Vitamin A (retinol, retinoic acid) is a nutrient important to vision, growth, cell division, reproduction and immunity. Vitamin A also helps the heart, lungs, kidneys, and other organs work properly. Vitamin A also has antioxidant properties. Antioxidants are substances that might protect your cells from free radicals. Free radicals might play a role in heart disease, cancer and other diseases.
Vitamin A plays an important role in your vision. To see the full spectrum of light, your eye needs to produce certain pigments for your retina to work properly. Vitamin A deficiency stops the production of these pigments. Your eye also needs vitamin A to nourish other parts of your eye including the cornea. The cornea becomes dry, leading to clouding of the front of the eye, corneal ulcers and vision loss.
Without enough vitamin A your eyes can not produce enough moisture to keep them properly lubricated. Over-the-counter lubrication eye drops contain vitamin A.
High intakes of some forms of vitamin A can be harmful. Getting too much preformed vitamin A (usually from supplements or certain medicines) can cause dizziness, nausea, headaches, coma, and even death. High intakes of preformed vitamin A in pregnant women can also cause birth defects in their babies. Women who might be pregnant should not take high doses of vitamin A supplements.