Fibromyalgia and irritable bowel syndrome – what’s the connection?

What are cytokines?

Cytokines small protein molecules that help control and regulate the immune system. They are released by cells of the immune system (primarily by white blood cells.) They act as messengers. Inflammatory cytokines (not surprisingly) stimulate inflammation, while anti-inflammatory cytokines do the opposite.

How do cytokines relate to inflammation?

Production of inflammatory cytokines happens at a very early step in the inflammatory cascade.

Note that inflammation is not a ‘single thing’ but is actually a long process – a chain of events. Once the inflammatory chain reaction starts – and inflammatory cytokines are generated – the process often (but not always) continues on to completion. The result in that case is ‘classic’ inflammation – the typical inflammation characterized by redness, swelling, warmth and pain.

Because of those symptoms, typical inflammation is relatively easy to detect. If a doctor looks at that area under a microscope, he or she can actually see the inflammation.

But there is another type of ‘inflammation’ that is much harder to detect. In this ‘other’ type of inflammation there is excess production of inflammatory cytokines, but that’s where the inflammation process seems to stop. So you don’t find redness, warmth or swelling – and it can’t be seen under a microscope. But it can still cause pain – and does.

Some call this ‘inflammation’, or a problem with the ‘inflammatory response system’, while others don’t call it anything. They just note that there is excess production of inflammatory cytokines.  That’s what we see in both irritable bowel syndrome and fibromyalgia. There is excess production of inflammatory cytokines. There is pain. There is no typical inflammation.

Fibromyalgia and irritable bowel syndrome

Fibromyalgia and irritable bowel syndrome frequently occur together (they are frequently “co-morbid”.) Up to around 40% of those with fibromyalgia have irritable bowel syndrome (reported figures vary from around 30% to around 60% or even higher.)

Also, up to around 30% of those with irritable bowel syndrome have fibromyalgia. So the ‘overlap’ goes both ways.

It seems that having fibromyalgia increases your risk of developing irritable bowel syndrome – and having irritable bowel syndrome increases your risk of developing fibromyalgia. That’s pretty good evidence that the two conditions are related, and that the overlap isn’t just a ‘coincidence’.

How are fibromyalgia and irritable bowel syndrome related?

As it turns out, both fibromyalgia and irritable bowel syndrome are characterized by excess production of inflammatory cytokines, as demonstrated in the study briefly summarized below.

Those with irritable bowel syndrome were found to have elevated levels of IL-6 and IL-8 (both of which are pro-inflammatory cytokines.) Those with irritable bowel syndrome and either fibromyalgia or chronic fatigue syndrome had an elevation in those same cytokines, plus an elevation in two additional inflammatory cytokines (IL-1 and TNF.)

The three conditions are (obviously) not identical, but if inflammatory cytokine excess plays a role in the cause of each – as seems the case – then it’s easy to see why having one increases your odds of developing the other.

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