What is it?
It is a group of fat-soluble vitamins that come from animals and plants.
Animal-derived vitamin A is referred to as retinol or preformed vitamin A and is the most biologically active form.
Some plant-derived vitamin A, (medically known as retinal), usually can be converted to the active, or retinol form of vitamin A, especially the colourful fruits and vegetables. These carotenoids are referred to as “provitamin A.”
What does it do?
Retinol is carried in the bloodstream to the retina at the back of the eye, where it’s stored and used to help us see in dim light. It plays a vital role in the production of rhodopsin, the visual pigment in the retina that is essential for the eyes to adapt to the dark.
Vitamin A also maintains the health of the cells that line our nose, throat, respiratory, digestive and urinary tracts. Vitamin A activates the immune cells in these tracts to enable us to fight infection.
In our bones retinol helps to produce red blood cells and integrate iron into Haemoglobin to carry oxygen to all of our body tissues.
Retinol is also vital both pre- and during pregnancy to ensure the healthy formation of all the baby’s vital organs.
Preformed vitamin A is found in a number of animal-based foods. Because 70 to 90 percent of the body’s vitamin A is stored in the liver naturally this is the richest source. Just three ounces of beef liver provides almost ten timed the daily requirement for women, whilst three ounces of chicken liver provides roughly double.
Other common sources include shrimp, eggs, whole milk, yoghurt, butter, and cheese.
Carotenoids are found in colourful vegetables like carrots, pumpkin, apricots, broccoli, and dark leafy greens. Of these carotenoids, only beta-carotene and beta-cryptoxanthin can readily be converted into retinol.
Because vitamin A is fat-soluble, it’s absolutely vital to take these foods with some fat. Beta-carotene in oil has about half the activity of pre-formed vitamin A, and without oil, it has just one-sixth of the activity! When you gently heat the food, the carotenoids are released into the oil, increasing absorption. So take supplements with a fat-containing meal.
Signs of Deficiency:
One of the first signs is xerophthalmia (extreme dryness of the eyes), and left untreated can cause blindness. Other signs include dry and scaly skin, frequent diarrhea, and respiratory infections.
Risk of Deficiency:
The global risk is primarily pregnant and breastfeeding women, newborns, and children. In developed countries, vitamin A deficiency is found in those who are malnourished, alcoholics, take certain medication, or have cystic fibrosis, Crohn’s disease, ulcerative colitis, or pancreatic insufficiency.
For overall health, take a multivitamin that provides 5,000 IU of vitamin A with 50 percent as retinyl/retinol acetate or vitamin A acetate, and 50 percent as beta-carotene and/or mixed carotenoids.
Smokers: Do not purchase supplements that provide more than 2,500 IU of beta-carotene.
People who regularly eat liver or take cod liver oil should not take supplements containing preformed vitamin A (retinyl/retinol acetate). Instead, choose supplements that provide beta-carotene or mixed carotenoids.
Risk of Toxicity:
The upper limit is 10,000 IU and going over it can be really dangerous for pregnant women. Prenatal vitamins should contain no more than 3,000 IU of preformed vitamin A (the RDI for pregnant women).
Vitamin A is vital for our immunity vision, digestive health, immunity, and bone health together with vitamin C and iron. Zinc is necessary for transporting it to the liver.