Can multi-vitamins go bad/expire?
March 28, 2006 11:09 AM   Subscribe

Can multi-vitamins go bad/expire?

I've kept this massive jar of Centrum (stupid Sam's club) for about 4 or 5 years now and will occasionally get in a healthy mindset and take a pill a day for about a month. I'm not really concerned about the expense of replacing the vitamins, if need be, but I'd hate to trash the lot if they're still decent. This search turned up some links about vitamins losing potency but didn't give any post-expiration timeline of when taking them becomes redundant. I've kept the jar in a kitchen cabinet except for the three times I've moved since the purchase, so I don't think exposure to heat, light, or moisture is a factor. The flip side of that; I can't find any expiration date on the jar. Should I just dump them and move on? Double my intake? Go back into semi-healthy mode and pretend I get my nutrional RDA from my diet alone?
posted by redsnare to Health & Fitness (8 answers total)
i just checked my big bottle of multivitamins. i bought it two and a half years ago and it just expired last month, so it seems like after four or five years, your centrum has probably expired too. i have no idea whether or not expired multivitamins are harmless.
posted by clarahamster at 11:12 AM on March 28, 2006

I've got some long-expired multivitamins that I occasionally take in a fit of enthusiasm - they haven't done me any harm, though I have no idea whether they've done me any good either.
posted by altolinguistic at 11:14 AM on March 28, 2006

I have also bought a big amount of Centrum some time ago (A big pot of 100, plus a free small pot of 30, and a lame plastic bottle), and they expired about a year ago. I am taking them now, and they haven't killed me yet. Your mileage may vary.

About doubling it: not recommended. It contains some lipossoluble vitamins that aren't good in excess. Probably 2 pills a day are still way below the excess threshold, but... why risk?

Also, a good part of centrum is inorganic minerals, like Chrome or Magnesium. I doubt these lose potency anytime sooner than a couple hundred years.
posted by qvantamon at 11:17 AM on March 28, 2006

This page says
Supplements generally never expire, but light and heat can often reduce the quality of the vitamin.
posted by aeighty at 11:22 AM on March 28, 2006

Best answer: They're expired (I assume) but probably not useless.

The expiration date is the date when the active ingredient is at 90% of the potency that the label says. The equation used to figure that is A^(-kt) where A is the amount of active ingredient, k is the halflife, and t is the time. Financial wizards and physicists among us will recognize the equation, as it's the same one used to figure continuously compounded interest and radioactive decay.

Since a multivitamin has a bunch of ingredients in it, probably the expiration date was figured based on the ingredient with the shortest half-life, ie, the one that decays fastest.

So, there is probably some viable vitamin left in there. My multivitamin has an expiration date about 2 yrs after the date I purchased them.

Personally I would trash them, buy a much smaller bottle, and take those.

As far as doubling goes these are 2 things to watch out for:

Vitamin A can be toxic in excess (there are reports of people dying after eating bear liver which has a lot of it). If the Vitamin A is in the form of beta carotene, however, your body can regulate the amount that gets turned into Vit A. So, beta carotene = good.

Iron is also not a good thing to take too much of, especially if you are a man. (It has been shown to increase men's risk of cardiac problems).
posted by selfmedicating at 11:33 AM on March 28, 2006 [3 favorites]

Because some organic comounds break down over time, the vitamin maker can only guarantee the potency for a certain period of time after the manufacture date.
posted by pmbuko at 11:38 AM on March 28, 2006

Response by poster: Thanks for the answers, folks. I thought about the radiocarbon dating formula but wasn't sure it would apply - interesting stuff, though. Glad to see I'm not the only one getting sporadic bites from the health/fitness bug.
posted by redsnare at 12:29 PM on March 28, 2006

Of course, what they break down into woudl be of interest...
posted by wilful at 5:06 PM on March 28, 2006

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