Vitamins Flashcards
(39 cards)
What is a vitamin?
Vitamins are organic compounds that are required for growth, maintenance of normal health and metabolism, reproduction. Cannot be synthesized in the body – with some exceptions.
Which are the vitamins that can be produced in the body?
Vitamin D – individuals without suffucuent exposure to UV light require a dietary source of vitamin D.
Niacin – can be found in beans, whole grains, nuts. Can be synthesized from the amino acid tryptophan, at low dietary intakes of tryptophan a dietary niacin source is needed.
Vitamin K – produced by the microbioata in the small intestine. New born infants haw low stores – they are usually given a prophylactic dose of vitamin K
What are come common reasons for vitamin deficiency?
Common reasons fro vitamin deficiency
1. Inadequate intake/absorption – poor diet, losses during food preparation (especially with water solubale vitamin), low bioadvailability of vitamins.
- Increased requirements – pregnancy and lactation, growth, ageing.
Other factors: diseases, fat mal-absorption (A, D, E and K), drugs, alcohol and smoking.
Which are the fat soluble vitamins?
Fat soluble (A, D, E, K)
Which are the water soluble vitamins?
water soluble (B(8 different) and C)
Define vitamers and provitamins
Vitamers – members of the same family e.g. tocopherol, belong to the vit E family.
Provitamins – precursors that can be converted to yield a metabolically active form of the vitamin, e.g. 7-dehydrocholestrol -> cholecalciferol (vitamin D)
Where can vitamin A be found?
Vitamin A in animal food -> retinol (aldehyde form retinal and retinoic acid) can be found in liver, fish oil, milk, eggs, butter.
Carotenoids (with provitamin A-activity) (beta-carotene, alfa-carotene, beta-cryptoxhantine.
Carotenoids – yellow, orange, green , and red pigments synthesized by plants. Sources: yellow-orange fruits and vegetables and dark green leafy vegetables.
Where is vitamin A digested and absorbed?
~70-90% of dietary retinol absorbed in the small intestine (carotenoid uptake is lower).
Transported together with fatty acids.
How is fat soluble vitamins absorbed?
Consist of 7 steps.
- Release from food matrix.
- Solub. in fat, bile, pancr. secr.
- Micelle formation
- Uptake into mucosa (sv: slemhinna)
- Packag. chylomicrones
- Transport with the lymph to tissue and the liver.
- Storage in the liver.
Describe the overview of the absorption, metabolism and transport of carotenoids.
Carotenoids (betaC) are partly metabolized to retinol (RE) within the intestinal cells and incorp. In chylomicrons, stored in the liver or distr. In LDL to various tissues.
Describe bio-availability of carotenoids.
The more processed the better bio-availability.
Physicochemical properties: species of carotenoids (LUTEIN* > alfa-, beta-carotene > lycopene. TRANS vs cis isomers. FREE vs esterified vs protein bound.
Food matrix and processing: particle size (PUREE>chopped>leas/whole). Raw vs PROCESSED.
Mechanical and thermal pre-treatments of crushed tomatoes: effects on consistency and in vitro accessibility of lycopene. Higher release of lycopene after longer crushing time combined with high- temp treatment. Both particle size and heat treatment are important factors.
Factors that can improve the uptake of carotenoids from fruit and vegetables. Heat treatment (denature protein associated with it), homogenization (pureeing, chopping, grating) (When we create samller particles we also make the caratones more assaisable for the enzymes aswell as destroying cellstructures), addition of fat( solubalisation)
What is the function of vitamin A?
Vitamin A plays essential roles in: vision, growth and development, cell differentiation, immune functions, reproduction, maintenance of healthy skin, hair and membranes.
What are some symptom of vitamin A deficiency?
Night blindness is one of the first signs of vitamin A deficiency. In ancient Egypt, it was known that night blindness could be cured by eating liver. Vitamin A deficiency contributes to blindness by making the cornea very dry and damaging the retina and cornea.
Signs in order of severity:
1. Night blindness – impairment/inability to see in dim light (reversible)
- Conjunctival xerosis/bitots spot (dryness and foaming accum. Of the inner eye lids/membranes)
- Corneal xerosis (dryness of the cornea)
- Xeropthalmia (keratinization and ulceration of the cornea) causes blindness.
What are some groups at risk of Vitamin A deficiency?
