How Does Vitamin A Deficiency Affect Vision?

Vitamin A is an essential nutrient for the eye. It is also called retinol or retinoic acid, which is the biologically active form of Vitamin A. Retinol is taken up by the cell and releases retinal that binds with scotopsin to produce the protein Rhodopsin this helps the eye tolerate light sensitivity. However, a deficiency of Vitamin A influences the level of rhodopsin which can directly affect vision.¹ According to WHO, about 250,000 to 500,000 children are affected by Vitamin A deficiency and loss of vision.²

What is vitamin A deficiency?

Vitamin A deficiency is also called Hypovitaminosis, when your body does not have the essential amount of Vitamin A to function properly due to a nutritional deficiency or improper diet. This causes eye-related problems, but further problems include a weakened immune system and an increased risk of infection. People in developing countries, children, pregnant women and comorbidities are at high risk of Vitamin A deficiency.³

Benefits of vitamin A

Vitamin A is an essential nutrient that is required to maintain the healthy functioning of the body. It helps to provide support to the immune system, good vision, and helps support normal development.

Some health benefits of Vitamin A are:

• Improved eyesight: Vitamin A has a significant role in normal vision. It helps in the production of retinal pigments that protect the eye surface and provides the best vision
• Protects skin: Retinoids, a compound of Vitamin A, can be applied topically to protect skin from UV rays and are used in treating acne
• Bone health: Balanced levels of Vitamin A maintain strong and healthy bones. Vitamin A provides a synergistic effect with the intake of Vitamin D 
• Supports immune system: Vitamin A boosts the immune system by regulating the anti-inflammatory response and activation of T-lymphocytes that help to fight against infections
• Antioxidant: Vitamin A has antioxidant properties that help to eliminate free radicals from the body involved in the degeneration of our cells
• Healthy reproduction: Vitamin A facilitates the process of egg development and, at the time of conception, it helps to maintain spermatogenesis

Sources of vitamin A

Vitamin A is available in two types including:

• Preformed vitamin A: available in retinol and retinyl ester forms. It is naturally found in animal sources and dairy-based products

• Animal Sources: beef, lamb, chicken, turkey, fish, and Cod liver Oil. Beef is the main source that provides vitamin A in rich quantities
• Dairy Sources: The retinol form of Vitamin A is present in milk, cheese, yogurt, eggs, etc
• Provitamin A: available in a carotenoid form such as carotene. It is widely available in plant-based food including vegetables and fruits

• Vegetables: Carrots are a high source of Carotene. Green vegetables including spinach, broccoli, kale, and sweet potatoes provide beta-carotene
• Fruits: Mango and Cantaloupe are enriched with 19% to 20% Vitamin A respectively, while other fruits that provides Vitamin A are watermelon, papaya, apricot, grapefruit, etc 

• Dietary supplement: Acetate or Palmitate form of Vitamin A supplements is available in the market as a dosage of capsules or a combination of multivitamins tablets⁴

Vitamin A and eye health

Vitamin A is an essential nutrient for your eye health. It is responsible for producing pigments in the retina which is required for better vision. Vitamin A provides nourishment to the cornea that helps you to see in low light and lubricates your eye to avoid any irritation. Vitamin A helps to produce rhodopsin which is a photoreceptor that improves night vision. The deficiency of Vitamin A affects your eyesight - it can lead to myopia, night blindness and corneal inflammation.³

Causes of vitamin A deficiency

Vitamin A deficiency are due to the following reasons:

• Inadequate Diet: Less intake of food that is rich in sources of Vitamin A, and children who are not breast-fed by their mothers have a higher tendency to develop Vitamin A deficiency
• Liver Disease: The liver is responsible for the storage of Vitamin A. If the liver does not absorb Vitamin A, it affects the normal functioning of cells and can cause toxicity
• Pancreatic Disease: Pancreatic problem leads to vitamin deficiency because it is unable to break down complex food into essential nutrients
• Chronic Diseases: Chronic conditions such as coeliac disease affects the absorption of Vitamin A in the body⁵

Signs and symptoms of vitamin A deficiency

The following are signs that you have a deficiency of Vitamin A:

• Night Blindness: It is the early sign of vitamin A deficiency - mild deficiency doesn't have any effects
• Eye infections such as dry eye, inflammation of the cornea, bad vision, corneal ulcer, etc
• Xerophthalmia, in which eyes are unable to produce tears
• Derma problems such as itchy skin, dry hair, hair loss
• Respiratory Problems

When to see a doctor?

If you notice any signs of vitamin deficiency, consult your doctor. It’s better to take professional guidance and avoid self-treatment - the doctor will diagnose according to your symptoms. The blood test used to diagnose vitamin deficiency will confirm that you have a vitamin deficiency or any other condition. Investigation of the eye should be done because it is the main indicator of vitamin A deficiency.

Complications

If Vitamin A deficiency is not treated, it can cause severe complications:

• Eye diseases: such as keratitis (inflammation of the cornea), xerophthalmia, and night blindness 
• Skin Problems: such as pruritus (itchy skin) due to increased dryness of the skin
• Fertility issues: Vitamin A deficiency affects the reproduction health of males and females
• Growth Problems: vitamin A is involved in the growth and development process, especially in children.
• Chronic Infection: Deficiency of Vitamin A affects the immune system which leads to severe infections⁶

Treatment and prevention

Vitamin A deficiency can be overcome naturally by increasing the intake of foods rich in Vitamin A, including green vegetables, fruits, dairy products, and meat. Therefore, maintain a balanced diet that provides you with natural sources of vitamin A.⁷

If it causes any severe problems which may result in permanent disease, then it should be treated with vitamin supplements. The daily recommended dose of Vitamin A is 0.7mg for an adult; however, vitamin supplements should be taken after consultation with a health professional because an increased dose could cause vitamin A toxicity.

Summary

Vitamin A has a significant role in vision and regulation of the immune system. The deficiency of Vitamin A develops night blindness. Vitamin A is found in animal and plant-based products. Severe deficiency of Vitamin A deficiency can be treated with supplements, with the consultation of health care professionals.