For a long time we have known that vitamin D plays an important role in keeping
bones strong. Vitamin D
is essential in combination with calcium to reduce the risk of osteoporosis and to speed
the healing of bone fractures. For this reason, we supplement our milk with vitamin D, and
the U.S. Food and Drug Administration recommends a daily dose of 400 international units.
However, recent scientific studies strongly suggest additional roles for vitamin D in
maintaining good health, and also suggest that the daily dose should be two to five times
the current recommended minimum.
Long term studies of large numbers of people are beginning to show that lower intake of
Vitamin D is associated with a higher risk of developing cancer. Scientists have observed
a relationship between low blood levels of vitamin D and the occurrence of prostate cancer,
and low vitamin D levels are associated with a higher risk of developing colon cancer and
other cancers of the digestive system. There may even be a link between the risk of
certain autoimmune diseases and low levels of vitamin D.
Although for a long time the standard recommendation has been a daily allowance of 400
international units of vitamin D per day, new information strongly suggests that most
people should get up to 2000 units per day. It is very unlikely that doses up to 10000
units per day will cause any toxic effects.
The sun is a potent source of vitamin D, and any time ultraviolet radiation hits the skin,
Vitamin D is synthesized naturally in the body. Unfortunately, ultraviolet radiation is
also linked to the development of skin cancer, so perhaps we should keep using our
sunscreen and look to other sources for our daily vitamin D dose.
It is difficult to get adequate doses of vitamin D from food alone. The two best food
sources are fatty fish and vitamin supplemented milk, but a typical glass of milk only
contains 50 to 100 international units of vitamin D. A typical serving of salmon may
contain 300 to 400 units, and a can of sardines has between 200 and 300 units.
To get a regular daily dose of vitamin D in the 1000 to 2000 international unit range, it
is probably easiest and most effective to add a daily supplement to normal good nutrition.
Vitamin D supplements (the vitamin D3 type are best) are readily available at a reasonable
price. Considering the evidence accumulating steadily that adequate doses of vitamin D
provide substantial health benefits, this is one investment in daily supplements that may
pay significant dividends in quality and quantity of life.
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