Vitamin A – Deficiency, Foods, and Side Effects

Vitamin A – Deficiency, Foods, and Side Effects

The human body needs vitamin A for the proper functioning of its immune system eyes, skin and many other parts as it is essential for the reproduction and growth of our body cells.

This vitamin is an essential component of Rhodopsin, which is a protein that absorbs the light in retinal receptors and supports the normal functioning and differentiation of conjunctival membranes and cornea.

In simple terms, Vitamin A is an essential component for keeping healthy eyesight.

A study at National Institute of Health proved that vitamin A contains fat-soluble retinoids (compounds) called retinol, retinal, and retinyl esters, all relate to eyesight.

It also plays a critical role in proper functioning of vital organs: heart, brain, kidneys, lungs and liver.

Forms of Vitamin A

Vitamin A is available in our diet in two forms:

  1. Preformed Vitamin A
  2. Provitamin A

Preformed vitamin A is scientifically called retinol and its esterified form is retinyl ester.
The other one is provitamin A carotenoids. Carotenoids can be converted into retinol when needed so they reduce the risk of overdose because an overdose of retinol can be toxic. Apart from that, carotenoids are the basic compound elements that turn leaves and other organisms yellow, hence an overdose of this vitamin can also turn your urine yellow, but that is mainly harmless.

Chemical structure fo Retinol.

Chemical structure fo Retinol. Image courtesy of Wikipedia.

There are three types of carotenoids: the most important one is called beta-carotene while the other two are called alpha-carotene and beta-cryptoxanthin.

Nutrition Sources of Vitamin A Types

  • Sources of the first form: Preformed Vitamin A, are foods we get from animals. That includes fish, egg, and meat (especially liver) as well as dairy products.
  • The human body gets the second form of Vitamin A through plants. It converts the plant pigments into Provitamin A carotenoid.

Symptoms of Deficiency

Severe deficiency of this vitamin may cause serious eye problems, including night blindness or loss of vision. Such deficiency can occur due to both reasons, i.e., dietary (intake) or metabolic (absorption). We’ll discuss this topic in detail in the next segment. Let’s check out the symptoms first.

  • Unhealthy skin
  • Improper bone growth
  • Infections in the digestive, respiratory, and urinary tracts

Good News

Vitamin A is found in lots of food items and if we take a balanced diet that is full of variety, we can be sure we won’t face its deficiency ever. That’s because Vitamin A is a pretty common vitamin found in most our regular food items. This is the reason that this kind of deficiency is rare in developed countries. It usually occurs in backward and undeveloped areas where people have to stick with just one kind of diet which may not contain Vitamin A.

Okay, so we should check the list of foods that contain Vitamin A, but before that, we need to understand how much of it do we really need?

Our Vitamin A Needs

Food and Nutrition Board (FNB) of the Institute of Medicine of the National Academies (formerly National Academy of Sciences) has recommended the DRIs (Dietary Recommendations for nutrient Intakes) for Vitamin A. Here’s the recommended intake guide distributed by age and gender.

  • Children Male/Female :  0–6 months       400 mcg
  • Children Male/Female :  7–12 months     500 mcg
  • Children Male/Female :  1-3 years             300 mcg
  • Children Male/Female :  4–8 years           400 mcg
  • Children Male/Female :  9–13 years          600 mcg
  • Female:                              14–100 years      700 mcg
  • Male:                                  14–100 years      900 mcg
  • Pregnant Ladies:              14–18 years        750 mcg
  • Pregnant Ladies:              19–51 years        770 mcg
  • Lactating Ladies:              14–18 years        1200 mcg
  • Lactating Ladies:              19–51 years        1300 mcg
mcg = micrograms. 1000 mcg = 1 milligram.

Foods Rich Vitamin A

Preformed Vitamin A is found in the highest quantity in beef/lamb liver and fish oils. Other sources are milk and eggs that include some Provitamin A as well. But most of dietary Provitamin A comes from leafy greenish, orange and yellow vegetables, fresh fruits and dry fruits, and some edible vegetable oils.

Here’s a detailed list of foods rich in Vitamin A.

  • Beef liver, pan fried, 3 ounces: 6,582 mcg
  • Sweet potato, baked in skin, 1 whole: 1,403 mcg
  • Spinach, frozen, boiled, half a cup: 573 mcg
  • Carrots, raw, half a cup: 459 mcg
  • Pumpkin pie, commercially prepared, 1 piece: 488 mcg
  • Ice cream, French vanilla, soft serve, 1 cup: 278 mcg
  • Cheese, ricotta, part skim, 1 cup: 263 mcg
  • Herring, Atlantic, pickled, 3 ounces: 219 mcg
  • Salmon, sockeye, cooked, 3 ounces: 59 mcg
  • Cantaloupe, raw, ½ cup: 135 mcg
  • Peppers, sweet, red, raw, half a cup: 117 mcg
  • Mangos, raw, 1 whole: 112 mcg
  • Fortified cereal 1 cup: 127–149 mcg
  • Skim milk, with added Vitamin A, 1 cup: 149 mcg

nutrition note
Doctors recommend the foods with a mixture of ingredients both from animal and plant sources so that our diet could contain both forms of the vitamin.

Vitamin A Supplements: Things to Remember

Vitamin A Supplement

Image courtesy of Walmart

Vitamin food / dietary supplements are pretty common and usually considered harmless… But still, there are things you should remember while thinking of taking supplements.

Health Risks from Excessive Intake

We’ve already mentioned that vitamin A is a fat-soluble vitamin, so it is can be stored in our bodies, unlike B-complex vitamins or Vitamin C. Fat-soluble vitamins (A, D, E and K) get stored in several places in our bodies, especially in the liver.

The body stores the excess amount of it for future consumption. That’s why its level can accumulate and then a complication may occur. When the first form, i.e., preformed vitamin A is stored in excess amount, its significant toxicity (hypervitaminosis A) may take place.

What happens with hypervitaminosis A

Usually, hypervitaminosis A takes place due to a rapid intake of a massive amount in the shape of supplement dosage. It may cause the following side effects:

  • Increased intracranial pressure (pseudotumor cerebri)
  • Nausea and headache
  • Dizziness or coma
  • Irritation of skin
  • Pain in the bones or joints
  • Increased fracture risk
  • Lungs cancer boost
  • Birth defects
  • Heart disease
  • and even DEATH!

When someone consumes too much of vitamin A, the tissue levels in his body take a long time to fall when they discontinue their intake. That can result in liver damage and remember this damage is not always reversible.

But Don’t Worry

Even though hypervitaminosis A’s symptoms make it look like something that would take your sleep away, you don’t have to worry much. It is very rare when a person became a victim of it due to eating vitamin A through natural way. Only in some cases of Eskimos, the patient is found affected when he ate livers of polar bears. So, if you take this vitamin in through natural method, i.e. through food, you won’t get affected with hypervitaminosis A… Unless you’re planning to eat a polar bear.

Except for this only Eskimo case, there’s no record of any this vitamin overdose through a natural diet. However, if you are taking supplements, make sure you have the advice of a qualified medical practitioner. Fat-soluble vitamins, should not be taken through self-medication.

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