Vitamin A
Vitamin A helps so many processes in the human body. Vitamin A helps the eyes to see and the skin to heal. Vitamin A bolsters the immune system and helps lungs overcome symptoms of asthma.
Vitamin A is found in plenty of readily available foods, so Americans should have no trouble incorporating this vital nutrient into their diets.
What exactly is vitamin A?
Vitamin A is part of the carotene family of nutrients, such as alpha- and beta-carotene. This substance is soluble in fat, meaning the human body stores vitamin A in fat cells until the body requires it. Other vitamins such as vitamin C are water-soluble, meaning they filter out through the blood, kidneys and urine. Carotenoids are the best kind of vitamin A, and they are found in all kinds of healthy foods.
What foods contain vitamin A?
Carrots contain plenty of vitamin A. One cup of chopped raw carrots contains 428 percent of one person’s daily supply of vitamin A.
Other foods that contain vitamin A include pumpkins and squash. Dark, leafy vegetables, such as spinach, kale, green leaf lettuce and mustard greens contain tons of vitamin A. Tree nuts also have a lot of vitamin A. People who want to get more vitamin A in their diet might try to eat a salad at least once per day. Even a small plate of greens and carrots can make a difference.
Some animal products contain a different type of vitamin A from vegetables. These are called preformed retinoids because the animal proteins that contain this type of vitamin A were already processed within the body of the animal. Eggs, dairy products, liver and kidney contain vitamin A, but this isn’t nearly as healthful at the vitamin A found in vegetables.
How does vitamin A help the body?
Vitamin A is absolutely essential for eyesight. This vitamin is a part of rhodopsin, a chemical that responds to light in the eye’s retina. Vitamin A also helps the cornea function properly. This essential nutrient helps cells communicate with one another, especially in the lungs, heart and kidneys. Vitamin A also aids in human reproduction and the immune system.
What diseases or disorders does vitamin A prevent or help?
Vitamin A may improve age-related macular degeneration, glaucoma and cataracts. Because this nutrient plays a role in the body’s immune system, vitamin A can aid in stopping or preventing infections. Vitamin A might also help with certain skin conditions, such as acne, psoriasis, eczema, cold sores, sunburn and wounds.
When people don’t get enough vitamin A in their foods, they can ingest supplements or use vitamin A on the skin. The type and dosage of supplementation depends on the body’s needs.
What are suggested doses for vitamin A supplements?
People normally supplement with oral vitamin A, although topical vitamin A in creams may protect the skin against UV radiation and sunburn while helping wounds heal. The current recommended daily allowance of vitamin A is 5,000 IUs for adults.
Vitamin A supplements may have as much as 5,000 International Units (IUs) of preformed vitamin A in them as part of a multivitamin. The U.S. Food and Nutrition Board set the upper tolerable intake of preformed vitamin A at 10,000 IUs per day. Prolonged exposure to very high amounts of vitamin A may cause a very rare disorder called hypervitaminosis A. By comparison, ½ cup of raw carrots contains 9,189 IUs of vitamin A, but carrots contain the carotenoid form of vitamin A as opposed to the preformed variety.
Modern medical science notes that upper tolerable limit of vitamin A comes from preformed vitamin A in supplements, and the preformed vitamin A comes from animal sources. The plant-based source of vitamin A, the carotenoids, has no upper tolerable limit because the body converts the carotenoids (beta-carotene, alpha carotene) into usable substances more readily compared to preformed vitamin A.
Conclusion
The best way for patients to get vitamin A is through vegetables. Kale, carrots, spinach and green leaf lettuce all contain plenty of vitamin A for the human body to convert to useful substances. Getting more vegetables in the human diet is always a good idea, and vitamin A is just one reason why. Although supplements are good in a pinch, the substances found in supplements are the less-effective form of vitamin A.
Patients should consult with a doctor when they decide to add a vitamin A supplement to their diet. Vitamin A might interfere with certain medications or it may make symptoms of some disorders and diseases worse if people already take medications for them.
Vitamins, nutrients and supplements affect different people in different ways, so patients must keep that in mind when they discuss vitamin A supplements with their doctor.
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Sources:
National Institutes of Health Office of Dietary Supplements, “Vitamin A.” Updated Aug. 31, 2016.
https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/
Oregon State University Linus Pauling Institute, “Vitamin A.” Medically reviewed in March 2015.
http://lpi.oregonstate.edu/mic/vitamins/vitamin-A#supplements
Self Nutrition Data, “Foods Highest in Vitamin A.” Accessed Feb. 6, 2017.
http://nutritiondata.self.com/foods-011098000000000000000.html?maxCount=388
Self Nutritioni Data, “Carrots, Raw.” Accessed May 27, 2017.
http://nutritiondata.self.com/facts/vegetables-and-vegetable-products/2383/2
