Vitamin D encourages the absorption and metabolism of calcium and phosphorous, it is a steroid vitamin. Individuals who are exposed to normal quantities of sunlight directly onto the skin generally get plenty of vitamin D, because sunlight encourages adequate vitamin D synthesis in the skin.
Vitamin D is also an immune system regulator, it helps keep our bones healthy, it may reduce multiple sclerosis risk, it likely helps keep the brain working well later in life, experts believe it helps us maintain a healthy body weight, it can reduce frequency and severity of asthma symptoms, it has been shown to reduce rheumatoid arthritis risk in women, it probably protects us from low level radiation damage, and has cancer protecting qualities (click here to read about this in more detail).
The report found that from 2001 to 2006, referring to people in the USA aged 1 year or more:
- 67% had vitamin D blood levels between 50 and 125 nanomoles per liter (adequate)
- 24% risked having inadequate vitamin D blood levels
- 8% had less than 30 nanomoles per liter of vitamin D in their blood, placing them at serious risk of vitamin D deficiency
- 1% had excessively high vitamin D blood levels
The authors revealed that vitamin D deficiency risk varied according to sex, age, race and ethnicity. Younger individuals, males, and non-Hispanic white people appear to have a lower risk than the rest of the population.
In both periods, 1988-1994 and 2001-2002 vitamin D deficiency risk grew nationally in males and females, and remained unchanged between 2001-2002 and 2005-2006.
The report also informs that:
- Males have a lower risk of vitamin D deficiency than females
- Non-Hispanic white individuals have a lower risk of vitamin D deficiency/inadequacy compared to non-Hispanic black or Mexican-American people
- Pregnant and breastfeeding women are less likely to be vitamin D deficient compared to non-pregnant or non-breastfeeding women of childbearing age
People who live in the tropics, or near the tropics and expose their unprotected skin to two 15-minute sessions of sunlight each week will naturally produce enough vitamin D for their body's requirements. Those who live very far from the equator will not get enough sunlight exposure for their vitamin D requirements during many months of the year. Cloud cover, smog and sunscreens will reduce the amount of vitamin D your skin can synthesize when exposed to the sun during those 15-minute sessions.
Individuals who do not produce enough vitamin D because of low sunlight exposure will have to make sure they get it from the food they eat, or possibly supplements.
Over the last couple of centuries a considerable proportion of people have spent more and more time indoors, resulting in less exposure to sunlight. Most nations started adding some types of vitamin D to bread, pastries, oil spreads, margarine, milk and other dairy products, and breakfast cereals.
The best natural dietary sources of vitamin D are some fish, such as tuna, mackerel and salmon, and fish liver oils. Beef liver, cheese and egg yolks also have vitamin D. Mushrooms may have varying amounts. Most people today get their dietary vitamin D from fortified foods.
"Vitamin D Status: United States, 2001-2006"
Anne C. Looker, Ph.D.; Clifford L. Johnson, M.P.H.; David A. Lacher, M.D.; Christine M. Pfeiffer, Ph.D.; Rosemary L. Schleicher, Ph.D.; and Christopher T. Sempos, Ph.D.
CDC/NCHS Data Brief. Number 59, March 2011