Vitamin D Facts

Vitamin D is different from other vitamins because it can be made from sunlight on our body. The body makes vitamin D from a precursor that the body makes from cholesterol. With enough time in the sun a person doesn't need to eat or drink foods with vitamin D in it. Ultraviolet rays from the sun hit the precursor in the skin and converts it to the previtamin D3 which then works its way into the body in 36 hours. It converts to its active form with the help of the body's heat. The kidneys and liver are also part of the process so if those organs are affected by disease then a person could become vitamin D deficient.

What Vitamin D does for your body

Vitamin D is actually a hormone that is needed for bone growth and maintenance. Vitamin D maintains blood concentrations of calcium and phosphorus. By absorbing these minerals the bones can grow denser and stronger.

Vitamin D also helps cells of the immune system, brain and nervous system, pancreas, skin, muscles, cartilage, and reproductive organs. Some evidence suggests that vitamin D may protect against tuberculosis, gum inflammation, multiple sclerosis, and some cancers.

Vitamin D Deficiency

Factors that can lead to a deficiency include dark skin, breastfeeding without supplementation, lack of sunlight, and not using fortified milk. When there is a lack of vitamin D calcium doesn't get absorbed properly and increases the risk of diseases like osteoporosis.

The elderly are greatly at risk for deficiency because their skin, liver, and kidneys lose their capacity to make and activate vitamin D. On top of that, a lot of older adults tend to avoid the sun and put on sunscreen when they go outside. These days, the wisdom of applying sun screen every time we go outside is being questioned for all ages. Some doctors are now saying to get 15 to 30 minutes of unprotected sun exposure on as much of your body as possible per day. I try to get 30 minutes at least every day I have time, but on days where I intend on being outside for more than an hour, I will wear sunscreen or wear protective clothing including a hat if necessary. It only takes a few minutes to get your daily dose of D depending on skin pigment. Any more sun exposure is wasted and of course puts us at greater risk for wrinkles, skin cancer, etc.

UV rays from a tanning lamp and tanning beds may also stimulate vitamin D synthesis and increase bone density, but there are potential problems with skin damage with their use. The FDA warns that if lamps are not properly filtered they can cause damage to the eyes, blood vessels, and skin.

Dark skinned people living in northern regions are especially vulnerable to a vitamin D deficiency. Deficiencies tend to create bone loss and fractures. Vitamin D supplementation can help to reduce bone fractures in the elderly.

Vitamin D Toxicity

The amount of D made by the skin and found in foods are well within safe limits, but supplements containing the vitamin in concentrated form should be used with caution. Excess vitamin D raises the concentration of blood calcium which forms stones in the kidneys. Calcification can harden the blood vessels and is especially dangerous in the major arteries of the heart and lungs.

It is impossible to get too much vitamin D from sun exposure. Recent research has shown that higher limits of vitamin D in the body are safer than previously thought.

Here is some information from globalrph.com on the subject of safe amounts of D one can take.

Reviewers, from the CRN, Mount Sinai Hospital in Toronto and Crieghton University in Nebraska, pooled data from 21 clinical trials using doses ranging from 10 to 2,500 micrograms (100,000 IU). The risk assessment also included data from animal studies, some of which used “extraordinarily high doses of vitamin D3”.

“The lack of adverse effects in clinical trials that used intake up to 1,250 micrograms [50,000 IU] vitamin D per day and the lack of adverse effects at lower doses inspires a high level of confidence in the data from the strongly designed clinical trials that used 250 micrograms [10,000 IU] vitamin D per day,” said the reviewers.

“Newer clinical trial data are sufficient to show that vitamin D is not toxic at intakes much higher than previously considered unsafe,” said the reviewers. (globalrph.com)

They also pointed out that 60 percent of northern populations may be vitamin D deficient.

I also found this on the same site, which is apparently got their information from http://newsroom.ucr.edu/cgi-bin/display.cgi?id=1968.

Currently, the recommended daily intake of vitamin D is 200 IU for people up to 50 years old; 400 IU for people 51 to 70 years old; and 600 IU for people over 70 years old.

“The consensus among UC scientists who signed this statement is that 2,000 IU per day of vitamin D3, a form of vitamin D, is the appropriate intake for most adult Americans,” said Norman, an international expert on vitamin D. “This intake is the National Academy of Sciences/Institute of Medicine’s upper limit for daily intake, and is 400 IU less than the National Academy of Sciences/Institute of Medicine’s ‘no adverse health effect’ level. Scientific concerns about this level of intake are minimal, based on the findings of the National Academy of Sciences.”

Norman explained that a 2000 IU daily intake of vitamin D can be achieved by a combination of sunshine, food, supplements, and possibly even limited tanning exposure. “While more research on this topic is highly desirable, it should not delay recommending a 2,000 IU daily intake of vitamin D for most people,” he said.

Vitamin D and Disease Prevention

Some other facts from www.hsph.harvard.edu/.

Evidence that vitamin D may play a role in preventing type 1 diabetes comes from a 30-year study that followed more than 10,000 Finnish children from birth: Children who regularly received vitamin D supplements during infancy had a nearly 90 percent lower risk of developing type 1 diabetes than those who did not receive supplements.

The flu virus wreaks the most havoc in the winter, abating in the summer months. This seasonality led a British doctor to hypothesize that a sunlight-related “seasonal stimulus” triggered influenza outbreaks.

Several case-control studies, when analyzed together, suggest that people diagnosed with tuberculosis have lower vitamin D levels than healthy people of similar age and other characteristics.

Nearly 30 years ago, researchers noticed an intriguing relationship between colon cancer deaths and geographic location: People who lived at higher latitudes, such as in the northern U.S., had higher rates of death from colon cancer than people who live closer to the equator. The sun’s UVB rays are weaker at higher latitudes, and in turn, people’s vitamin D levels in these high latitude locales tend to be lower. This led to the hypothesis that low vitamin D levels might somehow increase colon cancer risk.

Vitamin D may also help increase muscle strength.

There is also a ton of stuff about research on vitamin D at Doctor Mercola's site. He's a firm believer in getting vitamin D from sunlight.  I've found a lot of useful information on his site while I can't swear to agree with everything he says, but he has been ahead of the curve on a few issues, according to Tv's  Doctor Oz. Mercola has also been a guest of Doctor Oz in the past.

Sources: 
Understanding Nutrition Eleventh Edition  

http://www.globalrph.com/vitamin_d.htm

J.N. Hathcock, A. Shao, R. Vieth, R. Heaney. Risk assessment for vitamin D. American Journal of Clinical Nutrition; January 2007, Volume 85, Pages 6-18.

http://newsroom.ucr.edu/cgi-bin/display.cgi?id=1968

http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vitamin-d/index.html

Books on Vitamin D  for further research.
 

Articles

Vitamin D Reduces Risk of Diseases
Vitamin D influences more than 200 genes. This includes genes related to cancer and autoimmune diseases like multiple sclerosis.

Vitamin D affects your DNA through the vitamin D receptors (VDRs), which bind to specific locations of the human genome.

Osteoporosis facts and prevention for women and men
To prevent osteoporosis weight lifting, resistance training, and getting calcium and vitamin D is crucial.

The Vitamin D Battle - Recent government recommendations have increased the daily recommended guidelines for vitamin D, but still some doctors argue for higher daily intakes.

Vitamin D and Your Teeth
Studies have linked geographical variations in dental health and tooth loss to sun exposure.

Dental caries has been shown to be inversely related to mean hours of sunlight per year, with people living in the sunny west having half as many cavities as those in the much less sunny northeast. As reported by the Vitamin D Council.