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Vitamin D may fight cancers

Study to point out value of sunshine and supplements

By Henry L. Davis NEWS MEDICAL REPORTER
Updated: 05/31/07 6:45 AM

Scientists have long noticed that people who live in northerly regions of the world like Buffalo have higher cancer rates than those in places with more sunshine.
A growing amount of research now indicates why: vitamin D.
The “sunshine vitamin” — because our skin produces it when exposed to sunlight — is known for building healthy bones. But, otherwise, the nutrient has never received much attention. That’s likely to change.
Dozens of laboratory and geographical studies in recent years suggest that vitamin D deficiency is common and that the risk of cancer, as well as other illnesses, is higher among individuals with low vitamin D levels.
In April, the head of Roswell Park Cancer Institute made the case for vitamin D in a presentation at the 2007 meeting of the American Association for Cancer Research. Next month, scientists are expected to release the first major study of vitamin D in humans that shows a significant protective effect against a range of cancers.
“The data are very persuasive,” said Dr. Donald Trump, president and chief executive officer of Roswell Park.
He and others warn that there have been no long-term studies directly comparing vitamin D to a placebo, and they may never be done because of the cost and complexity.
Still, the existing evidence is compelling enough for prostate, colon, breast and other cancers that experts advise taking supplements, and the American Cancer Society is revising its skin cancer prevention recommendations, with the vitamin D findings in mind. This gets to the dilemma about vitamin D.
Promising medical claims for vitamins A and E failed to meet earlier expectations, so scientists are cautious about what they say about vitamin D. Moreover, if vitamin D is beneficial and exposure to the sun is harmful, people will require clearer information about the best way to get it and how much they need.
“The answer is to use common sense,” said Dr. Bruce Hollis of the Medical University of South Carolina.
He, like many other vitamin D researchers, advocates balancing small amounts of sun exposure with larger amounts of vitamin D supplements from pills or fortified food.
Experts at the Institute of Medicine of the National Academy of Sciences set recommended dietary requirements of nutrients. For vitamin D, the agency has recommended 200 IU (international units) per day up to age 50, 400 IU per day to age 70 and 600 IU per day for individuals over 70. They also set an upper limit of 2,000 IU that’s considered the most a person should safely take to avoid vitamin D toxicity.
The recommended intakes are based on levels needed to prevent rickets, a softening of the bones in children from vitamin D deficiency potentially leading to fractures and deformity. Vitamin D boosts the absorption of calcium, which is important to bone health.
Hollis and 14 other nutrition experts consider the guidelines outdated and called for an urgent overhaul in an editorial in the March edition of the American Journal of Clinical Nutrition. They complained that the guidelines give the public the impression that they are receiving enough vitamin D when an overwhelming amount of research indicates they are not.
“The current dietary requirement is a joke,” Hollis said.
The group of experts did not identify new limits. But vitamin D advocates suggest the recommendation should be increased to 1,000 IU and perhaps as high as 2,000 IU. They also say the upper limit for daily intake could safely be set at 10,000 IU.
“We need clinical studies to confirm the links between vitamin D and different cancers, as well as studies to learn the sufficient doses to inhibit cancer,” said Gary Schwartz, a vitamin D researcher at Wake Forest University. “The thing is that’s going to be very expensive and take 20 years. The question is, what do we do in the interim?”
Vitamin D doesn’t fit the classic definition of a vitamin, which is a substance the body can’t make and must be supplied in the diet.
There are different forms and sources, including from plants and animals. Some foods, such as salmon and other oily fish, naturally supply small amounts. Other foods, such as milk, are fortified with the vitamin.
Cholecalciferol, or vitamin D3, is the naturally occurring form of vitamin D. It’s made in large quantities when sunlight strikes bare skin or can be taken as a supplement. African- Americans and other people with dark skin, as well as residents of regions that receive less sun, produce less vitamin D and experience higher cancer rates.
The various forms of vitamin D are converted by the kidneys and liver into hormones — also confusingly referred to as vitamin D — that do the real work.
Research suggests vitamin D helps regulate cell growth and differentiation, the process that determines what a cell becomes. This is important in cancer. Cells should change normally, such as the way skin cells form throughout life, and not proliferate wildly to produce a malignant tumor.
As such, vitamin D is seen both as a protectant against cancer and as a potential treatment.
“Vitamin D may inhibit cells from growing and dividing and may kill tumor cells in some cases. It may also cause cancer cells to change into more mature, harmless cells,” said Dr. Candace Johnson, senior vice president for translational research at Roswell Park.
In recent years, the cancer center has put together a large, well funded vitamin D research team.
The researchers have demonstrated in laboratory tests that several forms of vitamin D control cells in ways that can prevent cancer and regulate proteins that affect tumor growth.
The institute also recently started a clinical trial of high-dose vitamin D replacement in individuals with high risk of lung cancer, and other scientists there are looking at boosting the effect of chemotherapy by adding vitamin D.
“The evidence for vitamin D deficiency makes sense,” said Johnson. “Our ancestors lived without clothes near the equator and got plenty of sunlight. But over thousands of years, people moved north, put on clothes, started living and working in buildings, and using sun screen. We have moved away from the sun.”
Indeed, Trump has tested hundreds of his and other doctors’ patients from Buffalo and found 70 percent of them vitamin D deficient.
Although cautious about the vitamin’s potential, he said individuals should take low-cost supplements and have their vitamin D level regularly measured, like cholesterol, to make sure they are not getting too much.
hdavis@buffnews.com