Premature infants – preterm infants do not have adequate liver stores of vitamin A at birth – increased risk of eye, chronic lung, and gastrointestinal diseases.
Infants and young children in developing countries – in women with vitamin A deficiency, breast milk volume and vitamin A content are suboptimal. The most common and readily recognized symptom of vitamin A deficiency in infants and children is xerophthalmia.
Pregnant and lactating women in developing countries – pregnant women need extra vitamin A for fetal growth and tissue maintenance and for supporting their own metabolism. WHO estimates 9.8 million pregnant women around the world have xerophthalmia as a result of vitamin A deficiency. Other effects – increased maternal and infant morbidity and mortality increased anemia risk and slower infant growth and development.
How is zinc and vitamin A connected?
Severe zinc deficiency often accompanies vitamin A deficiency. Zinc is required to make retinol binding-protein(RBP) -> a deficiency in zinc limits the bodys ability to move vitamin A stores from the liver to body tissues.
What are som risk with to high vitamin A intake?
Potential and major adverse effects:
1. Tetratogenicity (increases risk of birth defects) – pregnant women are advised not to consume >3mg/d.
- Excessively high intakes – accumulation in liver and other tissues (>7-9 mg/d).
- Reduced bone mineral density – may result in osteoporosis.
How does antioxidant supplement impact cancer incidence?
Supplementation with vitamin C, vitamin E or beta-carotene failed to reduce cancer risk. (totally 7,627 women who were at high risk of cardiovascular disease in the study). Additionally, beta-carotene use was associated with a modest excess of lung cancer, which is consistent with previous reports.
However, epidemiological evidence show that high dietary intakes of carotenoids are associated with a low incidence of CVD and some forms of cancer. -> dietary sources (food) of vitamins provide a combination of “phytochemical” nutrients that may have beneficial effects… and at a “natural” level.
Where can vitamin D be found?
Vitamin D comes in two forms D2 and D3.
We can obtain vitamin D2 from the provitamin ergosterol (in plants, micro-organisms) that becomes D2 – ergocalciferol.
Vitamin D3 from 7-dehydrocholesterol (animal products and formed in the skin) becomes vitamin D3 – cholecalciferol.
Food sources of vitamin D
Fish, milk, egg, mushrooms.
How is vitamin D converted in the body?
Conversion of 7-dehydrocholestrol in the body. Skin -> liver -> kidney -> target tissues
Enzymatic conversion by enzymes in the liver and the kidney.
Describe the metabolism of vitamin D.
Vitamin D3 either from food or provitamin D3 (7-DCH) via the skin -> plasma vitamin D3 -> vitamin D3 in the liver -> 25 (OH)D3 by enzymes hydroxylase from the liver to the kidney 25(OH)D3 -> 1,25 (OH)2D3 via enzyme hydroxylase -> plasma 1,25 (OH)2D3. Hydroxylases comes from the PTH (parathyroid hormone).
What is the main function of vitamin D in the human metabolic processes?
Increased active calcium absorption: maintain normal blood levels of calcium and phosphate, mineralization of bone, muscle contraction, cellular functions, gene transcription -> Ca-transporting and bone matrix proteins.
What is the action of calcitriol (“active vitamin D”)?
Increases absorption of Ca and P, maintains Ca-homeostatic in interaction with PTH, regulates its own renal production/degradation?, facilitates skeletal mineralisation, stimulates bone resorption (urinary Ca-reabsorption in kidney)
What can cause vitamin D deficiency and what are some results of it?
Reduced intake/uptake (low fat) or synthesis of cholecalciferol. Disorder associated with abnormal gut function: small bowel disorders, pancreatic insufficiency, bilary obstruction. Reduced synthesis in skin or enhanced degradation 25OHD.
Rickets (children) – poor absorption of calcium -> “soft bones”
Osteomalacia (adults) – inadequate bone mineralization -softening and weakening of bones. Loss of bone mass (low vitamin D- and Ca-status) -> fragile bones.
What are some factors that can redige the skin synthesis of vitamin D?
Latitude and season – both influence the amount of UV-light reaching the skin. In winter no vit D prod. At latitudes >42 degree N/S.
The ageing process . the thinning of the skin reduces the efficiency of the process. Pigmentation – people with darker skin may need 3-6 times longer exposure. Clothes -religious or culture habits
