Vitamin A is an essential micronutrient. Our bodies cannot manufacture it and therefore it has to be included in our diet. Vitamin A supports the daily replacement of skin cells and ensures that tissues such as the conjunctiva are able to produce mucous and provide a barrier to infection. Vitamin A is also essential for vision under conditions of poor lighting, for maintaining a healthy immune system, cell recognition, for growth and development and for reproduction. It also helps the heart, lungs, kidneys, and other organs function correctly.
The main symptom of Vitamin A Deficiency is vision loss and blindness. Vitamin A plays an important role in your vision. To see the full spectrum of light, your eye needs to produce certain pigments for your retina to work properly. Vitamin A deficiency stops the production of these pigments, leading to night blindness. Your eye also needs vitamin A to nourish other parts of your eye, including the cornea. Without enough vitamin A, your eyes cannot produce enough moisture to keep them properly lubricated. People with night blindness do not see well in the dark. As the vitamin A deficiency worsens, the conjunctiva dries out and corneal ulcers (open sores) appear. If untreated it eventually leads to vision loss and blindness.
The two main sources of vitamin A are animal and plant sources. All sources of vitamin A need fat in the diet to aid absorption. In animal sources, vitamin A is found as retinol, the ‘active’ form of vitamin A. Liver, including fish liver, is a very good source of Vitamin A. Other animal sources are egg yolk and dairy products such as milk (including human breast milk), cheese, butter, and fatty fish such as tuna and herring. Plant sources contain vitamin A in the form of carotenoids, which have to be converted during digestion into retinol before the body can use it. Carotenoids are the pigments that give plants their green color and some fruits and vegetables their red or orange colour. Fruit and vegetable sources that are rich in carotenoids are often orange. Plant sources of vitamin A include mangoes, papaya, squashes, carrots, red peppers, sweet potatoes and maize (but not the white varieties). Other good sources of vitamin A are red palm oil and Buriti palm oil. Plant foods that are rich in beta-carotene also include dark green leafy vegetables, such as broccoli, spinach, and turnip greens. It is important that all sources of vitamin A are not overcooked, as this can reduce the vitamin A content. Ultraviolet light can also reduce the vitamin A content of food, so drying of fruits such as mangoes should not be done in direct sunlight.
Vitamin A is essential to our health but too much of it can cause harm to our body. The most common side effects of chronic vitamin A toxicity, often referred to as hypervitaminosis A, include vision disturbances, joint and bone pain, poor appetite, nausea and vomiting, sunlight sensitivity, hair loss, headache, dry skin, jaundice, delayed growth, decreased appetite, confusion and even death. High-dose vitamin A supplements should be avoided unless prescribed by your doctor. So, better stick to the appropriate dose of Vitamin A supplements as follows: one dose of 100,000 IU for infants 6-11 months of age and 200,000 IU for children 12-59 months of age every 4-6 months, while for adults 900 mcg daily for men and 700 mcg daily for women. But still the natural sources of Vitamin A is better than supplements to get rid of the bad effects of overdosage. Therefore, eat right for a better eyesight!
-PNC-ZDN Rowence Zorilla
1. What is vitamin A and why do we need it?
2. Everything you need to know about vitamin A