And while that does not make it a rich source of vitamin A it makes sense to talk a little about “iu” before we go any further into the story of the vitamins so let’s briefly look at what an iu is…
International Units vs Milligrams
Measuring how much of a vitamin a food has does not seem like it would be a big deal but some Food scientists publish their results in iu or International Units and some in milligrams.
The reason is that the vitamins in a food have different forms in any particular food some of which are more active and effective than others. In those cases it makes more sense to publish the vitamin content in terms of “activity” which is measured in iu rather than just how much there is in mg.
Vitamin A was discovered to be essential for sight during animal experiments and found to exist in foods a number of forms such as the carotene version in vegetables and retinol in animal tissues.
The Carotene Family is huge because there are hundreds of different versions in plants, fruit and vegetables – a few commonly mentioned family members are beta carotene, lycopene and lutein.
Both beta carotene and alpha carotene ( and other carotenes) can be converted to retinol in the body and act as a storage tank in a way for this vital vitamin.
Beta carotene is sometimes called provitamin A or previtamin A to express the fact that beta carotene can be converted into Retinol when needed.
Beta Carotene vs Retinol
So you may be wondering whether we need to eat both the carotene provitamin A as well as Retinol?
The answer is no – because we can safely consume large amounts of carotenes in a healthy diet and only when the body needs retinol will it produce it by converting it from beta carotene. And since retinol is fat soluble it can build up in our tissues and particularly in the liver and potentially be hazardous.
Beta Carotene is Safer
That means that the plant forms of vitamin A are safer versions of this vital vitamin to include in your diet. They can build up in your tissues if your intake of sweet potato and carrots and kale is truly and madly gargantuan but all that happens then is a slight bronze or orange tint in your skin which may not even be noticed and which fades if your intake goes back to normal.
What Does Vitamin A do?
I mentioned in passing that we get vitamin A from sweet potato, carrots and kale so with such rich sources of the vitamin delivering many health benefits you can expect vitamin A to do a lot in the body.
It is most well known for its role in vision and in particular night vision. As far back as 1816 animal experiments done to find out why so many babies were dying in Paris found that scars on the cornea of the eye and then death occurred when something was missing from the diet. It took over a 100 years to work out that the missing something was vitamin A.
And it’s not just visual acuity that we get from vitamin A – it contributes to the health of the skin and of what may be called our inner skin.
The power of vitamin A to heal skin lesions is well known and many commercial skin lotions and potions are based on it. Generally they will use a synthetic version of the vitamin rather than the natural version because they may have a patent for the synthetic version and will make a higher profit by selling.
No one makes money telling you to eat sweet potatoes!
But it is not just your skin that benefits from a diet rich in vitamin A – your inner health gets a boost too.
Starting at your lips and going right down the throat and windpipe and gullet right through your stomach and intestines there is an “inner skin” or mucous membrane.
And on this thin and delicate membrane rests the health of your body.
If this membrane is unhealthy we cannot absorb the nutrients we swallow, if this membrane is inflamed by allergens or toxic sprays on our food we struggle to get the nutrition we need.
And if the membrane that lines the windpipe and lungs is unhealthy and inflamed we may struggle to breathe and suffer from asthma and other respiratory diseases.
This membrane – our inner skin – needs nourishment, it needs vitamin A for it’s health ( and vitamin C too but we haven’t got there yet 🙂 )
On the health of the inner skin rests our entire life – no kidding and no exaggeration because it is the mechanism for us to take in both food and oxygen. Without good delivery of both vital nutrients we decline in health and eventually die.
Knowing that vitamin A is a matter of life or death we ask an obvious question…
Where we get Vitamin A From?
We’ve mentioned a few already and they are the richest sources of beta carotene…sweet potato, carrots and kale. But there are lots of others and basically if you have a healthy diet, one with lots of vegetables you hardly need to bother about vitamin A even though it is so important.
Greens – Turnip greens, mustard greens, collard greens and spinach are rich sources too.
Squash and Pumpkin – rich sources of beta carotene
Apricots – dried apricots and peaches are not just totally yummy they pack a punch of beta carotene too.
Tomatoes – a different carotene here – lycopene
How much Vitamin A do I need?
The RDA for retinol is 2300 iu for for adult females, 3000 iu for adult males but my recommendation is eat tons of healthy vegetables rich in beta carotene and forget the numbers. If you really want to take a supplement as a kind of health insurance then consider taking
Last Words on Vitamin A
Basing your diet on vegetables gives you much more than vitamin A, it gives you a sound foundation to be healthy and resist cancer, heart disease and diabetes as well as other chronic diseases that are common on poor diets. By all means take a good vitamin A supplement or a good multi-vitamin but help it along with a multi-vegetable dinner plate as well.