There are two sources of dietary vitamin A, active forms and precursors. Active forms of vitamin A are obtained from animal products. These are known as retinoids which include retinal and retinol. Another sources of vitamin A is precursors. It is also known as provitamins. Provitamins are obtained from fruits and vegetables containing yellow, orange and dark green pigments. These pigments are known as carotenoids, the most well-known being beta-carotene. Our body can convert carotenes into retinol. Adequate intake of beta-carotenes has been linked with low risk of certain cancers.
Vitamin A is essential for the following body functions:
* Healthy vision
* Eyes
* Skin health
* Immune function
* Embryonic development and reproduction
* Bone grow
* Gene transcription
* Reducing risk of heart disease
* Antioxidant Activity
Sources of Vitamin A:
| Food / 100g | Amount (µg) |
| Carrots | 835 |
| Broccoli leaves | 800 |
| Sweet Potato | 709 |
| Kale | 469 |
| Spinach | 654 |
| Pumpkin | 369 |
| Collard greens | 333 |
| Cantaloupe melon | 169 |
| Peas | 38 |
| Broccoli | 31 |
| Winter Squash | |
| Leafy vegetables |
RDA = Recommended Dietary Allowances
AI* = Adequate Intakes
UL = Upper Limit
µ = one millionth, 0.000001
Vitamin A Deficiency
Vitamin A deficiency may occurs when a person
* consumes inadequate vitamin A from diet
* has chronic malabosortion of lipids problem.
* has impaired bile production and release problem.
* is practicing low fat diet
* is exposed to oxidant, such as cigarette smoke, regularly
* has zinc deficiency.
Symptoms of deficiency include:
* poor night vision
* gradual lose of sight
* reduced resistance to infection
Vitamin A Overdose
Excessive vitamin A is stored in liver. This can cause liver, bone damage, double vision, headache and other side effects because excessive vitamin A can be poisoness.