E7. Micronutrients Flashcards
what are micronutrients?
Substances required in small amounts for normal metabolism but which cannot be synthesised by the body in sufficient quantities.
what is the major division of micronutrients based on solubility?
- fat soluble (ADEK)
- water soluble (Bs,C)
Vitamin deficiencies?
-Vit A- impaired night vision
-Vit D- impaired calcium absorption and bone mineralisation
-Vit C- breakdown of connective tissue (Scurvy)
-Vit B12- megaloblastic anaemia
-Vit K- haemorrhagic disease
Vitamins and their sources?
ONE NOTE
Describe vitamin A
RNI: 600-700mg/day
Sources:
Dairy fat, eggs, liver, fatty fish, carotene in veg
How is vitamin D (cholecalciferol; D3) formed?
-Formed in skin by action of UV light on 7-dehydrocholesterol
-Pre-cursor of 1,25-dihydroxycholecalciferol (1,25-DHCC)
(also known as calcitrol)
-Produced in kidney, regulated by parathyroid hormone
-Calcitrol acts on nuclear receptors
-Stimulates gene synthesis of Ca2+ binding protein to increase Ca2+ absorption from GIT
-Enhances Ca2+ reabsorption from kidney
Sources of vitamin D
> 90% of vitamin D supply is derived from ultraviolet B light
-Oily fish including trout, salmon, mackerel, herring, sardines, anchovies, pilchards, and fresh tuna
-Cod liver oil and other fish oils
-Egg yolk
-Supplemented breakfast cereals, mainly supermarket “own brands” in the UK
-Margarine and infant formula milk
Vitamin D requirements?
-Fair skinned person: 20 minutes to 30 minutes of sunlight exposure on the face and forearms at midday 2-3 times per week should generate enough vit D in summer in UK.
-Darker skin & elderly: need increased exposure or frequency (2 to 10 fold).
-BUT, 6 months of year, 90% of UK UVB levels too low for vit D synthesis.
-Require dietary sources
Vitamin D deficiency leads to?
Rickets (increase in cases), osteoporosis
Also link to:
CVD
Diabetes (1 & 2)
Bowel cancer
Breast cancer
Risks of vitamin D deficiency?
-Caused mainly by poor exposure to sun.
-Living in Northern Latitudes
-Clothing- no exposure of skin to sunlight
-Working indoors
-Not being able to get outside
-Poor nutrition or absorption
Describe vitamin E
-Safe intake 3-4 mg/day
-Antioxidant (readily oxidised)
-Prevents damage to phospholipids
-Sources:
Vegetable oils, whole grain cereals, green leafed veg, seeds, nuts, eggs
Describe how vitamin K works
-Safe Intake 1mg/kg/day
-Required for posttranslational modification of prothrombin and clotting factors VII, IX and X
-NB warfarin blocks vit K reductase
what are the sources and deficiency related to vitamin K?
-Sources:
Liver, green leafy veg, some veg oils, milk
-NB interaction with warfarin
-Deficiency:
New born- possibility of haemorrhage.
-All new born given vit K.
Describe vitamin B12
-RNI 1.5 mg/day
-Sources:
Meat, fish, eggs, fermented foods.
-Deficiency:
Megaloblastic anaemia; degeneration of spinal cord
-Risk:
Vegan diet, poor absorption eg pernicious anaemia- inadequate production of Intrinsic Factor required for GI uptake
Describe folic acid
-RNI 200mg/day (non-pregnant)
-Sources:
Green leafy vegetables, liver
-Deficiency:
Megaloblastic anaemia; neural tube defects
-Risk:
Poor diet, malabsorption, phenytoin
Vit B12 and Folate Pathways?
ONE NOTE
Folic acid deficiency?
-Deficiency effects cells in which there is high turn over of DNA
eg red blood cells
-Megaloblastic anaemia- large, immature blood cells
-Pernicious anaemia- impaired uptake of vit B12.
-Development of spinal cord (myelin as well)
Describe Thiamin(e) (vit B1)- RNI, sources and risk
-Thiamin(e) (vit B1) required for metabolism
-RNI 1mg/day
-Sources:
Fortified breakfast cereals, fortified flour, wholegrain, pulses, vegetables, milk
-Risk:
Poor diet, alcoholics, refined flour
Describe Thiamin(e) (vit B1) deficiency
-Poor metabolism of carbohydrate, accumulation of pyruvate
-Reduced lipid and myelin biosynthesis.
-Beriberi- effects on sensory and motor nerves, muscle wasting, paralysis
Thiamine in metabolism?
one note
Describe nicotinic acid/ niacin(vit B3)- RNI, sources, deficiency, risk
-Required for metabolism
-RNI 17mg/day
-Sources:
Meat, cereals, fish
-Deficiency:
Pellagra- dermatitis, diarrhoea, dementia (eventually death)
-Risk:
Poor diet, alcoholics,
Describe Vitamin C (Ascorbic acid)- RNI, sources, deficiency and risk
-RNI 40mg/day
-Sources: Fruit, salad & leafy veg.
-Deficiency: Scurvy
-Risk: Poor diet
role of vitamin C?
-Antioxidant
-Required for proline hydroxylase.
Converts proline to hydroxyproline- required for collagen
what is scurvy?
-bleeding gums, loose teeth, leaky blood vessels, impaired wound healing.
-Caused by impaired synthesis of collagen
other vitamins?
-Vit B2
-Vit B6
-Biotin
-Pantothenic acid
minerals and trace elements?
one note
Describe calcium- RNI, sources, deficiency and risk
-RNI 700mg/day (pint of milk)
-Sources:
Milk & milk products, fish (esp. if bones eaten), green veg, pulses, supplemented flour
-Deficiency: Long term- osteoporosis
-Risk: Poor diet (vit D & low intake)
how much calcium do adults contain and what is it needed for?
-Adults contain approx. 1.2kg
-Needed for:
Bones (99%)
Cell signalling
Muscle function
-Calcium laid down in bones by early-mid 20s
-After menopause, calcium balance in bones becomes negative
-Impairment of calcium absorption eg coeliac disease
Long-term use of Corticosteroids effects?
-Long-term use of Corticosteroids increase risk of osteoporosis (bone demineralisation).
-Patients may require calcium supplement (up to 1500mg/day).
-Also, reduced uptake in GI disease.
eg Crohn’s Disease/ Coeliac disease
-Increased risk of osteoporosis, therefore patient requires increase in calcium intake.
Describe iron- RNI, sources, deficiency and risk
-RNI 8.7mg/day (M), 14.7mg/ day (F)
-Sources: Meat, fish, cereals, green veg.,
-Deficiency: Anaemia
-Risk: Chronic blood loss, vegetarian diet low in iron
Iron role in metabolism?
-Component of haemoglobin, myoglobin, and enzymes.
-Mostly stored as ferritin
Iron role in absorption?
-Haem iron absorbed better than non-haem iron.
-Vitamin C aids absorption
-calcium & tea inhibit absorption
Symptoms of iron deficiency?
-Anaemia –Fatigue, restlessness, impaired performance, thermoregulation, immunity.
-Common in infants, preschool children, adolescents and women of childbearing age (menstruation)
-Most common micronutrient deficiency in the world.
Describe vitamin/ mineral supplements
-Shouldn’t be required with healthy, balanced diet
-Can cause toxicity.
-Be aware of supplements containing high doses.
ONE NOTE
