It's probably no surprise to learn that an estimated one-third of Americans are trying to cut down on gluten or go gluten-free and as many as one in 10 Aussies avoid or limit their consumption of wheat-based products. Indeed, celebrities like Gwyneth Paltrow, Miley Cyrus and Victoria Beckham proclaim the virtues of a gluten-free diet to their legions of Instagram followers.
Here in New Zealand, supermarket aisles are filled with gluten-free products and café menus offer gluten-free options as more of us than ever shun the much-maligned protein in pursuit of better health, trimmer waistlines and less bloating.
But while going gluten-free may be a lifestyle choice for some, for people diagnosed with coeliac disease – an estimated one in 70 New Zealanders – it's a lifelong commitment to prevent vitamin and mineral deficiencies as well as a raft of long-term conditions like type 1 diabetes, infertility and osteoporosis. Yet despite our growing obsession with gluten, Coeliac New Zealand estimates 80 per cent of Kiwis with coeliac disease are unaware they have the condition.
Coeliac disease is a permanent autoimmune disorder that causes a reaction to dietary gluten, a protein found in wheat, barley, rye and oats. The cells lining the small bowel, aka the small intestine, are damaged and inflamed, which causes flattening of the tiny, finger-like projections, called villi, which line the inside of the bowel.
Villi break down and absorb nutrients in food, but when they are flat they're unable to function properly, which may lead to vitamin and mineral deficiencies.
People with coeliac disease are often troubled by gut issues such as bloating, abdominal pain and diarrhoea, lethargy and anaemia, and can also suffer from infertility, migraines, abnormal liver function, arthritis, osteoporosis, autoimmune diseases such as type 1 diabetes and thyroid disease, and some types of cancer. Women are two to three times more likely than men to have coeliac disease, and they're usually diagnosed around the age of 40.
However, symptoms vary considerably, from classic presentations to vague symptoms or no symptoms at all, which means many people are unaware they may have the condition.
"It's a really common condition that's frequently undiagnosed," says gastro-enterologist Dr Jason Tye-Din, head of coeliac research at the Walter and Eliza Hall Institute of Medical Research in Australia.
"Even though people have, in many cases, symptoms that should prompt testing, because of the broad way it can present and the relatively non-specific nature of many symptoms such as a tummy upset or feeling tired, coeliac disease often goes undiagnosed."
Dietitian Julie Leeper from Dietary Specialists says many people assume coeliac disease carries obvious, uncomfortable symptoms, when in many cases the opposite is true.
"Classically what we're seeing is people who are coming to us feeling a little bit tired," she says. "We see quite a number of people who are coming in just feeling a bit off-colour, and we even see people who are asymptomatic. They're not having any symptoms, but they're being picked up with a general screen for coeliac disease."
If you suspect you may have coeliac disease, the first step is to visit your GP.
"It's estimated 65,000 New Zealanders have coeliac disease but 80 per cent are unaware they do, so people who have even some of the symptoms need to work together with their GPs in the first instance to join the dots and consider that coeliac disease may be the cause of their overall unwellness," says Catherine Murray, president of Coeliac New Zealand.
A simple blood test screens for the condition, and a definite diagnosis is made via a gastroscopy – a simple procedure done under light sedation that takes about 10 minutes – in which several tiny samples of the small bowel are taken.
Switching to a strict gluten-free diet for life is the only treatment for coeliac disease. This restores the small intestine to full function, and an early diagnosis will help to prevent other health issues arising from a prolonged lack of nutrients.
"Treatment of the disease is very effective at resolving symptoms," says gastroenterologist Tye-Din. "People's lethargy goes away, their tummy symptoms that they may have had all their lives, the bloating or the cramps may go away, often within days of starting a strict gluten-free diet. And the long-term risks, for instance, of fertility or recurrent pregnancy loss, anaemia or even potentially the cancer risks are reduced by adequately treating the disease."
You must be born with the genetic predisposition to develop coeliac disease, but whether that predisposition develops into the condition depends on a heap of environmental factors that scientists don't yet fully understand.
"Pretty much everyone with coeliac disease has one of two tissue types – HLA-DQ8 or HLA-DQ2," says Dr Campbell White, a spokesperson for the New Zealand Society of Gastroenterology. "These are quite common tissue types that occur in about 30 per cent of the population, but you have to have either one first."
