Cytokine

Cytokines are small signalling proteins that cells use to communicate, particularly within the immune system. They coordinate inflammation, direct immune cells to where they are needed, and regulate how strongly and for how long a response continues.

Their names appear frequently in health writing: interleukins, tumour necrosis factor alpha, interferons. Most act locally over short distances, unlike hormones, and most have multiple effects depending on which cell receives them and what else is happening at the time.

They are not divisible into good and bad, which is where popular anti-inflammatory content goes wrong. The same molecule can be protective in one context and damaging in another, and an immune system without them would be no immune system at all.

Exercise produces its own cytokine response, and this is one of the more interesting findings in the field. Contracting muscle releases signalling molecules sometimes called myokines, including interleukin-6, which behaves differently when released from muscle during exercise than when released during infection, and appears to contribute to the anti-inflammatory effects of regular training.

Chronic low grade cytokine signalling is the mechanism behind what is often called inflammaging, the persistent low level inflammation associated with obesity, inactivity, poor sleep and ageing, and with cardiovascular and metabolic disease.

Measuring individual cytokines has little consumer value. They fluctuate rapidly, assays vary, and hs-CRP is the general marker actually used clinically.

In practice, the levers that reduce chronic inflammatory signalling are exercise, losing excess visceral fat, sleep and not smoking, rather than anything sold as anti-inflammatory.