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The influence of malnutrition in disease aetiology, pregnancy, and in growth and development

Health and Social Behaviour: The influence of malnutrition in disease aetiology, pregnancy, and in growth and development

Malnutrition can be a case of not enough food, too much food, or the wrong types of food.

Over nutrition is usually associated with an excess of energy.

  • This can lead to obesity and increases the risk of other associated diseases such as heart disease, diabetes and hypertension.
  • It can also lead to an excess of certain nutrients (e.g. vitamins and minerals) which can have many adverse effects, including toxicity, if occurring for a prolonged time period.

Under nutrition is a deficiency of energy or of any of the nutrients essential to life.

  • A prolonged deficiency of energy can cause the individual to become thin, lose muscle and be prone to infection and disease.
  • A deficiency of nutrients can lead to many symptoms, including skin rash, depression, hair loss, tiredness, brittle bones and bleeding gums.

Symptoms of a prolonged excess or insufficiency of energy are often visible (an underweight, pale individual, with protruding bones or an overweight individual with excess central adiposity), but this can also be picked up at an earlier stage by
looking at markers such as weight, BMI and other anthropometric measures.

An excess or deficiency of nutrients can be missed more easily. It is often not obvious until symptoms show, and sometimes this can be at an advanced stage. They can, however, be identified at an earlier stage by using blood biochemistry or urine
analysis tests.

During Pregnancy

Maternal energy intake

  • The NICE Fertility guidance (2004) reports that women who have a BMI of more than 29 are likely to take longer to conceive and those women who are not ovulating will increase their chance of conception by losing weight.
  • There is substantial evidence that obesity (excess energy intake) in pregnancy contributes to increased morbidity and mortality for both mother and baby. The CEMACH Maternal Death Enquiry (Why Mother’s Die) found that approximately 35% of
    women who died (who had a recordable Body Mass Index) were obese.
  • Intrauterine growth retardation (IUGR) results in Low Birth Weight (LBW). Intra-uterine growth restriction is a condition where a baby's growth slows or ceases when it is in the uterus.
  • Low birth weight is defined as a full term (>37 weeks gestational age – a baby born over 37 weeks since conception) birth weight of less than 2500g.
  • IUGR is the most significant precursor of malnutrition in infancy.
  • IUGR is a serious public health problem in developing countries but only effects about 2% in developed countries.
  • The major determinant of IUGR is maternal undernutrition, characterised by low pre-pregnancy body weight and short maternal stature (the mother being short in height), and an inadequate / low gestational weight gain.
  • Other risk factors for IUGR are maternal anaemia (low body iron), smoking and infections (especially malaria).
  • LBW due to IUGR increases risk of infant mortality and morbidity. It increases susceptibility to severe malnutrition in childhood, as well as poor cognitive, mental and physical development.
  • Evidence also suggests that LBW due to IUGR also increases the risk of chronic diseases in adulthood, which therefore increases the health burden on society (see 2a epidemiological paradigms section of the syllabus)
  • Continual LBW and stunting perpetuates an intergenerational cycle of malnutrition, poverty and disease.

Iron-deficiency anaemia

  • Iron deficiency is the most common nutritional deficiency in the world, and is considered a major public health problem.
  • Iron Deficiency Anaemia (IDA) affects over 2 billion people worldwide, across all age groups.
  • The highest rates are in infants, children, teens and women of child-bearing age.
  • The prevalence in higher in developing countries than developed countries.
  • The predominant cause of IDA is insufficient iron in the diet.
  • Iron deficiency can permanently handicap children at a crucial time in their scholastic development.
  • Iron deficiency is influenced by the amount of iron in the food and the bioavailability of this iron (how easy it is for the body to absorb it).
  • Haem iron is from animal sources and is readily available for absorption. Non-haem iron is from plant sources and is not very bioavailable. Its availability is also influenced by other factors in the diet (e.g. vitamin C increases its
  • Iron plays a central role in oxygen transportation around the body (as part of haemoglobin in blood).  Iron also features in the normal defence systems of the body against infection.
  • It also plays a large part in the neurotransmitter systems in the brain, influencing behaviour change in terms of attention, memory and learning.
  • Maternal iron deficiency increases risk of maternal mortality and morbidity, and also increases risk of foetal morbidity, mortality and LBW.
  • The World Health Organisation (WHO) is actively developing strategies to prevent iron deficiency, including iron supplementation (especially in pregnant women); iron fortification of certain foods (the UK, USA and Canada practice this); and
    dietary modification to increase the bioavailability of iron.

