Vitamin A, also called Retinol is a fat-soluble vitamin readily available as retinol in animal products and as beta carotenoids in fruits and vegetables.
Beta-carotene is converted in the intestinal mucosa into retinol and absorbed.
Where Can You Find This Vitamin?
Animal sources include:
- Liver (highest)
- Egg yolk
Plant sources include:
- Carrots and green leafy vegetables
- Orange coloured fruits and vegetables such as:
Are all enriched with Vitamin A.
Being a compulsory vitamin for health, Vitamin A acts on almost all the parts of the human body.
Children 1-3 years
Children 3-8 years
Children 9-17 years
Pregnant and lactating
750 and 1200mcg/day
It is vital not to exceed these doses as it can be highly toxic especially during pregnancy and can lead to devastating birth defects.
Benefits of Retinol
There are many benefits associated with this vitamin including some of those below:
Process of Vision
Vitamin A is compulsory to produce ‘pigments’ in the retina of the eye and acts as a fundamental component that contributes to overall eye health predominantly ‘night vision’.
One of the earliest signs mimicking deficiency is night blindness.
Daily intake of retinol with zinc can have a beneficial effect preventing and controlling ‘Age-related macular degeneration’ that causes blindness in the older population.
Normal Functioning of the Immune System
Being initially named ‘the anti-infective vitamin’, retinol is mandatory to maintain a healthy immune system.
It aids the normal functioning of body surface areas both external and internal including the skin, mucosal layers lining respiratory system, urogenital system, and gastrointestinal tract.
When they are healthy, microbes are prevented from gaining entry into our body acting as the first line of defense.
Also,in response to an infection retinol helps concert CD4 lymphocytes into other types and increases production of cytokines necessary to combat infection.
Maintains normal Skin Health
Vitamin A facilitates the conversion of immature skin cells into epidermal cells and helps to maintain a healthy and acne free skin.
It downregulates sebaceous glands in the skin and minimises the sebum production causing less sebum. Excess sebum clogs skin pores and leads to acne (pimples) formation.
This sebum also makes a good media for bacteria, so with a daily intake of adequate Vitamin A, there will be fewer skin infections.
As an antioxidant
In a recent study 100, 000 I.U. of Vitamin A was given to mice on alternate days that showed a marked reduction in tissue oxidation and suggested that retinol also might be considered as a potential antioxidant similar to Vitamins C and E.
Erythropoiesis (Red Cell Production)
Mature blood cells derive from stem cells in bone marrow. Recent studies have shown retinol helps in differentiating pluripotent stem cells into red blood cells thus taking an active part in erythropoiesis.
Also, it helps mobilising iron deposits to bone marrow which later forms haemoglobin that carries oxygen.
Effect on Bone Metabolism
Retinol has a positive effect on bone formation and remodelling. Most Vit A enriched food are also rich in calcium.
However too much can be hazardous to the bone as it causes bone loss by activating osteoclasts.
Development of Fetus
Vit A is essential in developing baby’s organs like heart, lungs, eyes and ears.
Retinol causes expression of many genes responsible for the development of collagen and laminin present in the extracellular matrix of the fetus ( in between cells).
Especially for Women
Regular Vit A intake from food or supplements can reduce heavy and painful periods.
Vaginal fungal infections like ‘candida’ will be less and there is increasing evidence that transmission of HIV from an infected mother to baby will be less likely with supplements.
What Happens With An Insufficient Intake
Deficiency is rare in USA and UK but more prevalent in sub-Saharan Africa and south Asia.
WHO says around 190 million under 5 children worldwide suffer from deficiency and recommend supplementation of under 5 in high-risk areas. Around 250,000 children become blind each year and half of them die within 12 months of onset.
First ‘symptom’ saying you are deficit is the night blindness which means difficulty in seeing at night which if untreated can become permanently blind.
The skin may become keratinized and other mucosal barriers will be weakened resulting in increased infections like pneumonia, diarrhoea and UTIs.
Younger the patient more hazardous the effects will be.
Inadequate intake during pregnancy can cause birth defects that will not be corrected by ‘after-birth’ supplements.
Early identification and management is crucial.
Safety Considerations When Taking Vitamin A
It’s crucial to maintain the daily dosage without exceeding which can be very tricky.
Excess chronic intake leads to a condition known as ‘Hypervitaminosis A’ which is characterised by acute signs like nausea, headache, loss of appetite and dizziness ultimately causing cerebral oedema.
Chronic (long-term) toxicity will cause liver damage as its stored there.
Although Vitamin A is beneficial for the normal development of the fetus, excess can lead to fetal malformations as well.
So pregnant women must stick to the daily requirement and should not take more than 3000mcg/day.
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