What is Vitamin D?

Vitamin D is unique among vitamins in that it can be provided to your body through food or from exposure to the sun or tanning bed.  Sunshine is a significant source of vitamin D because UV rays from sunlight triggers vitamin D synthesis in the skin.  Vitamin D functions as an important hormone by sending a message to your intestines to increase the absorption of calcium by as much as 80%.  Vitamin D is well known for maintaining normal calcium levels,¹ but it is involved in so much more! Please read on.

You Are Probably Vitamin D Deficient!

In March 2006, Mayo Clinic Proceedings printed a shocking article about the high prevalence of vitamin D deficiency.² The highly respected author, Michael Holick of the Boston University School of Medicine says "Vitamin D inadequacy has been reported in approximately 36% of otherwise healthy young adults and up to 57% of general medicine inpatients in the United States and even higher percentages in Europe!   Low sunlight exposure, age related decreases in vitamin D synthesis in your skin, and diets low in vitamin D contribute to the high prevalence of vitamin D inadequacy.

Supplemental doses of vitamin D (taken together with calcium and magnesium) and sensible sun exposure could prevent deficiency in most of the general population" according to Holick.  A few comments on choosing the best vitamin d supplement are noted toward the bottom of this web page.

Vitamin D Sources

Sunlight is the best source of vitamin D.  It can provide you with your entire vitamin D requirement. Children and young adults who spend a short time outside two or three times a week will generally synthesize all the vitamin D they need.  If you are older, you have diminished capacity to synthesize vitamin D from sunlight exposure and possibly use sunscreen or protective clothing in order to prevent skin cancer and sun damage, so you should consider getting your vitamin D from food and supplements.

The application of sunscreen with an SPF factor of 8 reduces production of vitamin D by 95%.  In latitudes around 40 degrees north or 40 degrees south (Boston is 42 degrees north), there is insufficient UVB radiation available for vitamin D synthesis from November to early March.  Ten degrees farther north (Edmonton, Canada) this "vitamin D winter" extends from mid October to mid March.  According to Dr. Michael Holick, as little as 5-10 minutes of sun exposure on arms and legs or face and arms three times weekly between 11:00 am and 2:00 pm during the spring, summer, and fall at 42 degrees latitude should provide a light-skinned individual with adequate vitamin D and allow for storage of any excess for use during the winter with minimal risk of skin damage. ³⁵

To learn about vitamin D from food sources and recommended levels click here.

Vitamin D Deficiency

Rickets

In infants and children, severe vitamin D deficiency results in the failure of bone to mineralize.  Rapidly growing bones are most severely affected by rickets.  The growth plates of bones continue to enlarge, but in the absence of adequate mineralization, weight-bearing limbs become bowed.  Although fortification of foods has led to complacency regarding vitamin D deficiency, nutritional rickets is still being reported in cities throughout the world.^{18, 19}

Osteomalacia

Although adult bones are no longer growing, they are in a constant state of turnover.  In adults with severe vitamin D deficiency, the collagen bone matrix is preserved but bone mineral is progressively lost, resulting in bone pain and osteomalacia (soft bones) ...more on Osteomalacia

Muscle Weakness and Pain

Vitamin D deficiency causes muscle weakness and pain in children and adults.  In a cross-sectional study of 150 patients referred to a clinic in Minnesota for the evaluation of persistent, muscle and bone pain, 93% had vitamin D deficiency!²¹

Muscle pain and weakness was a prominent symptom of vitamin D deficiency in a study of Arab and Danish Moslem women living in Denmark.²⁰

Another trial found that supplementation of elderly women with 800 IU/day of vitamin D and 1,200 mg/day of calcium for three months increased muscle strength and decreased the risk of falling by almost 50% compared to supplementation with calcium alone.²²

Risk Factors for Vitamin D Deficiency

If you find yourself in any of the categories below, you would be well advised to get a blood test to determine your vitamin D levels.

Sunscreen Use

Osteomalacia has been documented in women who cover all of their skin whenever they are outside for religious or cultural reasons.^{26, 27}  The application of sunscreen with an SPF factor of 8 reduces production of vitamin D by 95% creating a similar problem to covered skin.¹

Dark Skin

People with dark skin synthesize less vitamin D on exposure to sunlight than those with light skin.¹  The risk of vitamin D deficiency is particularly high in dark-skinned people who live far from the equator.

Breast Fed Infants

Infants who are exclusively breast fed are at high risk of vitamin D inadequacy, particularly if they have dark skin and/or receive little sun exposure.¹⁹  Human milk generally provides 25 IU of vitamin D per liter, which is not enough for an infant if it is the sole source of vitamin D.  Older infants and toddlers exclusively fed milk substitutes and weaning foods that are not vitamin D fortified are also at risk of vitamin D deficiency.¹⁸  The American Academy of Pediatrics recommends that all infants that are not consuming at least 500 ml (16 ounces) of vitamin D fortified formula or milk be given a vitamin D supplement of 200 IU/day.¹⁹

Aging

The elderly have reduced capacity to synthesize vitamin D in the skin when exposed to UVB radiation, and are more likely to stay indoors or use sunscreen.  Institutionalized adults are at extremely high risk of vitamin D deficiency without supplementation.^{24, 25}

Inflammatory Bowel Disease

If you suffer from inflammatory bowel disease like Crohn’s disease you may be at increased risk of vitamin D deficiency, especially if you have had small bowel surgery.²⁹

Fat Malabsorption Syndromes

Cystic fibrosis and cholestatic liver disease impair the absorption of dietary vitamin D.²⁸

Obesity

If you are overweight, it increases your risk of vitamin D deficiency.³⁰  Once vitamin D is synthesized in the skin or ingested, it is deposited in body fat stores, making it less bio-available if you have large stores of body fat.

Vitamin D Supplement?

There are many health benefits of vitamin D, but it is not always practical to get your vitamin D from sunshine, and quite difficult to get adequate amounts from your diet so for many people, a vitamin D supplement is a practical way to ensure adequate levels of this important protector are always available in your bloodstream.

Since a large body of science shows vitamin D works closely with calcium and magnesium, it is best to take your vitamin D in combination with calcium and magnesium to maintain a proper balance.  Recent literature also shows most calcium supplements have too little vitamin D to be effective.  And some of them use synthetic vitamin D2.  A much better form is natural vitamin D3 which stays in your system longer and with more effect.  To learn about an extraordinary vitamin D3 supplement with bio-available plant-sourced calcium and magnesium, please click here

References

More Vitamin D Info

New research shows avoiding rays may lead to a vitamin D deficiency Knoxville News Sentinel, TN - 21 hours ago Now, the recommendation is to get 15 minutes of sun at the peak of the day three times a week to help avoid a vitamin D deficiency. ...

Citizen Low vitamin D boosts depression risk in seniors Reuters - May 5, 2008 And blood levels of parathyroid hormone, which increase with vitamin D deficiency, were 5 percent higher in people with minor depression and 33 percent ... A new study is out on vitamin D deficiency and depression South Carolina Now Health:Vitamin D levels linked to depression Trading Markets (press release) Lack of vitamin D linked to depression in elderly AFP Age Concern - Best Syndication all 32 news articles