Vitamin A
Vitamin A, also called retinol, is a fat-soluble vitamin. Our bodies store fat-soluble vitamins in the liver and fatty tissues. The active form of vitamin A is found in animal tissue. Red, orange, and dark green vegetables and fruits contain precursor forms of vitamin A called carotenoids. Our bodies can convert some of these carotenoids into vitamin A.
Functions
Here are some of vitamin A's functions:
- Plays an essential role in vision
- Plays an important role in cell differentiation and cell division
- Helps in the formation and maintenance of healthy skin and hair
- Helps with proper bone growth and tooth development
- Helps the body regulate the immune system
- Plays an essential role in the reproduction process for both men and women
Recommended Intake:
The recommended daily dietary allowance for vitamin A is measured in micrograms (mcg) of Retinol Activity Equivalents (RAE).
| Age Group (in years) | Recommended Dietary Allowance | |
|---|---|---|
| Females | Males | |
| 1 – 3 | 300 mcg of RAE | 300 mcg of RAE |
| 4 – 8 | 400 mcg of RAE | 400 mcg of RAE |
| 9 – 13 | 600 mcg of RAE | 600 mcg of RAE |
| 14 – 18 | 700 mcg of RAE | 900 mcg of RAE |
| 14 – 18 Pregnancy | 750 mcg of RAE | n/a |
| 14 – 18 Lactation | 1,200 mcg of RAE | n/a |
| 19+ | 700 mcg of RAE | 900 mcg of RAE |
| 19+ Pregnancy | 770 mcg of RAE | n/a |
| 19+ Lactation | 1,300 mcg of RAE | n/a |
Vitamin A Deficiency
Vitamin A deficiency is rare in the US, but it is common in developing countries. Here are some of the symptoms:
- Night blindness
- Decreased resistance to infections
- Decreased growth rate
- Diarrhea
Vitamin A Toxicity
As a fat-soluble vitamin, vitamin A is stored in the body and not excreted in the urine like most water-soluble vitamins. Therefore, it is possible for vitamin A to accumulate in the body and reach toxic levels. For adults, the tolerable upper intake level (UL) for vitamin A from dietary sources and supplements combined is 3,000 RAE daily. It is less in children. Symptoms of toxicity include the following:
- Nausea
- Vomiting
- Headache
- Blurred vision
- Dizziness
- Poor coordination
Too much vitamin A can cause severe birth defects. Pregnant women, and those who may become pregnant, should not take too much vitamin A from dietary sources and supplements.
Major Food Sources
| Food | Serving size |
Vitamin A content
(mcg of RAE) |
|---|---|---|
| Beef liver, cooked | 3 ounces | 6,582 |
| Milk, fat-free | 8 ounces | 149 |
| Whole egg, boiled | 1 large | 75 |
| Sockeye salmon, cooked | 3 ounces | 59 |
The following foods contain carotenoids, which the body converts into vitamin A.
| Food | Serving size |
Vitamin A content
(mcg of RAE) |
|---|---|---|
| Sweet potato, baked in skin | 1 whole | 1,403 |
| Carrots, raw | ½ cup | 459 |
| Mango, raw | 1 whole | 112 |
| Red bell pepper, raw | ½ cup | 117 |
| Cantaloupe, raw | ½ cup | 135 |
| Apricots, dried, sulfured | 10 halves | 63 |
| Spinach, cooked | ½ cup | 573 |
| Tomato juice, canned | 12 ounces | 42 |
Health Implications
Populations at risk for vitamin A deficiency
The following populations may be at risk for vitamin A deficiency and may require a supplement:
- People with a reduced ability to absorb dietary fat. Because vitamin A is a fat-soluble vitamin, fat is required for its absorption. Some conditions that can cause fat malabsorption include Crohn's disease, cystic fibrosis, celiac disease, pancreatic enzyme deficiency, and liver disease.
- Children living in developing countries.
Tips for Increasing Your Vitamin A Intake:
Here are some tips to help increase your intake of vitamin A:
- Pack cut carrots in your lunch for an afternoon snack.
- Slice a peach, mango, or apricot on to your breakfast cereal or oatmeal.
- Substitute a sweet potato for your baked potato.
- Eat fruits and vegetables raw whenever possible. Vitamin A can be lost during preparation and cooking.
- Steam vegetables, and braise, bake, or broil meat instead of frying. This will help retain some of the vitamin content.
RESOURCES:
Academy of Nutrition and Dietetics
http://www.eatright.org
American Society for Nutrition
http://www.nutrition.org
CANADIAN RESOURCES:
Dietitians of Canada
http://www.dietitians.ca
Health Canada Food and Nutrition
http://www.hc-sc.gc.ca/fn-an/index-eng.php
REFERENCES:
Dietary Supplement Fact Sheet: Vitamin A. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/. Updated July 25, 2012. Accessed February 7, 2013.
Fairfield KM, Fletcher RH. Vitamins for chronic disease prevention in adults: scientific review. JAMA. 2002;287(23):3116-26.
Vitamin A deficiency. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what. Updated November 22, 2011. Accessed February 7, 2013.
Vitamin A overdose. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what. Updated June 22, 2010. Accessed February 7, 2013.
Last reviewed February 2013 by Brian Randall, MD
Last Updated: 2/7/2013