nos-trum. pronunciation: \nos'-trum\. noun. Etymology: Latin, neuter of noster our, ours.
1. a medicine of secret composition recommended by its preparer but usually without scientific proof of its effectiveness.
2. a usually questionable remedy or scheme.
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Friday, October 22, 2010

Another Supplement Claim Bites The Dust - Folic Acid

Folic acid is prescribed for pregnant women.  Convincing evidence exists that it prevents a certain birth defect in the fetus.  However, claims that folic acid prevents cancer or heart disease look like a wash.

USA Today (Oct 18) points the way to a new study of folic acid, published in the Archives of Internal Medicine, was a meta-analysis.  I've talked about this before:  meta-analyses gain their power from combining multiple published studies into one, increasing the data available on a given question.  Their weakness is that no two studies are ever exactly the same; either the researchers didn't use the same population, or a different dose, or they didn't study the effect for the same period of time, etc.  It's a challenge for scientists to take studies with minor differences and decide how to select the data that can be meaningfully compared, even if the broad question is the same.  In some cases they have to exclude studies because they are just too different.

Folic acid is a vitamin that is prescribed specifically in pregnancy to prevent spina bifida, but is present in most multi-vitamins as a part of the "shotgun" approach to making sure you aren't "vitamin deficient."

[Don't get me started on the concept of vitamin deficiency.  Unless you have some disease or other physiologic abnormality (like starvation or alcoholism) it's very hard to be deficient in a vitamin.  All the claims that processed foods destroy vitamins to such an extent that we don't get enough have never been substantiated.]

You might ask how researchers could suspect that folic acid could help heart disease and cancer.  Here's the logic:  a protein building block (amino acid) named homocysteine--found in the blood--has been measured at higher levels in those patients who are at risk for heart and other problems.  Taking folic acid lowers the level of homocysteine.  Therefore, maybe taking folic acid will lower the risk of disease.

I've written several times about the danger of seeing things too simply.  The fact that homocysteine is higher in those at risk doesn't mean it's the cause of the risk.  It may just be a coincidence.

The study in question here followed 37,000 people for five years, with and without folic acid.  There were no differences in the rates of heart disease, diabetes, or cancer.

Now, you can argue that we should study the impact for 10 or 20 years.  For cancer, it's conceivable that a longer "incubation" period could bring about a measurable effect.  For example, cigarette smoking doesn't cause cancer in five years.  But for heart disease, if you don't see some kind of population impact after five years, it's very unlikely that going longer will show anything different.

For Onion Peelers,
Folic acid allocation yielded an average 25% reduction in homocysteine levels. During a median follow-up of 5 years, folic acid allocation had no significant effects on vascular outcomes, with rate ratios (95% confidence intervals) of 1.01 (0.97-1.05) for major vascular events, 1.03 (0.97-1.10) for major coronary events, and 0.96 (0.87-1.06) for stroke... There was no significant effect on the rate ratios (95% confidence intervals) for overall cancer incidence (1.05 [0.98-1.13]), cancer mortality (1.00 [0.85-1.18]) or all-cause mortality (1.02 [0.97-1.08]) during the whole scheduled treatment period.

And as a final warning, one author, Dr. Jeffrey A. Tice,
suggested that consumers be cautious about high-dose supplements. "High doses of other vitamins with a strong scientific rationale for long-term health benefits, such as the antioxidants vitamin E and beta carotene, are now known to be harmful," Tice said.  "Be wary of the current enthusiasm for vitamin D and omega-3 fatty acids until large randomized studies are completed," he added. "The best way to optimize your health is to exercise regularly, eat a nutritious diet, avoid smoking and maintain a healthy weight." (USA Today)
That says it all.

Doc D

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