What is Vitamin A?
Vitamin A is one of the most essential micronutrients for human health. Vitamin A is also known as retinol, retinoic acid, retinaldehyde and provitamin A carotenoids. But in truth, these are all different types of vitamin A and not just names as vitamin A is a group of chemical compounds. All these chemical compounds serve different purpose in the body and make vitamin A extremely important for body’s proper growth and functioning.
What is Vitamin A’s function in the body?
Vitamin A is present in two forms – retinoids from animals and dairy (retinol, retinyl esters, retinaldehyde) and carotenoids from plants. Retinol is the most abundant form that converts to other active forms such as retinoic acid and retinaldehyde for use by the body and is also stored as retinyl ester in the tissues, mostly liver, for later use as needed. A carotenoid is first converted into retinol and then used or stored.
Vitamin A functions at two levels – in the visual cycle in retina and in maintaining the growth and health of cells. Vision in dim light is greatly dependent on the availability of retinol in the body to produce chemicals enabling low light vision.
What are Vitamin A’s benefits?
Vitamin A is mainly known for supporting vision, immune functions, cell repair and growth and development. Vitamin A is also an anti-oxidant, so helps slow down age related cellular degradation and helps in dealing with inflammatory effects of environment and diet.
Vitamin A benefits for skin
The retinol form of vitamin A is what is most beneficial for the skin. There’s strong research that applying retinol creams, or creams that contain retinol or ingredients that convert to retinol, reduce wrinkles on the skin. Doctor’s help should always be taken before choosing such creams as they can be quite powerful but only if taken in the right concentration and form. There’s a lot of information on choosing the right vitamin A products for the skin, and you should make a well researched decision to avoid undesirable effects.
Vitamin A benefits for hair
Just like all cells need vitamin A for growth, so do the hreair. It also helps in keeping hair strong and healthy by repairing damage and reducing breakage. When it comes to vitamin A for hair, diet sources are the most useful as any hair shampoo or conditioner is washed off within minutes without adding much benefit.
Vitamin A deficiency diseases
People with a healthy well-rounded diet do not easily get deficient in vitamin A as it is a micronutrient and is not needed by the body in large quantities. Because of its main functions in supporting vision and immune system, vitamin A deficiency can cause night blindness, weak immunity and cell degradation which will start becoming visible with poor eye health, dry skin, respiratory infections and low iron and high vitamin D levels (too much sun exposure can deplete vitamin A levels).
Vitamin A is extremely important for newborn children too as this is a period of growth and and rapid transformations and there’s a high need for things supporting cell growth. It will also reduce risk of catching infections, which is common among small kids still getting used to the new world.
A lack of vitamin A can also effect Iron metabolism in the body if deficiencies of both nutrients coexist. People with low hemoglobin see maximum improvement when increasing vitamin A along with iron, and conversely, people with vitamin A deficiency mostly have low iron levels.
Vitamin A dosage?
Vitamin A daily requirement or the amount specified as RDA is 3,000 IU (=900 mcg/RAE) for adult males and 2,333 IU (=700 mcg/RAE) for adult females; and the upper limit is defined as 10,000 IU (=3000 mcg/RAE) for all adults.
How to calculate vitamin A dose?
Vitamin A dose is measured in IU (International units), mcg RAE (mcg Retinol Activity Equivalent).
1 mcg retinol = 1 mcg RAE or 3.3 IU
1 mcg beta-carotene = 1/12 mcg RAE or 1.6 IU
1 mcg other provitamin cerotenoids = 1/24 mcg RAE or 0.8 IU
To put these numbers in perspective, 1/2 sweet potato or 3/4 cup carrot or 1 cup spinach or 3/4 tsp cod liver oil are enough to get the daily dose of vitamin A.
What are good Vitamin A sources?
As described earlier, vitamin A is available in two forms – preformed retinoids and proformed cerotenoids. Supplements mostly contain the active form retinol. Vegetarian food contains carotenoids and non-vegetarian and dairy food contains retinoids.
Vitamin A rich foods in India
Vegetarian – carrots, sweet potatoes, spinach, broccoli, mango, bell peppers
Animal sources – milk, egg, cod liver oil, salmon, yogurt, tuna, beef liver
A more comprehensive and better list of vitamin A food sources can be found here.
Vitamin A in carrots
1/2 cup carrot juice is more than sufficient to provide daily vitamin A dose.
Vitamin A in milk
Milk has vitamin A although not in sufficient quantity for a day. A cup of milk provides roughly 3-5% of daily vitamin A.
Vitamin A in common vegetables
1 cup cooked spinach provides almost 100% of daily vitamin A.
It should be mentioned that various sources report various values of vitamin A depending on whether the food is raw or cooked, accompanying meal and a person’s body. It is therefore wise to take precaution and eat things in moderate quantities.
How should Vitamin A be consumed?
Preformed vitamin A is easily absorbed by the body but absorption of provitamin A carotenoids varies depending on the diet source and the amount of fat in the meal. So as a general tip, do not try to go for a fat-free diet and include some oil, nuts, ghee, etc. in your meals for increasing the absorption of certain vitamins and minerals.
Also, vitamin A comes with a risk of overdosing so moderation is key. The conversion efficiency of carotenoids to active form is low, about 1/12th of preformed vitamin A, so it’s unlikely to overdose from plant sources. If consuming from animal sources and supplements, monitor your intake quantity closely to not consume more than recommended dosage as these will likely have easily available to the body form of retinol.
Vitamin A overdose/toxicity
As vitamin A is fat-soluble and gets stored in the liver, its concentration can accumulate over time and lead to hypervitaminosis A. This can cause blurred vision, bone deterioration and increased fracture risk, hair thinning, skin irritation and even death. As carotenoids have a low efficiency while converting to retinol, it is hard to overdose when eating plant sources. But if your diet includes more of preformed vitamin A from animals products, dairy or supplements the vitamin A levels can build up pretty quickly if eaten in large amounts. Even if you stop eating vitamin A after that and the built up concentration starts coming down, the resulting liver damage might not always be reversible.
Vitamin A is extremely essential for proper growth and maintenance of cells, vision and immunity. Low levels of vitamin A can also negatively impact how iron and zinc are metabolised in the body, whereas high levels can deplete vitamin D. Plant based foods are less effective than animal based food sources in providing vitamin A. On the good side, that means you can eat more of them to get other micronutrient benefits without worrying much about vitamin A toxicity.
It is wise to follow the precautionary principle when it comes to diet. Don’t eat anything daily for too long and take breaks in between, like eating vitamin A rich food just 2-4 times every week. Eat well-rounded meals and do not follow any diet form also for too long that tells you to overdose on one component of the diet and leave out others.