Vitamin A is a fat-soluble vitamin that plays an important role in bone growth, maintaining healthy teeth, mucus membrane development, reproduction, cell development and vision, especially in low light. Vitamin A also helps regulate and boost the immune system. Vitamin A can be absorbed from animal sources, such as retinol, or from colorful fruits and vegetables like carotenoids. One popular carotenoid is beta-carotene, which is an antioxidant that might protect you from or help fight certain illnesses and diseases.
Sources
Retinol can be found in foods that come from animals like eggs, meat, liver, milk, cheese and butter. Some breakfast cereals may also be vitamin A-fortified. Many of these dietary sources contain significant saturated fats and cholesterol, with the exceptions of fat-free fortified milk and some fortified breakfast cereals. You can find beta-carotene in foods like carrots, sweet potatoes, cantaloupe and dark, leafy greens like spinach.
Recommended Dietary Allowances
According to the Office of Dietary Supplements at the National Institutes of Health, the recommended daily dietary allowance of vitamin A for males over age 19 is 900 mcg, and 700 mcg for females over age 19. Your doctor can make specific dosage recommendations. For example, you may need more vitamin A if you are a pregnant or lactating female.
Deficiency
A vitamin A deficiency is rare in developed countries. In the United States, people who have severely restricted diets, certain malabsorption problems or problems with alcohol may have vitamin A deficiencies. A deficiency most notably affects vision, which may first be noticed as night blindness. A deficiency also minimizes your ability to fight infections, which is why low levels of vitamin A can be so dangerous. If it is determined that you are vitamin A deficient, a doctor may recommend a supplement.
Hypervitaminosis A
Hypervitaminosis A means there are high storage levels of vitamin A in your body that can cause toxicity. Most cases of hypervitaminosis A occur when an adult takes excess amounts of vitamin A supplements. Signs of vitamin A toxicity are nausea, vomiting, headache, dizziness and blurred vision. Too much vitamin A taken consistently can cause birth defects. Excess beta-carotene can turn skin orange or yellow, but this color change, which isn't harmful, subsides after decreased intake.
Ongoing Studies
The Office of Dietary Supplements says there are studies being done that suggest diets rich in beta-carotene and vitamin A are associated with a reduced risk of various types of cancer. In addition, ongoing studies suggest an excess intake of vitamin A from animal products may be a risk factor for osteoporosis. The studies have not produced conclusive information, as of 2011. Talk to your doctor if you have questions.
Member Comments