Sources of Vitamin D Vitamins D3 and D2 occur naturally in some foods, and both versions of the vitamin are added to certain “fortified” products. Foods provide relatively small doses of D compared with amounts made by the skin in response to UVB light. (IU = international units.)

 Cod-liver oil (1 tbsp): 1,360 IU D3  Cooked tuna, sardines, mackerel or salmon (3–3.5 oz): 200–360 IU D3  Shiitake mushrooms (fresh, 3.5 oz): 100 IU D2 (dried, 3.5 oz): 1,600 IU D2  Egg yolk: 20 IU D3 or D2  Fortified dairy products, orange juice or cereals (one serving): 60–100 IU D3 or D2  Full-body exposure to UVB (15 to 20 minutes at midday in summer, fair skin): 10,000 IU D3

Tissues Affected by Vitamin D The VDR receptor protein (above) is found in many body tissues as well as circulating immune cells, indicating a role for active vitamin D in regulating gene activity in those locations. The list below includes some of the tissues and cells where 1,25D action has been established.

 Bone  Brain  Breast  Fat  Intestine  Immune cells  Kidneys  Liver  Nerves  Pancreas  Parathyroid gland  Prostate  Skin keratinocytes

D Makes a Difference Growing evidence suggests that chronically low levels of vitamin D raise a person’s risk for certain major illnesses. Examples of findings based on a population’s blood serum D levels or UV exposure include:

 30% to 50% higher risk for breast, prostate and colon cancers at serum 25D levels below 20 ng/ml  Five times higher risk of ovarian cancer among women living at high latitudes (for example, Norway and Iceland) than women living at equatorial regions  77% lower risk for all cancers among Nebraska women age 55 and older taking 1,100 IU of D3 daily over a three-year period compared with a placebo group  62% lower risk for multiple sclerosis at serum 25D levels above 40 ng/ml than at 25 ng/ml or less  80% lower lifetime risk for autoimmune (type 1) diabetes in Finnish children given 2,000 IU of D3 daily during first year of life

  • Cod-liver oil (1 tbsp): 1,360 IU D3
  • Cooked tuna, sardines, mackerel or salmon (3–3.5 oz): 200–360 IU D3
  • Shiitake mushrooms (fresh, 3.5 oz): 100 IU D2 (dried, 3.5 oz): 1,600 IU D2
  • Egg yolk: 20 IU D3 or D2
  • Fortified dairy products, orange juice or cereals (one serving): 60–100 IU D3 or D2
  • Full-body exposure to UVB (15 to 20 minutes at midday in summer, fair skin): 10,000 IU D3

Tissues Affected by Vitamin D The VDR receptor protein (above) is found in many body tissues as well as circulating immune cells, indicating a role for active vitamin D in regulating gene activity in those locations. The list below includes some of the tissues and cells where 1,25D action has been established.

  • Bone
  • Brain
  • Breast
  • Fat
  • Intestine
  • Immune cells
  • Kidneys
  • Liver
  • Nerves
  • Pancreas
  • Parathyroid gland
  • Prostate
  • Skin keratinocytes

D Makes a Difference Growing evidence suggests that chronically low levels of vitamin D raise a person’s risk for certain major illnesses. Examples of findings based on a population’s blood serum D levels or UV exposure include:

  • 30% to 50% higher risk for breast, prostate and colon cancers at serum 25D levels below 20 ng/ml
  • Five times higher risk of ovarian cancer among women living at high latitudes (for example, Norway and Iceland) than women living at equatorial regions
  • 77% lower risk for all cancers among Nebraska women age 55 and older taking 1,100 IU of D3 daily over a three-year period compared with a placebo group
  • 62% lower risk for multiple sclerosis at serum 25D levels above 40 ng/ml than at 25 ng/ml or less
  • 80% lower lifetime risk for autoimmune (type 1) diabetes in Finnish children given 2,000 IU of D3 daily during first year of life