Carb your enthusiasm
Chips, pizza, pasta, fries, rice. Food heaven for lots of us but, if some are to be believed, food hell for people with AS. Many people with the condition believe that cutting out starchy foods improved their symptoms. Some are so convinced of the benefits they’ve posted YouTube videos and started websites to get the starch-free message out there.
It’s clear there’s strong feeling out there, but is there strong science to match? Together with Consultant Rheumatologist (and blogger) Dr Shashank Akerkar, This AS Life looks at the theory – and practice – behind kicking carbs to the kerb.
Giving genes a jolt
So what links starch and AS? It’s a good question, with quite a long answer. Current thinking has it that for AS, our genes play a big part. A gene called HLA-B27 is a popular culprit,1 – it’s found in almost 90% of one AS population2 – although no one is certain yet how it leads to developing AS.3
However for AS, genes aren’t the whole story – 10% of North Europeans who have the HLA-B27 gene don’t have AS.4 And in identical twins (who share identical genes) if one twin has AS, there’s only a 40% chance the other twin develops it too.5
Scientists believe something in our environment may trigger a change in people with the HLA-B27 gene. This trigger sets off a sequence of events that leads to the development of AS.6 So what’s the trigger? And what does not eating bread have to do with it?
"It's clear there’s strong feeling out there, but is there strong science to match?"
An accidental bad guy?
In the 1980s, a British researcher called Alan Ebringer found a potential suspect – a bacteria called Klebsiella pneumonaie.7 The bacteria lives in our gut, happily munching on – you guessed it – undigested starch.7
It turns out there’s a degree of similarity between the structure of Klebsiella and the part of HLA-B27 (plus three types of collagens found in joints and other organs including the eye) that rogue antibodies in AS attack.8,9 Professor Ebringer guessed that a Klebsiella infection could be the environmental trigger that leads to AS.7,10
The theory goes like this: a person with the HLA-B27 gene is infected with Klebsiella, which lives off the starch from food in the gut. When a person’s immune system kicks into action, making antibodies to fight off the Klebsiella bacteria, these antibodies mistake HLA-B27 (plus the joint and eye collagens) for bad guys too. They start to attack the body instead, leading to the development of AS.10
Science fact or science fiction?
The theory is called the ‘molecular mimicry hypothesis’ and it’s a popular one with researchers investigating autoimmune disease like AS.10 It’s a good theory – if a little complicated – but how does going low-starch work in practice?
Read part two of our carb-heavy article to find out.
This article was written by Dr Shashank Akerkar, with help from the resident experts at ThisASLife.com. A social site, helping the whole AS community to: Learn. Share. Inspire. Discuss.
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10. Rashid T, Ebringer A. Autoimmune Dis 2012; 2012:539282.