Vitamin A

Vitamin A is a essential fat-soluble vitamin that plays a vital role in various bodily functions, including vision, immune system, and cell growth. There are two forms of vitamin A: preformed vitamin A and provitamin A carotenoids. Preformed vitamin A is found in animal products, while provitamin A carotenoids are found in plant-based foods.

Sources of Vitamin A

• Preformed vitamin A: liver, fish liver oils, eggs, and dairy products
• Provitamin A carotenoids: carrots, sweet potatoes, spinach, kale, and other colorful fruits and vegetables

Functions of Vitamin A

Vitamin A has several important functions in the body:

1. Vision: Vitamin A is essential for the proper functioning of the retina and low light and color vision.
2. Immune system: It plays a crucial role in maintaining the integrity of the skin and mucous membranes, which act as barriers to infection.
3. Cell growth and differentiation: Vitamin A is involved in the growth and specialization of cells, particularly in the development of the embryo and fetus.

Deficiency and Toxicity

A deficiency of vitamin A can lead to night blindness, increased susceptibility to infections, and in severe cases, xerophthalmia (a condition that can lead to blindness). On the other hand, excessive intake of vitamin A can lead to toxicity, which can cause symptoms such as nausea, dizziness, and even liver damage.

Recommended Intake

The recommended dietary allowances (RDAs) for vitamin A vary by age and gender. For example, the RDA for children ages 4-8 is 400 micrograms per day, while for adult males it is 900 micrograms per day and for adult females it is 700 micrograms per day.

Quiz

1. What are the sources of preformed vitamin A?
   1. Liver
   2. Fruits
   3. Whole grains
2. What is the function of vitamin A in the body?
   1. Vitamin A is essential for the proper functioning of the _________
   2. Vitamin A plays a crucial role in maintaining the integrity of the _________
3. What are the potential consequences of vitamin A deficiency?
   1. Night blindness
   2. Xerophthalmia
   3. Increased susceptibility to infections