May 23, 2006
The warnings against direct sunlight in the summer should be taken with a grain of salt. The vitamin D synthesized in the skin in the wonderful sunshine, prevents, amongst other things, weakening of the heart, if we look at the latest research.
Sooner or later in the course of the summer a dermatologist will appear on television to warn against direct exposure to the sun. It may lead to skin cancer and also threatening is the feared, deadly birthmark cancer, the incidence of which has risen dramatically in step with more and more people desiring a tan. This is partly true.
On the other hand it is prudent to be skeptical when someone advices us to act against what is natural. Can it really be true that the sun is so dangerous when people in our part of the world have been far more exposed to the sun through thousands of years?
Vitamin D is made in the skin when it is in the sunlight, but not from September till May, when the sun is too low on the horizon to be used for this in our part of the world. Since our diet only contains minimal amounts of this vitamin, in the wintertime we use the vitamin which has been built up in the skin in the course of the summer. During the winter approximately 85 % of the daily D-vitamin usage is taken from reserves, even in cases where the diet is rich in D-vitamin. All in all, approximately 100 mcg. is used in a day.
But what happens if the reserves are too small?
In the past half-year a number of studies have shed light over the mysteries of vitamin D. According to one study, the vitamin can help against tuberculosis, which we know was a widespread disease in the 19th and beginning of the 20th century, when many people lived under dire conditions in the cities.
Another study of over 14,000 Americans showed that the people with the largest D-vitamin reserves generally had far better lung function than those with the smallest stores. The difference is as big as the difference between ex-smokers and people who have never smoked before. A possible explanation is that the D-vitamin secures the necessary repairs of worn-out cells.
At about the same time, one of the veterans of vitamin-D research, the American Cedric Garland, concluded that now the proof that vitamin D protects against cancer (especially breast cancer, cancer of the colon and prostate cancer) was very strong. Strong enough to make him regard the connection as definite. He has reviewed all relevant research done since 1966.
Weak Heart and Arthritis
His claims can be compared to the fact that David Feldman of Stanford University now wants to conduct an experiment with calcitriol (the active form of vitamin D, which is made in body from vitamin D in the skin or the food) and ordinary arthritis medication against prostate cancer. In laboratory studies he has found that calcitriol slows the growth of prostate cancer by 25 %, while the combination with arthritis medication slows it by 70 %. A true break-through if it is true.
Everyone knows that vitamin D is necessary for the bones, but it is also necessary for the muscles. A deficiency leads to both muscle pain, weak muscles and for example, a tendency to fall in the elderly. But what about the heart? The heart is also a muscle, and weakening of the heart (cardiac insufficiency) because of atherosclerosis or increased blood pressure occurs in as many as 50,000 Danes. It is a dangerous condition with a high mortality rate.
A German study of 123 patients with a weak heart showed that on average they had quite small amounts of vitamin D in their blood stream, close to a deficiency in the traditional sense. Half of them were given supplements of 50 mcg. D3-vitamin each day for nine months. This is five times as much as the elderly are traditionally recommended given, and is also the upper limit, of what is not dangerous to ingest.
The study was too small to show a difference in mortality, but it did show something interesting. It concerns the protein TNF-alpha, which is produced by the white blood cells in connection with inflammation. TNF-alpha is meant to be a major cause of weakening of the heart. In the patients left untreated, the blood’s content of this protein increased by 5 %. In those treated, there was no worsening. This indicates a stabilizing effect on the inflammation.
This is especially interesting for another reason. TNF-alpha is an important cause of pain and swelling in arthritis. So important that new types of arthritis medication, which blocks TNF-alpha, fittingly, are considered wonder-drugs. If vitamin D decreases the effect of TNF-alpha on the weakened heart, maybe the same happens in arthritic joints. This would also confirm the old assumption that vitamin D protects against arthritis.
When in the sun, one should be sensible and avoid sunburns. Stay in the shadow if the sun is very strong and do not lie about for hours in the sun all covered up in greasy sun lotion.
Also important to know is that it is a risk rather than a virtue to stay out of the sun in the summer.
By: Vitality Council
1. Schleithof S S et al. Vitamin D supplementation improves cytokine profiles in patients with congestive heart failure: A double blind randomized placebo-controlled trial. Am J Clin Nutr 2006;83:754-9
2. Heaney R et al. Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. Am J Clin Nutr 2003;77:304-10.
3. Moreno J, Krishnan AV, Feldman D. Molecular mechanisms mediating the anti-proliferative effects of Vitamin D in prostate cancer. J Steroid Biochem Mol Biol. 2004 Nov;92(4):317-25