Vitamin A is important for the overall development and maintenance of the body. Our body does not produce vitamin A on its own. It needs to be supplemented through diet; that's why it's called an essential vitamin.
The retina is the film screen, located at the very back of the eye. It contains two important cells that process the light entering our eyes.
The rod cells help us see in low light, while the cone cells help our color vision. The rod cells contain an important protein called rhodopsin, which moderates low light vision. A form of vitamin A called the retinal helps activate rhodopsin.
This is why a severe deficiency of vitamin A can cause night blindness.
Vitamin A is also crucial for maintaining skin integrity and forming new skin cells. Since vitamin A is an excellent antioxidant, including it in your diet every day can lower your risk for heart attack.
We all know that carrots are a good source of vitamin A. They are a rich source of a molecule called beta-carotene. Beta-carotene is a provitamin A. Provitamins are substances that are converted into active vitamins in the body.
Beta-carotene is what is responsible for the bright orange color of the carrot. All plants provide vitamin A in the form of beta-carotene, among other forms.
Vitamin A is present as retinol, a form of active vitamin A, in animal food sources. Now, the beta-carotene from plant sources must be converted to active vitamin A for it to be useful to the body.
Let’s see how that happens.
The structure of beta carotene resembles that of a dumbbell - two ring-like structures joined by a chain. This chain is cut in a particular way to give rise to two molecules of retinol, or active vitamin A. This cleavage happens in the liver.
Image: Cleavage of beta-carotene to retinol
Vitamin A in the body can be converted or interconverted into different formats. The retinol and retinal forms are interchangeable, while there’s only a one-way conversion from retinal to retinoic acid.
Image: Different forms of active vitamin A
The retinal form of vitamin A is absorbed by the intestinal villi along with fats. From there, it is transported to and stored in the liver. Whenever there's a requirement for vitamin A, retinal is released by the liver. It then binds to the specific retinol-binding protein, which serves as a carrier to transport it to various locations of the body.
The cleavage or the cutting of beta-carotene to form retinol is carried out by an enzyme called Beta Carotene Oxygenase or Monooxygenase. This enzyme is produced by the gene called BCMO1 or BCO1.
Every person has two copies of the BCMO1 gene. But, about 45 percent of the population carries at least one change or variation in the gene that reduces the enzyme activity. This results in a significantly impaired ability to convert beta-carotene into retinal.
Depending on which combination of variants someone has, beta-carotene conversion can be nearly 70 percent lower than its normal efficiency.
Vitamin A deficiency has serious health implications.
Knowing your BCMO1 gene status can help you gauge your genetic risk for vitamin A deficiency. This can be done through a genetic test.
Most genetic tests provide your DNA information in the form of a text file called the raw DNA data. This data may seem like Greek and Latin to you.
At Xcode Life, can help you interpret this data. All you have to do is upload your raw data and order a nutrition report. Xcode Life then analyzes your raw data in detail to provide you with comprehensive nutrition analysis, including information on your vitamin A requirements.
Vitamin A is important for good vision, healthy eyes, healthy skin, and to fight infections.
Yet, it cannot be synthesized by the body.
Therefore, it becomes an essential nutrient that needs to be included in the diet.
Conversion of beta carotene to vitamin A is an important metabolic pathway which is genetically influenced.
Vitamin A refers to the interconvertible compounds retinal and retinol.
Both these can be converted into various other metabolites that are functionally important.
The transformation into these metabolites is irreversible.
Retinoic acid is one such metabolite.
Foods like milk, liver, fish oil, and eggs contain preformed vitamin A.
Beta carotene found in carrots and green leafy vegetables can be converted in the body into vitamin A, an important source for vegetarians.
Beta carotene is an ideal provitamin A carotenoid, and it needs to be converted into active vitamin A in the body.
Carotenoids are found in plants, and they are responsible for the distinct colors that some fruits and vegetables boast of.
Carrots get their orange color because of beta carotene.
According to the National Institute of Health, the following are the recommended units for the daily intake of beta carotene:
Once it is consumed, beta carotene is converted into vitamin A, which is then utilized by the body for various functions.
It is estimated that nearly 50% of vitamin A in a diet is due to beta carotene and other such carotenoids.
The major organs that are associated with beta carotene conversion are the liver and the intestines.
The liver is associated with storing significant proportion of retinoid.
There are two enzymes associated with beta carotene conversion to vitamin A, including:
Converting beta carotene to vitamin A is extremely variable with the estimated number of low responders to dietary beta carotene as high as 45%.
Genetic variants in the BCMO1 gene are associated with the conversion of beta carotene into retinol.
Check your Ancestry DNA or 23andMe raw data results for SNP rs7501331 that you carry[table “64” not found /]
Check your Ancestry DNA or 23andMe raw data results for SNP rs12934922 that you variants[table “65” not found /]
Enzyme activity based on genetic variant carried
A study by researchers from Newcastle University showed that individuals who carry the T allele of rs7501331 have a 32% reduction in enzyme activity while individuals who carried T allele for both rs7501331 and rs12934922 had a 69% reduction in enzyme activity.
A more recent study by researchers from the same university showed that apart from these two genetic variants in the BCM01 gene, there were other variants that had an influence on enzyme activity.
Other variants of interest are rs11645428, rs6420424, and rs6564851.
Vitamin A is important for vision and is used in the treatment of cataracts and age-related macular degeneration.
It is also important for the skin and immune system.
Vitamin A deficiency is major public health across the world. Each year, approximately 250,000–300,000 vitamin A-deficient children become, and half of them have been reported to die within a year after getting blind.
The following are some of the symptoms of vitamin A deficiency:
Hand-picked content for you: Genes can Influence your Vitamin A requirement- Here’s how
Beta carotene is considered pre-vitamin, but it also is known to have certain benefits.
Each carrot is known to contain about 10 - 50 mg of beta carotene, apart from other nutrients.
The following are some of the foods rich in beta carotene[table “66” not found /]
Source: Non-Provitamin A and Provitamin A Carotenoids as Immunomodulators: Recommended Dietary Allowance, Therapeutic Index, or Personalized Nutrition?
Excess of retinoids is known to lead to teratogenic effects.
High levels of beta carotene are known to increase the risk for certain types of cancers.
One study found that there was an increased risk of lung cancer after β-carotene supplementation among smokers and people who drank more than 11 g ethanol/d.
High levels of beta carotene can affect the skin and lead to a condition known as carotenodermia.
The soles of the feet and the palms turn yellow.
Too little beta carotene or too much both have their share of risk, which makes genetic testing for vitamin A needs important.
How well your body converts beta carotene into retinol or vitamin A will help you identify the amount of beta carotene that should be consumed, from the diet or as a supplement.
Upload your 23andme raw data or any other ancestry raw data to avail Xcode Life’s Gene Nutrition Report can be used to identify your vitamin A needs.
Does your 23andme, Ancestry DNA, FTDNA DNA raw data have vitamin A information?
|CHIP Version||Vitamin A SNPs|
|23andMe (Use your 23andme raw data to know your DRD2 Variant)|
|V5 23andme (current chip)||Present|
|AncestryDNA (Use your ancestry DNA raw data to know your DRD2 Variant)|
|v1 ancestry DNA||Present|
|V2 ancestry DNA (current chip)||Present|
|Family Tree DNA (Use your FTDNA raw data to know your DRD2 Variant)|
|OmniExpress microarray chip||Present|