Eyes, Immune, Vitamins, Nutrition | January 24, 2018 | Author: Naturopath
Vitamin A is one of the fat-soluble vitamins, along with vitamins D, E, and K. Fat-soluble vitamins are absorbed in the presence of fats in the diet, and can be stored in the body’s fatty tissue.
Vision. Vitamin A is required for the normal functioning of the retina and also helps lubricating the eyes.
A deficiency can lead to night blindness, and in severe cases deficiency can lead to blindness.
In developing countries, vitamin A deficiency is the leading cause of preventable blindness in children.
Growth and development. Vitamin A is involved in foetal development of organs, particularly in the development of the spinal cord, limbs, heart, eye ears and lungs.
Immune system. Vitamin A is required for maintaining the integrity of epithelial cells throughout the body. These are the cells that line the internal and external surfaces of the body (such as the airways, digestive tract, and urinary tract) and provide the first line of defense of the immune system Thus, deficiency of vitamin A can impair the barrier against infection, and can increase the risk of respiratory and gastrointestinal infections, especially in children. In addition, vitamin A is involved in the development of T-cells - A type of white blood cell that is part of the immune system and help protect the body from infection and may help fight cancer.
Cancer. Beta-carotene belongs to a group of compounds called phytonutrients. Phytonutrients are components of plants that are powerful antioxidants, and may reduce cancer risk. Women with higher blood concentrations of beta-carotene from food sources are at decreased risk of breast cancer.
Vitamin A is available over the counter in multivitamins in varying amounts, and as individual supplements. Some of the supplements have a combination of vitamin A and beta-carotene, and some have one or the other. Vitamin A in supplements often comes in the form of retinol or retinyl palmitate, but other forms can be used. Hence, to know the dose of the supplement, it is important to read the label and determine the actual vitamin A content, expressed in international units (IU).
Vitamin A can also be found in skin ointments.
In Australia deficiency of vitamin A is rare as we get enough in our diet. However, your doctor may recommend vitamin A or beta-carotene supplement or cream if you suffer from:
Too much vitamin A can be toxic as it can accumulate in your liver and may result in liver damage.
Recommended daily intakes:
Men – 900 mcg/day (3,000 IU)
Women – 700 mcg/day (2,333IU)
When taken in excess of 3000 mcg (10,000 IU), vitamin A can cause birth defects. If you are pregnant, or considering becoming pregnant, consult your doctor or pharmacist before taking any supplements that contain A.
Unlike vitamin A, high doses of beta-carotene are not toxic. Too much carotene-rich food in your diet (such as large amounts of carrots) or prolonged and excessive consumption of beta-carotene supplements can turn your skin yellow-orange, a harmless condition that gradually disappears when the amount is reduced or eliminated.
One group that should avoid taking supplements of vitamin A or beta-carotene supplements are people at high risk for lung cancer. A study of 18,314 smokers, former smokers, and workers exposed to asbestos found that taking high doses of these supplements over a long period of time actually increased the incidence of lung cancer.
Vitamin A from foods is considered safe. As the body makes vitamin A from beta-carotene, you can increase levels of vitamin A in your body, while at the same time enjoy the health benefits of the antioxidants in beta-carotene by:
Bakker, M.F. et al., Plasma carotenoids, vitamin C, tocopherols, and retinol and the risk of breast cancer in the European Prospective Investigation into Cancer and Nutrition cohort 1,2. Am J Clin Nutr. Available at: http://ajcn.nutrition.org/content/early/2016/01/20/ajcn.114.101659.full.pdf
Linus Pauling Institute Oregon State University 2015. Vitamin A |. Available at: http://lpi.oregonstate.edu/mic/vitamins/vitamin-A#introduction
National Cancer Institute. Definition of fat-soluble vitamin - NCI Dictionary of Cancer Terms. Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms?cdrid=560348
National Institutes of Health 2016. Vitamin A — Health Professional Fact Sheet. Available at: https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/#h7
Omenn, G.S. et al., 1996. Effects of a Combination of Beta Carotene and Vitamin A on Lung Cancer and Cardiovascular Disease. New England Journal of Medicine, 334(18), pp.1150–1155. Available at: http://www.ncbi.nlm.nih.gov/pubmed/8602180
University of Maryland medical Center 2015. Vitamin A (Retinol). Available at: https://www.umm.edu/health/medical/altmed/supplement/vitamin-a-retinol
Villamor, E. & Fawzi, W.W., 2005. Effects of vitamin a supplementation on immune responses and correlation with clinical outcomes. Clinical microbiology reviews, 18(3), pp.446–64. Available at: http://www.ncbi.nlm.nih.gov/pubmed/16020684