How Much Vitamin A Do We Need?
Vitamin A is vital for healthy eyes and skin, preventing infection and strengthening our immune system and whole host of important cellular functions in our bodies. But just how much vitamin A do we need to prevent deficiency?
Vitamin A Deficiency
A true vitamin A deficiency should only occur when a person’s diet is lacking in both retinoids (preformed vitamin A) from animal sources like liver, meats, eggs and dairy products, and certain carotenoids (pro-vitamin A) from plant sources like yellow and orange vegetables and green leafy plants.
It is unlikely that a person eating a varied diet will be seriously deficient in vitamin A. Most of us have good reserves stored in our body, for use when we are not getting enough from what we eat. However certain factors might increase someone’s chances of being low in vitamin A.
One 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 in the diet is needed to absorb vitamin A.
Protein is important too. As vitamin A is transported through the body by binding with certain proteins, a diet very low in protein may inhibit proper utilization of vitamin A.
Viral infections, liver disease, long-term illness and chronic diarrhea will all be likely to drastically deplete the 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 a knowledgeable healthcare professional.
Vitamin A Deficiency and Zinc
Zinc is important to vitamin A metabolism and a deficiency in zinc (common in Western diets) may affect just how much vitamin A your body is able to properly use. 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 retinol into retinal which is so important for the eyes. And finally, a zinc deficiency may result in a decrease in the body’s ability to release stored vitamin A in the liver.
Vitamin A to Vitamin D Ratio
Vitamin A and Vitamin D work together in the body in many important ways. A significant lack of either can be disruptive to their various functions. Since Vitamin D is often 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 to be 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 sunny climates and lacking good sources of Vitamin D in their diets aren’t getting anywhere near that.
Vitamin A Recommended Daily Intake
The recommended dietary intake (RDI) of vitamin A for males over 14 is 900 mcg (3000 IU) per day and the RDI for females over 14 is 700 mcg (2333 IU). For children 9 to 13 the RDI for vitamin A is 600 mcg (2000 IU). Children 4 to 8 the RDI is 400 mcg (1333 IU). And for children 1 to 3 the RDI is 300 mcg (1000 IU).
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 in excessively high doses.
How Much Vitamin A?
In summary, vitamin A is an extremely important vitamin to our health and well-being. It’s likely that most people in Western countries are getting enough to prevent actual deficiency. But if you find yourself vulnerable to viruses and infections, or have regular skin or eye problems, a bit more vitamin A in the diet (but not too much) may be helpful.
A good way to do this would be with a high quality cod liver oil with a good ratio of vitamin A to vitamin D. Supplements high in synthetic retinal acetate or retinal palmitate are not recommended.