ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Vitamin A

Updated on March 23, 2012

What Is Vitamin A?

Vitamin A is one of the four fat soluble vitamins. It was first isolated in 1913 by American researchers. It is found in foods in two different forms:

  • natural vitamin A, known as retinol (from animal foods)
  • provitamin A, or carotenoids, which can be converted into vitamin A in the body (found in both plant and animal foods). The most important of the carotenoids is called beta-carotene.

Vitamin A is stored in the body and therefore supplies do not have to be restocked on a daily basis as is the case for some other vitamins.

What Does Vitamin A Do For You?

  • It aids night vision - the old saying that "carrots will make you see in the dark" has some scientific basis since carrots are an excellent source of this vitamin.
  • It is essential for continuing healthy eyes and vision.
  • It maintains the body's layers of lining tissues (particularly in the nose, throat, lungs and digestive system) and is important for the proper function of the respiratory system.
  • It helps the growth and maintenance of bones, skin, gums, teeth, nails and hair. In fact, vitamin A is really essential for the healthy maintenance of most parts of the body.

Source

Food Sources for Retinol

Important

  • Liver (100g serving)

Moderate

  • Dairy products - full fat cheese (25g serving), full cream milk (250 ml serving), eggs (1)
  • Fats - butter, margarine (10g serving)
  • Enriched foods e.g. Milo/Ovaltine (10g serving)

Low or Nil

  • Meat (trace)
  • Fish (trace)
  • Fruit
  • Vegetables
  • Cereals
  • Pulses
  • Nuts
  • Skim milk and low fat dairy products
  • Yeast products

Food Sources for Beta-Carotene

Important

  • Fruit (tropical and orange-coloured) — apricots, cantaloupe, mango, pawpaw (100g serving)
  • Vegetables (orange-coloured and green leafy) -carrots, sweet potatoes, broccoli, spinach, pumpkin (50-100g serving)

Moderate

  • Cheese, full fat (25g serving)
  • Fats - butter, margarine (10g serving)
  • Fruit - apples, pineapple, oranges, bananas, berries (100g serving)
  • Vegetables - Brussels sprouts, peas, cabbage,
  • tomatoes, beans, sweet corn (50-100g serving), parsley (5g/2 sprigs serving)

Low or Nil

  • Fish (trace)
  • Potatoes
  • Meat
  • Cereals
  • Pulses
  • Nuts
  • Eggs
  • Yeast products e.g. Marmite

What Destroys Vitamin A?

Vitamin A, including that formed from the carotenoids, is not easily destroyed in the cooking process.

Storage away from light and air helps prevent loss.

There is always loss (about 20%) in the canning of fruit and vegetables. Certain preservatives used in making processed meats (frankfurters, salami) are destructive to vitamin A.

Vitamin A's absorption into the body is blocked by acute protein deficiency or a serious lack of fat in the diet.

Deficiency Problems and Symptoms

Vitamin A deficiency is one of the two most widespread nutritional deficiencies in the underprivileged countries of the world.

"Night blindness", or the inability of the eyes to adjust to darkness, is a major health problem when serious deficiency occurs. Total blindness can occur in advanced cases.

A degenerative disease of the eye's cornea, also leading to blindness, is another result of a deficiency. So are skin complaints and inflammations.

Minor deficiency can cause difficulty in eyesight adjustment on entering a dark room from bright sunlight.

The main symptoms of deficiency are dry, scaly skin, poor sight and eye pain.

Recommended Daily Intake

The recommendation is 750 micrograms which includes both retinol and vitamin A formed from carotenes.

Toxicity

Large doses of vitamin A in its retinol form are highly toxic, even fatal.

Early Antarctic explorers who were forced to eat their husky dogs suffered severe illness and even death due to the high amount of retinol in the dogs' livers.

More than 10,000 micrograms per kilo of body weight per day can induce toxic symptoms that include skin problems, bald patches and liver malfunction.

Although natural vitamin A (retinol) can be toxic in excess, a high intake of carotenes (e.g. in fruit and vegetables) is not dangerous, but skin can sometimes become orange-colored.

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: "https://hubpages.com/privacy-policy#gdpr"

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized. (Privacy Policy)
    CloudflareThis is used to quickly and efficiently deliver files such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisements has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)