The widely circulated
rumor that Kurt Vonnegut told newly graduating MIT students to "wear sunscreen" is
actually a myth. Had he really made such a recommendation, it would have
for his "Breakfast of Champions" to include a vitamin
Vitamin D deficiency appears to be an increasingly prevalent, but largely unrecognized,
problem. According to various studies, the prevalence of vitamin D deficiency
ranges from 4.2% to greater than 90%, depending on the race, health, and lifestyle
of the people surveyed, their geographic location, and the criteria used to
diagnose deficiency. While it is well known that severe vitamin D deficiency
causes rickets, osteoporosis, and osteomalacia, it is not generally known that
even a mild deficiency may cause such problems as muscle weakness, fibromyalgia,
impaired balance, and depression.
In the course of human evolution, the main source of vitamin D has been exposure
to sunlight. Ultraviolet B (UVB) light from the sun stimulates the synthesis
of vitamin D from a precursor molecule in the skin. Food, on the other hand,
is a relatively poor source of the vitamin; only cod-liver oil, oily fish,
and vitamin D-fortified dairy products provide more than trace amounts. With
respect to vitamin D-fortified milk (the main food source of the vitamin for
many people), many commercial brands of milk contain less than the label indicates.
In one study, 26 of the 42 milk samples (62%) contained less than 80% of the
amount of vitamin D claimed on the label, and no vitamin D was detected in
3 of the 14 samples of skim milk tested.1
Because most diets do not provide adequate amounts of vitamin D, people who
do not receive enough sun exposure are at risk of developing a deficiency.
Those with dark skin and elderly people are at greatest risk, because they
have a reduced capacity to synthesize vitamin D in response to sunlight exposure.
In addition, people who live above 35 degrees latitude or in areas with a lot
of atmospheric pollution may not obtain adequate amounts of UVB, even if they
do go out in the sun. In modern America, most work and leisurely activity is
done indoors. Because of the fear of developing melanoma, other skin cancers,
or wrinkles, many people purposely avoid the sun, or else block the beneficial
UVB by applying sunscreen to their body. While excessive sun exposure is certainly
unwise, sunlight deficiency seems to be an ever-increasing problem.
Several years ago, five patients were reported with severe myopathy associated
with vitamin D deficiency.2 Each of these patients had been confined to a wheelchair
because of severe weakness and immobility. In all five patients, treatment
with high-dose vitamin D for 4 to 6 weeks resulted in a resolution of body
aches and pains and a return of normal muscle strength. In each case, vitamin
D deficiency had not been suspected initially, and the symptoms had been attributed
to other causes.
Vitamin D deficiency also might be a contributing factor to depression, particularly
seasonal affective disorder (winter depression), which occurs during the time
of the year when vitamin D levels are the lowest. In a small randomized trial,
administration of a single 100,000-IU dose of vitamin D was more effective
than a month of daily phototherapy (light therapy) in patients with seasonal
affective disorder.3 Moreover, in the group treated with phototherapy, there
was a significant correlation between the improvement of depression and the
improvement in vitamin D status. That observation suggests that the effectiveness
of phototherapy in cases of seasonal affective disorder is due at least in
part to an increase in vitamin D synthesis in the skin.
Fibromyalgia and generalized aches and pains have also been attributed by some
investigators to vitamin D deficiency. In a recent study of 150 residents of
Minneapolis, Minnesota, who presented with persistent, nonspecific musculoskeletal
pain, 93% were found to have either marginally (65%) or severely (28%) deficient
serum concentrations of 25-hydroxyvitamin D.4 The patients in this study were
not given vitamin D supplements, so a cause-effect relationship between their
symptoms and vitamin D deficiency was not established. However, in a study
of 299 patients in Saudi Arabia with chronic low back pain associated with
abnormally low serum levels of 25-hydroxyvitamin D, supplementation with vitamin
D for 3 months resulted in clinical improvement in every case.5
Numerous studies have shown that vitamin D supplementation helps prevent age-related
bone loss and reduces the risk of fractures. Part of the benefit of vitamin
D in relation to fracture prevention appears to be due to an improvement in
balance and/or muscle strength, which leads to fewer episodes of falling. In
a double-blind study, supplementation of elderly individuals with 800 IU per
day of vitamin D reduced body sway (a measure of balance) and reduced the frequency
of falling by 47%, compared with a placebo (p < 0.04).6
The potential benefits of vitamin D are not limited to better musculoskeletal
health and mood. A recent epidemiological study indicated that supplementation
with vitamin D during the first year of life is associated with a 92% reduction
in the risk of developing schizophrenia in males, although females were not
benefited.7 There is also some evidence that adequate vitamin D intake may
help prevent multiple sclerosis, other autoimmune diseases, and some types
A complete nutritional history should include an assessment of both dietary
vitamin D intake and sunlight exposure. Vitamin D status can be determined
by measuring the serum concentration of 25-hydroxyvitamin D. When vitamin D
supplementation is indicated, the minimal amount should be 400 IU per day for
adults. Some studies have shown that 800 IU per day is more effective for maintaining
bone density than is 400 IU per day. While researchers had long believed that
doses higher than 1,000 IU per day are potentially toxic, more recent evidence
has suggested that doses up to 4,000 IU per day are safe.8 I usually recommend
800 to 1,000 IU per day for patients who need supplemental vitamin D. For individuals
with fibromyalgia or depression, in whom the possibility of vitamin D deficiency
is being considered, the initial dose may be as high as 2,000 IU per day, tapering
to 1,000 IU per day after a 2-4 weeks. In lieu of vitamin D supplementation,
it has been suggested that adequate vitamin D status can be attained by daily
exposure of the hands, face, and arms, or arms and legs, to sunlight for a
period equal to 25% of the time it would take to develop a light pinkness of
the skin (i.e., one-quarter of the minimum erythema dose).9 That level of exposure
is said to be sufficient to satisfy the bodyÕs vitamin D requirement,
and to synthesize enough of the vitamin to store in the skin for use at times
when sunlight exposure is inadequate.
Alan R. Gaby, MD
1. Holick MF, et al. The vitamin D content of fortified milk and infant
formula. N Engl J Med 1992;326:1178-1181.
2. Prabhala A, et al. Severe myopathy associated with vitamin D deficiency
in western New York. Arch Intern Med 2000;160:1199-1203.
3. Gloth FM III, et al. Vitamin D vs broad spectrum phototherapy in
the treatment of seasonal affective disorder. J
Nutr Health Aging 1999;3:5-7.
4. Plotnikoff GA, Quigley JM. Prevalence of severe hypovitaminosis
D in patients with persistent, nonspecific musculoskeletal pain. Mayo
Clin Proc 2003;78:1463-1470.
5. Al Faraj S, Al Mutairi K. Vitamin D deficiency and chronic low back
pain in Saudi Arabia. Spine 2003;28:177-179.
6. Pfeifer M, et al. Effects of a short-term vitamin D and calcium
supplementation on body sway and secondary hyperparathyroidism in elderly
women. J Bone Miner Res 2000;15:1113-1118.
7. McGrath J, Saari K, Hakko H, et al. Vitamin D supplementation during
the first year of life and risk of schizophrenia: a Finnish birth cohort
study. Schizophr Res 2004;67:237-245.
8. Vieth R, et al. Efficacy and safety of vitamin D3 intake exceeding
the lowest observed adverse effect level. Am
J Clin Nutr 2001;73:288-294.
9. Holick MF. Vitamin D: importance in the prevention of cancers, type
1 diabetes, heart disease, and osteoporosis. Am
J Clin Nutr 2004;79:362-371.