Vitamins are substances that your body needs to grow and develop normally. There are 13 vitamins your body needs. They are
- Vitamin A
- B vitamins (thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B-6, vitamin B-12 and folate )
- Vitamin C
- Vitamin D
- Vitamin E
- Vitamin K
- Absorbed with dietary fat in small intestine
- 40-90% absorption efficiency
- Absorption typically regulated by need
- need à absorption
- Transported away from small intestine in chylomicron via blood and lymph (depending on size)
- They are not easily excreted through urine.
- Substantial amounts are stored in liver and fat tissue.
- Therefore, toxicity is possible.
Vitamin A is a fat soluble vitamin, and therefore, needs to be consumed with fat in order to have optimal absorption. High vitamin A foods include sweet potatoes, carrots, dark leafy greens, winter squashes, lettuce, dried apricots, cantaloupe, bell peppers, fish, liver, and tropical fruits.
Role in vision : Vitamin A (retinal) is an essential precursor for formation of the visual pigment, rhodopsin, in the retina of the eye. Retinal plays an important role in vision, especially night vision. Lowers cataract incidence.
Role in growth. Helps regulate cell development, cell differentiation and cell division.
Role in Bone and teeth formation. Promotes the proper growth of bones and teeth. Bone cells (osteoblasts and osteoclasts ) depend on vitamin A for their normal functioning.
Is important in the formation and maintenance of healthy hair, skin and mucous membranes.
Boosts the body’s immune system helping to increase body resistance to infectious diseases.
Problems associated with Vitamin A
Vit. A deficiency:
1)“Night blindness” – First detectable sign of vitamin A deficiency
- Inability to see in dim light or inability to recover sight after a flash of bright light
2)Increased susceptibility to infection and cancer and anemia equivalent to iron deficient.
3)Prolonged lack of vitamin A (keratinization of the cornea, a condition known as xerophthalmia).
4)Abnormal bone development in fetal and neonatal life.
Vit. A excess:
Hypervitaminosis A in humans
Symptoms include dry, pruritic skin with excessive itching and increase in intracranial pressure.
is becoming an increasing problem in Western countries because of self-medication and over prescription.
has occurred through eating polar bear or seal liver by polar explorers.
Eat polar bear liver sparingly, 30 grams contain 450,000 IU of retinol! Continued ingestion causes peeling of the skin from head to foot.