Gluten - is it really all that bad?
Eat no wheat. That is the core, draconian commandment of a gluten-free diet, a prohibition that excises wide swathes of popular foodstuffs - bread, pasta pizza, cake and biscuits, to name but a few.
For the approximately one in 100 Australians who have a serious condition called coeliac disease, that is an indisputably wise medical directive.
Now medical experts largely agree there is a condition related to gluten other than coeliac. In 2011 a panel of coeliac experts convened in Oslo and settled on a medical term for this malady: non-coeliac gluten sensitivity.
What they still do not know: how many people have it, what its long-term effects are, or even how to reliably identify it. Indeed, they do not really know what the illness is.
The definition is less a diagnosis than a description - someone who does not have coeliac, but whose health improves on a gluten-free diet and worsens again if gluten is eaten. It could even be more than one illness.
''We have absolutely no clue at this point,'' said Dr Stefano Guandalini, medical director of the University of Chicago's Coeliac Disease Centre.
Kristen Golden Testa could be one of the gluten-sensitive. Although she does not have coeliac, she adopted a gluten-free diet last year. She says she has lost weight and her allergies have gone. ''It's just so marked,'' said Golden Testa, who is health program director in California for the Children's Partnership, a national non-profit advocacy group.
She did not consult a doctor before making the change, and she also does not know whether avoiding gluten has helped at all. ''This is my speculation,'' she said. She also gave up sugar at the same time and made an effort to eat more vegetables and nuts.
Many advocates of gluten-free diets warn that non-coeliac gluten sensitivity is a wide, unseen epidemic undermining the health of millions of people. They believe that avoiding gluten - a composite of starch and proteins found in certain grassy grains such as wheat, barley and rye - gives them added energy and alleviates chronic ills. Oats, while gluten-free, are also avoided, because they are often contaminated with gluten-containing grains.
Others see the popularity of gluten-free foods as just the latest fad, destined to fade like the Atkins diet and avoidance of carbohydrates a decade ago.
Indeed, Australian and New Zelanders spend millions of dollars on food labelled gluten-free each year and the market is growing. It helps that celebrities such as Miranda Kerr have touted going gluten free for weight loss and general health improvements.
For coeliac experts, the anti-gluten zeal is a dramatic turnaround; not many years ago, they were struggling to raise awareness among doctors that bread and pasta can make some people very sick. Now they are voicing caution, tamping down the wilder claims about gluten-free diets.
''It is not a healthier diet for those who don't need it,'' Guandalini said. These people ''are following a fad, essentially''. He added, ''And that's my biased opinion.''
Nonetheless, Guandalini agrees some people who do not have coeliac receive a genuine health boost from a gluten-free diet. He just cannot say how many.
As with most nutrition controversies, most agree on the underlying facts. Wheat entered the human diet only 10,000 years ago, with the advent of agriculture.
''For the previous 250,000 years, man had evolved without having this very strange protein in his gut,'' Guandalini said.
''And as a result, this is a really strange, different protein which the human intestine cannot fully digest. Many people did not adapt to these great environmental changes, so some adverse effects related to gluten ingestion developed around that time.''
The primary proteins in wheat gluten are glutenin and gliadin. Gliadin contains repeating patterns of amino acids the human digestive system can't break down. (Gluten is the only substance that contains these proteins.) People with coeliac have one or two genetic mutations that somehow, when pieces of gliadin course through the gut, cause the immune system to attack the walls of the intestine in a case of mistaken identity. That, in turn, causes fingerlike structures called villi that absorb nutrients on the inside of the intestines to atrophy, and the intestines can become leaky, wreaking havoc. Symptoms vary widely and the vast majority of people who have the disease do not know it. Plus, not everyone who has the genetic mutations develops coeliac.
After testing blood samples from a century ago, researchers discovered that the rate of coeliac appears to be increasing. Why is another mystery. Some blame the wheat, as some varieties now grown contain higher levels of gluten, because gluten helps provide the springy inside and crusty outside desirable in bread.
There are also people who are allergic to wheat (not necessarily gluten), but until recently, most experts had thought that coeliac and wheat allergy were the only problems caused by eating the grain.
For 99 out of 100 people who don't have coeliac - and those who don't have a wheat allergy - the undigested gliadin fragments usually pass harmlessly through the gut, and the possible benefits of a gluten-free diet are nebulous, perhaps non-existent for most. But not all.
Anecdotally, people like Golden Testa say gluten-free diets have improved their health. Some people with diseases such as irritable bowel syndrome and arthritis also report alleviation of symptoms, and others are grasping at gluten as a source of a host of other conditions, though there is no scientific evidence to back most of the claims.
Experts have been sceptical. It does not make obvious sense, for example, that someone would lose weight on a gluten-free diet. The opposite often happens for coeliac patients as their intestines recover.
They also worried that people could end up eating less healthfully. A gluten-free muffin generally contains less fibre than a wheat-based one and still offers the same nutritional dangers - fat and sugar. Gluten-free foods are also less likely to be fortified with vitamins.
But those views have changed. Crucial in the evolving understanding of gluten were the findings, published in 2011, in 'The American Journal of Gastroenterology'. In the double-blind study, people who suffered from irritable bowel syndrome, did not have coeliac and were on a gluten-free diet were given bread and muffins to eat for up to six weeks. Some of them were given gluten-free baked goods; the others got muffins and bread with gluten.
Thirty-four patients completed the study. Those who ate gluten reported they felt significantly worse.
That influenced many experts to acknowledge that the disease was not just in the heads of patients. ''It's not just a placebo effect,'' said Dr Marios Hadjivassiliou, a neurologist and coeliac expert at the University of Sheffield in England.
Even though there was now convincing evidence gluten sensitivity exists, the researchers of the experiment noted, ''No clues to the mechanism were elucidated.''
What is known is that gluten sensitivity does not correlate with the genetic mutations of coeliac, so it appears to be something distinct from coeliac.
How widespread gluten sensitivity may be is another point of controversy.
Dr Thomas O'Brien, a chiropractor and anti-gluten crusader, said 30 per cent of his patients had antibodies targeting gliadin fragments in their blood. ''If a person has a choice between eating wheat or not eating wheat,'' he said, ''then for most people, avoiding wheat would be ideal.''
Guandalini said finding out whether you are gluten sensitive is not as simple as O'Brien's antibody tests, because the tests only indicate the presence of the fragments in the blood, which can occur for a variety of reasons and do not necessarily indicate a chronic illness. For diagnosing gluten sensitivity, ''There is no testing of the blood that can be helpful,'' he said.
- Sydney Morning Herald