Your nutritional status plays a major role in determining the health of your eyes and your ability to see. Fat soluble vitamin A helps maintain proper vision. Night blindness, or a decreased ability to see at night, usually occurs as the first sign of vitamin A deficiency.
Vitamin A supports the synthesis of rhodopsin, a protein in the cells of your retina. Rhodopsin absorbs incoming light and helps transmit nerve signals from your optic nerve to your brain. These nerve signals translate into vision. Without sufficient vitamin A, your body could not properly make rhodopsin and your vision would become impaired.
Vitamin A deficiency usually results from a failure to meet dietary needs of vitamin A. Vitamin A deficiency may also result from malabsorption due to digestive diseases, such as celiac disease and Crohn’s disease. Liver disease and cirrhosis can also reduce the ability to absorb vitamin A and lead to a vitamin A deficiency.
In addition to night blindness, vitamin A deficiency can also lead to extreme dryness and damage to the cornea, a condition called xerophthalmia. Left untreated, xerophthalmia can lead to blindness. In her book “Nutrition and You,” Joan Salge Blake identifies vitamin A deficiency as the number one cause of preventable blindness in children worldwide. Vitamin A deficiency can also cause stunting of the bones.
Consume adequate amounts of vitamin A each day to prevent vitamin A deficiency. According to the Linus Pauling Institute, males require 900 micrograms of vitamin A daily, whereas females require 700 micrograms. The most popular sources of vitamin A in the American diet include milk, cereals, cheese, eggs, carrots, sweet potatoes and spinach, according to Blake. Fat in the intestinal tract can help increase fat soluble vitamin A absorption and decrease your risk of developing a vitamin A deficiency.
Vitamin A Supplements
If you take vitamin A supplements to help prevent a deficiency, avoid potentially dangerous side effects by taking them under a doctor's supervision. Exceeding the recommended daily allowance can cause liver failure according to the University of Maryland Medical Center. Excessive consumption of vitamin A and beta-carotene can increase triglycerides as well as your risk of dying from heart disease, especially if you smoke. UMMC warns that smoking or drinking alcohol while taking vitamin A supplements might increase your risk for lung cancer. They also caution that taking supplemental vitamin A in addition to prenatal vitamins can cause birth defects.
- Nutrition and You; Joan Salge Blake
- Linus Pauling Institute: Vitamin A
- Merck Manuals Online Medical Library: Vitamin A
- University of Maryland Medical Center: Vitamin A (Retinol)