vitamins-fat soluble Flashcards
what are vitamins and what is the function of them?
-Vitamins are all organic compounds- all contain carbon
Functions:
-essential for many body processes
-play role in digestion, utilisation of CHO, proteins and fats
-Do not produce energy when broken down
-are co-enzymes -they assist enzymes and other biological factors that release energy from CHO, protein and fats
how are vitamins classified?
-classified according to solubility
Fat soluble vitamins-function in fatty tissues (cell membranes/ nerve tissues)
Water sol vitamins- function in watery areas (fluids outside/ inside body cells)
what are the water soluble vitamins?
-Vit C
-B vitamins:
Niacin B3
Pantothenic Acid
Riboflavin B2
Folic Acid Thiamin B1
Biotin
Vit B6
VIT B12
what are the differences between fat soluble and water soluble vitamins?
-Absorption- fat sol vit absorbed into lymph then blood/ protein carrier
-water sol absorbed directly into the blood
-Storage- fat sol are stored long term in liver and adipose tissue
-water sol are stored short term- not easily stored
-excretion -fat sol are less readily excreted and remain in fat storage sites
-water sol vitamins are detected by kidney and removed in urine
what is vitamin A and how is it absorbed?
-retinol
-carotenes are also source of vitamin A as they can be converted into retinol
-Retinol needs bile salts, vitamin E and adequate protein to be absorbed
-Carotene not absorbed as efficiently (only 9-17%)
where is vitamin A stored and how is it transported?
-Stored in liver, kidney and pigment layer of eye
-Transported by being bound to retinol binding protein and pre-albumin
functions of vitamin A?
-vision
-bone growth
-reproduction
-epithelial growth and differentiation
-overall growth
-anti infection
How does vitamin A contribute to vision?
-Controls the speed at which eye adjusts from bright to dim light
-causes rhodopsin to be resynthesised in the dark and broken down when exposed to light
Effect of vitamin A deficiency?
-night blindness- people take a long time to recover enough rhodopsin to be able to see in dim light
-May also cause collapse of eye ball
-causes epithelium cells to beecome dryer and harder as more vitamin A that senters cell the greater the mucus secretions
-increased possibility of infection
What are the signs of vitamin A deficiency?
-follicular hyperkeratosis
-rough skin
-changes in taste and smell
what factors affect vitamin A deficiency in low income countries?
-dietary inadequacy (low fat, low protein)
-low liver reserves at birth
-low levels in breast milk
-frequent infections
name the Dietary sources of vitamin A
Retinol(found only in animal sources):
-meat (49%)
-liver (44.5%)
-fats (23%)
-milk/dairy (22%)
Carotene
-vegatables (83%)
-carrots (55%)
-milk/ dairy (5%)
Effect of vitamin A excess/ whats it caused by?
-caused from taking supplements
-can accumulate in liver and result in birth defects, permanent damage to liver/eyes
-reduced bone density
recommneded intake of vitamin A
500ug-men, 400ug- women, 250ug- children
what is vitamin D also known as and why is it different from other vitamins?
-differs from other vitamins as body can synthesise it with help of sunlight so is non essential
-aka calciferol
vitamin D functions?
-bone making and maintenance
-assists in absorption of dietary calcium
-helps make calcium and phosphorus available in blood
vitamin D sources?
-produced in skin by U.V radiatio of 7-dehydrocholesterol
-dieatary-firsh-liver oil, flesh of oily fish, egg yolk, liver
where is vitamin D absorbed?
-in intestine
Describe how vitamin D is activated in the body?
-starts in liver cells where it is hydroxylated
-then in kidney its further hydroxylated to metabolically active form of the vitamin. Parathyroid hormone is essential for this to happen
Where does vitamin D act within body?
-gut (calcium absorption)
-kidney (calcium excretion)
-bone (calcium storage/ bone formation)
-parathyroid gland (inhibits parathyroid hormone release)
what is the result of a vitamin D deficiency?
-rickets (symptoms- skeletal deformity, bow legs, poor growth, delayed dental eruption, fractures)
-osteomalacia (muscle weakness & skeletal pain, x rays showing loss of bone density
which groups are most at risk of vitamin D deficiency and what are the risk factors?
-Uk asians
-inc uv light deprivation, exposure to sunlight, fibre, less calcium in diet, less animal foods in diet
-Housebound/institutionalised- (lack of exposure to sunlight)
what can an excess of vitamin D cause?
-leads to increase calcium absorption- leads to calcium depositis in soft tissue
-from sunlight- can cause skin cancer
what is vitamin E and what is its functions?
-is an antioxidant
Functions:
-effective in preventing oxidation of polyunsaturated fats
-important antioxidant effect in lungs where cells are exposed to high conc of oxygen
-helps prevent heart disease by protecting LDL from oxidation
