No, megadoses of vitamin C won't cure a coronavirus infection

The world is awash in treatments for COVID-19, the illness caused by coronavirus. Or at least that's what you might think if you just searched the internet.

The truth is, we don't yet have any effective treatments for COVID-19, although thousands of scientists are working furiously to try to create them.

Today we'll look at just one of the supposed treatments, which is being actively promoted on social media and many websites: vitamin C.

For those who don't want to read further, I'll start with the conclusion: vitamin C won't help to prevent or to treat coronavirus infection. I wish we had such a simple solution, but we don't.

Now let's back up a bit. Why would anyone think that vitamin C might be effective in treating this terrible virus? Vitamin C is an essential nutrient, and we all need it, but most people get plenty of vitamin C in their normal diet. As I've written before, taking vitamin C supplements is unnecessary but probably harmless, although megadoses carry the risk of kidney stones.

The modern craze with vitamin C started with Linus Pauling, a brilliant chemist and a Nobel Prize winner. Late in his career, he wrote a book promoting vitamin C as a miracle cure for many illnesses, including the common cold (which is caused by a virus). He had very little good evidence for this belief, but his promotion of vitamin C led to hundreds of studies testing his hypothesis. The bottom line: vitamin C doesn't work at preventing or curing the common cold. (See Paul Offit's book if you want more details on this and many other "miracle" cures.)

But wait, someone might object: haven't some of those vitamin C studies (as in this review paper) shown a benefit against the common cold? Well yes, but when you run hundreds of studies of a treatment that doesn't work, this is what happens: negative studies are hard to get published, but positive studies are easier. Run enough studies, and a few of them, merely by chance, will show a small positive effect. That's what we've seen with vitamin C.

Today, though, everyone is looking for a cure for COVID-19, and not surprisingly, many people (even some doctors) are claiming vitamin C is the answer. I've seen Twitter users explain, very confidently, that you just need to take 12,000 mg of vitamin C and you'll get better. This website comes right out and states that high-dose vitamin C will cure coronavirus, based on a widely-shared video from a doctor in China. (I won't provide the link because it has already done enough damage.)

It's almost impossible to disprove a claim that a treatment works. For example, I could claim that ginger snap cookies helps to prevent coronavirus infection. That's right! Ginger snaps, made with real ginger, which seems to have magical curative properties. If you object, I could demand that you prove me wrong–but the onus is on me, as the one making the claim, to first provide some genuine evidence. We haven't seen anything like that for vitamin C.

We need well-controlled experiments to know with any confidence that a treatment works. Some doctors at Wuhan University have started a trial of vitamin C to see if it has any benefits for COVID-19, but results won't be available for many months. I'm skeptical, but at least they're approaching the question the right way.

Dozens of studies of new treatments for COVID19 are being launched right now, with remarkable speed due to the urgency of the pandemic.The WHO has just launched trials of the 4 most promising existing drugs (which don't include vitamin C, I should add). To obtain a believable, positive result, we need to see evidence that a carefully administered treatment provides a significant benefit over what we're doing now–which is little more than supportive care, unfortunately.

Meanwhile, we'll have to wait and hope that one of the plausible efforts currently under way will yield an effective treatment. We've been down this road too many times with vitamin C, though, and the chances that it will have any effect are, based on past experience, close to zero.

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!]

Got cold. Try zinc?

Having a cold is no fun.  Sore throat, runny nose, general feeling of all-around blechiness.  About the only good thing I can say about colds is that they don't last long, usually about a week.

We still don't have a cure for the common cold, but it's not for lack of trying.  For decades, Nobel laureate Linus Pauling promoted mega-doses of vitamin C as a way to prevent colds, but he turned out to be wrong on that one.  Somewhere in the neighborhood of 200 different viruses cause us to get colds, and we don't seem to be able to get rid of any of them.

In recent years, the most popular new remedy is zinc, usually in the form of a lozenge.  The evidence for zinc's effectiveness is not entirely clear, but a review published just last month, which looked at 13 different studies, concluded that zinc seems to help, just a little bit.  All 13 studies were randomized controlled trials, the gold standard of research, and collectively they included 966 people.

That sounds encouraging, but the benefit was disappointingly small: zinc seemed to shorten the duration of a cold by about one day.  So instead of being sick for 7 days, you might be sick for 6 days.

Or maybe not: Dr. Terence Davidson from UC San Diego argues that if you look at just the more rigorous studies, the effect vanishes entirely.

Chunks of elemental zinc

Then there are the worrisome reports that Zicam, a zinc-based cold remedy, causes people to lose their sense of smell.  (This may not sound so terrible, but some people reported a permanent loss.  Imagine never being able to smell fresh-baked bread again.)  In 2009, these reports led the FDA to issue a warning advising consumers to stop using three particular Zicam products.  In addition to over 130 reports directly to the FDA, Zicam's manufacturer had over 800 additional complaints about loss of sense of smell.

In an ironic twist, Zicam markets its products as homeopathic remedies, which means that the FDA cannot regulate them. It also means that they shouldn't contain any active ingredients, because homeopathic preparations are diluted until they contain nothing at all.  But Zicam does contain zinc, quite a lot of it, and the FDA's warning letter demanded that Zicam stop marketing these products because they had never demonstrated that they were safe and effective.

Zicam markets a wide range of zinc-containing products, and the FDA's warning only affected three of them.  Zicam's website today states that "there is no valid, scientific evidence showing a link between Zicam and anosmia [loss of sense of smell]."  Strictly speaking, this is correct, but there have been published reports suggesting a link, such as this one from 2006 and this one from 2009.  These studies looked at nasal sprays, not lozenges, suggesting that the risk (if any) comes from spraying the zinc product directly up your nose.

Aside: Zicam also claims that their products cure allergies too, for which there is not a shred of evidence.  Their website makes the sweeping claim that "all Zicam products are both effective and safe when taken as directed." I see no reason to trust these guys.

Conclusion: I'm not taking zinc.  The side effects might be minimal, but the benefit is very small and possibly zero.  I'll stick with hot tea, which at least makes my throat feel better.  Or chicken soup.  That can cure almost anything.