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Got a cold? Eat caterpillars

Why medinical zinc is not all it's cracked up to be.

How’s this for impact? At the end of January, a research group in Manchester published a paper on the essential role of zinc in the human immune system. A week later, the price of zinc rose on the international metals markets after its longest slump in 25 years.

Amazing? Of course not. These are two entirely unrelated events. But it’s the ability to separate coincidence from causality that allows us to distinguish old wives’ tales from useful information.

Zinc has been in medical use since at least the 2nd century BC. A set of pills found in the remains of a ship wrecked off the Tuscan coast in 140BC are 75 per cent zinc. They were almost certainly used to treat eye and skin disorders, a practice documented by the Roman polymath Pliny in the 1st century AD.

Zinc is still used for this purpose. It has antiseptic and antiviral properties, which is why it is often embedded in dressings for wounds. What’s more, anecdotal evidence has long suggested that taking zinc supplements helps fight the common cold. But anecdotal evidence isn’t the most trustworthy: sometimes it sees cause and effect where there is none.

Even individual studies haven’t been enough to give us the answer; depending on how they are carried out, they can produce conflicting results. Fortunately, we’ve developed even more sophisticated techniques: dissection, analysis and pooling of the scientific studies themselves. This has allowed us to draw a firm and reliable conclusion. In the case of zinc, it’s this: take at least 75mg a day and “there is a significant reduction in the duration of cold”, according to a gold-standard Cochrane Review, which looks at primary research in health care. Ancient wisdom, in this case, has some validity.

What the ancients didn’t know is the mechanism involved. Zinc deficiency, it turns out, causes more than 3,000 types of protein in the body to function inefficiently or not at all. The body responds to this as stress, causing the immune system to leap into action. Specifically, according to researchers at Manchester University, zinc deficiency unleashes a molecule called interleukin-1-beta. This is part of the armoury of the immune system. The trouble is that, in the absence of any infection to clear, firing the immune response’s weaponry just causes damage.

The zinc deficiency, as the researchers point out, could easily be resolved using dietary supplements. And this increased medical use of zinc could have an economic impact.

Not, it has to be said, in the metals markets, where the rising price of zinc is linked to China’s construction boom. But zinc use for medical purposes could be worth about $25bn a year in the US alone. That is the estimated annual impact of common colds, in terms of lost productivity. The Cochrane Review has found that taking zinc supplements for at least five months can reduce that. It certainly reduces school absences and the prescription of antibiotics for children with the common cold.

Because colds are caused by a virus, antibiotics do nothing for sufferers, yet doctors prescribe them as a placebo to get worried parents out of their surgery. So zinc supplementation also slows the spread of antibiotic resistance. Here’s a final tip in case the price of zinc lozenges skyrockets: a daily 100g of cooked caterpillars contains all the zinc you need.

You’re welcome.

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article first appeared in the 19 February 2014 issue of the New Statesman, The Space Issue

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Why relations between Theresa May and Philip Hammond became tense so quickly

The political imperative of controlling immigration is clashing with the economic imperative of maintaining growth. 

There is no relationship in government more important than that between the prime minister and the chancellor. When Theresa May entered No.10, she chose Philip Hammond, a dependable technocrat and long-standing ally who she had known since Oxford University. 

But relations between the pair have proved far tenser than anticipated. On Wednesday, Hammond suggested that students could be excluded from the net migration target. "We are having conversations within government about the most appropriate way to record and address net migration," he told the Treasury select committee. The Chancellor, in common with many others, has long regarded the inclusion of students as an obstacle to growth. 

The following day Hammond was publicly rebuked by No.10. "Our position on who is included in the figures has not changed, and we are categorically not reviewing whether or not students are included," a spokesman said (as I reported in advance, May believes that the public would see this move as "a fix"). 

This is not the only clash in May's first 100 days. Hammond was aggrieved by the Prime Minister's criticisms of loose monetary policy (which forced No.10 to state that it "respects the independence of the Bank of England") and is resisting tougher controls on foreign takeovers. The Chancellor has also struck a more sceptical tone on the UK's economic prospects. "It is clear to me that the British people did not vote on June 23 to become poorer," he declared in his conference speech, a signal that national prosperity must come before control of immigration. 

May and Hammond's relationship was never going to match the remarkable bond between David Cameron and George Osborne. But should relations worsen it risks becoming closer to that beween Gordon Brown and Alistair Darling. Like Hammond, Darling entered the Treasury as a calm technocrat and an ally of the PM. But the extraordinary circumstances of the financial crisis transformed him into a far more assertive figure.

In times of turmoil, there is an inevitable clash between political and economic priorities. As prime minister, Brown resisted talk of cuts for fear of the electoral consequences. But as chancellor, Darling was more concerned with the bottom line (backing a rise in VAT). By analogy, May is focused on the political imperative of controlling immigration, while Hammond is focused on the economic imperative of maintaining growth. If their relationship is to endure far tougher times they will soon need to find a middle way. 

George Eaton is political editor of the New Statesman.