Vitamin and mineral supplements are a multibillion dollar industry. Because my patients take many supplements, I decided to do a review of different vitamins and supplements that people commonly take. In this post, we will discuss what Vitamin A does for us.
During the COVID 19 Stay at home lockdown, my 2 teenage sons were making their own lunches. No surprise that the frozen chicken nuggets diet was their mainstay for lunch as I needed to work and they needed to be self sufficient. So I insisted that they ate carrots, both to provide their veggies, as well as maintain their eye health. They tried to get out of it by telling me that carrots being good for your eyes was a myth propogated by the British RAF to throw off the German Luftwaffe. I didn’t know this so we looked up the story and this is what I found in the Smithsonian magazine website: they said that during the WW2 1940 Blitzkrieg the German Luftwaffe was trying to bomb British targets at night. To thwart them, there was a country wide black out at night, but the RAF had also developed a new secret weapon, the onboard Airborne Interception Radar. This helped the RAF pinpoint the enemy bombers before they reached the English Channel. they didn’t want to let the Germans know that they had this new technology. So they floated the rumor that the British pilots were able to accomplish this because they ate carrots and had better night vision.
This myth was able to succeed because:, were there popular writings from the '30s (newspapers, books, notable studies, etc) that were already making the leap from "vitamin A deficiency causes night blindness, so mega dosing vitamin A will enhance night vision".
That being said, Carrots do contain a generous amount of Vitamin A per serving of only ½ cup raw carrots. To get the equivalent amount from soft serve French vanilla icecream, you would need to eat 2 cups. But I’m not telling my sons that because I know what they would choose. But liver tops the list, and ancient Egyptians knew that they could treat night blindness by eating liver. I prefer carrots.
Because our bodies do not manufacture Vitamins, they need to be consumed.
. There are 2 forms of Vitamin A:
1) Provitamin A or beta carotene from plant sources, like green leafy veggies, sweet potatoes, and of course, carrots! The provitamin needs to be metabolized into active Vitamin A. Since this process is regulated internally, you cannot get toxic amounts of Vitamin A from vegetable sources. , individuals who ingest large amounts of provitamin A (from plant sources) may develop yellow-tinged skin (carotenemia) without developing vitamin A toxicity. Carotenemia is particularly common among infants and toddlers who are eating large amounts of pureed vegetables (particularly carrots and green leafy vegetables), and may be initially confused with jaundice. The skin discoloration resolves spontaneously when you reduce the intake of these foods.
Preformed Vit A or (retinols) are obtained from animal sources like liver, kidney, egg yolk and butter. These do not need activation, so you can eat too much of this, and is more likely to cause chronic toxicity if you consume more than 10-20 times the RDA, This can show up as alopecia, ataxia, bone and muscle pain and liver toxicity. Since Vit A is a group of fat soluble retinoids. the liver is where more than ½ of our body’s Vit A is stored and this can reach toxic levels.
There are other carotenoids like lycopene found in tomatoes which are not converted to Vit A.
Besides the well known benefits to vision, this group of substances called retinoids dramatically contributed to the treatment of leukemia. Acute Myelogenous leukemias are a group of deadly leukemias which need heavy duty chemotherapy to combat them. A subset of AML, called Promyelocytic leukemia, PML was particularly deadly because it caused life threatening bleeding which was difficult to control in the time that the chemotherapy was initiated to fight the leukemia cells.
In the 1980s a group in China decided had found that a derivative of retinoic acid called all trans retinoic acid or ATRA made immature cells transform into mature cells in the petridish in lab experiments. Since there were resource and time constraints in China, they decided to take a leap into treating PML, and lo and behold, the immature leukemic cells started maturing into normal cells. Unfortunately, they found that this change was not permanent, and they still needed to follow up with regular chemotherapy. But this bought them time to control the bleeding that PML caused and greatly improved survival rates. This was incorporated into standard treatment of PML, even before the presence of the Retinoic acid receptor was discovered on the PML cell. ATRA does have side effects, so it should only be used by people who know what they are doing.
Retinoic acid and carotenoids have several therapeutic uses.
Vitamin A treatment of children with measles infection in resource-limited countries where deficiency is endemic appears to reduce complications and mortality related to measles. This is an important piece of information to put in your backpocket as measles outbreaks increase even in developed countries due to lack of vaccination.
Retinoic acid has been used for many hyperkeratotic and hyperproliferative disorders of skin. Synthetic oxidative metabolites of Vitamin A such as Isotretinoin can be used topically or systemically to treat a variety of skin disorders.
Because carotenoids are antioxidants, they were investigated for possible prevention of cardiovascular disease. However, randomized trials of Vitamin A and beta-carotene have shown no benefit in prevention of coronary heart disease; In fact, there is some evidence that beta-carotene supplementation may increase mortality from cardiovascular disease and may increase the risk of lung cancer.
What does Vit A do for the eyes?
It is an essential building block for an important group of proteins in the eye called retinol binding proteins.. It is also important in the normal development and functioning of the conjunctiva and cornea.
Deficiency of Vit A is common in malnourished populations. Unfortunately world wide, it is present in 30 % of children under five, and almost half in subSaharan Africa and south asia suffer from Vit A deficiency. Approximately 500,000 preschool children become blind each year. Mass supplementation in these populations has made a significant impact on the eye complications of Vit A deficiency, but has also decreased hearing loss in children with ear discharge which is a marker of ear infection.
Another group of eye diseases associated with Vit A deficiency is a condition called Xerophthalmia. The tear glands don’t produce enough moisture causing severe dry eyes and damage of the cornea and retina and treatment with Vit A can reverse these changes.
Deficiency of Vit A is rarely seen in well nourished populations, unless you had fat malabsorption. This can be seen in bowel diseases like Crohn’s disease or Celiac disease, or pancreatic or liver diseases.
Deficiency can also cause skin problems , destruction of hair follicles., poor bone growth, and even immunity problems
Vitamin A is also important for normal development and functioning of the heart, lung, and kidneys.
So how do I get my Vit A? From carrots.