Vitamin A Deficiency Vs Toxicity: How Much Vitamin A Do We Need?


Prevent deficiency in vitamin aVitamin A is vital for healthy eyes and skin, preventing infection and strengthening our immune system and whole host of important cellular functions in your body. But just how much vitamin A do we need to prevent deficiency?

On the other hand, too much vitamin A can be toxic so how much is too much? The answers, along with the RDA of vitamin A for adults, children and pregnant women can be found ahead.

What Causes Vitamin A Deficiency?

A chronic deficiency in vitamin A should only occur when a person’s diet is lacking in both preformed vitamin A from animal sources like liver, eggs and dairy products, and provitamin A from plant sources like yellow and orange vegetables and leafy greens.

It is unlikely that a person eating a varied diet will be dangerously deficient in vitamin A as reserves can be stored in your body for days when you are not getting enough from what you eat.

However certain factors might increase your chances of being mildly deficient in vitamin A, which can still impact your health and appearance in negative ways.

One of the most common of these is a diet very low in fat or a medical condition that interferes with the body’s ability to absorb dietary fat. Being a fat soluble vitamin, some fat intake is needed to absorb vitamin A effectively.

Protein is important too. As vitamin A is transported through the body by binding with certain proteins, a diet very low in protein can inhibit proper vitamin A uptake and utilization.

Viral infections, liver disease, long-term illness and chronic diarrhea will all be likely to drastically deplete your body’s reserves of vitamin A. Additionally, those who have diabetes, are undergoing cancer treatment or are recovering from surgery may all benefit from a higher intake of vitamin A, though this should be monitored by their treating physician.

How Zinc Deficiency Impacts Vitamin A

Zinc is necessary for vitamin A metabolism and a deficiency in zinc (common in Western diets) can affect just how much vitamin A your body is able to utilize.

Zinc is involved in the synthesis of retinol binding protein that transports retinol to the various places it is needed in the body. Without enough retinol binding protein, vitamin A cannot get where it needs to go to provide maximum benefit.

Zinc is also needed to change vitamin A retinol into the retinal form which is so important for your eyes. Finally, a zinc deficiency may result in a decrease in the body’s ability to release stored vitamin A in the liver.

Clearly zinc is a very important mineral to your health and wellbeing. There’s much more on the dangers of zinc deficiency here.

The Importance of the Vitamin D to Vitamin A Ratio

Vitamin A IntakeVitamin A and Vitamin D work together in the body in many synergistic ways. A significant lack of either can be disruptive to their various functions.

Since Vitamin D is usually harder to obtain, particular if a person isn’t getting much sunshine, it is likely that many people living in cooler climates have a Vitamin A to Vitamin D ratio heavily in favor of Vitamin A.

A good ratio of Vitamin A to Vitamin D is believed to be at least 10 to 1, and some recommend 5 to 1 as even more beneficial. Following this ratio, if a person had a Vitamin A intake of approximately 5000 IU, they’d be looking for a Vitamin D intake of at least 500 IU, better still up around 1000IU.

Most people living away from warmer climates and lacking good sources of Vitamin D in their diets aren’t getting anywhere near that, particularly in winter. One effective solution is to take cod liver oil with a balanced ratio of vitamin A to vitamin D.

This lemon oil flavored bestseller is the one I use and it’s been of noticeable benefit to my skin, eyes, immunity and overall health. Take a teaspoon daily for best results. It will also cover your omega-3 needs as well.

Recommended Daily Allowance

According to the Mayo Clinic, these are the medically recommended amount of vitamin A to get in your diet daily:

  • For males over 14 the RDA for vitamin A is 900 mcg (3000 IU) and the RDA for females over 14 is 700 mcg (2300 IU).
  • For children 9 to 13 the RDA for vitamin A is 600 mcg (2000 IU). For children 4 to 8 the RDA is 400 mcg (1300 IU) and for children 1 to 3 the RDI is 300 mcg (1000 IU).
  • The vitamin A RDA for pregnant women 19 and older is 770 mcg (2,600 IU) and 1,300 micrograms daily (4,300 IU) for lactating women 19 or older.

There is some debate as to whether these amounts are optimal for health or simply adequate to prevent vitamin A deficiency. The Weston A Price Institute has some interesting articles on vitamin A if you have time.

In 2001, the Food and Nutrition Board of the Institute of Medicine (in the USA) set the tolerable upper limit for adults of preformed vitamin A at 3000 mcg (10,000 IU) per day.

Whilst therapeutic doses of vitamin A for specific health conditions may be higher, they should be monitored by a knowledgeable healthcare professional. Vitamin A is fat soluble and as such can accumulate in the body and be toxic at excessively high doses.

Vitamin A Toxicity and Overdose

A vitamin A intake of more than 25,000 IU for adults and 10,000 IU for children a day for several months can be damaging to the human body. Children are more vulnerable to vitamin A toxicity than adults so keep vitamin supplements with preformed vitamin A well out of their reach.

Chronic vitamin A toxicity is usually only seen with a excessive intakes of supplemental vitamin A, though in theory regularly eating large amounts of a very high source of vitamin A, like beef or chicken liver, could also lead to excess levels of vitamin A in your body.

Hypervitaminosis A is the term given for the condition caused by vitamin A overdose. Symptoms include loss of appetite; dizziness; headaches; dry, itchy skin; hair loss; blurred vision and reduced bone mineral density, leading to joint pain and even eventually osteoporosis.

Severe cases of hypervitaminosis A, while very rare, may lead to liver damage and hemorrhage.

To avoid vitamin A overdose read the labels on any health supplements containing synthetic preformed vitamin A and keep your intake under 10,000 IUs a day. Most vitamin supplements do not exceed 10,000 IUs when taken at the recommended dosage.

Also remember that beta-carotene, often used in multivitamin supplements, is a carotenoid and will not be converted to vitamin A once the body has what it needs.

How Much Vitamin AWhile many supplements will list beta-carotene as vitamin A, it isn’t really until it’s converted by your body. As this conversion is estimated to be at a ratio of at least 12 to 1 of beta-carotene into vitamin A, the whole practice of listing beta-carotene as Vitamin A is actually pretty misleading.

Women who are pregnant should discuss their vitamin A needs with a healthcare professional to avoid getting either too much or too little preformed vitamin A.

People with liver disease, those at risk of osteoporosis, smokers and those who regularly drink a lot of alcohol should also be careful about ingesting too much vitamin A from vitamin supplements.

How to Take Vitamin A

Vitamin A is extremely important to your health and wellbeing. It’s likely that most people in Western countries are getting enough to prevent actual vitamin A deficiency.

However, if you find yourself vulnerable to viruses and infections, or have regular skin or eye problems, then this page explains how a bit more vitamin A in your diet (but not too much) can be highly beneficial.

A simple and healthy way to prevent a deficiency in vitamin A is with a high quality cod liver oil with a good ratio of natural vitamin A to vitamin D. Supplements high in synthetic vitamin A may be toxic and are not recommended.

Photo 1: woodleywonderworks / Photo 2: grongar / Photo 3: nathanmac87

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