A first degree relative – parent, sibling or child – of someone with coeliac disease has about a 10 per cent chance of also having the condition.
Tye-Din says genetic factors contribute to 30 to 40 per cent of the risk of coeliac disease, and among Western populations the predisposing genes are very common. In Australia, his research found more than half of the population have at least one of the main genes. The remainder of the risk comes from environmental factors, which is especially relevant as research shows coeliac disease is on the rise.
"If you look at countries like the United States or Finland, in the past 60 years there's been a four-fold rise in the prevalence of coeliac disease," says Tye-Din. "And that's much more than just increased awareness and testing. It's actually a true rise in how common the disease is."
Scientists have proposed a variety of environmental theories, such as the 'hygiene hypothesis'.
"In the Western world, the fact we are living in such sterile conditions now means our immune system doesn't develop and mature in a normal way, which is increasing the risk of autoimmune disease, and certainly there's some evidence of that happening when it comes to coeliac disease," says Tye-Din.
There's also some evidence to suggest exposure to viruses during infancy may be linked to an increased risk.
"People seem to have the tissue type and then they are exposed to something, probably a virus, at a time of their life when their immune system is developing," says White. "It hasn't fully been worked out yet, but there's clearly some sort of interaction going on between food, the virus and the immune system."
So what of the folks who give up gluten in the absence of an official diagnosis of coeliac disease? Tye-Din says many people believe a gluten-free diet is a healthier alternative, but evidence says otherwise.
"There's not a lot of evidence to say outside of people with true coeliac disease gluten is particularly harmful, and in many cases when we look at the drivers for this rise in people adopting gluten-free diets, we see there's a lot of non-evidence based sources like celebrity endorsement."
In fact, a gluten-free diet can be distinctly unhealthy. To compensate for the missing taste and texture of gluten, many gluten-free foods are packed with less-than-healthy substitutes – and research shows those with coeliac disease are more likely to have nutritional deficiencies than people who don't.
"For people who go on a gluten-free diet, often they will get caught up in all the gluten-free products that are available," says dietitian Leeper.
"You can get gluten-free pies, gluten-free doughnuts, the works. People think they're missing out on things, so they'll eat all these gluten-free foods and sometimes they end up putting on a lot of weight and they forget about the general rules of healthy eating. It's best to stick to naturally gluten-free foods like meat, chicken, fish, eggs, vegetables and fruit."
What's more, research published in Nutrition & Dietetics found families could be paying up to 17 per cent more for a gluten-free diet – and for some single items as much as 500 per cent more.
Some people go gluten-free and notice an improvement in symptoms like abdominal pain, bloating, lethargy and headaches – a set of symptoms called 'non-coeliac gluten sensitivity' that don't show up in tests for coeliac disease – but what appears to be gluten intolerance may instead be an intolerance to wheat's carbohydrate component.
Landmark Australian research published in the journal Gastroenterology found a low FODMAP diet, which reduces these poorly-digested carbohydrates that are found across all food groups, can be more effective in reducing symptoms than going gluten-free.
Crucially, gluten-rich foods are typically high in FODMAPs – aka fermentable oligosaccharides, disaccharides, monosaccharides and polyols. These are 'short-chain' carbs which may be poorly absorbed in the small intestine, triggering symptoms like wind, abdominal bloating and distension, abdominal pain, constipation or diarrhoea.
"A gluten-free diet may be low in FODMAPs, and it may be the low FODMAPs that are making those people feel better, rather than the fact that they're gluten-free," says White.
Ultimately, if you're toying with going gluten-free, White says it's important to get tested for coeliac disease before you quit bread, pasta and pizza.
"One of the problems we have is with people who come to see us and they've already excluded gluten for a long period of time," he says. "Then it becomes quite difficult to know whether they didn't have coeliac disease at all or they had coeliac disease and they've been treated, because once you've been on a gluten-free diet for a period of time it becomes a lot more difficult to make that diagnosis."
Murray agrees: "If you're thinking about giving a gluten-free diet a try, get to the GP and get the simple blood test. When the result comes back, if it comes back as clear, then it's not a problem to go on a gluten-free diet if you want to give it a go. But if it comes back as you've possibly got coeliac disease, then have the gastroscopy and you'll know for sure, because it makes a big difference to whether you need a lifelong gluten-free diet or whether you choose to dabble in it for other reasons."
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