Vitamin A. This first to be discovered vitamin is found in a wide variety of fruits and veggies as well as eggs. Vitamin A deficiency is rare in North America but worldwide the World Health Organization estimates that 250 000 to 500 000 vitamin A-deficient children become blind every year, half of them dying within 12 months of losing their sight. The World Health Organization is working to supply Vitamin A supplements and foods rich in Vitamin A to needy countries around the world including in Asia, Africa and South America.
Vitamin A can also be harmful in high doses. This can be a problem if large doses of supplements are taken over a long period of time and can damage the eye and other organs. It is uncommon to overdose on Vitamin A with food but acute overdose can occur from eating polar bear liver or chronic overdose can happen over a long period of time from taking supplements like cod liver oil which will harm the liver, eye, and skin. As with all supplements it is important to be aware of recommended dosages and keep in mind that more is not better as the body is a finely balanced system. It is not possible to overdose on Vitamin A by eating fruits and vegetables since plant-based vitamin A precursors such as beta-carotene (in addition to other mixed carotenoids) are regulated by the body which prevents overdose.
Vitamin A can be measured but it is too costly to be practical in third world countries. In North America Vitamin A deficiency is uncommn so if Vitamin A deficiency is suspected then a secondary cause such as celiac disease may be investigated. Most overdoses of Vitamin A are due to over supplementation and the treatment is to stop the supplementation.
Any time vision changes are noted it is a good idea to contact your optometrist or ophthalmologist to investigate possible causes. While reduced night vision can be a symptom of Vitamin A deficiency, in North America it is more likely to be caused by other more common disorders such as cataracts. If you have questions about laser vision correction or wish to book a complimentary evaluation with Dr. Anderson Penno, contact Western Laser Eye Associates.