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Why Vitamin D?

milkphoto © 2008 Chris Chan | more info (via: Wylio)Recent studies show that health experts are all agreeing on one thing: everyone should get 2,000 IU of Vitamin D a day. But why specifically Vitamin D? What is it about this vitamin that makes a significant difference in our lives? Read on.

What is Vitamin D?

Vitamin D is a steroid vitamin, a group of fat-soluble prohormones, which encourages the absorption and metabolism of calcium and phosphorous. People who are exposed to normal quantities of sunlight do not need vitamin D supplements because sunlight promotes sufficient vitamin D synthesis in the skin.

Five forms of vitamin D have been discovered, vitamin D1, D2, D3, D4, D5. The two forms that seem to matter to humans the most are vitamins D2 (ergocalciferol) and D3 (cholecalciferol).  Vitamin D for humans is obtained from sun exposure, food and supplements.

Why Vitamin D?

Data collected from the National Health and Nutrition Examination Survey, USA found that 9% (7.6 million) of children across the USA, was vitamin D deficient, while another 61 percent, or 50.8 million, was vitamin D insufficient.

Researchers at the University of Minnesota found that Vitamin D levels in the body at the start of a low-calorie diet predict weight loss success, suggesting a possible role for vitamin D in weight loss.


  • It is crucial for the absorption and metabolism of calcium and phosphorous, which have various functions,  especially the maintenance of healthy bones.
  • It is an immune system regulator.
  • It may be an important way to arm the immune system against disorders like the common cold, say scientists from the University of Colorado Denver School of Medicine, Massachusetts General Hospital and Children’s Hospital Boston.
  • Vitamin D may have a key role in helping the brain to keep working well in later life, according to a study of 3000 European men between the ages of 40 and 79.
  • Vitamin D is probably linked to maintaining a healthy body weight, according to research carried out at the Medical College of Georgia, USA.
  • It can reduce the severity and frequency of asthma symptoms, researchers from Harvard Medical School found after monitoring 616 children in Costa Rica.
  • It has been shown to reduce the risk of rheumatoid arthritis in women.
  • A form of vitamin D could be one of our body’s main protection against damage from levels of radiation, say radiological experts from the New York City Department of Health and Mental Hygiene.
  • Various studies have shown that people with adequate levels of vitamin D have a significantly lower risk of developing cancer, compared to people with lower levels. Vitamin D deficiency was found to be prevalent in cancer patients regardless of nutritional status, in a study carried out by Cancer Treatment Centers of America.
  • Sunlight and vitamin D requirements

    If you live in the tropics and can expose your unprotected skin to two sessions of 15 minutes of sunlight each week your body will naturally produce adequate amounts of vitamin D. The following factors may reduce your body’s vitamin D synthesis:

    • If you live far from the equator, your sunlight exposure will be less during many months of the year.
    • Cloud cover
    • Smog
    • Sunscreens

    If your body cannot produce enough vitamin D because of insufficient sunlight exposure you will need to obtain it from foods and perhaps supplements. Experts say that people with a high risk of vitamin D deficiency should consume 25 μg (1000 IU) of vitamin D each day so that there is a good level of 25-hydroxyvitamin D in the bloodstream. Elderly people, as well as people with dark skin should consume extra vitamin D for good health.

    Vitamin D and nutrition

    Over the last few hundred years human lifestyles have changed. The industrial revolution resulted in more indoor work and less exposure to sunlight. Many societies around the world wore more clothing over the centuries, further reducing skin exposure to sunlight. These changes have brought with them a significant reduction in the natural production of vitamin D and subsequent diseases.

    Countries responded to these changes by fortifying some foods with vitamins D2 and D3, examples include breakfast cereals, bread, pastries, oil spreads, margarine, milk and other dairy products. Initially, some scientists complained that nutritional fortification and recommended supplementation doses were not making up for the shortfall. These people were ignored, and sometimes ridiculed – however, over the last few years studies indicate that they may have been right after all.

    Not that many foods contain vitamin D. Some fish, such as salmon, tuna and mackerel, as well as fish liver oils are considered to be the best sources. Some vitamin D is also present in beef liver, cheese and egg yolks. Most of these are Vitamin D3. Some mushrooms provide variable amounts of vitamin D2.

    Most of the food sourced vitamin D in the western diet comes from fortified foods – where vitamin D is artificially added. Most US milk is fortified with 100 IU/cup of vitamin D.

    Below is a table of some healthy foods that contain vitamin D:

    Food Serving IUs Vitamin D
    Fortified Milk 1 cup 127
    Fortified Soy Milk 1 cup 114
    Fortified Orange Juice 1 cup 142
    Salmon (cooked) 3.5 ounces 360
    Tuna (canned) 3 ounces 200
    Shrimp (canned) 3 ounces 152
    Egg (whole 1 egg 211
    Kellogs low-fat granola with raisins 2/3 cup 40
    Raisin Bran Cereal 3/4 cup 68
    Total Cereal 1 cup 34
    Kix Cereal 1 cup 32
    Quaker instant oatmeal for women 1 packet 154

    Am I at risk for Vitamin D deficiency?

    If you are African American or Hispanic you could be at a higher risk for low vitamin D than if you are white. This is because skin that has a dark pigment can prevent most of the sun’s ultraviolet radiation from reaching the deeper layers of your skin where vitamin D is made.

    If you live in a place that gets very little sunshine, especially during the winter months, it’s harder to get enough vitamin D. To figure out if you live in one of these places, look at a map of the United States and imagine a line running between San Francisco and Philadelphia. If you live North of this imaginary line, it is necessary for you (during the winter) to get your daily intake of vitamin D through food or supplements.

    Sources: http://www.medicalnewstoday.com/

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