Five vitamins you shouldn't take

I used to take vitamin supplements almost every day. Taking vitamins seems like a good idea: after all, we know that vitamins are essential for life, and vitamin deficiencies can definitely hurt you.  I always thought that vitamins were an inexpensive way to get a little bit healthier.

Millions of Americans apparently agree with me. Close to half of the population in the U.S. takes vitamins, with multi-vitamins being the most popular.*  Vitamins are sold in virtually every grocery store, ranging from mega-markets like Wegmans to the organic Whole Foods chain.

The vitamin and supplements industry, which is immensely profitable, relies on the intuition that if a little bit of something is good for you, a bit more can't hurt.  Right?

Wrong.  If you don't have a serious vitamin deficiency, taking supplemental vitamins doesn't provide any benefit, in almost all cases that have been studied.  What's even more surprising is this: routinely taking mega-doses of vitamins might actually harm you.

So here are the top 5 vitamins that you should not take (unless your doctor recommends it):

1. Vitamin C.  Perhaps the most popular single vitamin supplement, vitamin C occurs in plentiful amounts in many fresh fruits and vegetables.  In the early days of global exploration, sailors often died from scurvy, caused by the lack of vitamin C.  Way back in the 1700's, Scottish doctor James Lind famously conducted an experiment that proved that citrus fruit cured scurvy, although vitamin C itself wasn't discovered until the 1930s.

Vitamin C gained its current popularity through the woefully misguided efforts of Linus Pauling, who published a book in 1970 recommending mega-doses of C to prevent the common cold. Although Pauling was a brilliant chemist (and Nobel laureate), he was completely wrong about vitamin C, as Paul Offit explains in detail in his new book, "Do You Believe in Magic?"

Vitamin C doesn't prevent or cure colds.  This question has been studied exhaustively: a review in 2005 covering 50 years worth of research concluded that

"the lack of effect ... throws doubt on the utility of this wide practice."  

Although Vitamin C is generally safe, megadoses of 2000 mg or more can increase the risk of kidney stones, which can be excruciatingly painful.

2. Vitamin A and beta carotene. Vitamins A, C, and E are all anti-oxidants, which have been promoted for their supposed anti-cancer properties.  The evidence doesn't support this: for example, in a large study supported by the National Cancer Institute*, smokers who took vitamin A were more likely to get lung cancer than those who didn't.

Vitamin A plays an important role in vision, but too much vitamin A can be toxic, causing multiple serious side effects. Perhaps the most famous cases of vitamin A toxicity occurred in early polar explorers, who ate the livers of their sled dogs, not realizing that the livers had excessively high amounts of vitamin A.  Antarctic explorer Douglas Mawson barely survived, and his companions died, probably of vitamin A poisoning.

3. Vitamin E. Long touted as an anti-cancer agent, vitamin E is a very popular supplement.  A large study last year, of 35,533 men, looked at vitamin E and the risk of prostate cancer. The authors found that the risk of cancer increased for men taking vitamin E.  In an even larger review done at Johns Hopkins University, Edgar Miller and Lawrence Appel found that the overall risk of death was higher in people who took vitamin E.  The Mayo Clinic summarizes the evidence this way:

"Evidence suggests that regular use of high-dose vitamin E may increase the risk of death from all causes by a small amount." 

4. Vitamin B6.  The B vitamins, including B6 and B12, are present in many foods, and deficiencies are rare.  But taking B6 supplements for a long time can be harmful, as NIH's website explains*:

"People almost never get too much vitamin B6 from food. But taking high levels of vitamin B6 from supplements for a year or longer can cause severe nerve damage, leading people to lose control of their bodily movements."

5. Multi-vitamins. This is the big one. With nearly 40% of Americans taking a multi-vitamin, they must be good for you, right? But a huge study that I wrote about last year, looking at 38,772 women over 25 years, found that the overall risk of death increased with long-term use of multivitamins, vitamin B6, folic acid, iron, magnesium, zinc, and copper.  Death, one must admit, is a pretty bad outcome.

On the evidence, supplementing your diet with any of these 5 vitamins carries little or no benefit, and may cause you harm.  This is why we do science, people. Our intuitions aren't always right: just because a little bit of something is good for you does not mean that a lot of it is even better.

Vitamins don't "boost your immune system," they don't promote joint health, they don't reduce stress, and they don't help prevent colds or other common ailments.

So what should one do?  Ignore the marketing, and treat supplements like you would any other medicine: take them with caution.  If you are taking regular vitamin supplements, or thinking about it, ask your doctor before doing so.

And by the way, 100 grams of spinach has healthy amounts of vitamins A, C, E, K, several B vitamins, and essential minerals including iron and calcium.

So ditch the vitamins and eat your spinach.  Or blueberries.  Blueberries are great.

[*The statistics and references used in this article were collected, in part, by the U.S. Centers for Disease Control, the U.S. Department of Agriculture, and the National Institutes of Health, all of which are currently shut down due to the stubborn actions of a minority of Representatives in the U.S. Congress.  Thanks, Congress!]