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Many people who are not exposed to adequate amounts
of sunlight are suffering from significant vitamin D deficiencies, especially
if their diets are also low in it. Therefore, the authors of this study
are recommending that the RDA (recommended daily allowance) for adults
be raised to 1000 IU.
Sunlight exposure of the skin is known to be the most
important source of vitamin D. This study looked at the vitamin D status
of sunlight-deprived individuals compared with those with normal sunlight
exposure. This Danish study used veiled Arab women and veiled ethnic Danish
Moslem women (Caucasian) and compared them the Danish population (controls).
Diet analysis of each group was also performed.
Serum levels of 25-hydroxyvitamin D were used as estimates
of vitamin D status. Parathyroid hormone (PTH) was also measured to control
for secondary hyperparathyroidism. Oral intake of vitamin D and calcium
were estimated through a historical food intake interview performed by
a trained clinical dietician.
Veiled Arab women displayed extremely low values of
25-hydroxyvitamin D, less than one-sixth that of the controls. The veiled
Danish women had levels less than one-half that of the controls. PTH was
found to be greatly increased amongst veiled Arab women, whose values
were nearly 6 times higher than controls. The veiled Danish women had
levels almost 3 times higher than controls.
Compounding the lack of sunlight problem was the fact
that the veiled Arab women had very low dietary vitamin D intake (including
supplementation), about 13 times lower than Danish Moslems and 7 times
lower than the controls.
The authors conclude that severe vitamin D deficiency
is prevalent amongst sunlight-deprived individuals. This deficiency may
be the result of a combination of limitations in sunlight exposure and
a low oral intake of vitamin D. Since the oral intake amongst veiled ethnic
Danish Moslems was approximately 600 IU, but they were still vitamin D-deficient,
they propose that 600 IU is insufficient to maintain proper vitamin D
status when sunlight exposure is limited. Therefore, they propose that
a minimum RDA of 1000 IU per day should be adopted.
J Intern Med 2000;
247: 260-268
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