Overview Of Vitamin A

"Eat your carrots, they will help you see in the dark", now this childhood fable is false, it does in fact hold some truth to it, carrots are high in beta-carotene which is converted into vitamin A. Vitamin A is important for healthy eyesight, but it will not give you night vision, sadly.

What Is Vitamin A?

Vitamin A is a group of essential vitamins our body needs to survive. These micronutrients cannot be made within the body and therefore need to be consumed within our diet. Vitamin A, along with D, E and K are fat soluble, which means they can dissolve and be stored within fat tissue, however the majority of vitamin A is stored within the liver. (1)

Vitamin A is sensitive to heat light and air. Cooking foods high in vitamin A will therefore void them of their vitamin A content.

The vitamin can exist in two forms, retinol and carotenoid. Retinol is called preformed vitamin A and is found within foods derived from animals, including dairy, fish and meat, especially liver. Carotenoid is called provitamin A, and the most important provitamin is beta-carotene. Beta-carotene is found in fruit and vegetables, especially orange coloured ones. The body converts beta-carotene into retinol (Vitamin A), within the small intestine. The conversion rate of beta-carotene to retinol varies between individuals. Variants in the BCM01 genes are associated with the conversion rate.

Provitamin A and preformed vitamin A must be metabolized intracellularly to form retinal and retinoic acid, the active forms of retinol, to then undertake the vitamins biological functions. (1)

Vitamin A Structure

Beta-carotene is responsible for giving some fruits and vegetables their orange colours, your body can convert beta-carotene into vitamin A. Therefore orange fruits and vegetables are excellent sources of vitamin A.

What Does Vitamin A Do Within The Body?

Vitamin A is crucial for maintaining healthy eyesight, promoting growth and development and protecting epithelium (tissue that forms the outer layer of the body's surface and other hollow structures).

The vitamin is also known for its anti-inflammation properties because of the vital role it plays in immune functions. Vitamin A protects the body from bacterial, parasitic and virus infections.

Retinol (Vitamin A1) is often used in anti-ageing formulas for its ability to boost the production of collagen, which is important for healthy skin. This plumps up the skin, reduces wrinkles and improves skin tone. Retinol is only found in animal derived foods, such as fish, liver and dairy produce. (2)

Retinal is needed by the retina of the eye. Retinal combines with proteins called opsin to form rhodopsin, which is a light absorbing molecule essential for colour vision and seeing in darkness. Vitamin A deficiency is the leading cause of preventable blindness.

Retinoic acid is important for cell and epithelial cell growth and maturation, which is vital for embryonic development (3). Furthermore it is vital for visual and immune system function. Like all retinoids, it has uses for visual and skin conditions. Low vitamin A intake is linked to a higher risk of cancer, but retinoids counteract this by suppressing carcinogenic changes. (4)

Vitamin A & Pregnancy

In embryonic development vitamin A is crucial for regulating embryo development, as too little or too much can result in congenital malformations (5). Vitamin A contributes to the development of babies eyes, and immune system and skin cell production. Vitamin A deficiency during pregnancy can affect a babies immune system, leaving them more susceptible to illness.

How much vitamin A do you need during pregnancy? The recommended daily intake is slightly higher at 100mcg per day. However a higher intake is required during the third trimester as the babies development accelerates exponentially.

Some foods high in vitamin A like liver should be avoided during pregnancy and some supplements such as cod liver oil because they contain high amounts of vitamin A.

How Much Vitamin A Do You Need?

The amount of vitamin A intake varies by age and gender. Therefore recommended daily intake (RDI) is used. (6)

How much vitamin A do i need

Although unlikely, you should be wary of supplements high in Vitamin A to avoid overdose, which may have adverse side effects including:

• Nausea

• Headaches

• Rash

• Dry skin

• Dry or cracked lips

• Weakness

Overdose of 10,000 IU daily during pregnancy is extremely teratogenic and can cause many birth defects.

10 Foods High In Pre Vitamin A

1. Beef Liver - 1 slice: 6,421 mcg (713% RDI)

2. Lamb Liver - 28 grams: 2,122 mcg (236% RDI)

3. Liver Sausage - 1 slice: 1,495 mcg (166% RDI)

4. Cod Liver Oil - 1 teaspoon: 1,350 mcg (150% RDI)

5. Salmon - half fillet 229 mcg (25% RDI)

6. Butter - 1 tablespoon: 97 mcg (11% RDI)

7. Cheddar - 1 slice: 92 mcg (10% RDI)

8. Hard Boiled Egg - 1 large egg: 74 mcg (8% RDI)

9. Cream Cheese - 1 tablespoon: 45mcg (5% RDI)

10. Feta Cheese - 28 grams: 35 mcg (4%)

10 Foods High In Pro Vitamin A

1. Cooked Sweet Potato - 1 cup: 1,836 mcg (204% RDI)

2. Cooked Kale - 1 cup: 885 mcg (98% RDI)

3. Cooked Carrot - 1 medium carrot: 392 mcg (44% RDI)

4. Raw Spinach - 1 cup: 141 mcg (16%)

5. Raw Lettuce - 1 large leaf: 122 mcg (14% RDI)

6. Mango - 1 medium mango: 181 mcg (20% RDI)

7. Grapefruit - 1 medium grapefruit: 143 mcg (16% RDI)

8. Watermelon - 1 wedge: 80 mcg (9% RDI)

9. Papaya - 1 small papaya: 74 mcg (8% RDI)

10. Apricot - 1 medium apricot: 34 mcg (4% RDI)

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