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).

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
• Problems with the cornea of the eye, including ulceration and scarring
• 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
• Lightheadedness
• 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

The following foods contain carotenoids, which the body converts into vitamin A.

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

American Society for Nutrition
http://www.nutrition.org

Eat Right—Academy of Nutrition and Dietetics
http://www.eatright.org

Canadian Resources

Dietitians of Canada
http://www.dietitians.ca

Health Canada
http://www.hc-sc.gc.ca

References

Vitamin A. Oregon State University Linus Pauling Institute website. Available at: http://lpi.oregonstate.edu/mic/vitamins/vitamin-A. Updated February 2015. Accessed February 24, 2016.

Fairfield KM, Fletcher RH. Vitamins for chronic disease prevention in adults: Scientific review. JAMA. 2002;287(23):3116-3126.

Vitamin A. Office of Dietary Supplements website. Available at: https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional. Updated August 31, 2016. Accessed February 24, 2017.

Vitamin A deficiency. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T115371/Vitamin-A-deficiency. Updated February 16, 2017. Accessed February 24, 2017.

Vitamin A Toxicology. EBSCO DynaMed website. Available at: http://www.dynamed.com/topics/dmp~AN~T526141/Vitamin-A#Toxicology. Updated February 6, 2017. Accessed February 24, 2017.

• Michael Woods, MD, FAAP
• 201702
• 20170224