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Prenatal Multivitamins and Iron: Not Evidence-Based

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When I was pregnant, I obediently took the iron pills and prenatal vitamins prescribed by my obstetrician. And I prescribed them for every pregnant patient I took care of as a family physician. I never questioned the practice. It seemed intuitively obvious that it was a good thing; we know pregnancy makes extra nutritional demands and depletes iron stores. It never occurred to me to question what I had been taught, because it seemed perfectly logical. I did question other things I was taught that didn’t seem so logical. In my internship, we were ordered to do episiotomies on every patient (the rationale was that it made birth less traumatic for the baby and prevented uncontrolled perineal tearing in the mother). I was severely chastised for omitting an episiotomy on a patient who begged me not to do one. She had had several babies and was stretchy enough to deliver easily without an episiotomy. In this case, my common-sense clinical judgment was vindicated by further research in the years after my internship; new evidence showed that routine episiotomies were of no benefit, practice changed in response to the new evidence, and episiotomies are no longer done routinely.

That was a long time ago. I have long since learned that even the most reasonable assumptions can be wrong. I happened to be right about episiotomies, but I might just as well have been wrong; and the only way to know whether a belief is true is to test it in controlled scientific trials. As Will Rogers said, “It isn’t what we don’t know that gives us trouble, it’s what we know that ain’t so.” It turns out that routine multivitamin and iron supplementation is not supported by any convincing evidence from scientific studies. And practice is changing. Recently, when one woman asked her OB what she should do about prenatal vitamins he pulled his wastebasket out from under his desk and said “put them there.” (more…)

Posted in: Herbs & Supplements, Nutrition, Obstetrics & gynecology

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Vitamins and Cancer Risk

One of the greatest triumphs of marketing over evidence was the incredible rise of vitamin supplement use in the 20th century. Supplement makers successfully created a “health halo” around vitamins, and taking your vitamins became a virtue, something mothers told their children to do. The evidence, however, does not tell such a simple story.

In recent years it has become increasingly apparent that there are unintended consequences to taking vitamin supplements, and in fact there may be a net negative health effect. This is especially true for those who are healthy and don’t need vitamins, and for those who exceed the recommend dosages.

A recent review of the last 20 years of literature on the subject, presented at the American Association for Cancer Research 2015 meeting, found an overall increased risk of cancer among vitamin users. Dr. Tim Byers presented the study, which echoes the result of a 2012 review that he and others published. He specifically refers to two famous studies showing an increased risk of cancer from vitamins.

The 2011 SELECT trial found an overall increased risk of prostate cancer among men taking vitamin E. (more…)

Posted in: Herbs & Supplements, Nutrition

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The benefits and risks of folic acid supplementation

Could a vitamin with proven benefits in one group cause harm to another? That’s the growing concern with folic acid, the vitamin that dramatically reduces the risk of neural tube birth defects such a spina bifida. Studies designed to explore the possible benefits of folic acid for heart disease, stroke and cancer are giving out some worrying signs: At best, folic acid is ineffective, and at worst it may be increasing the risks of some cancers. So what does this say about routine supplementation for the typical healthy individual, and its overall risk and benefit?

Folate (vitamin B9) is an essential nutrient found green, leafy vegetables, broccoli, peas, corn, oranges, grains, cereals, and meats. Folate has important roles in the synthesis of DNA, and consequently cell division. Significant folate deficiency can lead to macrocytic anemia. Folic acid, a synthetic form of folate, is used in multivitamins supplements because it is better absorbed.

Folic acid’s benefits in pregnancy are well documented. Supplementation before conception, and in the first few weeks of pregnancy, significantly and substantially lower the risk of several different birth defects, including neural tube defects (NTDs). The neural tube is the embryonic precursor to the brain and spinal column. NTDs include very serious defects like spinal bifida and anencephaly, birth without part of the brain.

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Posted in: Clinical Trials, Epidemiology

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