How Well Do You Convert Beta-Carotene to Vitamin A?

How Well Do YOU ConvertBeta-Carotene to Vitamin A-Everyone knows that carrots and sweet potatoes are great sources of vitamin A, right?

Well…  it turns out it isn’t that straightforward for everyone. The beta-carotene in orange fruits and vegetables has to be converted into the form of vitamin A that our bodies can use, and genetics plays a huge role in how well we do that conversion.

Almost half of us have variants in our BCMO1 gene which cause a 30% to 70% decrease in the amount of vitamin A that we get from beta-carotene.

Background information on Vitamin A:
Vitamin A is a general term that covers several different forms of the vitamin. Animal food sources mainly provide retinyl palmitate, which is broken down in the intestines to retinol. In this form, it is stored by the body and then converted to an active form for use.

The plant forms of vitamin A are called carotenes, such as beta-carotene which is found in abundance in carrots and other orange-colored foods. Beta-carotene is broken down by an enzyme in the intestines to also form retinol. Interestingly, most carnivores are poor converters of beta-carotene, and cats cannot create any vitamin A from beta-carotene.  [source]

About 80-90% of retinoids in the body is stored in the liver and used to maintain a steady level in the blood.[study] The body then used the retinoids in a variety of ways including in stem cells, photoreceptors in the eye, epithelial cells, embryonic cells, various immune cells, red blood cells, and much more.


Genetics of Beta Carotene Conversion:
Beta-carotene is converted by the enzyme β-carotene 15,15′-monooxygenase (BCMO1 gene) into retinol. It is then used by the body in the same way as preformed vitamin A from animal products is used or stored.

There are two gene variations in the BCMO1 gene that help determine a person’s ability to convert beta-carotene into the retinol a body uses. A study in 2008 shows that the SNP’s rs12934922 and rs7501331 control a person’s conversion rate of beta-carotene into retinol. People with a T allele on both rs12934922 and rs7501331 have a 69% decreased conversion of beta-carotene to retinol.  For people with only a single T in the rs7501331 SNP, the conversion is decreased by 32%.

Check your 23andMe results for rs7501331 (v.4 and v.5):
CC: normal
CT: decreased beta-carotene conversion
TT: decreased beta-carotene conversion
Check your 23andMe results for rs12934922 (v.4 and v.5):
AA: normal
AT: decreased beta-carotene conversion
TT: decreased beta-carotene conversion

Three other variants that are found near the BCMO1 gene have also been shown in a small study to affect the rate of conversion by about 50%

  • rs11645428 – GG has lower beta-carotene conversion
  • rs6420424 – AA has lower beta-carotene conversion
  • rs6564851 – GG has lower beta-carotene conversion

Lifehacks

If you are a vegan or vegetarian, your main source of Vitamin A is probably beta-carotene. If you don’t process it into retinol very well, you may want to increase your vegetables that are high in beta-carotene or supplement with a retinol form Vitamin A.

If you are supplementing with Vitamin A, check and see if your supplement is in the form of beta-carotene or retinol palmitate. If you have a decreased ability to convert beta-carotene to retinol, you may be getting less vitamin A than you think.

A word of caution: Vitamin A is a fat-soluble vitamin that can build up in the body, so you don’t want to go overboard with it. The upper daily recommended limit of vitamin A is 3000 μg/day (3 mg/day). Most supplements list the amount of vitamin A in IU (international units). One IU is equivalent to 0.3 μg (.0003 mg) for vitamin A. So 8000 IU would equal 2.4 mg retinol.

So how much beta-carotene is in carrot juice? According to the Nutridesk website, one cup of carrot juice contains 22mg of beta-carotene. That site also claims that for an average person, 1/12th of that beta-carotene is converted into retinol thus giving 1.8 mg of retinol per cup of carrot juice. If you are a poor converter of beta-carotene, you could be getting more like 0.5mg from a cup of pure carrot juice.

Carlson’s Vitamin A on Amazon.com is a good source of the retinol form of vitamin A

Beef liver is also an excellent source of vitamin A.  A three-ounce serving of liver packs a big punch with about 15,000 IU of vitamin A.

Why is vitamin A so darn important?
A deficiency in vitamin A can cause night blindness, worsen infectious diseases, and, when severe, cause blindness. It is used by the body in a variety of different ways. In the immune system, it is involved with both the innate and adaptive immune responses.[study] Vitamin A can also help with skin problems such as some types of acne and hyperkeratosis.[study]

More to Read:

 

Updated 5/2017

6 Replies to “How Well Do You Convert Beta-Carotene to Vitamin A?”

  1. Can a person be overly efficient at converting carotenes to retinol and so risk vitamin A sub-toxicity by eating a diet very high in carotenes?

    1. Good question :-) I don’t know of any genetic variants that cause extremely high rates of conversion. According to the Linus Pauling Institute at Univ. of Oregon, there is no worry of toxicity from eating sources of beta-carotene: http://lpi.oregonstate.edu/mic/vitamins/vitamin-A#toxicity I think the worst you will have from a diet that is very high in carotenes is turning orange – called hypercarotenosis.

  2. Question: I have a TT and a CT on the above, so I have a decreased beta-carotine conversion. My question though is about topical retinol/retin-A. Do these genetic markers affect the way the body absorbs vitamin-a topically? I am asking because the several times I was prescribed tretinoin or retin-a micro, I had an adverse reaction. I stuck through the so called purging and dry/red/flaky period of about 4-6 months but my skin only continued to get worse until I had to stop. The doctor had no explanation for me and basically said everyone takes well to these topicals. I guess I’m an anomaly. Just wondering if these alleles have something to do with this.

    1. Hi Amber,
      I don’t think that the decreased beta-carotene conversion would affect topical retin-A. My guess would be that you are somewhat allergic to something in the topical creme?
      I’ve read that you can open up the liquid vitamin A gel caps and put them directly on your skin. That may be a way to see if it is the vitamin A that is irritating your skin vs something else in the cream. You might want to try it on a weekend though –the vitamin A gel cap that I tried on my skin smelled a bit like fish and the odor lingered…
      Have you tried taking a true vitamin A internally? Personally, I had keratosis pilaris (little bumps) on the back of my arms and on my thighs since childhood and didn’t know what caused it. When I found out that I didn’t convert beta-carotene very well, I started taking vitamin A. After a month or so, I noticed that my arms were smooth, but I didn’t really make the connection to the vitamin A until I stopped taking it and the bumps came back. That was a few years ago, and I now kind of use the smoothness of my arms as a way to know if I’m getting enough vitamin A. Like the rest of the fat-soluble vitamins, I don’t want to go overboard on vitamin A.
      Good luck on getting it figured out!

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