Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: GlentoranMark on 28/08/2009 11:58:51

Title: Why don't we eat when we're ill?
Post by: GlentoranMark on 28/08/2009 11:58:51

Having just suffered (still suffering) from a bad flu, my appetite completely went and for 2 days solid all I had was a few pieces of toast and water. Now I'm drained, I'm finding it hard getting back on my feet. Surely eating regularly, my energy levels would be higher and I would find it easier to beat any diseases and recover quicker.

Why does my body not do what my brain says is logical?

Title: Why don't we eat when we're ill?
Post by: Nizzle on 28/08/2009 14:15:12

What we experience as the hunger feeling is caused by the hormone duo Ghrelin (http://en.wikipedia.org/wiki/Ghrelin) en Leptin (http://en.wikipedia.org/wiki/Leptin).

These Hormones also have different other functions throughout the body and are busy elsewhere when you're being attacked by a flu invasion.

I don't know the exact workings of it, but I'm sure it has to do with these hormones

Title: Why don't we eat when we're ill?
Post by: Pwee on 29/08/2009 10:09:31

I don't know it's hormonal background, but it is a part of the "Sickness Behavior". Sickness Behavior is the set of physiological, behavioral, emotional and cognitive changes that we usually go through under illness (usually under the effects of an infection, when lots of inflammatory processes are going on in the body).

Physiological components: fever, bigger concentration of acute phase proteins in the metabolism of the liver, decreased level of iron, zinc and cooper in the plasma.
Behavioral components: sleepiness, increased proportion of slow wave sleep (deep sleep), reduced food and liquid intake, reduced social, sexual and aggressive behaviors, lowered pain-tresshold and reactivity, reduction in grooming
Emotional components: depressive mood
Cognitive components: slower cognitive functioning, harder to concentrate

In the Wikipedia article (http://en.wikipedia.org/wiki/Sickness_behavior) it says about the "adaptive advantage" of the limited food intake:

Quote

Anorexia limits food ingestion and therefore reduces the availability of iron and zinc in the gut (and from gut absorption). Iron and zinc may aid bacterial reproduction so their reduction is useful during sickness.[13] Plasma concentrations of iron and zinc are lowered for this antibacterial reason in fever.

Science concerning sickness behavior is still in its infancy, mostly speculations about the advantages, but I don't know of other theories that explain the whys of these phenomena.

Title: Why don't we eat when we're ill?
Post by: Nizzle on 11/09/2009 13:39:02

Put some old molded biscuits on the table as well