Consequences of Malnutrition Flashcards
In which type of vitamin is overdose more likely: lipid-soluble, or water-soluble?
Lipid-soluble
Which type of vitamin needs to be replenished constantly: lipid-soluble, or water-soluble?
Water-soluble
Are vitamin and mineral deficiencies a big problem in Australia?
Low level problem but could be contributing to chronic disease
Why do vitamin and mineral deficiencies occur?
Modern Western diet can be poorly balanced/not variable enough
Individual diet may miss specific sources
Crops can lack nutrients because of availability in soil
Other disorders/lifestyles can interfere with absorption
In whom are vitamin and mineral deficiencies of concern?
Pregnant women
Young children
Elderly people
What does production of vitamin D need?
Exposure of skin to UV or dietary intake
In what foods is vitamin D found?
Fatty fish
Oysters
Eggs
Fortified margarine
Where does vitamin D act as a hormone?
Intestines
Kidneys
Bones
What are the roles of vitamin D?
Bone-making and maintenance by maintaining blood concentrations of Ca and P
- Enhances absorption from GIT
- Enhances re-absorption from kidneys
- Mobilises from bone into blood
How is vitamin D produced?
7-dehydrocholesterol > 2 steps in skin (using UV) > cholecalciferol (vitamin D3) > 1 step in liver/kidney > calcitriol
Is vitamin D3 active?
No
Is calcitriol active?
Yes
What happens in severe vitamin D deficiency in children?
Rickets
- Failure of normal calcification of bones
- Growth retardation
- Skeletal abnormalities
- Bent long bones of leg
Who are at higher risk of vitamin D deficiency?
Dark skinned people living very north/south
Fair skinned people who avoid sun exposure
Night shift workers, office workers, taxi drivers
Older people - skin, liver, and kidneys lose capacity to activate vitamin D
Older/disabled people who’re housebound/in care
People covered for religious reasons
Wat happens in vitamin D deficiency in adults?
Loss of Ca from bones > fractures
What is the role of calcium in the bones?
99% of body’s Ca in bones and teeth
Essential component of bone structure for rigid frame
Ca bank for blood levels Ca
What is the role of calcium in the blood?
1% in blood and cells Part of many enzymes Mediates hormonal responses Essential for blood coagulation Used in muscle contraction Needed for neuromuscular function
Who are at risk of rising blood calcium?
Breastfeeding babies whose intake of milk high
How are falling blood calcium levels elevated?
- Parathyroid hormone stimulates activation of vitamin D
- Vitamin D and parathyroid hormone stimulate Ca reabsorption in kidneys
- Vitamin D enhances Ca absorption in intestines
- Vitamin D and parathyroid hormone stimulate osteoclasts > break down bone > release Ca into blood
What do blood levels of calcium indicate?
Nothing - they’re always stable
How do you measure levels of calcium in bone?
No measures
Can measure bone mass and density
What foods in Australia are fortified?
Thiamine in bread
Folate and iodine in flour
Breakfast cereals voluntarily commonly fortified
What proportion of Australian women over 19 don’t have an adequate intake of folate?
9%
Who are recommended to take extra folate?
All women of childbearing age
What does a folate deficiency in pregnancy cause?
Neural tube development defects; eg: spina bifida
What cellular processes need folate?
DNA - Replication - Repair - Methylation Especially relevant during rapid cell division and development
Why is it important to have adequate amounts of folate before you find out you’re pregnant?
Neural tube development complete by 4 weeks
Very rare for woman to know she’s pregnant at this time > don’t often know until 6-8 weeks
What does folate deficiency in adults cause?
Macrocytic/megablastic anaemia
Characterised by large RBCs
Why does macrocytic anaemia occur in folate deficiency?
Slow repair of DNA damage
Is macrocytic anaemia because of folate deficiency common?
No, but some anticancer drugs can interfere with folate levels > deficiency
How is macrocytic anaemia treated?
Extra folate
What is the relationship between folate and vitamin B12?
Need each other for activation
What is vitamin B12 needed for?
Regenerated levels of methionine
DNA and RNA synthesis
Why do vitamin B12 levels decrease slowly?
Recycled for re-use
Where is vitamin B12 found?
Only in animal products
Almost all of vitamin B12 in plants inactive > vegans at risk of deficiency
How is folate activated?
Folate in food as polyglutamate = inactive
In intestine - breaks off glutamates > adds methyl groups > absorbed and delivered to cells = inactive
In cells trapped in inactive form
Vitamin B12 removes and keeps methyl group
- Removal of methyl activates folate
- Addition of methyl activates vitamin B12
How does a vitamin B12 deficiency lead to damage to myelin sheaths of peripheral nerves?
Levels of metabolic intermediates like methylmalonine CoA build up
Cause damage to myelin sheath
What are the symptoms of vitamin B12 deficiency?
Reduced performance on tests of intelligence and short-term memory
Creeping paralysis starting in extremities
What are the symptoms of an inability to activate folate?
Megablastic anaemia
- Often 1st symptom of vitamin B12 deficiency
What would be the effect of treating megablastic anaemia of a patient with vitamin B12 deficiency with folate?
Rapidly fix anaemia
Still have vitamin B12 deficiency
Peripheral nerve damage continues
What is the number one cause of preventable intellectual disability in children?
Iodine deficiency
What does a major iodine deficiency cause?
Goitre
Why may have mild iodine deficiency recently re-emerged in Australia?
Lower salt diet
Are difficulties in school caused by a mild iodine deficiency reversible with iodine supplementation?
Yes
What does severe iodine deficiency during pregnancy cause?
Severe and irreversible physical and mental retardation = cretinism
What is the most common deficiency in the world?
Fe
What is iron a part of?
Haemoglobin and myoglobin
P450 enzymes
Lysosomal enzymes
Ribonucleotide reductase
Why is iron never found free in the body?
Extremely toxic
How is iron kept in the body?
Bound to transport/storage proteins
From where is iron recycled in the body?
RBCs
How are iron stores depleted?
Shedding of intestinal and skin cells
Blood loss through menstruation in women
Why do children need more iron?
To increase blood volume
What is thiamine used for in the body?
Essential part of coenzyme thiamine pyrophosphate
What does severe thiamine deficiency cause?
Beriberi
- Oedema
- Muscle wasting
Is thiamine deficiency common in Australia?
No, rare
Except when caused by alcoholism
What are the dietary risks associated with alcoholism?
Low intake
Impaired absorption
Alterations in storage
Possibly increased excretion
How can absorption be impaired in alcoholism?
Damage to cells lining intestine
Alterations in function of pancreas > reduced digestive enzyme production
Alterations in fat absorption limits intake of lipid soluble vitamins
- A
- E
- D
How can storage be altered in alcoholism?
Decreased liver function > decreased vitamin A store
What vitamins and minerals are vegans at risk of being deficient in?
Vitamin B12 Vitamin D Fe Ca Zn
Why are calcium and vitamin D important in the elderly?
Vital for preventing loss of Ca from bones > reducing risk of fractures
Why may the elderly develop deficiencies?
Harder to shop for fresh foods Harder to cook Could be cooking for just 1 Tastes and appetites change Dental problems/dentures can make chewing harder Changes in digestion and absorption through - Age - Disease - Medication
