Night Blindness & Vitamin Deficiencies

Vitamin A is essential for healthy eyes. Vitamin A ensures that you are able to interpret sight correctly as well as be able to see at night when light is minimal. If you are deficient in vitamin A, your night vision can decrease and eventually lead to night blindness.

Physiology of Vision

Your retina, which is located at the back of your eye, contains light receptor cells called rods and cones. Rods and cones have different levels of sensitivity, but both play a part in allowing you to see. When light travels into your eye, it passes through your lens and reaches the retina. The retina then uses rods and cones to send messages through the optic nerve, which is the nerve passageway that carries information from your eye to your brain.

Vitamin A and Vision

Vitamin A is a component of two of the proteins, rhodopsin and iodopsin, required for vision. These proteins are located in the rods and cones of your retina. According to the Linus Pauling Institute, rhodopsin can detect very small amounts of light, which makes it vital for night vision. The protein absorbs incoming light with the help of vitamin A. The protein then sends messages to the brain through the optic nerve, allowing you to see. Without vitamin A, these essential proteins would not be able to properly interpret visual messages.

Deficiency of Vitamin A

According to the Linus Pauling Institute, the earliest symptom of a vitamin A deficiency is night blindness, also called impaired dark adaptation. When you are deficient in vitamin A, your cornea becomes very dry, which can make it difficult to see. Prolonged vitamin A deficiency can also lead to damage of the retina and cornea, which can actually lead to complete loss of vision. Vitamin A deficiency is the leading cause of blindness in children worldwide.

Daily Recommendations

In order to prevent a vitamin A deficiency and maintain your night vision, it is important to consume enough vitamin A to meet the daily recommendations set by the Food and Nutrition Board, which is a subgroup of the Institute of Medicine. Vitamin A recommendations vary based on age and sex. Babies up to 6-months-old require 400 mcg, of vitamin A and babies 6 months to 1 year of age require 500 mcg. Toddlers between the ages of 1 and 3 need 300 mcg daily and children between 4- and 8-years-old require 400 mcg each day.

Young males and females from the ages of 9 to 13 require 600 mcg of vitamin A every day. When a boy reaches the age of 14, his needs increase to 900 mcg. When a girl reaches 14, her needs increase to 700 mcg.

Food Sources

The best food sources of vitamin A include milk, cheese, eggs, fortified cereals, carrots, spinach, kale sweet potatoes, fortified cereals and organ meats, such as liver. "Nutrition and You" by Joan Salge Blake notes that adding 1 tbsp. of vegetable oil to your diet can increase the absorption of vitamin A because the vitamin is fat-soluble.