Sarah Izhar Content Writer
Content Writer
Vitamin A, or retinol, is an essential nutrient required to perform appropriate biological functions in our body. It is known as a group of fat-soluble compounds which includes retinol, retinal, and retinyl esters. Retinol plays a vital role in supporting the immune system, vision, health of the reproductive system, etc. The genetically modified rice variety called "Golden Rice'' is among the most well-known foods rich in vitamin A.
What is Vitamin A?
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Vitamin A is a fat-soluble vitamin present in most plant and animal-based food sources. It performs various functions in our body.
- Vitamin A or retinol improves the skin, eye related problems like night blindness, stimulates new red blood cell production, etc.
- It mainly has two forms: Preformed Vitamin A and Provitamin A carotenoids.
- Our body must convert these two forms into the active forms of vitamin A; retinal and retinoic acid, to consume the forms.
| Discovery of Retinol
|
Sources of Vitamin A
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Vitamin A is one of the nutrients that require fat for absorption and is stored in the body's fatty tissue and liver. These vitamins are found both in animal and plant sources and have two forms:
- Preformed Vitamin A: Preformed vitamin A is found in animal sources. These vitamins are absorbed in the form of retinyl esters directly by the small intestine, where they are converted into retinol.
- Carotenoids: These are also known as provitamin A and are pigments found in plant sources. Provitamin A is absorbed in the active form of Vitamin A which is retinol.
The below flow chart shows the sources of vitamin A:
Vitamin-rich Foods and Supplements
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Vitamin-rich foods and supplements should not be consumed beyond the recommended dietary allowance (RDA), which is 1000 µg for men and 840 µg for women. Consuming supplements in higher amounts can cause nausea, dry hair, headaches, dry skin, and enlarged liver.
Functions of Vitamin A
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The functions of vitamin A are very diverse in our body. It provides numerous health benefits, including:
Protects Visual Health
Vitamin A plays an important role in keeping our eyes disease-free.
- It also contributes to the formation of tear fluid and helps in preventing ‘Dry Eye Syndrome’.
- Deficiency of vitamin A can lead to night blindness and, if untreated, can lead to loss of vision.
- The active form of vitamin A, retinal, binds with opsin a protein, and forms rhodopsin which is responsible for color and low-light vision.
Reduces Cancer Risk
Carotenoid-rich foods contain antioxidants, which help neutralize harmful free radicals in the body.
- Retinoids inhibit the growth of cancerous cells present in the bladder, breast, skin, lungs, and ovaries.
- It is advised to consume carotenoid-rich foods like spinach, kale, tomatoes, carrots, bell peppers, etc.
Improves Skin Health
Retinol is considered one of the best options for skin health.
- It is best used for the treatment of wrinkles by stimulating collagen production and in treating hyperpigmentation and acne.
- Retinoid helps in removing dirt, oil, and dead skin from the pores to prevent acne formation.
Promotes Fertility
Too much intake of vitamin A during pregnancy can damage the fetus, resulting in birth defects and infection.
- Vitamin A deficiency can cause infertility in both males and females.
- It helps improve placental health and the growth and development of the fetus.
Boosts Immune System
Vitamin A plays an important role in the production of leukocytes.
- In addition to enhancing the antibody response, vitamin A also improves the mucosal lining of the body.
- It also helps in the production of the B and T cells.
Sample Questions
Ques. Vitamin A is mainly stored in the ________. (1 mark)
Ans. Liver
Ques. What is the relevance of vitamin A in our body? (2 marks)
Ans. Vitamin A serves different purposes in our bodies:
- Improves eyesight.
- Supporting gene expression
- Improves reproductive health.
- Strengthens the mucosal lining.
- Facilitates the formation of leucocytes.
Ques. What are some examples of the sources of vitamin A? (2 marks)
Ans. Following are examples of animal and plant-based sources found in Vitamin A:
| Type of Source | Examples |
|---|---|
| Animal-based sources | Cheese, butter, fish, cream, eggs, and cod liver, oil. |
| Plant-based sources | Kale, Spinach, papaya, mangoes, squash, lettuce, carrots, sweet potato, pumpkin, etc. |
Ques. What is the basic difference between preformed vitamin A and provitamin A in terms of the mechanism of absorption? (2 marks)
Ans. Preformed vitamin A and provitamin A differ in terms of mechanism of absorption.
The table below shows the difference between the two:
| Types of Vitamin | Mechanism |
|---|---|
| Preformed Vitamin A | Directly absorbed by the small intestine in the form of retinyl esters. |
| Provitamin A | Indirectly absorbed by first metabolizing vitamin A in its active form retinal |
Ques. How does vitamin A contribute to promoting fertility? (2 marks)
Ans. Vitamin A plays a crucial role in the following functions:
- Increase in sperm production in males
- Maturation of eggs in females.
- Maintains placental health
- Progression of fetus
Ques. List a few symptoms of vitamin A deficiency? (2 marks)
Ans. The following are the symptoms of vitamin A deficiency:
- Dry skin
- Dry eyes
- Night blindness
- Infertility
- Respiratory infections
- Poor bone health
- Weak immune response.
Ques. How can Vitamin A supplements prevent hair loss? (1 mark)
Ans. A deficiency of vitamin A can lead to the thinning of the hair and hair loss. Vitamin A supplements help in the development of sebum in the scalp, resulting in healthy hair follicles and reduced breakage.
Ques. What are the harmful effects of excess vitamin A consumption? (2 marks)
Ans. Overconsumption of vitamin A can lead to toxicity. It may cause one or more of the following risks:
- Clumsiness
- Nauseous
- Muscle and joint pain
- Hair loss
- Weight loss
- Liver impairment
- Birth deformities.
Ques. What functions does vitamin A play in the mucosal lining of the body? (2 marks)
Ans: The following functions are performed by vitamin A in the mucosal lining of the body:
- Vitamin A helps to strengthen the mucosal lining of the respiratory, digestive, and urinary tracts.
- A healthy mucous lining serves as a barrier against infections.
Ques. What is the recommended amount of vitamin A required in our diet? (2 marks)
Ans. As per the Recommended Dietary Allowance (RDA), the amount of vitamin A required in our diet lies in the range of:
900-1000 µg → For males
700-840 μg → For females
Ques. Can Vitamin A supplements have adverse effects on human health? (2 marks)
Ans. Yes. Vitamin A supplements are beneficial in moderation. In addition to providing health benefits for those who cannot obtain enough vitamins through food, it can also be a threat if consumed in large amounts. It is therefore advised to consult a healthcare professional for an adequate dosage.
Ques. How does vitamin A deficiency cause night blindness? (1 mark)
Ans. Vitamin A deficiency severely affects the rods of the cornea this eventually leads to the drying of the cornea and thus causes night blindness. Night blindness is also followed by the dysfunction of the cone.
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