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Vitamin A - What you need to know
Vitamin A - The Basics
Vitamin A is made up of retinol, retinal and four carotenoids which are the dietary precursors of retinol. It is needed by the eye to form retinal which is necessary for both low-light and colour vision. It also plays other roles within the body as a growth factor, much like a hormone. Adequate intake of Vitamin A is required for eyesight, skin health, as an antioxidant, bone metabolism, immune function and much more. Where do I get Vitamin A from? Vitamin A can be consumed from animal and vegetable sources. In animal sources it is consumed directly as retinol whereas in vegetable sources it is consumed in one of the carotenes, which the human body is able to convert into retinol. Herbivores and omnivores are able to convert carotenes to retinol but pure carnivores cannot. So a lion fed on nothing but carrots would, apart from getting very angry, go blind. Vitamin A is found in significant quantities in a broad variety of animal foods such as liver, cheese, egg and milk as well as a broad variety of vegetables and fruits, including carrot, broccoli, sweet potato, spinach, pumpkin, apricots, mangoes and melons. How much Vitamin A do I need? Recommended dietary intakes of Vitamin A depend on age, sex and other factors. The Australian National Health Recommendations are as follows:
It is possible to over consume Vitamin A as retinol. The body stops metabolising retinol from beta-carotene when it has enough Vitamin A, but direct and extreme over ingestion of retinol can be fatal. Upper recommended levels for healthy adults are 3000mcg. It may be that the body can handle much more than this, but it is of no benefit above these levels so the National recommendations suggest that intake be limited to this. |