What is vitamin A?
Vitamin A is a fat-soluble vitamin that is essential for good health. It is required for vision, growth, to fight infection and for bone health. There are two types of vitamin A, retinol and carotenoids. Retinol is a type of vitamin A found naturally in foods of animal origin. There are also plant-based sources of vitamin A called carotenoids that can be converted to retinol by the body. There are many carotenoids in plants and at least four types of carotenoids (beta-carotene, alpha-carotene, gamma-carotene, and beta-cryptoxanthin) that can be converted to retinol. Based on 2000 calorie diet, the recommended daily value of vitamin A for adults is 900micrograms.
What foods contain vitamin A?
Retinol is found in highest concentration in liver and cod liver oil. Low levels of retinol are also added to many fortified foods such as milk and fortified cereals. Added retinol is often listed on the food label as vitamin A palmitate.
Carotenoids are found in certain deeply colored green, yellow, orange, and red vegetables and fruits. Example of vegetables rich in plant-based vitamin A include pumpkin, sweet potato, carrots, green leafy vegetables (spinach, collard greens, kale, turnip greens,beet greens, dandelion greens, mustard greens), bell peppers, and tomatoes. Fruits rich in plant-based vitamin A include cantaloupe, watermelon, oranges, orange juice, tangerines, and peaches, among others. For information about the vitamin A content of selected foods, check on the USDA National Nutrient Database https://www.nal.usda.gov/fnic/vitamin-and-beta-carotene.
Are there other sources of vitamin A that I should know about?
Retinol is also found in multivitamins, vitamin A supplements and many combination vitamin A and D supplements. The supplement label provides information about the type of vitamin A in the preparation and how much vitamin A it contains. Retinol may be listed as retinyl acetate, vitamin A palmitate, or vitamin A acetate.
How can vitamin A intake affect my bone health?
Several observational studies based on bone density and hip fractures have shown that excess vitamin A intake from retinol is harmful to bones. There is no evidence of any association between the intake of plant-based vitamin A (including beta-carotene) and the risk of osteoporosis or related fracture. Controlled studies are needed to further test these observations.
What is the best way to get vitamin A?
You can easily get all of the vitamin A you need each day by consuming generous servings of foods high in plant-based vitamin A each day. To protect your bones, it makes sense to avoid consuming too much retinol. You can limit retinol in the following ways:
- Avoid sources of vitamin A that are high in retinol content. In the past, cod liver oil has been widely used as a source of vitamin D but it is not currently recommended for that purpose due to its high retinol content. In addition, liver, another source of vitamin A that is high in retinol, should not be eaten often.
- Read labels of multivitamins in order to select those that contain higher levels of plant-based vitamin A (beta-carotene) and lower levels of retinol. If you take a multivitamin, check the label to be sure it contains no more than 2000 IU to 3000 IU of retinol. There is no concern with plant-based vitamin A (such as beta-carotene) when taken in the common doses used in standard multivitamins.
- Do not worry about the small amounts of retinol added to fortified foods are not a concern if included in moderation as part of a nutrient-rich diet.
Is it true that some acne medications contain vitamin A (retinol) that can be harmful to my bones?
Oral synthetic retinoids that are taken for conditions such as severe acne contain high doses of vitamin A (retinol) that have been shown to be detrimental to bone health. If these medications are prescribed for you, your healthcare provider will advise you about the importance of avoiding supplements containing vitamin A during your treatment and about the best ways to protect your bones during and after treatment.