Facts – Introduction
It is a well-known fat soluble vitamin found in many supplements and foods.
Because Vitamin A (all-trans-retinol) has been shown to be useful in helping with night vision.
It is a precursor of rhodopsin, the photopigment in rods within the retina of our eye that helps us to see at night.
The retina is the back part of the eye that contains the cells that respond to light. These specialized cells are called photoreceptors. There are 2 types of photoreceptors in the retina: rods and cones.
The rod cells are sensitive to dark change, which help your eyes accommodate to the darkness.
Vitamin A, also known as the ‘eye vitamin’ forms a pigment called rhodopsin that helps the rod cells to adjust to the darker environment. Deficiency of this vitamin leads to “Night Blindness” where a child is unable to see in the night or in a dim light.
Vitamin A is a regenerative vitamin as it helps in the regeneration of the skin cells after a wound. It helps the skin to grow back. It also prevents the dryness of the skin and makes it supple.
TYPES – SOURCES
There are two types of vitamin A:
- Preformed vitamin A, also called retinol, is found in animal products. Good sources include liver (mostly), fortified milk, eggs, meat, cheese, halibut fish oil, ….
- Pro-vitamin A is found in plant-based foods. The most common type is beta-carotene, a carotenoid that produces dark pigments in plant foods. It’s responsible for the orange colour of carrots and the colours of many other fruits and vegetables, and even some animals.
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Here are some of the main sources containing Vitamin A:
- Gac fruit (beta-carotene in its cover)
- Liver (cow, pig, chicken, fish, turkey) (6500 μg 722%)
- Carrots (835 μg 93%)
- Broccoli leaves (800 μg 89%) – Less broccoli flowers – see below
- Sweet potatoes (709 μg 79%)
- Kale (681 μg 76%)
- Butter (684 μg 76%)
- Spinach (469 μg 52%)
- Pumpkin (369 μg 41%)
- Unwashed cabbage (333 μg 37%)
- Melon (169 μg 19%)
- Eggs (140 μg 16%)
- Apricots (96 μg 11%)
- Papaya (55 μg 6%)
- Mango (38 μg 4%)
- Broccoli (31 μg 3%)
- Bean (38 μg 4%)
- There are lots of antioxidant properties that neutralize free radicals in the body that cause tissue and cellular damage. It is also necessary for wound healing and skin re-growth.
- It is a critical part of the rhodopsin molecule, which is activated when light shines on the retina (the back of your eye balls).
- Genes involved in immune responses are regulated by Vitamin A, which means it is essential for fighting serious conditions like cancer and autoimmune diseases.
- Retinoic acid plays important roles in cell development and differentiation as well as cancer treatment.
- The amount of vitamin A you need depends on your age and reproductive status. Recommended intakes for vitamin A for people aged 14 years and older range between 700 and 900 micrograms (mcg) of retinol activity equivalents (RAE) per day.
- Recommended intakes for women who are nursing range between 1,200 and 1,300 RAE. Lower values are recommended for infants and children younger than 14.
Vitamin A Deficiency
1. Night blindness
- Night blindness is the difficulty for the eyes to adjust to dim light. People are unable to distinguish images in low levels of illumination, Although they have poor vision in the darkness, it’s normal to see when adequate light is present.
- In ancient Egypt, it was discovered that night blindness could be cured by eating liver, which later was found to be a rich source of vitamin A.
- A lack of vitamin A causes the cornea to become very dry. Consequently, this leads to clouding of the front of the eye, corneal ulcers, and vision loss. Continuous deficiency also causes damage to the retina, which also contributes to blindness.
- Infection depletes vitamin A reserves, which in turn make the affected ones more susceptible to further infection.
- Vitamin A deficiency is also associated with weakened immunity and a higher susceptibility to infectious diseases.
- It’s proved that children with vitamin A deficiency have higher instances of asthma, respiratory infections and sickness susceptibility.
- Vitamin A deficiency can affect hemoglobin transport, iron mobilization, healthy cell turnover for hair and skin maintenance.
That’s all we have for today’s lesson!
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