Anaemia is where someone does not have enough red blood cells or a lack of a substance called ‘haemoglobin’ which transports oxygen around the body.

There are several types of anaemia but the one which we are interested in, which is related to food poisoning, is ‘pernicious anaemia’.

Pernicious anaemia

This is a specific type of anaemia in which there is a lack of vitamin B12 in the body. Vitamin B12 is vital for the normal functioning of the body, creating red blood cells and a healthy brain and nervous system.

But vitamin B12 cannot be absorbed by itself: it needs to be combined with a protein produced by the stomach lining in order to do so. This substance is called ‘intrinsic factor’.

This intrinsic factor combines with Vitamin B12 and passes through the intestinal wall into the bloodstream. But if these cells become damaged, for example as a result of food poisoning or some other gastrointestinal infection then this will prevent absorption.

This protein - intrinsic factor - is unable to attach itself to vitamin B12 which then leads to a deficiency.

Pernicious anaemia is classed as an autoimmune disease: this is caused by a ‘fault’ within the immune system which forces it to turn upon itself and attack tissue within the body. In this case, it produces antibodies which attack the gastrointestinal tract resulting in an inflammation within the stomach lining.

How does pernicious anaemia relate to food poisoning?

Food poisoning occurs from the consumption of food or water which has been contaminated by a bacteria, virus or parasite. Once these invade the body via the mouth they then invade the walls of the intestine where they release toxins which cause an infection.

These bacteria can also prevent the absorption of vitamin B12.

An example of this is the fish tapeworm. An infection caused by the fish tapeworm causes symptoms similar to other cases of food poisoning which includes vomiting, diarrhoea, abdominal pains and weight loss. It also leads to a vitamin B12 deficiency.

If you contract food poisoning as a result of eating contaminated fish then you might also develop this complication due to damage within the small intestine.

What we do know is that there are people who are considered at ‘high risk’of food poisoning: this includes the very young and old, and those people with a weak immune system, e.g. as a result of an autoimmune disease.

So, if your immune system is functioning less well then expected then you are at a higher than normal risk of food poisoning and pernicious anaemia.

Symptoms of pernicious anaemia

These symptoms are similar to those for any type of anaemia. They include:

  • Frequent bouts of diarrhoea
  • Pale skin
  • Sore tongue/mouth
  • Weight loss
  • Poorly functioning immune system

Over time this starts to affect the nervous system resulting in muscle weakness, pins and needles in the fingers and toes and confusion.

Diagnosing pernicious anaemia

Your GP will examine you and will also check your pulse and temperature. He/she will carry out a blood test to determine the amount and appearance of your red blood cells. This test will also determine the level of vitamin B12 in your blood.

It will also check the amount of intrinsic factor (protein) in your blood as low levels of this are an indicator of pernicious anaemia. A lack of intrinsic factor means that vitamin B12 cannot be easily absorbed which leads to a deficiency (and pernicious anaemia).

Treatment for pernicious anaemia

This involves injections of vitamin B12 - a version known as ‘hydroxocobalamin’ which is given as an intramuscular injection, once every 2 days.

Around 6 injections are given which enables vitamin B12 to build up within the body.

Once this treatment has started the symptoms of anaemia tend to disappear quickly although you will undergo a blood test on an annual basis to check that this treatment is working.

You will require an injection of vitamin B12 once every 3 months to prevent the symptoms from re-occurring. This will continue for the rest of your life.

You can supplement this via your diet. Eat foods which are rich in vitamin B12 and consider taking a mineral supplement as well. Ask your GP for advice before doing so.

Food Poisoning Guide

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