7. the vitamins Flashcards
(33 cards)
What is a vitamin?
They are organic compounds that are required for:
- growth
- maintenance of normal health and metabolism
- reproduction
They cannot be synthesized in the body with some exeption
Which vitamins can be synthesized in the body?
- vitamin D: individuals with no sufficient UV light exposure have to take vitamin D from diet
- Niacin: can be syntheszed from tryptophan
- vitamin K: new born infants have low stores (produced by the microbiota)
Tell the common reasons for vitamin deficiency:
- Inadequate intake/absorption:
(poor diet, losses during food preparation, low bioavailability, drugs, alcohol, diseases) - Increased requirements:
growth, ageing, pregnancy
Categorised vitamins:
fat soluble: A,D,E,K
water soluble:
B8 8 vitamins) and C
What vitamers are?
members of the same family of vitamins (ex. tocopherol belong to vitamin E)
What Provitamins are?
They are precursors that can be converted to yield a metabolic activelly form of vitamin
What is vit A ? Where you can find that in food?
- retinol (liver, fish oils, milk, eggs…)
2. carotenoids (beta, alpha carotene) have yellow green orange pigments can be found in plants fruits
What are the caroteinoids?
Around 60 in human diet but few in the human plasma
Carotenoids: carotens/zantophylls
Some of them can be converted and have provitamin A activity
Conversion factor for vitamin A?
estimation of vitamin A activity:
1 micro gram of retinol activity equivalents=12 micro grams of beta carotene and 1 micro gram of retinol
Describe absorption of vitamin A and carotenoids
70-90% of dietary retinol absorbed in the small intestine, it is transported together with fatty acids
The metabolism is quite similar to fat absorption:
food –> relase of retinol and betacarotene from matrix –> micells (they are fat soluble in fat, bile…) –> chylomicron that enter in the mucosa and then blood stream and in the liver then it can go into tissues
Source of carotenoids that have high bioavailability:
fruits, tuber, papaya, peach, melon, tomato juice
low bioavailability: tomato, carrots, peppers spinach,
What effect the bio availability of carotenoids?
- physiocochemical properties: lutein, trans are the more available
- food matrix and processing: pureè and processed food have highes bio availability
Heat treatmnet
homogenization
addition of fat
can improve the uptake of carotenoids (more soluble and easily accessible by enzyme)
Vitamin A functions and deficiency?
It plays a role in:
vision, growth, cell differentiation, immune functions, reproduction, healty skin, hair, membranes
deficiency symptoms ( Zinc deficiency cause it is required to make retinol binding proteins):
night blindness, damage at retina and cornea
XEROPHTALMIA( dry eye syndrome):
night blindness, bitots spots, dryness of corena, cause blindness)
RICORDATI DI DISEGNARE LA CURVA DELLA DOSE DI VITAMINE CHE LE PIACE TANTO
Who’s at risk of vit A deficiency?
premature infants, young children in developing countries, pregnant and lactating women in developing countries
What happens if you have too high vit. A?
- teratogenicity (increase risk of birth defect) max 3 mg day
- Accumulation in liver and other tissues
- Reduce bone mineral density lead to osteoporosis
Give examples about controversies about vit.A?
- lycopene: prevent carcinogenesis and atherogenesis ( but studies shown negative effect of vitamin intake)
- beta carotene and vit.E supplements increase mortality rate
- supplements with vit.C, vitamin E or betacarotene fail in reduce cancer risks
- betacarotene associated with excess of lung cancer
- high beta carotens is also associated with low incidence of CVD and some other forms of cancer
Vitamin D:
ergosterol –> vitamin D2
7-dehydrocholesterol –> vitamin D3
this conversion can happen vith irradiation and UV light and take place starting from the skin
souces: fish, eggs, mushrooms, milk
Explain metabolism of vitamin D:
Both from skin and food: it pass through blood thaen liver then kidneys where it reach the active form: calcitriol
Main functions in huamn metabolic processes:
Increase active calcium absorption ( maintain normal blood levels of calcium and phosphate, mineralization of bone, muscle contraction, cellular functions, gene transcription)
What is the action of calcitriol?
increase absorption of Ca and P
maintain Ca-homeostasis in interaction with paratyroid hormone
regulate renal production/degradation
facilitate skeletal mineralisation
when there is too less calcium in blood we activate PTH (paratyroid hormone) to produce more cacitriol
Vitamin D deficiency
Rickets ( low Ca)
Osteomalacia (weak soft bones)
Osteoporosis (low dense bones)
Causes are: reduce intake and uptake of cholecalciferol (vit.D)
disorder with abnormal gut function
reduced synthesis in skin
what influence the reduce skin synthesis of vitamin D?
latitude and season
aging process
pigmentation
clothes
Toxicity:
cannot be caused by prolonged exposure to sun
over supplementation can cause high blood pressure and calcinosis
What’s vit.E?
Tocopherols
Tocotrienols
