necessary for energy metabolism, is met by synthesis from tryptophan.
All of the evidence is not yet in on this subject, so the question of the need for Vitamin B-6 supplementation above the Recommended Dietary Allowance of 2 milligrams a day for every woman on birth-control pills remains unresolved.
A woman should consult her gynecologist if she has any questions about her own B-6 intake. In general, it certainly seems wise to recommend that women on oral contraceptive agents make a special effort to include in their diet good sources of the vitamin. Among the best sources are meat, poultry, green leafy vegetables, potatoes and whole grains.
It is important to point out, in so far as grains are concerned, that about 75 percent of the Vitamin B-6 is removed in milling of white flour and is not replaced in the enrichment process. To be sure you are getting all the B-6 you can, use whole-grain breads and cereals as often as possible.
Copyright (c) 1983, The Washington Post Co.