Other studies have suggested that higher vitamin D levels help protect against colon, prostate, and breast cancer, but a long-term study of 50,000 men by researchers at Harvard School of Public Health suggests vitamin D may reduce the risk of all cancers. The study, which is still under review for publication, found that men who consumed higher levels of vitamin D reduced their overall cancer risk by at least 30 percent, according to lead author, Ed Giovannucci. The findings were statistically significant, he said, and a separate study of women is expected to produce similar results.
This is big stuff. Imagine an anti-cancer drug that reduced overall cancer deaths by 30%. It would be hailed as a medical wonder. But it is much better to avoid getting cancer in the first place.
Another interesting angle here is this huge benefit against cancer is coming from a vitamin that is not classified as an antioxidant. For decades researchers have been trying to use antioxidant free radical quenching vitamins such as beta carotene, vitamin E, and vitamin C to reduce cancer, heart disease, and other diseases. The results have been pretty disappointing. Now the biggest potential benefit turns out to be from a vitamin which is most likely operating by a mechanism unrelated to prevention of free radical damage.
Keep in mind that this result will not carry over to the world as a whole. Some populations are consistently exposed to enough sunlight for their skins to synthesize the amount of vitamin D that they need. But a 30% reduction in cancer in America looks to be possible. That would be an enormous boon, both lengthening lives and reducing medical costs.
This latest study does not come as a surprise. It builds upon a larger body of epidemiological evidence for a wide array of benefits from consumption of greater quantities of vitamin D. A previous analysis found that addition of Vitamin D and calcium to grains would reduce the incidences of fractures and colon cancer and save $3 billion per year for a cost of less than $20 million per year.
Currently, the federal government requires that manufacturers enrich cereal-grain products with five nutrients—iron and the vitamins thiamine (B1), riboflavin (B2), niacin (B3), and folate (B9). The total cost to U.S. consumers of adding calcium and vitamin D to the list should be no more than about $19 million a year, Harold L. Newmark of Rutgers University and his colleagues report in the August American Journal of Clinical Nutrition. Conservatively, they calculate, this investment would spare U.S. consumers some $3 billion in direct medical costs from illnesses and injuries stemming from their inadequate intake of calcium and vitamin D.
The human body can generate 10,000 to 12,000 international units (IU) of vitamin D from a half-hour of summer-sun exposure. The National Academies recommend that adults, depending on their age, get from 200 to 600 IU of the vitamin each day.
In practice, however, most people in the United States get a daily intake from food and sun exposure well below that recommended intake, especially during winter. People living in the United States and Europe or farther from the equator have trouble getting enough sun to maintain adequate blood concentrations of the vitamin. When people heed dermatologists' warnings about preventing skin cancer by limiting sun exposure and using sunscreen, they also reduce their vitamin D production.
Even the officially recommended amounts of vitamin D are probably well below the level that would provide maximal benefit. Click through on the following link to read an argument for getting 800 to 1000 IU of vitamin D daily.
Lots of aspects of modern society reduced sun exposure. For example work in office buildings contributes to a reduction in sun exposure and reduced vitamin D synthesis. So does the message from dermatologists to avoid sun as a way to lower the risk of skin cancer. This has led to a debate in medical circles about whether sun exposure increases or decreases net cancer risk. This debate has so upset the dermatologists that vitamin D researcher Michael Holick was forced out of Boston University's dermatology department since he veered too far from accepted orthodoxy among dermatologists about sun exposure. My own view is that moderate sun exposure most obviously decreases net cancer risk and that the evidence is building up to the point that science is going to vindicate Holick. By the way, Holick thinks the top daily safe dose for vitamin D is at least 5000 IU, which is much higher than the current officially recommended maximum daily dose (which is 2000 IU if memory serves).
Another element of modern society that is causing vitamin D deficiency is the migration of darker skin peoples to places further away from the equator. This has put them in environments where their darker skin pigment blocks the sun too much to allow sufficient vitamin D synthesis.
Global location and skin color also affect the amount of vitamin D a person's skin manufactures. UV intensity falls as one moves from the equator toward Earth's poles, increasing latitude. Evolution compensated by selecting for increasingly unpigmented skin in northern populations, says Boston University endocrinologist Michael F. Holick.
Melanin pigment protects the skin from the damage of UV rays but also lowers the skin's production of vitamin D. In the March American Journal of Clinical Nutrition, Holick quantifies this effect: Fair-skinned people who sunburn easily and rarely tan need just 2 to 10 percent as much sun exposure to produce a unit of vitamin D as do people with the darkest skin.
Given that blacks especially have higher rates of lactose intolerance the fortification of milk with vitamin D is not reaching a group most in need of dietary vitamin D.
Consumption of fruits appears to boost the level of the biologically active form of vitamin D in the blood. Though if you do not have enough vitamin D in your body the fruit can not make up for that deficiency.
Vitamin D does protect men from prostate cancer. In the USA and many countries, milk is fortified with vitamin D. Even so, calcium in mik and other foods lowers the amount of usable vitamin D in the body. Eating several servings of fruit a day keeps the level of vitamin D raised.
A high circulating level of the biologically active form of vitamin D (1,25(OH)2 vitamin D [1,25(OH)2D) is known to inhibit formation of cancer in the prostate. Eating a diet high in meat and milk and low in fruit reduces the level of this anti-prostate cancer vitamin. "High intakes of calcium and phosphorus, largely from dairy products, lower circulating 1,25(OH)2D level, and sulfur-containing amino acids from animal protein lower blood pH, which also suppresses 1,25(OH)2D production."
Fortification of foods with calcium alone may well have the effect of lowering the rate of colon cancer while boosting the rate of prostate cancer. One concern I have with the combined calcium and vitamin D food fortification is that the level of vitamin D added needs to be set to be enough to more than cancel any effects of calcium on increasing prostate cancer risk.
It is clear that in America the fortification of only milk with vitamin D is inadequate. The decreased consumption of milk prevents milk from being an avenue for boosting vitamin D in a growing portion of the population. Fortification of other milk products such as cheese and yogurt and even a boost in the level of fortification of milk seems called for. Also, the potential benefit of grain fortification with vitamin D is so large that it warrants urgent consideration. Higher vitamin D in diets would reduce the risk of cancers, type I diabetes, osteoporosis, unexplainable muscle and bone pain, hypertension, a wide array of auto-immune diseases (including multiple sclerosis), and possibly other disorders and diseases as well.
The studies about vitamin D and health are great news. The incidence of several major diseases can be reduced for a trivially low cost. We need many more such discoveries that show how to cheaply improve human health.
|Share |||Randall Parker, 2005 January 03 02:33 AM Aging Studies|