E7 Micronutrients: vitamins & minerals Flashcards
what are micronutrients?
- substances required in small amounts for normal metabolism
- can’t be synthesised by the body in sufficient quantities (except vitamin D perhaps)
describe vitamin D deficiency prevalence
- elderly: only around 15% reach recommended levels on a daily basis
- 1 in 8 white people
- 1 in 4 Afro-Caribbeans
- 1 in 3 Asian people
- 1 in 2 Asian women
describe vitamin C deficiency prevalence
- low income in UK
- 46% men
- 35% women in low income
what does vitamin C deficiency pose the risk of?
scurvy (common in Victorian times)
what are the 2 major divisions of vitamins and which vitamins are in each division?
fat soluble
ADEK
water soluble
Bs C
state a symptom of vitamin A deficiency
impaired night vision
state a symptom of vitamin D deficiency
impaired calcium absorption and bone mineralisation
state a symptom of vitamin C deficiency
- breakdown of connective tissue (scurvy)
- leads to loosening of teeth and bleeding gums
state a symptom of vitamin B12 deficiency
megaloblastic anaemia
state a symptom of vitamin K deficiency
hemorrhagic disease
state some sources of vitamin A
dairy products
dairy fat
eggs
fatty fish
carotene in veg
liver
state some sources of vitamin B1
fortified breakfast cereals
nuts
fortified flour
wholegrain
pulses
vegetables
milk
seeds
state some sources of vitamin B2
liver
dairy products
state some sources of vitamin B3
meat
wholemeal cereals
fish
state some sources of vitamin B6
liver
cereals
fruit
vegetables
state some sources of vitamin B12
meat
fish
dairy products
eggs
fermented foods
state some sources of vitamin C
fruit
salad
leafy vegetables
state some sources of vitamin D
- sunlight
- dairy products
- oily fish (trout, salmon, mackerel, herring, sardines, anchovies, pilchards, tuna)
- egg yolk
- cod liver oil and other fish oils
- supplemented breakfast cereals
- margarine
- infant formula milk
state some sources of vitamin E
green leafy vegetables
vegetable oils
whole grain cereals
seeds
nuts
eggs
state some sources of vitamin K
liver
green leafy vegetables
some vegetable oils
milk
state some sources of folic acid
liver
green leafy vegetables
whole grain cereals
what does RNI stand for?
reference nutrient intake
what is the RNI of vitamin A?
600-700 micrograms / day
what risk is there of vitamin A during pregnancy?
risk of teratogenic effects with vitamin A supplements in pregnancy
describe vitamin D and its synthesis
- formed in skin by action of UV light on 7-dehydrocholesterol
- precursor of 1,25-dihydroxycholecalciferol (1,25-DHCC), aka calcitriol
where is calcitriol produced? what is it regulated by?
- produced in kidney
- regulated by parathyroid hormone
what does calcitriol act on?
nuclear receptors
what does calcitriol stimulate and enhance?
- stimulates gene synthesis of Ca2+ binding protein to increase Ca2+ absorption from GIT
- enhances Ca2+ reabsorption from kidney
what is calcitriol involved in?
- the increase of plasma levels of vitamin D
- this is why low levels lead to bone issues such as rickets and loss of bone which leads to osteoporosis
how much sunlight do fair skinned, dark skinned and elderly people need for adequate vitamin D?
fair skinned person
- 20-30 minutes of sunlight exposure on the face and forearms at midday 2-3 times per week should generate enough vitamin D in UK summer
darker skin and elderly
- need increased exposure of frequency (2-10 fold increase)
is sunlight adequate for vitamin D production all year round?
- 6 months of the year, 90% of UK UV B levels are too low for vitamin D synthesis
- this can be okay because vitamin D is fat-soluble so it is stored in the body
- dietary sources are required as the stores deplete during the winter months
symptoms of vitamin D deficiency
rickets
osteoporosis
linked to:
CVD
diabetes (1&2)
bowel cancer
breast cancer
causes of vitamin D deficiency
caused mainly by poor exposure to sun
- living in Northern Latitudes
- clothing: no exposure of skin to sunlight
- sun cream use prevents action of UV making vitamin D
- working indoors
- not being able to get outside
- poor nutrition or absorption
what is the safe intake of vitamin E per day?
3-4 mg / day
describe vitamin E and its function
- antioxidant (readily oxidised)
- protects against reactive oxygen species
- prevents damage to phospholipids
safe intake of vitamin K per day
1 microgram / kg / day
what is vitamin K required for?
required for post translational modification of prothrombin and clotting factors VII, IX and X
what drug does vitamin K interact with?
- interacts with warfarin
- warfarin blocks vitamin K reductase
describe vitamin K deficiency in newborns
- possibility of haemorrhage
- all newborns given vitamin K because they are more likely to be deficient so this is a prophylactic standard
what is the RNI for vitamin B12?
1.5 micrograms / day
describe the symptoms of vitamin B12 deficiency
- megaloblastic anaemia
- degeneration of spinal cord
what are the risks of vitamin B12 deficiency?
- vegan diet
- poor absorption (eg. pernicious anaemia - inadequate production of intrinsic factor required for GI uptake)
what does a lack of Intrinsic Factor mean in risk for vitamin B12 deficiency?
- lack of Intrinsic Factor means less vitamin B12 and higher risk of anaemia due to less red blood cells
what is the RNI of folic acid for people who are not pregnant?
200 micrograms / day
describe folic acid deficiency symptoms
- megaloblastic anaemia
- neural tube defects
what is the most important part of pregnancy for folic acid to be taken and why?
