Fat-soluble vitamin A is consumed through diet and stored in the body as fat. As a result of insufficient dietary intake, vitamin A deficiency is most prevalent among the poor in developing nations and primarily affects children. In first-world, nutrient-rich countries, vitamin A deficiency is uncommon, but it can still affect people with inflammatory bowel disease and those who have had bariatric surgery.
Why is vitamin A important?
Epithelial cells, mucosal membranes, visual pigments, and the immune system all benefit from vitamin A.
Skin, eyes, lungs, digestive tract, urinary system, reproductive organs, etc., all contain epithelial cells.
Vitamin A deficiency negatively impacts conjunctival and corneal epithelial cells, resulting in decreased goblet cells, increased keratin deposits, abnormal cell growth, and increased inflammatory and infectious responses.
In addition to vision issues, vitamin A deficiency also contributes to skin issues, respiratory issues like pneumonia, urinary tract infections and stones, diarrhea, and infertility.
Since vitamin A is an antioxidant, it plays a crucial role in the immune system’s ability to fight off free radicals and the harmful effects they cause. Vitamin A deficiency lowers immunity, making a person more susceptible to infections and other illnesses that can cause morbidity and even death.
Children who lack vitamin A are more likely to suffer from decreased vision and are more likely to die from a variety of infectious diseases. According to the WHO, vitamin A deficiency is the leading preventable cause of childhood blindness. Vitamin A deficiency also affects maternal mortality and other unfavorable pregnancy and lactation outcomes.
Causes of deficiency:
The deficiency can be due to inadequate intake or inadequate absorption
1. INADEQUATE INTAKE:
Deficiencies may result from inadequate dietary intake. The Recommended Dietary Allowance for adults 19 years and older is 900 mcg for men and 700 mcg for women. For children, pregnant women, and lactating women, the RDA is 300 to 900, 770, and 1300 micrograms/day respectively.
2. Inadequate absorption:
- Malabsorption syndrome:
Inflammation of the gut or difficulty absorption of nutrients caused by diseases like Colitis, Crohn’s, and Celiac disease.
- Surgeries:
Intestinal surgeries such as gastric bypass, resections of the large and small bowel, and gallbladder removal, may interfere with the intestine’s ability to absorb vitamin A, raising the possibility of severe deficiencies and impairing vision, claims a study from Houston.
- Laxatives:
Chronic diarrhea brought on by the frequent use of laxatives can lead to vitamin deficiencies.
- Liver problems:
The liver is important in the production of enzymes necessary for vitamin A circulation and absorption within the body. Thus, issues with the liver like cirrhosis, long-term alcoholism, and hepatitis can result in vitamin deficiencies.
- Pancreatitis:
Pancreatic insufficiency can cause vitamin A deficiency by poor exocrine function and insufficient enzyme production for its absorption.
- Premature neonates:
Due to an immature GI tract with inefficient vitamin A absorption, low vitamin A stores, and increased needs during a period of rapid development, premature neonates are at risk for vitamin A deficiency.
- Additional Requirement:
Breast milk from mothers who are vitamin A deficient is unlikely to be able to adequately maintain vitamin A stores in nursing infants after six months postpartum.
Eye complications
The primary form of vitamin A found in blood and plasma is retinol. When liver vitamin A stores are severely low or excessively high, serum retinol levels reflect this. Therefore, serum retinol is a reliable indicator of vitamin A in the body. The concentration of retinol in the blood should not fall below 20 micrograms/dL. Vitamin A deficiency symptoms in the eyes first occur at concentrations lower than 10 micrograms/dL, according to a research.
The following are some of the various eye issues that vitamin A deficiency can cause:
Night blindness:
Vitamin A is a crucial part of the pigment rhodopsin, which is found in the rods of the retina. Rods are photoreceptors that are responsible for vision in low light. Night blindness results from decreased rhodopsin production brought on by vitamin A deficiencies.
Conjunctival xerosis (dryness):
The tear film has 3 layers. Third and the innermost layer is made of mucin which is secreted by our conjunctival goblet cells. Vitamin A is a crucial vitamin for the normal functioning of the cells. Vitamin A deficiency causes abnormal cell growth known as metaplasia and conjunctival goblet cell loss. This leads to dry and wrinkled looking conjunctiva.
Bitot spots:
These are typically described as a slightly elevated, triangular, white foamy lesion that appears in the white part of the eye, typically temporally. This is due to abnormal cell growth and keratin deposition in the conjunctiva.
Corneal xerosis:
The cornea becomes dry when the tear film’s integrity starts to deteriorate as a result of the loss of conjunctival cells. Vitamin A deficiency results in the loss of the cornea’s outer epithelial layer. The epithelial layer’s impaired barrier function and dryness make the cornea vulnerable to infections.
Ulceration of the cornea:
If the Vitamin A deficiency is not urgently corrected, the cornea may become ulcerated.
Keratomalacia
When the ulceration affects more than one-third of the cornea it starts melting away due to the process called necrosis which affects the cornea’s collagen’s structural makeup. Within a few days, the cornea can be completely destroyed.
Blindness:
Depending on the severity of the corneal pathology, corneal ulceration, and keratomalacia can result in corneal scarring, staphylomas (a forward bulging of a severely damaged cornea), or phthisis bulbi (a shriveled-up eye). All leading to corneal blindness.
Vitamin A food source
Vitamin A is consumed either as retinoid from animal products or as carotenoid from vegetables and fruits. Retinoid is an active form of vitamin A which has a high bioavailability and is absorbed 75-100% of the time while beta-carotene, the most common form of carotenoids, is a provitamin. As opposed to retinoids, they are converted into active forms inside the body and are less bioavailable.
| Vegan | Vegetarian (+vegan options) | Non-vegetarian (+vegetarian and vegan options) |
| Carrots, sweet potatoes, green leafy vegetables | Milk, cheese, yogurt | Animal liver, and liver products, Eggs, oily fish like sardines, cod liver oil |
IS IT NECESSARY TO TAKE VITAMIN A SUPPLEMENTS?
Not until your doctor has prescribed it to you. The WHO warns that excessive consumption of some vitamins and minerals may have adverse effects on people’s health. The potential side effects of multivitamins depend on the individual’s health issues.
1. Individuals taking supplements to meet their daily Vitamin A requirement can exceed the upper intake level. This can result in toxicity and have serious adverse effects on one’s health.
2. Lung cancer risk increases in smokers and possibly former smokers who take multivitamins with high levels of vitamin A or beta carotene.
3. Pregnant women should not take vitamin A because it may cause certain birth defects.
Therefore, it is in our best interests to take multivitamins with caution and seek professional medical advice. In the case of AMD, AREDS recommends that patients take vitamin A to improve their macular health.
QUICK SUMMARY
All the necessary vitamins and minerals are present in a well-balanced diet in the proper proportions. An individual who is generally healthy can effectively absorb these nutrients. A well-balanced, nutrient-rich diet helps prevent vitamin A deficiency. Vitamin supplementation is needed for patients who are unable to absorb nutrients, have malabsorption problems, or live in countries with limited resources. For at-risk groups, the WHO has recommended guidelines of vitamin A dosage. Therefore, prompt diagnosis and treatment are crucial.