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picox 04-10-2009 09:04 AM

Vitamin A Requirements
I am looking to change to a new "diet" and have been trying to calculate what nutrients I need to receive through supplementation.

All of the information that I have received about the nutrient values of my food items has come from the USDA database.

For Vitamin A, it includes both the number of RAE and the number of IU, as well as the amounts for certain provitamins of Vitamin A.

The thing is, according to the IU, I would be getting just about enough of Vitamin A. I am looking at a little over 3000 IU. However, according to the RAE, I would only be getting about 200-something micrograms. The RDA is 900.

What does this mean? Do I risk Vitamin A deficiency if I do not get additional Vitamin A from a dietary supplement?

janewhite1 04-10-2009 10:47 AM

Re: Vitamin A Requirements
First off, what is this diet that has so little vitamin A? It's so easy to get enough. Are you possibly leaving out some foods?

The difference between IU and RAE is this: The RAE is a new measurement that takes into account how easily your body can get to the vitamin, so it is probably more accurate.

However, I would be very careful about taking Vitamin A supplements. It's probably the easiest nutrient to overdose on, because the RDA is 3000 IU and the maximum safe intake from all supplements and dietary sources COMBINED is also 3000 IU. If you are going to take a vitamin A supplement, make sure that it contains no more than 100% of the RDA (50% is better), and make sure that most of it is in the form Beta Carotene.

picox 04-10-2009 12:23 PM

Re: Vitamin A Requirements
I thought that the Upper Limit for Vitamin A was 10,000 IU, not 3,000?

Most of my Vitamin A would be coming from some tomatoes and a peach. Most of the other pending fruits (as well as the nuts) do not seem to have much of any Vitamin A in them.

janewhite1 04-10-2009 01:21 PM

Re: Vitamin A Requirements
Tomatoes are a good source, so are the orange veggies (carrots, sweet potato.)

Animal products such as eggs and meat are also high in Vitamin A. Milk and breakfast cereal are usually fortified with A.

Are you trying to become vegan? In that case, you do need to plan very carefully and possibly take supplements.

picox 04-10-2009 02:07 PM

Re: Vitamin A Requirements
Yes, this "diet" that I am planning is all-vegan.

I am looking at some supplements that contain a mixture of Vitamin A Palminate and Beta-Carotene totaling 5,000 IU. How much of each is unknown, but that will keep me below 9,000 IU. Much less that 10,000 upper limit. Would that be cutting it too close?

And about following the IUs instead of the RAEs? What kind of difference would it make? I mean, I could theoretically be over-dosing according to IUs and deficient according to the RAEs.

janewhite1 04-10-2009 06:30 PM

Re: Vitamin A Requirements
Beta carotene is the form of A you get from plants. It might be possible to overdose on that, but it takes much much more than the RDA. Your body converts it to the active form of A as necessary.

Retinoic acid is the "active" form of vitamin A. It comes only from animal foods and from supplements. That, you can overdose at levels just 3-5 times the minimum necessary to maintain health.

If you are going vegan, keep in mind that you need protein from a variety of different plant sources to ensure that you get all essential amino acids. (see Complete Protein.)

Vegans also have a hard time getting vitamins D and B12. Most other nutrients, plant foods provide in ample quantities.

picox 04-12-2009 02:37 PM

Re: Vitamin A Requirements
I have been reading more into Vitamin A. It is sounding like, if you only receive pro-vitamin forms of Vitamin A (such as Beta-Carotene), the 10,000 IU limit does not apply. Is this correct? It is only for retinoids?

Because, according to my math, the 900 microgram RDA of Vitamin A would require 10,800 micrograms of Beta-Carotene. In IUs, that would be about 18,000. So, following the RAE RDA, you would have to exceed the IU upper limit.

janewhite1 04-12-2009 03:03 PM

Re: Vitamin A Requirements
Exactly right. If all your vitamin A is beta carotene, the upper limit is much higher. So just avoid supplements with large amounts of retinoic acid, the "pure" vitamin A.

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