I’m happy spring and warm weather are here! I can enjoy
walking and bike riding in a t-shirt and shorts, garments that allow the sun to
shine on my arms and legs. While I’m exercising, the ultraviolet rays from the
sun are triggering the synthesis of vitamin D inside my skin. This production
of vitamin D is a 2-step process that involves changing precursors of the vitamin
in the liver and then in the kidneys into the active form called D3 or 1,25(OH)2D.
What vitamin D does
Vitamin D is one of several substances called vitamins,
which the body needs to grow and develop normally. Vitamin D is famous for its
role in helping the body absorb the calcium needed for strong bones and in maintaining
an adequate level of calcium in the blood. A deficiency of vitamin D leads to a
softening of the bones that in children is called rickets and in adults osteomalacia.
Vitamin D also plays a role in promoting cell growth, in building our
immune function, and in reducing inflammation. New research is studying the role
these activities may play in the development of several chronic diseases, including
heart disease, multiple sclerosis, and diabetes. Checking the patient’s vitamin
D status is becoming a common laboratory test ordered by doctors, and levels
less than 30 nanomoles per liter (nmol/l) of blood indicates a deficiency.
How can we get this vitamin?
Food sources of vitamin D are mainly fatty fish like salmon,
trout, and sardines, as well as foods fortified with the vitamin, such as milk,
cereal, and a variety of snack bars. Food sources, however, may only provide about
200 international units (IU) per day, and the recommended intake for adult ages
51 to 70 years old is 400 IU/day—so people usually have to take supplements. A daily supplement of the
active form of vitamin D (D3) of from 800 IU to 1000 IU is often recommended and is
Vitamin D’s links to
Vitamin D’s connection to diabetes is still being studied,
but we do know that this vitamin is found in the beta cells that make insulin and
that insulin secretion is dependent on calcium—which, as was stated above, is
dependent on vitamin D. Providing adequate vitamin D has improved insulin
secretion in animals, but more research is definitely needed to confirm this in
While we wait for more study results, we must do what we can
to maintain an adequate level of vitamin D in the blood. Food sources,
supplements, or a little sunshine (just 15 to 20 minutes exposure three times a
week) is necessary.
Who’s at risk of a deficiency?
Those at greatest risk for vitamin-D deficiency are:
people who are obese,
because their increased fat stores interfere with how vitamin D is
released into the blood stream
others with limited sun
This last group includes:
people with darker skin
color, who have greater amounts of melanin in their skin, a substance that
acts as a natural sun blocker
people who wear clothing that covers
most of their skin
Even factors such as smog, cloudy weather, and how much sunscreen
we use can reduce the body’s ability to make vitamin D naturally. If you
haven’t had your vitamin D levels checked, I definitely recommend it!