There has been renewed interest in Vitamin A among ophthalmologists due to an unforeseen benefit. An essential nutrient, this vitamin is recognized as vital for vision, immune function, and overall health. Deficiency can cause xerophthalmia (dryness of the eyes) and night-blindness. The Age-Related Eye Disease Study (AREDS) sponsored by the U.S. government is offering new hope for people at risk for blindness due to macular degeneration.
Problem of Macular Degeneration
Age-related macular degeneration (AMD) is a major problem for persons over 50 years of age. There are two kinds of AMD—“dry” (atrophic) and “wet” (exudative). The “wet” form progresses more rapidly, and usually starts as atrophic. AMD involves damage to the macula, which is a spot in the center of the retina. The result is vision loss commencing in the center of the field of vision, and leading to total blindness. Until recently, there were few effective treatment options for persons diagnosed with AMD.
History and Results of the AREDS Study
This clinical trial began in 1992, and ended in 1998. Sponsored by the National Eye Institute, it involved 4,757 participants between 55-80 years old. The study evaluated the effects of high-dose anti-oxidants (including Vitamin A) and zinc on the research subjects. The results suggested that the treatment was effective. In consequence, Vitamin A supplements have been formulated and prescribed for people with “dry” AMD, and are enabling many to stave off vision loss for longer than was previously possible.
Blindness Related to Vitamin A Deficiency
According to the World Health Organization, Vitamin A is the leading global cause of preventable (and irreversible) blindness in children. Approximately 250 million preschool children were affected by vitamin A deficiency in 2012, and it is a major public health problem in Southeast Asia and Africa—where rice and carbohydrates are a dietary staple.
Foods Rich in Vitamin A
Organ meats (such as liver and giblets), carrots, sweet potatoes, and pumpkins are the top sources of Vitamin A (according to an article in Good Housekeeping). The USDA Dietary Guidelines also include collards and kale. For overweight individuals on a weight-loss diet, drinking carrot juice can be an excellent way of obtaining Vitamin A while limiting calories.
Risks of High-Dose Vitamin A
Vitamin A in pills needs to be taken at no more than the recommended daily allowance (unless prescribed by a physician) so as not to develop a toxic reaction. Usually, it is not necessary to take a supplement of Vitamin A beyond any typical multivitamin. Since this vitamin is not water soluble, it is possible to take too much—and have an adverse reaction. Symptoms of short-term (acute) toxicity can include nausea, headache, and dry skin. Symptoms of long-term toxicity (chronic) can include cirrhosis of the liver, bleeding in the lungs, bone pain, and seizure.
Since Vitamin A is included in most vegetables and fruits, it is not necessary for most people in the United States and Europe to take an additional Vitamin A supplement beyond a daily multivitamin.
Recommended Daily Allowance of Vitamin A
According to the Mayo Clinic, the recommended daily allowance of Vitamin A in adults is 900 micrograms (in men) and 700 micrograms (in women). For pregnant women (age 19 and older), the recommended daily allowance is 770 micrograms.