Vitamin supplementation: gilding the lilly

Quite a while back Time Magazine did a cover story on the exciting potential for vitamin supplementation in preventing , maybe even curing, various conditions. In the interest of the "equal time" policy whereby politicians of differing stripes are given equal opportunity to vent their spleen over the airwaves, it only seems fair to look at what the Time story, and many similar articles in the intervening time, didn't say.

To begin with, there's never been a study of normal, healthy people that showed lower disease incidence or increased longevity in the recipients of supplements. Not only that, the one study that looked at the effects of giving mega-doses of vitamin E to the elderly found a two-fold mortality rate in the pill poppers. This doesn't prove that vitamin E hastens one's demise, but it should at least give pause to the lemming -like rush to supplementation. True enough, there is some pretty good evidence that the incidence of certain cancers and some forms of heart disease might be reduced by large doses of some vitamins. On the other hand, there are equally convincing pieces of research showing that these same supplements may, in fact, increase the risk of other forms of cancer and heart disease. This is not, however, the kind of stuff about which people want to read.

As a for instance, let's consider the ten percent of the population that, often unknowingly, carries a gene for the condition heterozygous hemochromatosis, a.k.a. iron overload. Vitamin C, or ascorbic acid, enhances iron absorption, and for many people, especially those trendy folks who reject meat in their diet, this is a good thing. For the aforementioned iron overloaders, however, it can spell big trouble--especially if they're given to mega-doses of vitamin C. It has been confirmed that the deaths of three iron overloading athletes was due to prolonged mega-dosing with vitamin C. Another problem with Vitamin C supplementation is that it can ultimately spell big trouble for those people with a tendency toward oxalate build-up...the end result being the dread kidney stone. Again, not a majority of the population, but like the 40 percent chance of rain on the deluged picnic, if you're the guy with the kidney stone, it's a pertinent piece of information. In a similar vein, some people who take supplemental calcium (as opposed to getting it from dairy products, say) are setting themselves up for an attack of kidney stones since the supplement (and not the dietary form) can combine with oxalic acid and produce the resulting kidney stones...calcium oxalate.

Enough with vitamin C already...how about the encouragement for supplementation with beta-carotene? A little biochemistry lesson here: beta-carotene (found naturally enough in carrots) is a precursor to vitamin A, otherwise known as retinol. As with many situations in life, you can get too much of a good thing and a study done with beta-carotene is exhibit A. It had been observed that smokers with high blood levels of beta-carotene had a greater resistance to lung cancer. Aside from getting the smokers to quit (not the easiest task in the world) some researchers thought it would be great if just giving a beta-carotene supplement would do the trick. Unfortunately the experiment had to be stopped half way through when it was observed that those taking the supplement had a risk almost twice as high as the non-takers for developing lung cancer. Apparently high blood levels of beta-carotene might simply be a marker for something else that's going on in their diet or life...so back to the drawing board. We also know that excessive intakes of retinol (mostly through supplements) can wreak havoc on bone health.

All of this brings two things to mind: 1. For most nutrients it's safer to get them from food via a well balanced diet (vitamin D and fish oil being an exception, since most people don't have adequate dietary intakes); and 2. watch out for words like "may" and "might"...weasel words that are used to evade or retreat from a direct or forthright statement or position. If an ad states that vitamin X might help reduce your risk of a specific illness, remember that "might" carries with it the implied "might not".