Facts About Vitamin A and How It's Used

Vitamin A Facts

Basic Facts About Vitamin A

First and foremost, vitamin A (along with vitamins D, E and nutrients are only absorbed when fat is present in the diet! This means that if you cut out all the fat from your diet, you'll become deficient in these critical vitamins that support life. This is one of the many important reasons why dietary fat is critical for healthy living!

Now that we have that out of the way, let's dive right into some more facts about vitamin A that you may be curious about...

Reference Nutrient Intake (RNI)

A.K.A. Recommended Daily Allowance (RDA)

The recommended intake of vitamin A is somewhat elusive to the general public, since it's measured in a code labeled as "RE". Since there are various derivatives of vitamin A that all have different functions, it's obvious how the recommended intake could be somewhat complicated - I'll try to simplify it here. Understanding certain facts about vitamin A require a general knowledge of this system.

They've come up with a system of measurement called Retinol Equivalents, abbreviated RE. The table below is a summary of this measurement...

RE Values (1mcg = 0.001mg)
1 RE =...	1 mcg retinol
	6 mcg beta-carotene
	12 mcg of other beta-carotene derivatives

Just as a side note, other references will refer to International Units (IU) instead of Retinol Equivalents (RE). Basically, 1 RE is the same as 3.5 IU when from an animal source. When coming from plant sources, 1 RE is the same as 10 IU. Confusing I know - I just stick with RE since it's a bit more straight-forward.

With these facts about vitamin A under our belts, it's a bit easier to understand the recommended allowance. The table below illustrates the recommended intake for individuals varying in age and gender...

Recommended Daily Intake of Vitamin A (in RE, as described above)
Infants (0-1yr)	375
Kids (1-10 yrs)	500-700
Adult Males (11+ yrs)	1000
Adult Females (11+ yrs)	800
Pregnant	800
Lactating	1,200 - 1,300

Notice the pregnancy column. Excessive intake of vitamin A during pregnancy can cause miscarriage, developmental problems and malformations of the fetus. This doesn't mean you should eliminate vitamin A from the diet, but just try to avoid getting too much (this is why the recommended intake drops slightly during this period). Your doctor should have plenty to say about your vitamin A intake if you're pregnant. Check the vitamin A toxicity section for more information on this subject.

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Facts About Vitamin A Deficiency

Vitamin A deficiency in developed countries is extremely rare, especially since most of those individuals are eating enough fats and, hopefully, enough fruits and vegetables. It's more common in less-developed countries where higher-fat foods are scarce. If you recall some of the functions and other facts about vitamin A listed here, you may be able to guess some of the detrimental effects of having a vitamin A deficiency...

Night Blindness

Vitamin A is especially important for the visual cycle of your rods, which are mostly used in the relative absence of light (at night!). This is the earliest sign of a vitamin A deficiency. When untreated, night blindness can be irreversible, possibly leading to a condition called xeropthalmia. This essentially dries up the eyes, forming scar tissue in the cornea that ultimately results in blindness. Xeropthalmia is mostly seen in children of developing countries where dietary fat intake is very low. Without fat in the diet, it's impossible to absorb any form of vitamin A!

Growth and Development

A child deficient in vitamin A may show signs of growth abnormalities not related to any genetic defect like Achondroplasia or other dwarfing diseases. This is because retinoic acid, a byproduct of vitamin A metabolism, is responsible for the activation of genes that promote growth and differentiation of body tissues.

Darier's Disease (Acne) and Psoriasis

Vitamin A deficiency can also result in Acne and Psoriasis (chronic itching and silvery flaking of the skin). These conditions are usually caused be a deficiency or problem in the production of keratin. Since retinoic acid effectively helps produce new epithelial linings and promotes the synthesis of keratin, retinoic acid is often used as a treatment for such disorders.

Some topical treatments (in the form of a cream that you would rub into your skin) are used to treat acne and normal aging. The main drug used for this purpose is Tretinoin which is simply a solution of trans-retinoic acid. This drug is pretty potent and toxic in large amounts, which is why you can't use it all over your body (it's only a topical solution!). The usage of cis-retinoic acid has a completely different purpose...

A more potent, oral drug called isotretinoin (a.k.a. Accutane), a solution of cis retinoic acid), is used when conventional acne therapies are ineffective. None of the oral or topical vitamin A medications are to be used in pregnancy so as to avoid birth defects.

Immune System

Vitamin A also plays a role in immune infection. A deficiency may also cause an increase in bacterial and viral infections!

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Facts About Vitamin A and Pregnancy

I know I've really hammered this topic, but it's important!

Again, taking in too much vitamin A while pregnant can cause lethal problems with the fetus. But, not having enough vitamin A in the diet can also result in fetal death. The key is to take in enough without overdoing it! See the table above...

The drug isotretinoin (a.k.a. Accutane) is also a hot topic in this area. Its normal use is to treat Acne and Psoriasis when other treatments are too weak. But, taking this medication while pregnant can cause some problems...

Basically, the drug is teratogenic (damaging to a developing fetus) and shouldn't be taken by any woman of child-bearing age. It's highly unethical to prescibe a teratogenic drug to any woman during this age period since they may not know if they're pregnant (the risk is too great for harming the fetus). The only exception is in the instance of disfiguring or debilitating Acne and Psoriasis and with proof of a non-pregnant state and documentation of current and prior use of oral contraceptives. Again, the possibility of pregnancy must be completely eliminated before taking this drug.

Many treatments with this drug can also cause an increased risk of cardiovascular disease since higher levels of LDL (bad cholesterol) and free lipids circulate through the blood during treatment.

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Facts About Vitamin A and Aging Drugs

There's been a huge market for anti-aging creams and supplements related to UV damage, smoking, or other sort of environmental damage that results in wrinkles and leathery skin. One of these drugs is a prescription drug called Retin-A. The results of this drug are extremely sporadic. Some report the erasing of shallow wrinkles, others report no help for deeper wrinkles, and still others report extreme skin irritation and frequent, uncharacteristic sun damage when taking the drug.

The drug basically removes the top protective layers of skin thereby removing superficial wrinkles. Removing these layers may promote the occurrence of skin cancer. Other drugs work in this manner as well, so be careful and make informed decisions under the guidance of your dermatologist or general physician.

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