Yesterday I was reading an article about a woman who habitually eight matchsticks for years. Yes, she ate unused matches. It struck me, as I am sure it would other people, as bizarre and disturbing. But she was diagnosed with iron deficiency. There was a simple cure. A sad story. In feline terms she was engaging in pica, the eating of non-nutritious foods.

Iron is a major component of haemoglobin, a type of protein in red blood cells that carries oxygen from the lungs of a cat to all parts of the body. Without enough iron there aren’t enough red blood cells. This is anaemia. There are many causes of anaemia one of which is bleeding too much! That sounds crude but an injury would be a cause.
Another, relatively rare cause would be a poor diet. This may occur if the cat’s caregiver is a vegan or vegetarian and is feeding their cat poor-quality food, low in protein resulting in health problems including iron deficiency.
An instinctive, unconscious response of the cat might be to eat non-nutritious foods to make up for the iron deficiency.
In rare cases, exposure to toxins may also cause iron deficiency anaemia in cats. I just want to flag up a possible reason for pica which is a rather enigmatic feline health problem. It is often considered to be idiopathic (without a clear cause). When one cause is iron deficiency, it is a box that a cat owner can tick and resolve by feeding iron rich foods; lean meat such as turkey, pork, beef and chicken and of course standard cat food of a high quality which automatically contains enough iron.
Tuna treats are also good as an iron supplement. That’s handy as most domestic cats like or love tuna.
PS: on the market at present there are commercially prepared cat foods using plant protein. These are balanced diets because the foods contain all the usual nutrients that a domestic cat requires. It is just that the protein comes from plants. These foods will not cause iron deficiency pica!
Below are some more articles on diet.