14. Micronutrients Flashcards
What is the role of micronutrients?
Maintenance of homeostasis in adults
Most important in children: energy supply, body growth and development
What are the different types of micronutrients within the body?
Organic micronutrients - vitamins
Inorganic micronutrients - trace elements
What are the fat soluble vitamins?
Briefly describe these
A D E K
These can be stored in the body
These are toxic in the body when they are in excess
What are the water soluble vitamins?
Briefly describe these
B, Folate, Biotin, C
These are not normally stored within the body
Often act as conenzymes
If these are in excess then they are excreted in the urine
What are trace elements?
Dietary minerals that are necessary in very minute quantities for the normal function of the organism
What are the trace elements required by humans?
Calcium Phosphorus Iron Selenium Zinc Copper
What is kwashiorkor?
Protein-wasting malnutrition - sufficient levels of other food groups e.g. carbohydrates but insufficient protein levels
The patients tend to be young
Patients present with ascites
What is marasmus?
These is severe malnutrition of most food groups, including carbohydrates
More common in older patients
What is ascites?
Accumulation of fluid in the periteoneal cavity
Very common when there is portal hypertension
What are the clinical consequences of malnutrition?
Impaired wound healing
Impaired immune response - predisposes to infection
Reduced muscle strength
Inactivity - leads to pressure sores, thromboembolism
Increased risk of postoperative complications
Depression and self-neglect
What is the clinical outcome of vitamin D deficiency?
Osteomalacia and Rickets
Give the pathway of vitamin D metabolism in the body
NEED TO KNOW
Vitamin D2 Ergocalciferol - derived from plant sources
Vitamin D3 Cholecalciferol - formed in the skin or is ingested
Vitamin D2 and D3 are delivered to and hydroxylated by the liver to Calcidol
Calcidol is the major circulating form of vitamin D - further hydroxylated by the kidneys to Calcitriol
Calcitriol is regulated by parathyroid hormone PTH
What lifestyle factors can lead to reduced levels of vitamin D?
Lack of exposure to the sun Smoking Obesity Alcohol Exercise
What disease factors can lead to reduced levels of vitamin D?
Reduced skin biosynthesis Decreased bioavailability Drug-related interactions Increased excretion Impaired hydroxylation Exclusive breast feeding > 6/12 months
What is osteomalacia?
Reduced bone strength
Can lead to increased number of bone fractures, bone pain, bending of bones, muscle weakness, waddling gait
What is rickets?
Defective calcification of bones prior to epiphyseal fusion
Growth retardation
What is the clinical outcome of a Thiamine/B1 deficiency and what is the importance of this?
Wernicke’s Encephalopathy
Korsakoff’s psychosis
These are entirely preventable but once these occur, they are entirely irreversible
What is the role of vitamin B1/Thiamine?
Involved in carbohydrate metabolism - absorbed in the jejunum
What are the clinical presentations of thiamine/vitamin B1 deficiency?
Anorexia and weight loss
Cognitive impairment
Muscle weakness
Most commonly seen in malignancy and alcoholism
Why is thiamine essential in the body?
Thiamine is required for the removal of pyruvate from the Kreb’s cycle
If this does not occur, there is a build up of pyruvate and so there is a conversion of this to Lactic acid
A build up of lactic acid leads to lactic acidaemia and death of neurones
What is the clinical outcome of Vitamin B3/Niacine deficiency?
Describe this
'Pellagra' Early - loss of appetite, generalised weakness, irritability, abdominal pain, vomiting Late - Vaginitis Oesophagitis Diarrhoea Depression Seizures Casal's necklace
What are the clinical presentations of a B12 deficiency?
Anaemia, glossitis, malabsorption and diarrhoea, anorexia, sensory disturbance, gait abnormalities, memory loss and disorientation
What is meant by refeeding syndrome and why does it occur?
Anabolic state - main energy source is carbohydrates
Catabolic state - main energy source is fat and proteins
If someone is starving and in the catabolic state and they are suddenly given many sugars (carbohydrates) then they do not have the right regulatory mechanisms as these have all been down-regulated
Also, during starvation, you are missing the water soluble vitamins
If then fed carbohydrates, require the Krebs cycle for the metabolism of this but this cycle requires the water soluble vitamins e.g. Thiamine SO presents as refeeding syndrome
The patient essentially ends up with all of the water soluble deficiency states at the same time
What is essential in the treatment of refeeding syndrome
Must give the patient water soluble vitamins e.g. pabrinex
What is the treatment and management for refeeding syndrome?
Aggressive electrolyte replacement Nutritional supplementation Treat any underlying medical problems Early dietician review May need cardiac monitoring
