The Multiple Causes
of Vitamin D Deficiency

There are enough different causes of vitamin D deficiency that it's a condition that's reached epidemic proportions. Whenever studies are done to measure vitamin D levels in large groups, the results show that, regardless of the age or cultural background of the subjects, chronic deficiencies are widespread.

Primary Cause of Vitamin D Deficiency
is a Lack of Sun Exposure

Sun exposure has always been man's primary source of vitamin D. Until modern times, human beings spent a great deal of time outdoors. But as ancient man migrated from subtropical to less temperate climates, this has changed dramatically.

Over many generations, the shift from a hunter-gatherer to an agricultural-based to an industrialized society also meant less vitamin D from sun exposure. Today, many of us work indoors and use our cars to get from place to place, instead of walking.

In addition, the natural sunlight that generates vitamin D in your skin cannot penetrate any type of glass, so you don’t generate vitamin D by getting sunlight through a window.

The overuse of sunscreens is another one of the major causes of vitamin D deficiency. While the use of sunscreen may be useful in minimizing the risks of skin cancer, sunscreens also prevent the manufacture of Vitamin D, even if you're outdoors for a long time.

See my page on Sunscreen Facts for tips on using sunscreens.

Applying sunscreen with even
a minimum SPF factor of 8 reduces your
body's production of vitamin D by 95%.

Where you live determines how much vitamin D you get. Sunlight is strongest at the equator, where it comes from directly overhead, rather than at an angle, and has the shortest distance to travel through the earth’s atmosphere. The UV radiation is about four times as strong at the equator as it is at the Arctic circles.

If you live north of the 30th parallel in the northern hemisphere (most of the USA and all of Europe), or south of the 30th parallel in the southern hemisphere, the sun is not strong enough for about half of the year to produce any vitamin D. The further you go away from the equator, the shorter the vitamin D season gets.

To find the latitude where you live, try this easy-to-use International Latitude/Longitude Finder

See Vitamin D From Sun Exposure for more information
on getting vitamin D from sun exposure.

Other Significant Causes of
Vitamin D Deficiency

Causes of Vitamin D Deficiency: Dark Skin

African-Americans and other dark-skinned races need significantly more UV exposure to produce adequate vitamin D. This is because the higher melanin (the pigment that darkens skin) content in darker skin reduces the skin's ability to produce vitamin D from sunlight. A typical person with very deep skin pigmentation has sun protection that’s similar to a sunscreen with a SPF of 15-30.

Causes of Vitamin D Deficiency: Obesity

Some studies have shown that obese individuals may be less able to effectively manufacture Vitamin D. Another problem with overweight individuals is that some of the vitamin D gets stored in your fat and can’t be easily released. At the same time, overweight people have an increased need for stronger bones to support their higher weight, something vitamin D is essential for.

Causes of Vitamin D Deficiency: Aging

You lose some of your ability to synthesize and absorb vitamin D as you age. As you grow older and your skin grows thinner, the amount of the vitamin D precursor (a derivative of cholesterol) in your skin decreases, too.

After the age of 60, people are more likely to have had an experience with skin cancer, and subsequently started to use sunscreen more often. Also, old people are more likely to stay indoors, especially those in nursing homes or similar institutions.

Causes of Vitamin D Deficiency: Air Pollution

Severe air pollution can sometimes block UV radiation too effectively. If the air pollution contains large amounts of ozone, UV penetration can be significantly reduced, sometimes to a dangerously low level for some people.

Causes of Vitamin D Deficiency:
Liver, Kidney and Bowel Disorders

We know that vitamin D is formed when your skin is exposed to sunlight. However, the complete vitamin D absorption process is a little more complex. The vitamin D first goes to your liver to become activated and modified into something called 25-hydroxy vitamin D. This is what labs measure to determine your blood level of vitamin D. It then goes to your kidneys where it gets modified to its active form.

Individuals with improperly functioning organs may suffer deficiency symptoms even if their blood levels of Vitamin D are adequate, since Vitamin D is processed into hormones in the liver and kidneys,

People with inflammatory bowel diseases such as Crohn's disease are also at increased risk of vitamin D deficiency symptoms, due to their inability to process vitamin D properly.

Making Sure You Get Enough Vitamin D

Given all of the factors mentioned, it's not surprising that numerous studies have shown that the overwhelming majority of the population suffers from vitamin D deficiency. Low vitamin D levels are now known to be at the root of many chronic illnesses.

"We estimate that vitamin D deficiency is
the most common medical condition in the world."

Dr. Michael F. Holick, Vitamin D expert

You can find specific information at my page on
Symptoms of Vitamin D Deficiency

How do you know if you're deficient in vitamin D? If you have habitually avoided direct sun exposure, and don't take any vitamin D supplements, you almost certainly have low vitamin D levels. The only way to determine this for sure is to get your vitamin D levels tested. You can arrange a test with your health care provider or get a test kit that will allow you to do this at home.

See Vitamin D Blood Test for more details.

Fortunately, getting enough vitamin D is easy if you take deliberate steps — in the summer months, just spend a few hours each week sunbathing. Your skin produces more than 10,000 units of vitamin D with just 30 minutes summer sun exposure in a bathing suit (without sunscreen). In the winter months, take natural vitamin D supplements in the form of D-3 (cholecalciferol). Nutritionists are now recommending a minimum of 1,000 to 2,000IU a day for general preventive health, even more if you're chronically deficient.

See Vitamin D Dosage for more details.


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