What is Vitamin A?
Vitamin A is a fat-soluble vitamin. There are actually a few different (but related) compounds that can be called Vitamin A. These compounds are classified as retinoids, and vary based on whether they come from a plant or an animal source. There are also plant foods that provide carotenoids – a precursor to Vitamin A, which can be converted to the vitamin once it’s in our bodies. Beta-carotene is the most popular.
What does Vitamin A do for my body?
The major functions of Vitamin A include vision health, supporting reproduction, regulating growth, and maintaining the health of epithelial tissues (membranes) and skin.
For our vision health, Vitamin A keeps the cornea clear and it helps convert images to nerve impulses so we understand what the heck we’re looking at! Though, amazingly, only one-thousandth of the body’s Vitamin A is in the retina. In fact, most of it is everywhere else in our body!
The cells in surface membranes carry most of the vitamin, where cell differentiation occurs. That’s a fancy term for a cell developing to perform a specific function.
Vitamin A also supports reproduction by participating in sperm development in men and the development of a fetus when a woman is pregnant.
Plus, the vitamin helps bone-remodeling to occur as children grow taller, helping to destroy unneeded parts as the bone tissues are dismantled and reformed, bigger and better than before!
Finally, beta-carotene has the bonus of acting as an antioxidant in our bodies if it’s not converted to Vitamin A.
Related Reading: Antioxidants
Deficiency of Vitamin A would occur after one or two years of not consuming enough of the vitamin (or protein, which Vitamin A needs to be transported around the body as part of a lipoprotein). This is because we have an abundance of Vitamin A in our fat stores and in our liver. In children, the symptoms would show much sooner, because they are using their stores up faster in order to grow!
Night blindness is a symptom of deficiency, wherein your eyes are unable to adjust to sudden changes in brightness. Turning out a light would result in near-blindness in the dark, and turning it back on would produce a blinding effect until your eyes got used to the light, taking much longer than a person who has adequate stores of the vitamin.
Eventually, total blindness is a real concern for those who are severely deficient in Vitamin A.
Keratinization is another side effect of the deficiency. This occurs when the skin cells are unable to change shape, so they secrete the protein keratin and become rough and dry.
Toxicity occurs through overconsumption of animal food or supplements, but not plants. This is because beta-carotene (found in fruits and vegetables) is not converted efficiently enough to cause a toxicity of Vitamin A. You’ll just get a nice, yellow-orange glow! (Yes, the rumors are true!)
Symptoms of toxicity include fragile bones caused by Vitamin A breaking down more tissue than is being rebuilt, which can lead to osteoporosis. Birth defects are also possible, a consequence of abnormal cell death in the spinal cord.
Pregnant women should be aware of the effects of the acne treatment Accutane, as it is a high dose of Vitamin A to help treat cystic acne deep within the skin. This high dose of the vitamin can lead to birth defects, so Accutane must not be taken when pregnant or looking to become pregnant.
How much Vitamin A do I need?
The American and Canadian recommendation is 900 micrograms RAE/day for men, and 700 mcg RAE/day for women. (RAE stands for retinol activity equivalents, which is basically just saying “all the things that are retinoids and beta carotene, which can be turned into a retinoid”…Don’t worry about it!) Do note that an upper limit has been set of 3000 mcg RAE/day to avoid toxicity!
Where can I find Vitamin A in my diet?
Because Vitamin A is a fat-soluble vitamin, you will find it in the fat of dairy and in animal products, as well as fruits and vegetables as beta-carotene. This means that skim milk will have no Vitamin A, because it contains no fat! Low-fat milks are often fortified to include more of the vitamin, though. Eggs contain Vitamin A in the yolk, and liver or liver oils have extremely abundant sources!
Related Reading: Focus on Food – Eggs
Color is a great indicator of the presence of beta-carotene in a fruit or vegetable, but isn’t 100% reliable. Oranges, yellows, and deep greens are often high in the carotenoid, but corn or bananas have none. Examples of good sources include cantaloupe, tomatoes, sweet potato, carrots, spinach, kale and broccoli!
Related Reading: Focus on Food – Carrots
A well-balanced diet of plant and animal sources is guaranteed to get you provide you with adequate amounts of Vitamin A!
What are your favorite sources of Vitamin A? I seriously love cantaloupe and broccoli!