Iodine Deficiency Disorder

  • Iodine deficiency disorder (IDD) refers to a number of physical effects arising from a deficiency of dietary iodine.
  • It is a significant problem in 130 countries - 740 million people are affected worldwide.
  • Iodine is needed for the production of thyroid hormones within the body. These are essential for normal human growth and development, and a deficiency can cause retardation of growth of all organs.
  • Extreme iodine deficiency in pregnancy and infancy can cause cretinism.
  • Thyroid hormones are needed for the transition from life in the womb, to life outside the womb.  Iodine deficiency can lead to a lack of these hormones, which can lead to still births.
  • The brain is very susceptible to damage during the foetal and early post natal periods. A post natal deficiency of iodine causes a slowing of mental processing which can permanently impair mental development. Studies have shown that iodine
    supplementation in early life can lead to substantial improvements.
  • Excessive intakes of goitrogens in food can interfere with iodine uptake and metabolism within the body. Goitrogens are found in cassava and brassica vegetables. Cassava has been identified as an important contributor to IDD, as it is a staple
    in many areas.
  • Marine fish, milk and meat are good sources of iodine.
  • IDD is a serious public health issue, mainly in developing countries. It could be largely eradicated if mass community programmes were undertaken.
  • It is relatively scarce in developed countries due to the introduction of iodization of salt.
  • Public health initiatives for correcting IDD require individuals to be provided with adequate levels of iodine. This can be done by the iodization of salt (favoured by USA and New Zealand), iodized oil injections (New Guinea, China, Indonesia)
    or iodized oil by mouth.  However, the cost of these programmes is sometimes an issue affecting successful implementation.

In Growth and Development

Vitamin A - Vitamin A deficiency (VAD)

  • Vitamin a deficiency (VAD) leads to xerophthalmia, and may result in blindness in children.
  • VAD is the leading cause of preventable blindness in children and increases the risk of disease and death from severe infections. In pregnant women VAD causes night blindness and may increase the risk of maternal mortality.
  • In 1994, WHO gave a global estimate of 2.8 million preschool children clinically affected by vitamin A deficiency, and 251 more are sub-clinically deficient.
  • Xerophthalmia is a severe drying of the eye surface caused by a malfunction of the tear glands. The most common cause is a decreased intake or absorption of vitamin A. Symptoms include night blindness and eye irritation.
  • Xerophthalmia is treated with artificial eye moisturizers and vitamin A supplementation.
  • There is increasing evidence that, in deficient populations, vitamin A supplementation can reduce morbidity, mortality and blindness.
  • Yellow and orange fruit and vegetables are rich in carotenes, (part of the vitamin A family) so are a good source of vitamin A.
  • Food fortification, for example sugar in Guatemala, maintains vitamin A status, especially for high-risk groups and families.
  • Promoting breast feeding is a key way to prevent VAD in babies.

Protein Energy Malnutrition – kwashiorkor and marasmus

  • There are 3 forms of Protein Energy Malnutrition in children – Kwashiorkor, Marasmus and Marasmic Kwashiorkor.
    1. Kwashiorkor has a high mortality and is characterised by an oedematous appearance and moon face, with scaly and ‘crazy-paving’ pigmentation, sparse discoloured hair and ulcerated skin. Fat on limbs and trunk hide atrophied muscle
      mass.  Kwashiorkor can often occur in an epidemic form once a measles outbreak has affected a community.
    2. Marasmus children are wrinkled and shrunken, growth retarded and skeletal. There is no oedema but severe muscle wasting. Oedema is fluid retention and it occurs when there is too much fluid (mainly water) in the body's tissues,
      causing swelling to occur in the affected area.  Marasmus has lower mortality rates than kwashiorkor.  
    3. Marasmic kwashiorkor occurs if a Marasmic child is overfed early and with a diet too high in sodium, which causes oedema.
  • The dominance of these 3 forms varies, reflecting breastfeeding and weaning practices, the staple foods in the area and recurrent infections.
  • As well as severe forms of malnutrition, there are many other forms of mild and moderate childhood undernutrition.

Stunted growth

  • Undernutrition in childhood is characterised by growth failure, defined by a body weight and height less than the ideal for their age.
  • Presence of undernutrition in children is assessed using weight for age, height for age and weight for height (see growth charts).
  • Stunting can be the result of complex interaction between quality and quantity of food eaten, and the effect of chronic low-grade intestinal, respiratory and other infections.
  • Children who become stunted through malnutrition are likely to develop poorly and have deficits in intellectual and cognitive development and social behaviour.


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  • NICE (2004). Fertility: assessment and treatment for people with fertility problems.
  • Food Standards Agency website [accessed April 2008]
  • World Health Organisation [accessed May 2008]
  • Prevention and control of iron deficiency anaemia in women and children. Report of the UNICEF/WHO Regional Consultation. February 1999.
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  • Garrow J.S, James W.P.T, Ralph A. Human Nutrition and Dietetics (10th Edition). Churchill Livingstone (2001)
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© Rebecca Nunn 2008