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Causes - Malnutrition

Malnutrition is when you lack nutrients. This can be due to a poor diet or problems absorbing nutrients from food.

Certain things can increase your risk of becoming malnourished.

Health conditions

Conditions that can lead to malnutrition include:

  • Long-term conditions that cause loss of appetite, sickness and changes in bowel habit, such as cancer and liver disease
  • mental health conditions, such as depression or schizophrenia, which can affect mood and desire to eat
  • conditions that mean you cannot digest food or absorb nutrients well, such as Crohn's disease or ulcerative colitis
  • dementia, this can cause someone to neglect their wellbeing and forget to eat
  • an eating disorder, such as anorexia

You can also become malnourished if your body needs more energy. Your body might need more energy if:

  • it is healing after a serious injury such as a burn
  • if you have involuntary movements such as a tremor
  • it is healing after surgery


Some medicines may increase your risk of malnutrition.

Some medicines have side effects – such as loss of appetite, diarrhoea or nausea. This could mean you eat less or don't absorb as many nutrients from your food.

Physical and social factors

Other things that can cause malnutrition:

  • teeth that are in a poor condition or dentures that do not fit, this can make eating difficult or painful
  • a disability or impairment that makes it difficult to move around, cook or shop for food
  • living and being socially alone
  • not knowing much about nutrition or cooking
  • relying on alcohol or drugs
  • having a low income or living in poverty

Causes of malnutrition in children

In Ireland, malnutrition in children is often caused by a long-term health condition.

For example:

  • childhood cancers
  • congenital heart disease
  • cystic fibrosis
  • cerebral palsy.

Children may become malnourished because of an eating disorder. A behavioural or psychological condition could mean they avoid or refuse food.

Malnutrition from a poor diet is rare in Ireland. But it may happen if a child is neglected, abused or living in poverty. Call the ISPCC on 01 522 4300 if you're worried about a child.

Content supplied by the NHS and adapted for Ireland by the HSE

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 24 March 2021
Next review due: 24 March 2024