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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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Scotland's vast deficit remains an obstacle to independence

Though the country's financial position has improved, independence would still risk severe austerity. 

For the SNP, the annual Scottish public spending figures bring good and bad news. The good news, such as it is, is that Scotland's deficit fell by £1.3bn in 2016/17. The bad news is that it remains £13.3bn or 8.3 per cent of GDP – three times the UK figure of 2.4 per cent (£46.2bn) and vastly higher than the white paper's worst case scenario of £5.5bn. 

These figures, it's important to note, include Scotland's geographic share of North Sea oil and gas revenue. The "oil bonus" that the SNP once boasted of has withered since the collapse in commodity prices. Though revenue rose from £56m the previous year to £208m, this remains a fraction of the £8bn recorded in 2011/12. Total public sector revenue was £312 per person below the UK average, while expenditure was £1,437 higher. Though the SNP is playing down the figures as "a snapshot", the white paper unambiguously stated: "GERS [Government Expenditure and Revenue Scotland] is the authoritative publication on Scotland’s public finances". 

As before, Nicola Sturgeon has warned of the threat posed by Brexit to the Scottish economy. But the country's black hole means the risks of independence remain immense. As a new state, Scotland would be forced to pay a premium on its debt, resulting in an even greater fiscal gap. Were it to use the pound without permission, with no independent central bank and no lender of last resort, borrowing costs would rise still further. To offset a Greek-style crisis, Scotland would be forced to impose dramatic austerity. 

Sturgeon is undoubtedly right to warn of the risks of Brexit (particularly of the "hard" variety). But for a large number of Scots, this is merely cause to avoid the added turmoil of independence. Though eventual EU membership would benefit Scotland, its UK trade is worth four times as much as that with Europe. 

Of course, for a true nationalist, economics is irrelevant. Independence is a good in itself and sovereignty always trumps prosperity (a point on which Scottish nationalists align with English Brexiteers). But if Scotland is to ever depart the UK, the SNP will need to win over pragmatists, too. In that quest, Scotland's deficit remains a vast obstacle. 

George Eaton is political editor of the New Statesman.