Ah, Vitamin A, we hardly know you. Vitamin C is the most famous, and Vitamin D is all over the news these days. Even the B Vitamins get publicity with their inclusion in energy drinks. Don’t even get me started on Vitamin E. But, Vitamin A never gets any love. Even though without it you wouldn’t be able to see to read this post. So let’s give Vitamin A it’s moment in the spotlight. It’s long overdue.
Types of Vitamin A
In nature, Vitamin A comes in several different types. These types can be broken into two broad categories; from animal sources and from plant sources. The main difference lies in how the body uses the two. Plant sources (carotenoids) need the body to convert them to the active forms. While animal sources are already in the active forms (retinal, retinol, retinoic acid).
Bottom line, the Vitamin A from plants and animals is different, but through the magic of the human body it all ends up the same.
What is it good for?
You’re probably familiar with Vitamin A as being good for eyes, especially night vision. But the known benefits don’t stop there:
- Vitamin A is important for cell growth and division, making it especially important for growing children.
- It’s also necessary for proper immune function. Severe cases of measles have been linked to Vitamin A deficiency.
- It’s also important for reproduction (ooh la la).
- And, the plant sources (carotenoids) are potent antioxidants. Check back for Friday Focus for a full discussion of this benefit.
As with most vitamins, all benefits are not fully known. The above are the benefits for Vitamin A are known and generally accepted.
How much do we need?
For adults the Recommended Daily Allowance is 5,000 IU. Some studies have shown increased benefits up to 20,000 IU. (Although that daily intake is not widely accepted.)
Where do we get it?
Do you like liver? (My father is probably the only person who answered yes to this.) Vitamin A is stored in the liver. One 4 ounce serving of liver has 7 days worth of Vitamin A. If you’re not into liver, you can get Vitamin A from plant sources. Look for bright yellow and orange vegetables (carrots! pumpkin, squash) or dark leafy green vegetables.
Not getting enough?
Vitamin A deficiency is one of the leading causes of blindness in the world, especially in developing countries. Other, less severe, consequences result from Vitamin A deficiency:
- Dry, flaky skin
- Immune function decrease
- Growth effects
- Bone thickening
- Kidney stone formation
- Respiratory infection susceptibility
Getting too much
As we discussed in a previous post, since Vitamin A is fat-soluble, a potential for toxicity does exist. Although, since the body will stop converting plant sourced Vitamin A (beta-carotene) when stores are full, overdose from plant sources or beta-carotene based supplements is unlikely. True overdose primarily comes from ingestion of animal sources.
Symptoms of overdose include: fatigue, swelling, vomiting, liver enlargement, constipation, and joint pain. Toxicity can be reversed by decreasing Vitamin A intake.
The established limit for toxicity is 50,000 IU daily. This is well above the RDA of 5000 IU. It is also significantly higher than theorized optimal doses above the RDA (20,000 IU).
Now that you mention it….
- Vitamin A intake above 10,000 IU daily is not recommended in pregnant women.
- There’s evidence those with Vitamin A deficiency may be more likely to get cancer, and a more aggressive form of cancer.
So that’s an all too brief moment in the spotlight for Vitamin A. Now that you have a better understanding of the vitamin at the top of the alphabet, I hope you agree it’s Vitamin A is for Awesome!