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.

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