Lower-than-optimal blood levels of
vitamin D is becoming more common. It is thought this may be because
people are spending less time outside (especially in winter and in
areas far from the equator) and wearing more sunscreen. It is
difficult to get enough in the diet. Very important for our bones,
but is turning up as a factor in many aspects of health.
Low-carb sources include salmon, tuna,
eggs, yogurt, and liver.
Vitamin D is a fat-soluble vitamin that
plays a role in many important body functions. It is best known for
working with calcium in your body to help build and maintain strong
bones. Vitamin D is also involved in regulating the immune system
and cells, where it may help prevent cancer.
Your body stores vitamin D and can make
it when your skin is exposed to sunlight. Vitamin D is also found in
some foods, mostly ones like milk that have been fortified with
vitamin D. There are two forms of vitamin D: ergocalciferol (vitamin
D2) and cholecalciferol (vitamin D3). Some research suggests that
cholecalciferol is better at raising levels of vitamin D in the
blood.
In children, a vitamin D deficiency can
cause rickets, a disease that results in soft, weak bones. In
adults, many people may not be getting enough vitamin D, especially
those who live in northern areas (like the northern half of the U.S.)
and the elderly. People with dark skin do not absorb sunlight as
easily as those with light skin, so their risk of low vitamin D is
even higher. One study of childbearing women in the Northern U.S.
found that 54% of African-American women and 42% of white women had
low levels of vitamin D.
That’s important because researchers
are beginning to find that low levels of vitamin D may be linked to
other diseases, including breast and colon cancer, prostate cancer,
high blood pressure, depression, and obesity. The evidence doesn’t
prove that too little vitamin D causes these conditions, but that
people with higher levels of vitamin D are less likely to get these
diseases.
Your body make vitamin D when your skin
is exposed to the sun. The color of your skin affects the production
of vitamin D. A fair-skinned person may need only about 45 minutes
of sunlight a week to get enough vitamin D, while a person with dark
skin may need up to 3 hours.
Clouds, smog, clothing, sunscreen, and
window glass all reduce the amount of sunlight that actually reaches
the skin. In northern areas, it is hard to get enough vitamin D from
sunlight during the winter, so people living there may need to take
vitamin D supplements. In the U.S., people who live above a line
running from Los Angeles to South Carolina may not get enough vitamin
D in winter.
Vitamin D is included in many
multivitamins. It can be found alone as softgel capsules, tablets,
and liquid in over-the-counter strengths from 50 - 1,000 IU. Higher
doses are also available, but it is best to ask your doctor what the
safest, most effective dose for you would be. For those who have
trouble digesting fat, vitamin D injections are also available by
prescription.
Recommended dietary allowances for
vitamin D are listed below. Seniors and people who don’t get
exposed to much sunlight may need to take supplements. Seniors may be
at risk of developing vitamin D deficiency because, as we age, the
body does not make as much vitamin D from sunlight, and it has a
harder time converting vitamin D into a form it can use.
If you are concerned about your vitamin
D levels, ask your doctor whether you should take a supplement, and
how much.
Adult
- 19 - 50 years: 600 IU (recommended dietary allowance)
- 70 years and older: 800 IU (recommended dietary allowance)
- Pregnant and breastfeeding females: 600 IU (recommended dietary allowance)
Because of the potential for side
effects and interactions with medications, you should take dietary
supplements only under the supervision of a knowledgeable doctor.
Taking too much vitamin D can cause
several side effects. However, scientists don’t all agree on how
much is too much.
Side effects may include - being very
thirsty, metal taste in mouth, poor appetite, weight loss, bone pain,
tiredness, sore eyes, itchy skin, vomiting, diarrhea, constipation, a
frequent need to urinate, and muscle problems.
You cannot get too much vitamin D from
sunlight, and it would be very hard to get too much from food.
Generally, too much vitamin D is a result of taking supplements in
too high a dose.
People with the following conditions
should be careful when considering taking vitamin D supplements -
high blood calcium or phosphorus levels, heart problems, kidney
disease, sarcoidosis, and tuberculosis.
No comments:
Post a Comment