Your food ‘intolerance’ could be wrong – here’s why

This is Everyday Science with Clare Wilson, a subscriber-only newsletter from The i Paper. If you’d like to get this direct to your inbox every week, you can sign up here. Cooking for a group of friends can be complicated these days. Some may have allergies, and a growing number of people say they cannot tolerate certain foods – often wheat, dairy, or in one friend’s case, a seemingly random list of vegetables. While they – hopefully – don’t go into the details at the table, an intolerance typically means the food in question triggers symptoms like wind, bloating, abdominal pain, diarrhoea or constipation. Some of those who say they have a food intolerance are surely correct, but others may be mistaken. And a major cause of such errors are flawed intolerance tests that check for something called “IgG” antibodies, says Kirsten Jackson, a dietitian and spokesperson for the British Dietetic Association. Shorts Allergies, intolerance, and sensitivities One thing adding to the confusion is a rise in true food allergies in recent decades. With these, even a crumb of the food in question can trigger mouth tingling, rash, and throat swelling, and adrenaline injections may be needed to avoid potentially deadly anaphylactic shock. More common are what gets called food intolerance or sensitivity, which trigger the gut problems. The common mechanism is they involve certain components of the food being difficult to digest in the bowels’ upper regions, so they reach the large bowel, home to most of our gut bacteria. That has two unwelcome effects: it draws water into the large bowel, which can lead to diarrhoea, and when the bacteria in the bowels digest the food in question, they produce gas, which leads to bloating and pain, not to mention passing gas. With so many different foods that can cause reactions, it is unsurprising some people bothered by gut symptoms want to investigate them. Three common food intolerances Dairy: Some people stop making the enzyme needed for breaking down lactose – the main sugar in milk – as they get older, letting the sugar reach the lower bowel. Lactose intolerance can be lifelong or temporary, triggered by an infection. Gluten: Gluten is a protein in wheat, barley and rye. In a condition called Coeliac disease, the immune system reacts against gluten, and bowel cells get caught in the cross-fire, leading to pain and inflammation. But Coeliac disease may be confused with wheat intolerance, when the sugars formed from breaking down wheat starch cannot be digested, and so reach the large bowel. Fodmap (Fermentable, Oligosaccharides, Disaccharides, Monosaccharides andPolyols): These are a large group of sugars and other carbohydrates that some people digest poorly, leading to them reaching the large bowel. Fodmaps are in wheat, milk and certain vegetables, like onion, asparagus and cauliflower. Bad science creating ‘food fear’ That has led to a growing number of food intolerance or sensitivity tests, often sold online which check for IgG antibodies to specific foods through a finger-prick blood test. For instance, a company called YorkTest – whose products are on sale in Boots – says its IgG tests help you “find out whether you have an intolerance to 200 food and drink ingredients”. Several other brands of tests available online make similar claims. The problem is that positive tests for IgG antibodies do not show that someone is allergic, intolerant or sensitive to a food. In fact, these kinds of antibodies are a signal to the body that the immune system should not react to this food, says Professor George Du Toit, an immunologist at London Allergy Consultants – “The exact opposite is true. A positive test is a sign of tolerance.” IgG tests sound plausible, because many people know that antibodies are involved in allergic reactions. (In fact, the NHS uses a second type of antibody, IgE, to test people for food allergies – but these are different to IgG.) But many medical bodies and patient support groups reject IgG testing for food intolerances. This includes the British Dietetic Association, Guts UK and the British Society for Allergy and Clinical Immunology. “There is black-and-white evidence showing this does not work. People get these tests done and it creates eating disorders,” said Jackson of the British Dietetic Association. Risks of cutting out food Jackson regularly sees patients seeking help for irritable bowel syndrome (IBS) – when people have chronic gut symptoms for unknown reasons – who are wrongly convinced they have food intolerances because of such tests. “A typical person with IBS who reaches out for these tests, they get this list of foods that they’re now supposed to avoid,” she said. “That creates more food fear, and it worsens the relationship with food.” It is possible to be mistaken that you are intolerant of certain foods, because symptoms can also be triggered by stress, she said. “Chronic stress increases pain signalling. Some people might have a nervous system around their gut which is reading discomfort when gas levels rise just a little bit.” Jackson says some people become malnourished because they cut out so many different food groups. If they are avoiding wheat and pulses, they may be going short of fibre, while if they cut out dairy, they may be deficient in certain vitamins and minerals. Professor Helen Brough, a paediatric allergist and Director of Children’s Allergy Doctors, says the tests are especially harmful if used for children. They can “lead parents to unnecessarily eliminate important dietary staples such as milk, wheat and eggs”, she said. Even wholemeal bread could provoke painful symptoms (Photo: bhofack2/Getty Images/iStockphoto) Along with a colleague, Jackson has started a parliamentary petition to try to get IgG testing for food intolerances banned, along with another invalid technique where people send off samples of their hair for analysis. I emailed YorkTest for a comment but did not receive a reply. I also contacted Boots, which sells YorkTest food intolerance tests on its website. A spokesperson said: “Boots checks that the third-party products it sells comply with applicable legislation and regulatory requirements. Our pharmacy teams [are] available to offer advice and support to customers, including whether testing is appropriate for their individual circumstances or whether further advice from their GP may be beneficial.” But the fact that the tests are available from such a large pharmacy chain may contribute to people trusting them, said Jackson. “It’s a well-known British brand.” Jackson advises anyone who believes they have an intolerance to see their GP or a dietitian before cutting out food groups. People can usually be helped by structured elimination diets with step-by-step reintroductions of individual foods. I’ve also written The first death from bird flu this year, on a US dairy farm, has highlighted the pandemic potential of this virus. But an even more dangerous outbreak on a mink fur farm is going under the radar. 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