14. Micronutrients

Question 1

What is the role of micronutrients?

Answer 1

Maintenance of homeostasis in adults

Most important in children: energy supply, body growth and development

Question 2

What are the different types of micronutrients within the body?

Answer 2

Organic micronutrients - vitamins

Inorganic micronutrients - trace elements

Question 3

What are the fat soluble vitamins?

Briefly describe these

Answer 3

A D E K
These can be stored in the body
These are toxic in the body when they are in excess

Question 4

What are the water soluble vitamins?

Briefly describe these

Answer 4

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

Question 5

What are trace elements?

Answer 5

Dietary minerals that are necessary in very minute quantities for the normal function of the organism

Question 6

What are the trace elements required by humans?

Answer 6

Calcium
Phosphorus
Iron
Selenium
Zinc
Copper

Question 7

What is kwashiorkor?

Answer 7

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

Question 8

What is marasmus?

Answer 8

These is severe malnutrition of most food groups, including carbohydrates
More common in older patients

Question 9

What is ascites?

Answer 9

Accumulation of fluid in the periteoneal cavity

Very common when there is portal hypertension

Question 10

What are the clinical consequences of malnutrition?

Answer 10

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

Question 11

What is the clinical outcome of vitamin D deficiency?

Answer 11

Osteomalacia and Rickets

Question 12

Give the pathway of vitamin D metabolism in the body

NEED TO KNOW

Answer 12

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

Question 13

What lifestyle factors can lead to reduced levels of vitamin D?

Answer 13

Lack of exposure to the sun 
Smoking
Obesity 
Alcohol 
Exercise

Question 14

What disease factors can lead to reduced levels of vitamin D?

Answer 14

Reduced skin biosynthesis
Decreased bioavailability 
Drug-related interactions
Increased excretion
Impaired hydroxylation
Exclusive breast feeding > 6/12 months

Question 15

What is osteomalacia?

Answer 15

Reduced bone strength

Can lead to increased number of bone fractures, bone pain, bending of bones, muscle weakness, waddling gait

Question 16

What is rickets?

Answer 16

Defective calcification of bones prior to epiphyseal fusion

Growth retardation

Question 17

What is the clinical outcome of a Thiamine/B1 deficiency and what is the importance of this?

Answer 17

Wernicke’s Encephalopathy
Korsakoff’s psychosis

These are entirely preventable but once these occur, they are entirely irreversible

Question 18

What is the role of vitamin B1/Thiamine?

Answer 18

Involved in carbohydrate metabolism - absorbed in the jejunum

Question 19

What are the clinical presentations of thiamine/vitamin B1 deficiency?

Answer 19

Anorexia and weight loss
Cognitive impairment
Muscle weakness

Most commonly seen in malignancy and alcoholism

Question 20

Why is thiamine essential in the body?

Answer 20

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

Question 21

What is the clinical outcome of Vitamin B3/Niacine deficiency?

Describe this

Answer 21

'Pellagra' 
Early - loss of appetite, generalised weakness, irritability, abdominal pain, vomiting
Late - Vaginitis 
Oesophagitis
Diarrhoea
Depression 
Seizures 
Casal's necklace

Question 22

What are the clinical presentations of a B12 deficiency?

Answer 22

Anaemia, glossitis, malabsorption and diarrhoea, anorexia, sensory disturbance, gait abnormalities, memory loss and disorientation

Question 23

What is meant by refeeding syndrome and why does it occur?

Answer 23

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

Question 24

What is essential in the treatment of refeeding syndrome

Answer 24

Must give the patient water soluble vitamins e.g. pabrinex

Question 25

What is the treatment and management for refeeding syndrome?

Answer 25

Aggressive electrolyte replacement
Nutritional supplementation
Treat any underlying medical problems
Early dietician review
May need cardiac monitoring