October 27, 2008
Everyone needs vitamin D. As winter approaches, it can become more difficult for
those in northern climates to get what they need without taking supplements.
"There are three sources of vitamin D: natural sunlight, fortification of dietary
foods, particularly dairy products and some cereals and oily fish. The radiation
that converts vitamin D in the skin is the same wavelength that causes sunburn,
so careful application of sunscreen can inhibit vitamin D production. At northern
latitudes, there is not enough radiation to convert vitamin D, especially during
the winter. After the age of 70 the skin does not convert vitamin D effectively."
While natural sunlight can be a primary source of vitamin D, obstacles such as a
person's age, how a person's body converts sun exposure into vitamin D,
and lack of skin exposure to direct sunlight can make it difficult for some people
to maintain enough vitamin D in their blood for optimum health.
Food sources can be another way for people to get some vitamin D, but not all people
eat enough vitamin D rich foods, and not all vitamin D is created equal.
"Vitamin D is found in many dietary sources such as fish, eggs, fortified milk,
and cod liver oil. The sun also contributes significantly to the daily production
of vitamin D, and as little as 10 minutes of exposure is thought to be enough to
prevent deficiencies. The term 'vitamin D' refers to several different forms
of this vitamin. Two forms are important in humans: ergocalciferol (vitamin D2)
and cholecalciferol (vitamin D3). Vitamin D2 is synthesized by plants. Vitamin D3
is synthesized by humans in the skin when it is exposed to ultraviolet-B (UVB) rays
from sunlight. Foods may be fortified with vitamin D2 or D3. The major biologic
function of vitamin D is to maintain normal blood levels of calcium and phosphorus.
Vitamin D aids in the absorption of calcium, helping to form and maintain strong
While one of the most well known functions of vitamin D is to aid in the absorption
of calcium for strong bones, recent studies have found that vitamin D is involved
in many more aspects of good health.
"It has long been known as the vitamin that cured rickets. But today, vitamin
D is being hailed for being able to do much more than that. Scientists have known
for some time about vitamin D's role in helping the body absorb calcium, in
maintaining bone density, and in preventing osteoporosis. But new research suggests
it may also help protect against chronic diseases such as cancer, type 1 diabetes,
rheumatoid arthritis, multiple sclerosis, and autoimmune diseases. Yet many adults
have low blood levels of vitamin D. Vitamin D is not abundant in our usual food
choices, so we get most of the vitamin from sun exposure and multivitamins. The
problem is that the sun is not a reliable source for everyone. The season, time
of day, geography, latitude, level of air pollution, color of your skin, and your
age all affect your skin's ability to produce vitamin D. Further, the form of
Vitamin D found in most multivitamins is vitamin D2, which does not deliver the
same amount of the vitamin to the body as the more desirable D3 form."
Finding the right foods and multivitamins to complement or replace the vitamin D
that a person might otherwise get from the sun can be complicated.
"Adequate levels of vitamin D, also known as 'the sunshine vitamin',
are metabolised by the human body from as little as 15 minutes sun exposure during
the summer months. The vitamin plays a role in the absorption of calcium, which
is crucial for bone health, and in overall health and development. However during
the winter limited sunlight and absence of ultraviolet light at the right wavelength
(290 to 310 nm) in the north of the UK mean that many people - especially those
with darker skin or those who cover up most of the body for religious reasons -
are susceptible to deficiency. While vitamin D does also occur naturally in foods
like oily fish, eggs and fortified breads and cereals, the warning is that 'these
may still be inadequate when sunshine hours are limited'."
Whatever the source, vitamin D has shown that it can play a major role in helping
people improve both their mental and physical health.
"'Basically, what vitamin D does is increase levels of the [chemical] serotonin
in the brain,' he tells WebMD. Many antidepressant medications work the same
way. About 90% of patients in my hospital are vitamin D deficient, and I put them
on a vitamin D regimen, and it does improve their mood disorders' ... However,
if you are currently taking antidepressants, don't stop taking those drugs if
you begin taking the vitamin supplements. 'What this study suggests that is
vitamin D deficiency may be an explanation for depression, and that boosting vitamin
D levels may help prevent or ease symptoms,' Cannell tells WebMD. 'But how
much vitamin D you need depends on several factors, such as the environment you
live in, what time of year it is, your skin type, and sun exposure.'"
Doctors can do a blood test to see check the level of vitamin D in a person's
blood. This can help patients and doctors to work together to know how what changes,
if any, need to be made in order to improve vitamin D levels for optimal health.
Levels can be low for a number of reasons. People convert sunlight into vitamin
D at different rates depending upon their age and skin color. Working with a health
care professional can help each person determine what lifestyle choices and/or changes
they can make in order to be sure they are getting enough vitamin D.
Obstacles that the body faces when attempting to convert sunlight to vitamin D can
- "Dark skin: People with dark-colored skin synthesize less vitamin D on exposure
to sunlight than those with light-colored skin. The risk of vitamin D deficiency
is particularly high in dark-skinned people who live far from the equator. ...
- Aging: The elderly have reduced capacity to synthesize vitamin D in skin when
exposed to UVB radiation, and the elderly are more likely to stay indoors or use
sunscreen, which blocks vitamin D synthesis. ...
- Covering all exposed skin or using sunscreen whenever outside: Osteomalacia has
been documented in women who cover all of their skin whenever they are outside for
religious or cultural reasons. The application of sunscreen with an SPF factor of
8 reduces production of vitamin D by 95%.
- Fat malabsorption syndromes: Cystic fibrosis and cholestatic liver disease impair
the absorption of dietary vitamin D.
- Inflammatory bowel disease: People with inflammatory bowel disease like Crohn’s
disease appear to be at increased risk of vitamin D deficiency, especially those
who have had small bowel resections.
- synthesized in the skin or ingested, it is deposited in body fat stores, making
it less bioavailable to people with large stores of body fat."
Questions of the Week:
How can you determine whether or not you need more vitamin D in your life for optimum
health? How can you tell whether or not you need to raise the amount of vitamin
D you are getting from your diet and/or from your time in the sun? Based upon your
age, where you live, and your individual health needs, how can you determine what
would be the best sources of vitamin D for you? What factors would influence how
your vitamin D blood levels might vary from those of a friend or relative?
Please email me with any ideas or suggestions.
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