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 plays a very important role in the overall development and maintenance of the body. This fat-soluble vitamin is stored in the liver and is available externally in two forms
Vitamin A is known to support a variety of metabolic functions. It helps with better vision and improves your immunity. Getting the right dose of vitamin A also plays a role in keeping the skin and teeth healthy. The right amounts of vitamin A protect the skeletal system and the soft tissues in the body.
In pregnant women, right vitamin A levels help with tissue repair after delivery and also keeps the risks of infections low.
It took almost 130 years for researchers to identify the existence of vitamin A and understand its effects on the human body.
Early accounts of Vitamin A Deficiency (VAD) have only been recorded in terms of night blindness amongst children, soldiers, and sailors. Back then, the only solution offered was to consume cod liver oil or eat an excess of cooked liver. Doctors knew this worked, but didn’t understand why it worked.
There were innumerable studies that tried to understand the effects of nutritional deprivation on animals and human beings between the mid-1800s and 1900s.
In 1912, Sir Frederick Gowland Hopkins concluded in his clinical trial that an additional factor in milk apart from carbohydrates, fats, and proteins helped rats survive on only a dairy-based food plan. He won the Nobel Prize for this study later.
This additional factor was narrowed-down to be a fat-soluble nutrient in 1918 and was finally identified as vitamin A in 1920.
In 1931, the International Conference on Vitamin Standards was first held in London and the league set to make standards and recommended values for all identified vitamins, including vitamin A.
Though people all over the world have become conscious about their nutritional intake, WHO states that about 250 million preschool children are still diagnosed with VAD. Making the right change in food habits, identifying the effects of one’s genes in his/her vitamin A requirements and taking vitamin A supplements, if needed, will all help bring down the risk of VAD.
We humans cannot produce vitamin A in our body, hence it is called an essential vitamin. We need to obtain it through diet or supplements. Vitamin A can be derived from both plant and animal sources.
Animal sources provide vitamin A in its active form, retinol, while plant sources provide vitamin A as carotene, an inactive form, which in-turn needs to be converted into the active form, retinol.
The genetics of some individuals predispose them to less efficient conversion of biologically inactive carotene to active retinol. They are usually advised to consume animal sources of vitamin A or take vitamin A supplements or consume higher amounts of plant sources to compensate for lowered conversion efficiency.
We will look into more details of specific genes that influence this predisposition in the following sections.
Everyone knows carrots are a good source of vitamin A and that they can improve general eyesight.
Did you know where this idea stemmed from?
During World War II, the British government ordered citywide blackouts to prevent German bomber flights from identifying their targets. On the other side, the British defenses were safeguarding a secret Intercept Radar System that helped their British flyers see better despite blackouts. To keep this information a secret, the British Ministry let out official information stating their flyers were able to see better in the dark because of excess consumption of carrots!
This detail has taken deep roots and is believed to date.
According to the U.S Department of Health & Human Services, here are the recommended values of vitamin A at every stage in life.
When you consume more vitamin A than recommended every day, here are some of the possible side effects recorded.
When your Daily Value Intake of vitamin A is consistently lesser than the suggested levels, you could be at a higher risk of developing the below conditions.
Insufficient dietary intake
A key source of vitamin A to the body is the food we consume. Naturally, not including enough of vitamin A rich foods is a top non-genetic reason for Vitamin A Deficiency (VAD). Not taking enough vitamin A can be a result of an unhealthy lifestyle, lack of awareness on the importance of nutrients, or poverty/unavailability of food.
People who suffer from chronic diarrhea and respiratory infections are also prone to having lower levels of vitamin A in the body.
Avoiding animal sources of vitamin A
Though vitamin A is available in both plant and animal sources, vegans have to depend exclusively on fruits and vegetables for their vit A needs. When vegans don’t plan their diet well and don’t consciously include enough carotenoid-rich foods, they can be prone to VAD.Veganism is hence a growing cause of concern as a non-genetic influence for VAD. If you follow a vegan lifestyle, you should be working on carefully choosing your food sources to prevent nutritional deficiencies.
Infants whose mothers show signs of VAD end up not getting enough Vitamin A in breast milk and hence are at a higher risk of developing VAD related health complications.
Mutations in both the TTR gene and the RBP4 gene can cause low levels of retinol in the body. The TTR gene produces a protein called transthyretin that transports vitamin A internally. The RBP4 gene (Retinol Binding Protein 4) produces the RBP4 transporting protein that delivers vitamin A from the liver to the tissues around.
RBP works with transthyretin in the plasma and prevents the kidneys from filtering out excess vitamin A.
Two gene variations can cause VAD.
BCMO1 gene – The BCMO1 gene helps encode enzymes that convert the carotenes from plant-based food sources into forms that can be used by the human body.
CYP26B1 gene – This gene is responsible for bringing down the active form of vitamin A called retinoic acid. The SNP rs2241057 with G variant in this gene can cause an increased breakdown of retinoic acid and hence can result in lowered vitamin A levels in the body.
Here is what you should do to maintain the right levels of vitamin A in the body.
According to American Heart Association (2015), cardiovascular disease is the leading global cause of death, accounting for 17.3 million deaths per year, a number that is expected to grow to more than 23.6 million by 2030.
Low dietary intake of beta carotene is associated with chronic disease such as cardiovascular disease and vitamin A deficiency. It is well known that a greater intake of fruit and vegetables can help prevent heart diseases and mortality. Antioxidant compounds found in fruit and vegetables, especially dietary carotenoids such as beta carotenes, lycopene, lutein may influence the risk of CVD by preventing the oxidation of cholesterol in arteries.
Vitamin A in the diet can come from animal or plant sources. Vitamin A exist in the form of retinol or retinoic acid, the active form in animal sources, and in the form of carotenes in plant sources. Retinol, an active form of vitamin A cannot be made by our bodies and should be obtained from the food we eat. Carotenes must be converted into retinol for them to function as vitamin A in the body. BCMO1 is the enzyme responsible for this conversion. Individuals, especially vegetarians, who get their vitamin A primarily from plant- based foods rely on this conversion to meet their vitamin A needs.
Liver and fish oils are one of the richest source of retinol and other good sources includes eggs, especially egg yolks. Carotenes are found in green leafy vegetables, broccoli, sweet potatoes, orange and yellow vegetables and in vegetable oils.
BCMO1 gene produces BCMO1 enzyme. Individuals with certain genotypes have reduced ability to convert carotenes to retinol, due to reduced BCMO1 activity. Individuals who carry certain versions of this gene may have up to 60% less enzyme activity than others and such individuals may be at risk for vitamin A deficiency. It is recommended that these individuals consume more animal sourced vitamin A, such as fish, eggs, meat and milk products to get their active form of vitamin A, retinol to meet their requirements.
Watch out for these symptoms like oily skin, acne, dry eyes, poor night vision, immune system impairment that indicates insufficiency of retinol in your body. You can also check your vitamin A levels via a blood test.
Type of BCMO1 gene has been shown to influence the vitamin A levels in blood. Want to know what type of BCMO1 gene you have? Try Xcode’s nutrigenetics test which can tell you what versions of the BCMO1 gene are in your DNA. You can also learn about how your genes may influence other traits, including your risk for certain diseases. Write to us at firstname.lastname@example.org to find out more.