Sources of Vitamin D

SOURCES OF VITAMIN D

FOOD

  • Very few foods in nature contain vitamin D.
  • The flesh of fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best sources . Small amounts of vitamin D are found in beef liver, cheese, and egg yolks. Vitamin D in these foods is primarily in the form of vitamin D3 (cholecalciferol).
  • Some mushrooms provide vitamin D2 (ergocalciferol) in variable amounts.

Fortified foods provide most of the vitamin D in the American diet .

  • For example, almost all of the U.S. milk supply is fortified with 100 IU/cup of vitamin D. In the 1930s, a milk fortification program was implemented in the United States to combat rickets, then a major public health problem. This program virtually eliminated the disorder at that time. Other dairy products made from milk, such as cheese and ice cream, are generally not fortified.
  • Ready-to-eat breakfast cereals often contain added vitamin D, as do some brands of orange juice, yogurt, and margarine.
  • In the United States, foods allowed to be fortified with vitamin D include cereal flours and related products, milk and products made from milk, and calcium-fortified fruit juices and drinks. Maximum levels of added vitamin D are specified by law.

RECOMMENDED DAILY ALLOWANCE
IUs = International Units.
DV = Daily Value.

  • DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents of products within the context of a total diet. The DV for vitamin D is 400 IU for adults and children age 5 and older. (Note:  at the recently held Ditetitians’ Convention, RDA was raised to 2,000 IUs per day, which some holistic physicians have been asking for years. Although I don’t seem to see announcement about the change. Maybe they were just considering it?)
  • Recently many practitioners have raised the awareness about the growing prevalence of Vitamin D deficiency may be due to among other things use of sunblock or sunscreen, low fat milk (Vitamin D absorption is facilitated by fatty substances).

THE SUN CONNECTION

  • Most people meet their vitamin D needs through exposure to sunlight. Ultraviolet (UV) B radiation penetrates uncovered skin and converts a substance in the deep layer of the skin to previtamin D3, which in turn becomes vitamin D3.
  • Season, geographic latitude, time of day, cloud cover, smog, skin melanin content, and sunscreen are among the factors that affect UV radiation exposure and vitamin D synthesis . The UV energy above 42 degrees north latitude (a line approximately between the northern border of California and Boston) is insufficient for cutaneous vitamin D synthesis from November through February; in far northern latitudes, this reduced intensity lasts for up to 6 months. Latitudes below 34 degrees north (a line between Los Angeles and Columbia, South Carolina) allow for cutaneous (skin) production of vitamin D throughout the year.
  • Complete cloud cover reduces UV energy by 50%; shade (including that produced by severe pollution) reduces it by 60% . UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D . Sunscreens with a sun protection factor of 8 or more appear to block vitamin D-producing UV rays, although in practice people generally do not apply sufficient amounts, cover all sun-exposed skin, or reapply sunscreen regularly . Skin likely synthesizes some vitamin D even when it is protected by sunscreen as typically applied.
  • The factors that affect UV radiation exposure and research to date on the amount of sun exposure needed to maintain adequate vitamin D levels make it difficult to provide general guidelines. It has been suggested, for example, that approximately 5-30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis and that the moderate use of commercial tanning beds that emit 2-6% UVB radiation is also effective. Individuals with limited sun exposure need to include good sources of vitamin D in their diet or take a supplement.
  • Despite the importance of the sun to vitamin D synthesis, it is prudent to limit exposure of skin to sunlight . UV radiation is a carcinogen responsible for most of the estimated 1.5 million skin cancers and the 8,000 deaths due to metastatic melanoma that occur annually in the United States. Lifetime cumulative UV damage to skin is also largely responsible for some age-associated dryness and other cosmetic changes. It is not known whether a desirable level of regular sun exposure exists that imposes no (or minimal) risk of skin cancer over time.

RETURN TO THE TOP

Read more:

Vitamin D is Not Just For the Bones

Groups At Risk For Vitamin D Deficiency

Vitamin D Intake And Status

Vitamin D Deficiency

Vitamin D and Health

Health Risks from Excessive Vitamin D

Interactions with Medications

BBC Articles: Vitamin D as Protection and/or Treatment Against SeriousIllnesses like cancer, diabetes, chronic lung problems, etc)

Vitamin D A Super Nutrient???Dr. Julian Whittaker Thinks So

Click here to view the Vitamin D3 (Cholecaliferol) products featured here.


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