page_title: Vitamin A
section_title: Sources
hierarchical_section_title: Vitamin A / Sources
caption_attribution_description: Carrots on display at local greengrocer
context_page_description: Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol, retinal, and several provitamin A carotenoids. Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system, and for good vision. Vitamin A is needed by the retina of the eye in the form of retinal, which combines with protein opsin to form rhodopsin, the light-absorbing molecule necessary for both low-light and color vision. Vitamin A also functions in a very different role as retinoic acid, which is an important hormone-like growth factor for epithelial and other cells.
  In foods of animal origin, the major form of vitamin A is an ester, primarily retinyl palmitate, which is converted to retinol in the small intestine. The retinol form functions as a storage form of the vitamin, and can be converted to and from its visually active aldehyde form, retinal.
  All forms of vitamin A have a beta-ionone ring to which an isoprenoid chain is attached, called a retinyl group. Both structural features are essential for vitamin activity.
context_section_description: Vitamin A is found in many foods, including the following list. Bracketed values are retinol activity equivalences (RAEs) and percentage of the adult male RDA, per 100 grams of the foodstuff (average). Conversion of carotene to retinol varies from person to person, and bioavailability of carotene in food varies.
caption: Carrots are a source of beta-carotene
exif: {"Image Make": "Canon", "Image Model": "Canon EOS 400D DIGITAL", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2007:10:27 16:31:20", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "196", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "6132", "Thumbnail JPEGInterchangeFormatLength": "10157", "EXIF ExposureTime": "1/80", "EXIF FNumber": "8", "EXIF ExposureProgram": "Shutter Priority", "EXIF ISOSpeedRatings": "800", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2007:10:27 16:31:20", "EXIF DateTimeDigitized": "2007:10:27 16:31:20", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "207157/32768", "EXIF ApertureValue": "6", "EXIF ExposureBiasValue": "1", "EXIF MeteringMode": "Average", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "50", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "3888", "EXIF ExifImageLength": "2592", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "5766", "EXIF FocalPlaneXResolution": "3888000/877", "EXIF FocalPlaneYResolution": "432000/97", "EXIF FocalPlaneResolutionUnit": "2", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Manual", "EXIF SceneCaptureType": "Standard"}