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Is
It Possible To Overdose
On Vitamins?
Yes. Because
vitamins occur naturally in our food, we think they can't hurt us when
we take them as pills. But we can see that they can.
For example, you can overdose on vitamin A pills, but you can't overdose
on real foods high in vitamin A like carrots. Carrots contain
beta-carotene which your body must first convert into an active form of
vitamin A. But this process is not very efficient, so you wouldn't get a
toxicity this way. You'll get yellowish skin due to the pigments in
beta-carotene, but this is not harmful.
When I was a teenager, cod liver oil was so popular that parents were
forcing it on their kids and the resultant vitamin A and vitamin D
toxicity deaths became a national scandal.
All the fat-soluble vitamins (A, D, E, K) are stored in the body's fat
deposits so that toxic levels are easily attained. Overdose of the B
vitamins and vitamin C can occur if you are taking megadoses from
supplements, but it's less likely because they are water-soluble and
therefore quickly excreted in the urine.
Vitamin A toxicity is particularly interesting: 100,000 International
Units (IU) per day produce brain damage and death in laboratory rats.
(For simplicity, I use the human equivalent of the rat dosage.)
Naturally, researchers wanted to know what dosage the rats could take
without getting such drastic effects. They kept diminishing the dose
until, at 50,000 IU per day, the rats suffered no ill effects at all.
With 5000 IU being the RDA level and 100,000 IU the severely toxic,
50,000 IU seemed to be a maximum safe dosage. One university professor,
however, wanted to be absolutely sure, so he bred rats that received
50,000 IU per day to see whether their offspring would show ill effects.
The offspring were fine. So, feeding them the same diet, he let them
grow up, breed, and produce their own offspring.
The third generation showed teratological (monster) effects --
predominantly brain damage and hydrocephalus. It is apparent that while
loading up on vitamins may seem to be beneficial, such
"self-medication" could, in fact, produce changes in the body
that could have harmful results years or generations later.
In any case, taking the vitamin A pills available in many stores easily
attains 50,000 IU of vitamin A, just tenfold the RDA. Humans have a
natural tendency to want more of something that seems to be good for
them. (The "If one is good, two is better" mentality.) So it's
a natural temptation to megadose on vitamin and mineral pills.
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