Vitamins are organic compounds that the body needs in small quantities for maintaining normal functions such as metabolism and immunity. Like all micronutrients, they must come from the foods you eat as they cannot be produced by the body or are produced in insufficient quantities.
Nutritionists recognize 13 vitamins. They are labeled by the letters of the alphabet (A, C, D, E, and K) and, in case of the vitamin B complex, the letters are supplemented by numbers: B1, B2, B3, B4, B5, B6, B7, B9, and B12. They also have different chemical names, e.g. vitamin B1 is called thiamine, vitamin C is called ascorbic acid. Vitamins are classified as either: a) water soluble or, b) fat soluble.
B-complex vitamins and vitamin C are water soluble vitamins. Water soluble vitamins are digested quickly by the body. Any excess is removed from the body with the urine. Since they are not stored in the body, water soluble vitamins need to be regularly supplied through the diet or supplements.
The following vitamins are fat soluble: A, D, E, and K. Fat soluble vitamins cannot dissolve in water but can dissolve in fat or other organic compounds. Any excess amount is stored in the tissues or organs of the body, e.g. liver, fat tissues. It can be stored there for days or even months. Consuming high amounts of certain fat soluble vitamins may have very negative health effects, including poisoning, and in some cases may even lead to death.
This article will provide a brief information about vitamin A and its health effects.
Vitamin A is a fat soluble vitamin. There are two different types of vitamin A:
- Preformed vitamin A: It is an active form of vitamin A, and comes mainly from animal sources, e.g. meat, fish, dairy. This type of vitamin A is called retinoids, of which retinol is the most active form.
- Pro-vitamin A: It comes from fruits and vegetables and is called carotenoids, of which beta-carotene is the most common type. Pro-vitamin A can converted by the body into an active form of vitamin A.
Vitamin A is an essential micronutrients needed for the normal functioning of the body. Deficiency in vitamin A may cause blindness, itching in the eyes, brittle nails, fatigue, insomnia, depression, weak immune system and recurring infections, etc. The benefits of vitamin A include:
- Vision: Vitamin A produces pigments in the retina of the eye and helps to maintain moisture in the eyes. It helps human eyes to adjust to light changes and prevents night blindness. Deficiency in vitamin A is one of the major causes for blindness among children. It also helps to lower the risk of cataracts.
- Skin: Vitamin A helps to maintain moisture retention and keep skin soft and healthy. Therefore, many modern anti-aging beauty products contain vitamin A. It is claimed that vitamin A has wrinkle eliminating properties.
- Bone, teeth and tissue health: Vitamin A is essential in tissue formation and cell differentiation. For example, it helps in formation of dentin, which is a hard material found below the surface of the teeth. It also plays an active role in bone growth and soft tissue health.
- Muscle growth: It helps growth and repair of muscle tissues and ensures proper muscle growth in children. Vitamin A may help to prevent muscular dystrophy.
- Immune system: Vitamin A helps body’s immune system to effectively fight against infections by facilitating normal functioning of the white blood cells and keeping the moisture in the mucous membrane.
- Urinary system: It helps in preventing urinary stones due to the formation of calcium phosphate.
- Antioxidant properties: Vitamin A helps to fight against free radicals and toxins.
Natural sources for vitamin A include:
- Animal source: meat, liver, kidney, poultry, fish oil, egg yolk, cheese, cream, and butter are an excellent source of the active type of vitamin A.
- Plant source: mainly yellow and orange fruits and vegetables, including carrots, cantaloupes, apricots, sweet potatoes, pumpkin but also broccoli, spinach, green leafy vegetables. These provide a good source of beta-carotene.
Consumption of too much beta-carotene (precursor to vitamin A) does not cause an overdose in vitamin A and related toxic effects, although it may make your skin look orange. However, excess intake of vitamin A from animal source and/or supplements may have detrimental health effects. For instance, pregnant women are advised to avoid taking supplements with vitamin A unless recommended by their practitioner. The effects from a significant overdose of vitamin A include birth defects, growth retardation, enlarged liver or spleen, headaches, loss of appetite, etc.
Therefore, your intake of active forms of vitamin A should not exceed the recommended dosages. Please see below the Recommended Dietary Allowance (RDAs) of the Food and Nutrition Board of the Institute of Medicine.
So, how to make sure that you are getting enough vitamin A but not overdosing on it? First and foremost, maintain a healthy and well-balanced diet, which includes animal and/or plant sources of vitamin A. Also, do your homework before taking any supplements, and, if possible, consult with a nutritionist. By following these steps, you will make sure that you will fully enjoy the benefits of vitamin A without any side effects.
Recommended Dietary Allowance for vitamin A: (μg = 1/1,000,000 of a gram)