Field of Science

Don't take your vitamins

We've known for a long time that vitamins are good for you. Perhaps the best example is vitamin C, which completely cures scurvy, a disease that has plagued mankind for millenia. (It was described by Hippocrates some 2400 years ago.) Scottish doctor James Lind described how to cure scurvy with citrus fruit back in 1753, but it wasn't until 1932 that scientists Albert Szent-Gyorgyi and Charles Glen King identified vitamin C as the essential nutrient behind the cure for scurvy. (Szent-Gyorgi gave vitamin C the name ascorbic acid because of its anti-scurvy properties.)

Many other vitamins and micronutrients are required for good health, such as vitamins B and D, iron, folic acid, calcium, and potassium. Deficiencies in these vitamins cause all sorts of diseases, some of them very serious.

So it seems intuitively obvious that if a little bit of these nutrients is good for you, then a lot should be even better. Right? This intuition is the basis for the a huge and powerful nutritional supplements industry, which makes billions of dollars each year selling multi-vitamins and high-dose supplements in a bewildering variety.
The problem is, our intuition is wrong. Two separate studies published this past week, involving tens of thousands of subjects, showed that high doses of vitamins and supplements, rather than being helpful, can sometimes kill you.

In the first study, Jaakko Mursu and colleagues have been following 38,772 older women since 1986. The women in the study, whose average age was 62 back in 1986, have reported their use of multivitamins and supplements for the past 25 years. The news was not good: the risk of death INCREASED with long term use of multivitamins, vitamin B6, folic acid, iron, magnesium, zinc, and copper. The risk of death only decreased with the use of calcium. They also noted that in other studies, calcium had the opposite effect.

The authors concluded that there's
"little justification for the general and widespread use of dietary supplements,"
and the story was widely reported as showing that supplements are risky (Wall St. Journal) and unnecessary (New Zealand Herald).

In the second study, Eric Klein and colleagues studied 35,533 men over the past 10 years, looking at whether vitamin E or selenium would decrease the risk of prostate cancer. Both supplements have been claimed to have benefits, so the researchers randomly divided the subjects into four groups, giving them daily doses of (1) vitamin E only, (2) selenium only, (3) vitamin E and selenium, and (4) nothing (in the form of placebo pills).

The result: the risk of cancer INCREASED for the men taking vitamin E, selenium, or both. Although the increased risk is small, it is abundantly clear that neither of these supplements is helpful against prostate cancer.

Not surprisingly, the supplements industry hasn't taken this news lying down. The Council for Responsible Nutrition is an industry lobbying group representing the supplements industry (don't be fooled by the name). They released a statement by their vice president, Duffy MacKay (a naturopath, which is a form of quackery I'll have to treat separately in the future), grasping at the fact that, in the study, the increased risk of cancer from vitamin E plus selenium wasn't quite as big as the increase from vitamin E alone.
"This reinforces the theory that vitamins work synergistically," said MacKay.
Aha! So if I take even more supplements, perhaps my risk of cancer will go up only an eensy-teensy bit?

The Council released a second statement about the study on multivitamins, saying
"CRN maintains that nutrients may be robbed of their beneficial effects when viewed as if they were pharmaceutical agents, with scientists looking to isolate those effects, good or bad."
I see... so the benefits of supplements will disappear if we treat them as drugs: wouldn't that include taking vitamins and supplements as pills?

The supplements industry (Big Supp?), which is largely unregulated, has a darker side too: countless hucksters, many operating primarily through the Internet, who are making a fortune selling overpriced supplements (and advice on how to use them) that they claim will cure cancer, diabetes, and a host of other diseases. These include internet quack Mike Adams, who posted a response to this week's studies on his Nature News website, claiming:
"Recent attack on vitamins a fabricated scare campaign."
In Adams' response, he starts by arguing that the American Medical Association"has a long and sordid history of openly attacking vitamins and nutrition," a bizarre claim that has nothing to do with the study results even if it were true (it's not). He goes on to claim that the
"study data were ALTERED!"
(the all-caps is his) and
"voodoo statistics [were] used to alter the outcome."
I looked at the numbers he extracted from the paper to support these claims, and he failed - badly - to understand the data. Apparently for Mike Adams, statistics that he doesn't understand are just "voodoo."

So I'm afraid the news boils down to this: eat lots of fruit and vegetables, and a balanced diet, and you'll get all the micronutrients and vitamins you need. Supplements are only needed if you have a demonstrable deficiency. For most people, multivitamins and other supplements are a waste of money, and they might even be harmful. But hey, apples are in season right now, and spinach can be kind of tasty if you prepare it properly.

5 comments:

  1. I used to take vitamin tablets every day when I was a kid, given t me as they were meant to be 'healthy' and just top up any nutrients I might not be getting enough of.

    I stopped when I got to university because I could not be bothered. I haven't noticed any difference whatsoever since then.

    I'm pretty sure folic acid when pregnant is recommended, but other than that I'm lucky enough to be able to get a varied enough diet that supplements don't seem in any way necessary.

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  2. Lab Rat: right, folic acid is definitely recommended for pregnant women, for very good health reasons, primarily to prevent spina bifida in the baby. I don't want to suggest that all supplements are bad - it's just that routine use of supplements and multivitamins, when there's no particular reason for them, seems to be more harmful than helpful.

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  3. You might want to read this entry from Science-Based Medicine, which is on your blog roll. It offers a far more balanced and less polemic view on the matter. You could also read my take on the matter.

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  4. Breki: I read Steven Novella's blog post at Science-Based Medicine, and it's excellent. He has a different perspective from me, and makes different points, all of them excellent. I highly recommend his article. At your own post you argued that the vitamin E/selenium study is "not newsworthy." I can't agree with that. The reason NCI did the study is that there have been multiple claims over the years - some supported (weakly) by preliminary evidence - that both these supplements prevented prostate cancer. NCI funded a huge, very expensive study to investigate these claims, and the result is negative. Negative results like this very much deserve publicity - after years of promoting bogus cancer cure claims from the supplements industry, we need to try to re-educate the public.

    As for the other study, you wrote on your blog that the investigators "ignored all other possible mortality factors." Actually that's not true either - they acknowledged this concern explicitly and tried very hard to control for it. In an observational study they can't really control things very well, but they acknowledge that too.

    I should re-emphasize what I wrote at the end of my article: supplements are only needed if you have a deficiency in a vital nutrient. In that case, they are vital to your health. But as both of these new studies pointed out, an excess of certain vitamins and supplements can be harmful, which means that routine use of megavitamins - which is quite common in modern society - can do more harm than good.

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  5. I just reread Novella's column and can't see much difference in the basic conclusions or advice. Eat your veggies (and fruit) and there's little need for vitamins.

    I'm in total agreement. The only quibble I have is that millions eat little to no veggies or fruit and refuse to change their ways. The question then is: should people with relatively poor diets (in terms of nutrients, not calories) take a multiple vitamin? I used to do this before I ramped up my veggies to include every color most every day.

    I would also argue that not only is spinach tasty--raw or cooked a bit, but so is kale, collards, chard, all colors of beets, carrots and peppers, as well as cabbage, broccoli and brussel sprouts. I have some recipes that have induced my entire family and many friends to beg me to make kale-beet salad!

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