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Nutrition, Vitamins & Supplements for Seniors
Low Vitamin D Level Linked to Physical Problems in
Older Adults
Key role in bone health; may protect against
diabetes, cancer, colds, tuberculosis
 April 23, 2007 - Older adults who don't get enough
vitamin D either from their diets or exposure to the sun may be at
increased risk for poor physical performance and disability, according
to new research from Wake Forest University School of Medicine and
colleagues.
"With a growing older population, we need to
identify better ways to reduce the risk of disability," said lead author
Denise Houston, Ph.D. "Our study showed a significant relationship
between low vitamin D levels in older adults and poorer physical
performance."
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on
Nutrition, Vitamins & Supplements |
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The results are reported in the April issue of the
Journal of Gerontology: Medical Sciences.
About one-fourth of people over age 60 have low
vitamin D levels. Previous research has shown that vitamin D not only
plays a role in bone health, but possibly also in protecting against
diabetes, cancer, colds and tuberculosis.
"Recent findings showing the importance of vitamin
D status on multiple health outcomes underscore the need for more
research on the effects of low vitamin D levels in elderly populations,"
said Houston, an instructor in internal medicine - gerontology.
Vitamin D is naturally produced when skin is
exposed to the sun's ultraviolet rays. Foods such as fortified milk,
juice and cereals also contain vitamin D, but it is difficult to get
enough through diet alone, said Houston.
Older adults are particularly prone to low vitamin
D levels because they may get less exposure to sunlight and because
their skin is less efficient in producing vitamin D from sun exposure
compared to younger adults. Older adults also may not get enough vitamin
D from dietary sources.
"There is a growing awareness that the prevalence
of low vitamin D levels is common among the elderly," said Houston.
(Read more about Vitamin D
below news report.)
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Older
adults and Vitamin D
Americans age 50 and older are believed to be at increased risk
of developing vitamin D deficiency, according to the Office of
Dietary Supplements of the National Institutes of Health.
As
people age, skin cannot synthesize vitamin D as efficiently and
the kidney is less able to convert vitamin D to its active
hormone form.
It is estimated that as many as 30% to 40% of
older adults with hip fractures are vitamin D insufficient.
Therefore, older adults may benefit from supplemental vitamin D.
Read more about Vitamin D below news
report. |
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For the current study, researchers analyzed data
from the InCHIANTI study, which evaluated factors contributing to the
decline of mobility in late life. The study involved 976 people who were
65 years and older from two towns in the Chianti area of Italy. The mean
age of participants was 74.8 years. Data were collected from Sept. 1998
through March 2000.
Participants completed a short physical performance
test of their walking speed, ability to stand from a chair and ability
to maintain their balance in progressively more challenging positions.
In addition, handgrip strength, a predictor of future disability, was
measured using a hand-held dynamometer.
The researchers found that physical performance and
grip strength were about five to 10 percent lower in those who had low
levels of vitamin D. After looking at other variables that could
influence the results, such as body mass index, physical activity, the
season of the year, mental abilities, health conditions and anemia, the
results held true.
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Editors Notes:
The research is supported by the Italian Ministry
of Health and in part by the National Institute on Aging. Co-researchers
were Gary Schwartz, Ph.D., and Stephen Kritchevsky, Ph.D., both with
Wake Forest, Matteo Cesari, M.D., Ph.D, with the University of Florida,
Luigi Ferrucci, M.D., Ph.D., with the National Institute on Aging, Dario
Maggio, M.D., and Antonio Cherubini, M.D., Ph.D, both with the
University of Perugia in Italy, Mary Ann Johnson, Ph.D., with the
University of Georgia, and Benedetta Bartali, R.D., with Cornell
University.
Wake Forest University Baptist Medical Center is
an academic health system comprised of North Carolina Baptist Hospital
and Wake Forest University Health Sciences, which operates the
university's School of Medicine.
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The study wasn't designed to evaluate whether low
vitamin D levels actually cause poor physical performance, but the
results suggest the need for additional research in this area, said
Houston. She said vitamin D plays an important role in muscle function,
so it is plausible that low levels of the vitamin could result in lower
muscle strength and physical performance.
