Vitamin D deficiency may be a common but unrecognized problem among U.S. adolescents. Researchers found that among 11- to 18-year-olds living in Boston, nearly one-quarter were deficient in vitamin D, a nutrient that aids in calcium absorption and is vital for healthy bone development. If you wish to buy a Vitamin-D supplement. To learn more about the difference between calcitriol and and vitamin D3 known as cholecalciferol.
Vitamin D deficiency
The problem is preventable with an adequate
diet and time outdoors. The
body naturally synthesizes vitamin D when the skin is exposed to the sun, and
milk and certain other foods, including many breakfast cereals, are fortified
with the vitamin. But U.S. children increasingly fill up on soft drinks at the
expense of milk, and spend more time in front of the TV or computer than
outdoors.
Soft drink, juice and iced tea intake are related to a greater risk of
vitamin D deficiency. On the other hand, adolescents who drink milk
and eat cereal are less likely to be low on vitamin D.
A high proportion of pregnant women living in the northern United
States, and their newborns, have insufficient vitamin D levels, and taking
prenatal vitamins may not increase vitamin D levels adequately. A large
percentage of African-American women and nearly half of white women tested at
delivery had levels of vitamin D that were too low, even though more than 90
percent of them used prenatal vitamins during pregnancy.
What about too much Vitamin D and side effects?
Too much vitamin D ingestion can lead to vitamin D side effects such as
nausea, vomiting, poor appetite, weakness, and weight loss. Too much vitamin D
can also raise blood levels of calcium, causing mental status changes such as
confusion. High blood levels of calcium, known as hypercalcemia, can cause heart
rhythm abnormalities. Calcinosis, the deposition of calcium and phosphate in
soft tissues like the kidney can be caused by too much vitamin D.
Too much vitamin D and calcium intake has another potential side
effect. It can lead to an increase in total brain lesion volume. Dr. Martha E.
Payne of Duke University, Durham, North Carolina, believes too much vitaman D and calcium may lead to vascular
calcification, since calcium is taken up into the blood vessel walls. Dr. Martha
E. Payne evaluated calcium and vitamin D intakes by food frequency
questionnaires and MRI scans in 232 elderly men and women (average age, 71
years). All of the subjects displayed some brain lesions of varying sizes but
those reporting the highest intakes of calcium and vitamin D were more likely to
have higher total volume of brain lesions. Dr. Payne is concerned that too much calcium either through food or supplements may end up in the blood
vessel walls rather than the bone. She reported the study findings at a meeting
of the American Society for Nutrition, part of Experimental Biology in May, 2007
in Washington, DC.
Vitamin D and insulin
People with a low level of vitamin D in the blood have poorly functioning
insulin-producing cells and show a poor response to insulin, even when their
blood sugar levels are normal.
Vitamin D
recommended daily dosage
The recommended daily intake of vitamin D is
200 iu for adults younger than 50 years and 600 iu for those older than 70
years. Vitamin D supplementation is especially important in elderly persons
because skin synthesis and absorption of vitamin D may be impaired.
Vitamin D and colon cancer
Taking 1,000 to 2,000 international units (IU) of vitamin D each day may
reduce the risk of colorectal cancer, according to pooled data from published
studies. The current findings contradict some prior individual studies that
found that vitamin D intake did not seem to protect against colorectal cancer.
However, it is possible that the dose may simply have been too low to provide a
benefit. The present analysis, reported in the American Journal of Preventive
Medicine, included data from five studies that looked at the association between
blood levels of 25-hydroxy-vitamin D, which provides a good estimate of vitamin
D levels in the body, and colorectal cancer risk. Dr. Edward D. Gorham, from the
Naval Health Research Center in San Diego, California, and colleagues found that
as blood levels of vitamin D rose, the risk of colorectal cancer fell. Risk was
reduced by 54 percent in groups with the highest vitamin D levels relative to
those with the lowest levels. American Journal of Preventive Medicine, March
2007.
Vitamin D and fractures
Getting plenty of vitamin D can help prevent falls among people living in
nursing homes.
Vitamin D and multiple sclerosis
Vitamin D3 appears to be helpful in several diseases, including multiple
sclerosis. High doses of vitamin D may be required for therapeutic efficacy.
Patients with mulptle sclerosis can take enough vitamin D to double their blood
levels of vitamin D without the concern of causing hypercalcemia or
hypercalciuria.
Vitamin D and Pancreatic Cancer
Taking a Vitamin D supplement may reduce your risk for fatal pancreatic
cancer. Vitamin D has shown strong potential for preventing and treating
several types of cancer. Regions with greater sunlight exposure have lower
incidence and mortality for prostate, breast, and colon cancers. Harvard
University researchers examined data from two large, long-term health
surveys involving 46,771 men between 40 and 75 years old and 75,427 women
between 38 and 65. They found that people who took Vitamin D, 400 IU a day
had a 40 percent lower risk of pancreatic cancer. Those who took doses of
less than 150 IU per day had a 22 percent reduced risk of cancer. Taking
more than 400 IU a day did not reduce the risk further.
Most multivitamins include vitamin D usually at 100 to 400 units.
You could consider getting more sun exposure or taking an additional vitamin D
supplement. A supplement of 200 to 600 units a day is sufficient for most
people.
Vitamin D supplement decreases mortality
Dr. Philippe Autier, International Agency for Research on
Cancer in Lyon, France, and Dr. Sara Gandini, from the European Institute of
Oncology in Milan, Italy, reviewed 18 existing studies on the role of vitamin D
use on longevity and
found vitamin D ingestion reduced mortality by any cause by 7 percent. "Based on
the total body of evidence of health conditions associated with vitamin D
deficiency, abetted with the results from this meta-analysis, a more proactive
attitude to identify, prevent, and treat vitamin D deficiency should be part of
standard medical care," Dr. Edward Giovannucci, from Harvard School of Public
Health in Boston, writes in a related editorial. Archives Intern Med
2007;167:1730-1737,1709-1710.
Living in sunny states no guarantee
that vitamin D deficiency won't occur
Despite residing in a region with high chronic sun exposure, adults in
southern Arizona are commonly deficient in vitamin D deficiency, particularly
blacks and Hispanics. American Journal of Clinical Nutrition, March 2008.
Vitamin D side effects from too much vitamin D
Vitamin D questions
Q. Dr. John Cannell of the vitamin D council says that vitamin A blocks the
absorption of vitamin D3 and that supplementation with A is unnecessary and even
detrimental for that reason. What are your thoughts about this? If that
information is accurate would taking the vitamin A (in carotene forms)
separately from the vitamin D3 be OK?
Thank you for all your good work and for your very sensible recommendations.
A. Few people need to supplement with vitamin A. Most multivitamin
products contain vitamins A and D. For practical purposes we don't think it is
an issue taking a multivitamin supplement in terms of vitamin D absorption. We
don't think there is a need to take vitamin A supplement by themselves. If beta
carotene is considered to be taken as a supplement, it is preferable to consider
a carotenoid supplement that includes a number of different carotenoids. Or,
just eat a carrot every few days.
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