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Food allergies are increasing – because we’ve got rid of our worms

My Times column on dietary intolerance:


I suggest you finish your breakfast before reading this column.

When the National Health Service announced last month that it would no longer prescribe gluten-free food, it surprised me that it had been doing so in the first place. Whether you have genuine gluten intolerance — such as those with coeliac disease — or are merely following the fad, why should the taxpayer subsidise your diet, when the shops are groaning with gluten-free products? As I shall explain, perhaps the NHS should prescribe worms instead.

Where nutrition is concerned, the line between medical disorder and dietary preference has blurred. There are genuine medical issues relating to food, but they are hidden under a heap of fads. The recent news that milk consumption is dramatically down among young people seems to be because of a large amount of fashion with a small amount of disease.

It is the medical issue that concerns me here, but before I get to that, a word about fads. Lucrative obsessions among the wealthy with “clean” food, raw food, “detox” diets and “superfood” are pseudoscience, shamelessly exploiting gullible people and worsening the epidemic of eating disorders. Much of anorexia starts with “orthorexia”, or fussy eating, driven by irresponsible advice from celebrities who should know better. Nutrition education should be a priority, and public heath authorities need to get over their monomania about the sugar industry and start thinking about the damage being done by food fads.

At the heart of the problem is a misunderstanding of the concept of dose. Any kind of food is bad for you in excess, but that does not mean it is bad for you in small doses. Likewise, if something is harmful when missing from the diet, it does not mean it is good for you when supplied in overabundance. Vitamin C is vital for people with scurvy, but of zero benefit for people who are getting enough vegetables and fruit in their diet.

However, with that off my chest, there is nonetheless a growing food and health problem. Beneath the nonsense fads, beneath the worship of kale and goji berries and the absurd detox mythology, there clearly is increasing food intolerance among a smaller number of people. It urgently needs attention, because otherwise we might find in a few decades that more and more lives are ruined by allergies and illnesses.

This is a global issue. The menu in the restaurant in Guatemala City where I dined on Friday was sprinkled with symbols: gluten-free, dairy-free or peanut-free. These are real dangers for some people, who must avoid wheat, milk and nuts, three of mankind’s oldest staple foods. In a world where almost everything has been getting better, allergies have got steadily worse. Why?

I reckon the cause is now pretty clear: a lack of worms. The allergic reaction to these foods is caused by immunoglobulin E, a component of the immune system whose day job in the past was to combat parasitic worms. A recent study by the London School of Hygiene & Tropical Medicine found that key proteins from 31 species of parasites are very similar to allergenic proteins. A protein in birch pollen that triggers hay fever is very similar to a protein found in parasitic worms that causes the infection schistosomiasis, for example.

It’s not that the immune system is “bored” now we have got rid of worms. The theory is more persuasive than that: worms have the capacity to damp down inflammatory immune reactions in their hosts, the better to survive. So human immune systems evolved to “expect” suppression by parasites; without it they overreact. To put it another way, we outsourced part of the regulation of our immune system to parasites.

Milk intolerance may be different because in most parts of the world it is caused by a sugar, lactose, whose indigestibility is a genetic trait. The gene for lactase, the enzyme that tackles lactose, is switched off in mammals when they are weaned. Only in Europe and parts of Africa, where people began milking cows a few thousand years ago, did mutations spread that kept the gene for digesting lactose switched on during adulthood.

But much milk intolerance in westerners is probably not lactose intolerance, but an allergic reaction to a protein called beta casein A1. Hence the growing popularity of “A2 milk”, a product pioneered in New Zealand from cows that don’t make A1. So milk intolerance, too, may be about proteins and may also be related to wormlessness.

As recounted in a fascinating book, An Epidemic of Absence, by Moises Velasquez-Manoff, the correlation between the disappearance of worms and the appearance of asthma, allergies, type 1 diabetes and dietary intolerances is remarkably precise in time and place. In and around the Ethiopian town of Jimma asthma suddenly became common in the 1990s only in the places and at the time that hookworm was eradicated. No other factor — air pollution, dust mites, pesticides, viral epidemics — could explain the change. In Karelia, a region divided between Finland and Russia, very similar people had far more coeliac disease and allergies on the Finnish side, where sanitation was much better and parasites fewer.

Moreover, experiments have now been done to give allergic people hookworms or whipworms. Sure enough, their allergic symptoms — from asthma to irritable bowel disease — often clear up fast. A whole industry of “helminth hackers” has emerged in the United States supplying worm eggs through the post for people with intolerances. Be warned that it is not necessarily worth it.

Ideally, we would now work out how the worms regulate the immune system and replicate the effect with safe pharmaceuticals. That should not be beyond the wit of 21st-century science.

It is probably not just worms. The impoverishment of our gut flora — the bacteria in our intestines — in the modern world, as a result of excessive hygiene and antibiotics, looks increasingly likely to be the cause of various other health issues, including obesity and possibly autism, though early experiments on the latter are inconclusive. Open Biome is a “stool bank” that will supply you with faecal transplants from healthy people to enrich your gut garden. It will also pay good money for faecal donations from healthy people. Now there’s a tip you did not expect to read in The Times.

I do hope you enjoy your lunch.

By Matt Ridley | Tagged:  rational-optimist  the-times