- most important to take folic acid in the first 12 weeks
- because the neural tube closes after 12 weeks
what are the risks of folic acid deficiency?
poor diet
malabsorption
phenytoin
what two vitamin pathways are interlinked?
vitamin B12 and folic acid
what does a lack of folic acid mean?
sufficient DNA cannot be made
what does methotrexate inhibit in the vitamin B12 and folate pathways?
DHF reductase
where are vitamin B12 and folate deficiencies seen?
- affects cells in which there is high turnover of DNA (eg. red blood cells)
- patient presented with 4 weeks of numbness in hands and feet
- walking impaired
- drug history: 6 months of daily nitrous oxide use
diagnose, state causes and treatments
- vitamin B12 deficiency
cause
- nitrous oxide inhibits activity of vitamin B12
- reduced synthesis of myelin, impaired transmission of action potentials
treatment
- given vitamin B12
how does nitrous oxide affect vitamin B12?
inhibits vitamin B12 activity so you start to lose feeling as the myelin production is hindered
what is thiamine (vitamin B1) required for?
required for metabolism
what is the RNI of thiamine (vitamin B1)?
1 mg / day
state symptoms for thiamine (vitamin B1) deficiency
- Beriberi (effects on sensory and motor nerves)
- muscle wasting
- paralysis
- poor metabolism of carbohydrate
- accumulation of pyruvate
- reduced lipid and myelin biosynthesis
risks of thiamine (vitamin B1) deficiency
- poor diet
- alcoholics (metabolism of alcohol leads to B1 deficiency)
- refined flour
draw an image showing the thiamine (vitamin B1) pathways
what is the name for vitamin B1?
thiamin(e)
what is the name for vitamin B3?
nicotinic acid / niacin
what is vitamin B3 required for?
metabolism
what is the RNI for vitamin B3?
17 mg / day
state a symptom of vitamin B3 deficiency
pellagra
what are the 4 D’s of pellagra?
dermatitis
diarrhoea
dementia
death (if left untreated)
risks for vitamin B3 deficiency
poor diet
alcoholics
what is the name for vitamin C?
ascorbic acid
what is the RNI of vitamin C?
40 mg / day
symptoms of vitamin C deficiency
scurvy
symptoms of scurvy
- bleeding gums
- lose teeth
- leaky blood vessels
- impaired wound healing
- caused by impaired synthesis of collagen
how was it discovered that scurvy was caused by vitamin C deficiency?
sailors who had lemon juice were less likely to develop scurvy a study found
risks for vitamin C deficiency
poor diet
role of vitamin C
- antioxidant
- required for proline hydroxylase
- converts proline to hydroxyproline - required for collagen
state some minerals and trace elements
calcium
iron
potassium
sodium
phosphorus
zinc
copper
magnesium
selenium
iodine
manganese
molybdenum
fluoride
chromium
chloride
functions of potassium and sodium as minerals / trace elements
maintain electrical potential across membranes
function of selenium as a mineral / trace element
antioxidant that helps to relieve oxidative stress
RNI of calcium. what is this equivalent to in food?
- 700 mg / day
- pint of milk
sources of calcium
- milk and milk products
- fish (especially if the bones are eaten)
- green leafy vegetables
- pulses
- supplemented flour (supplemented with calcium as well as B vitamins)
symptom of long term calcium deficiency
osteoporosis
risk for calcium deficiency
poor diet (vitamin D and low intake)
what is calcium needed for?
bones
cell signalling
muscle function
when is calcium laid down in bones?
by early-mid 20s
what happens surrounding calcium in the menopause?
- calcium balance in bones becomes negative
- women are more at risk of weaker bones and osteoporosis after the menopause
state examples of diseases that cause impairment of calcium absorption
- coeliac disease (inflammation of GIT can reduce calcium absorption)
- GI diseases eg. Crohn’s disease / coeliac disease (patients with these diseases require increased calcium)
long term use of what type of drug increases risk of osteoporosis?
corticosteroids
RNI of iron for males and females
male: 8.7 mg / day
female: 14.7 mg / day
sources of iron
meat
fish
cereals
green vegetables
symptoms of iron deficiency
- anaemia
describe the rarity of iron deficiency
- common in infants, preschool children, adolescents and women of childbearing age (menstruation)
- most common micronutrient deficiency in the world
symptoms of anaemia from iron deficiency
fatigue
restlessness
impaired performance
thermoregulation
immunity
risk for iron deficiency
- chronic blood loss
- vegetarian diet low in iron
iron’s role in metabolism
- component of haemoglobin, myoglobin and enzymes
- mostly stored as ferritin
describe the absorption of iron including what aids and inhibits it
- active transport in small intestine
- haem iron (from animal sources) is absorbed better than non-harm iron (from plant sources)
- vitamin C aids absorption
- calcium and tea inhibit absorption
why are vegetarians more at risk of iron deficiency?
haem iron (from animal sources) is absorbed better than non-harm iron (from plant sources)
are vitamin / mineral supplements safe?
- shouldn’t be required with healthy, balanced diet
- can cause toxicity
- be aware of supplements containing high doses
when should vitamin A supplements be avoided?
- in pregnancy
- chronic use of high dose supplements should be avoided
what should be avoided with vitamin B6 supplements?
high dose or chronic dosing
what should be avoided with zinc supplements?
chronic high doses
describe the toxicity effects of vitamin A supplements
- teratogenicity
- effects on bone, muscle
describe the toxicity effects of vitamin B6 supplements
peripheral neuropathy
describe the toxicity effects of zincsupplements
anaemia
describe the toxicity effects of β carotene supplements
promotion of lung cancer in smokers