"But it's also possible that those with poor
physical performance had less exposure to sunlight resulting in low
vitamin D levels," she said.
Current recommendations call for people from age 50
to 69 to get 400 international units (IUs) of vitamin D per day and for
those over age 70 to get 600 IUs. Many researchers, however, suggest
that higher amounts may be needed.
"Higher amounts of vitamin D may be needed for the
preservation of muscle strength and physical function as well as other
conditions such as cancer prevention," said Houston. "The current
recommendations are based primarily on vitamin D's effects on bone
health."
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About Vitamin D by
Office of Dietary Supplements, National Institutes of Health |
Vitamin D is a fat soluble vitamin that is found in food and can
also be made in your body after exposure to ultraviolet (UV)
rays from the sun. Sunshine is a significant source of vitamin D
because UV rays from sunlight trigger vitamin D synthesis in the
skin.
Vitamin D exists in several forms, each with a different level
of activity. Calciferol is the most active form of vitamin D.
Other forms are relatively inactive in the body. The liver and
kidney help convert vitamin D to its active hormone form. Once
vitamin D is produced in the skin or consumed in food, it
requires chemical conversion in the liver and kidney to form
1,25 dihydroxyvitamin D, the physiologically active form of
vitamin D. Active vitamin D functions as a hormone because it
sends a message to the intestines to increase the absorption of
calcium and phosphorus.
The major biologic function of vitamin D is to maintain normal
blood levels of calcium and phosphorus. By promoting calcium
absorption, vitamin D helps to form and maintain strong bones.
Vitamin D also works in concert with a number of other vitamins,
minerals, and hormones to promote bone mineralization. Without
vitamin D, bones can become thin, brittle, or misshapen. Vitamin
D sufficiency prevents rickets in children and osteomalacia in
adults, two forms of skeletal diseases that weaken bones.
Research also suggests that vitamin D may help maintain a
healthy immune system and help regulate cell growth and
differentiation, the process that determines what a cell is to
become. |
Table 1:
Selected food sources of vitamin D
| Food |
International Units(IU) per serving |
Percent DV* |
| Cod liver oil, 1 Tablespoon |
1,360 |
340 |
| Salmon, cooked, 3½ ounces |
360 |
90 |
| Mackerel, cooked, 3½ ounces |
345 |
90 |
| Tuna fish, canned in oil, 3 ounces |
200 |
50 |
| Sardines, canned in oil, drained, 1Ύ
ounces |
250 |
70 |
| Milk, nonfat, reduced fat, and whole,
vitamin D fortified, 1 cup |
98 |
25 |
| Margarine, fortified, 1 Tablespoon |
60 |
15 |
| Pudding, prepared from mix and made
with vitamin D fortified milk, ½ cup |
50 |
10 |
| Ready-to-eat cereals fortified with
10% of the DV for vitamin D, Ύ cup to 1 cup servings
(servings vary according to the brand) |
40 |
10 |
| Egg, 1 whole (vitamin D is found in
egg yolk) |
20 |
6 |
| Liver, beef, cooked, 3½ ounces |
15 |
4 |
| Cheese, Swiss, 1 ounce |
12 |
4 |
*DV = Daily Value. DVs are reference numbers developed by the
Food and Drug Administration (FDA) to help consumers determine
if a food contains a lot or a little of a specific nutrient. The
DV for vitamin D is 400 IU (10 μg) for adults. Most food labels
do not list vitamin D content unless a food has been fortified
with this nutrient.
The percent DV (%DV) listed on the table above
tells you the percent of the DV provided in one serving. A food
providing 5% of the DV or less is a low source while a food that
provides 10-19% of the DV is a good source and a food that
provides 20% or more of the DV is high in that nutrient.
It is important to remember that foods that
provide lower percentages of the DV also contribute to a
healthful diet.
For foods not listed in this table, please
refer to the U.S. Department of Agricultures Nutrient Database
Web site:
http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.
For the
complete Fact Sheet on Vitamin D by the Office of Dietary
Supplements, click here.
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