Vitamin D and Cancer – Two Key Studies

By Martha M. Grout MD, MD(H)

Vitamin D may turn out to be the single most effective tool for cancer prevention. The more we learn about it, the more we see a consistent pattern that people who develop cancer have low levels of vitamin D.

Vitamin D is actually a hormone. It is found throughout the body and acts as a signaling mechanism to turn cells on and off. Calcitriol is the form made in optimal quantities by your body when your vitamin D blood levels are ideal. Calcitriol stops the aberrant progression of breast cancer by regulating cell cycles, forcing apoptosis (cell death). It resists signals from substances that cause cancer cells to grow, inhibiting invasion into normal tissue. Vitamin D also inhibits the formation of excessive blood vessel growth around the cancerous tumor, a process called anti-angiogenesis.[1] All in all, calcitriol, the most potent form of vitamin D, appears to be a potent chemotherapeutic agent to both prevent and treat breast cancer.

The first study of note about vitamin D and cancer came out in 1989. The Lancet reported that researchers in London found women who had vitamin D receptor-positive tumors had longer disease free intervals than women whose tumors had no measurable receptors for vitamin D.[2]

Then in the 1990s, scientists from the University of California at San Diego found that women in the sunniest regions of the United States were about half as likely to die from breast cancer as were women who lived in less sunny regions.[3] A group at the University Hospital in Quebec confirmed that vitamin D, especially when taken with calcium, significantly reduced abnormal mammograms. In fact they found women with the highest vitamin D intake had only one fourth as many abnormal densities on their mammogram as did women with the lowest intake.[4]

To date, there are two landmark studies that reveal that higher levels of vitamin D can cut in half – or more – the number of breast cancers in America.

Study #1: Creighton University School of Medicine

http://www.creighton.edu/publicrelations/newscenter/news/
2007/june2007/june82007/vitamind_cancer_nr060807/index.php

OMAHA, Neb., June 8, 2007 -- Most Americans and others are not taking enough vitamin D, a fact that may put them at significant risk for developing cancer, according to a landmark study conducted by Creighton University School of Medicine.

The four-year, randomized study followed 1,179 healthy, postmenopausal women from rural eastern Nebraska. Participants taking calcium, as well as a quantity of vitamin D3 nearly three times the U.S. government's Recommended Daily Amount (RDA) for middle-age adults, showed a dramatic 60 percent or greater reduction in cancer risk than women who did not get the vitamin.

The results of the study, conducted between 2000 and 2005, were reported in the June 8 online edition of the American Journal of Clinical Nutrition.

"The findings are very exciting. They confirm what a number of vitamin D proponents have suspected for some time but that, until now, have not been substantiated through clinical trial," said principal investigator Joan Lappe, Ph.D., R.N., Creighton professor of medicine and holder of the Criss/Beirne Endowed Chair in the School of Nursing. "Vitamin D is a critical tool in fighting cancer as well as many other diseases.

Other Creighton researchers involved in the study included Robert Recker, M.D.; Robert Heaney, M.D.; Dianne Travers-Gustafson, M.S.; and K. Michael Davies, Ph.D.

Research participants were all 55 years and older and free of known cancers for at least 10 years prior to entering the Creighton study. Subjects were randomly assigned to take daily dosages of 1,400-1,500 mg supplemental calcium, 1,400-1,500 mg supplemental calcium plus 1,100 IU of vitamin D3, or placebos. National Institutes of Health funded the study. Over the course of four years, women in the calcium/vitamin D3 group experienced a 60 percent decrease in their cancer risk than the group taking placebos.

On the premise that some women entered the study with undiagnosed cancers, researchers then eliminated the first-year results and looked at the last three years of the study. When they did that, the results became even more dramatic with the calcium/vitamin D3 group showing a startling 77 percent cancer-risk reduction.

In the three-year analysis, there was no statistically significant difference in cancer incidence between participants taking placebos and those taking just calcium supplements.

Through the course of the study, 50 participants developed nonskin cancers, including breast, colon, lung and other cancers.

Lappe said further studies are needed to determine whether the Creighton research results apply to other populations, including men, women of all ages, and different ethnic groups. While the study was open to all ethnic groups, all participants were Caucasian, she noted.

There is a growing body of evidence that a higher intake of vitamin D may be helpful in the prevention and treatment of cancer, high blood pressure, fibromyalgia, diabetes mellitus, multiple sclerosis, and rheumatoid arthritis and other diseases.

Humans make their own vitamin D3 when they are exposed to sunlight. In fact, only 10-15 minutes a day in a bright summer sun creates large amounts of the vitamin, Lappe said. However, sunscreen blocks most vitamin D production.

In addition, the latitude at which you live and your ancestry also influence your body's ability to convert sunlight into vitamin D. People with dark skin have more difficulty making the vitamin. Persons living at latitudes north of the 37th parallel -- Omaha is near the 41st parallel -- cannot get their vitamin D naturally during the winter months because of the sun's angle. Experts generally agree that the RDA* for vitamin D needs to be increased substantially, however there is debate about the amount. Supplements are available in two forms -- vitamin D2 and vitamin D3. Creighton researchers recommend vitamin D3, because it is more active and thus more effective in humans.

* RDA recommendations for vitamin D are 200 IU/d, birth-age 50; 400 IU/d, 50-70 years; and 600 IU/d, 70 years and older.

Study #2: Moores Center UCSD

In 2007, researchers at the Moores Cancer Center at University of California, San Diego (UCSD), published research findings[5] that women with higher levels of Vitamin D had lower levels of breast cancer. The researchers estimated that possibly half the cases of breast cancer and two-thirds of the cases of colorectal cancer in the United States could be prevented with higher levels of Vitamin D.

“For the first time, we are saying that 600,000 cases of breast and colorectal cancer could be prevented each year worldwide, including nearly 150,000 in the United States alone,” said study co-author Cedric F. Garland.

STUDY BACKGROUND: Inadequate photosynthesis or oral intake of Vitamin D is associated with high incidence and mortality rates of breast cancer in ecological and observational studies, but the dose-response relationship in individuals has not been adequately studied.

METHODS: A literature search for all studies that reported risk by of breast cancer by quantiles of 25(OH)D identified two studies with 1760 individuals. Data were pooled to assess the dose-response association between serum 25(OH)D and risk of breast cancer.

RESULTS: The medians of the pooled quintiles of serum 25(OH)D were 6, 18, 29, 37 and 48 ng/ml. Pooled odds ratios for breast cancer from lowest to highest quintile, were 1.00, 0.90, 0.70, 0.70 and 0.50 (p trend<0.001). According to the pooled analysis, individuals with serum 25(OH)D of approximately 52 ng/ml had 50% lower risk of breast cancer than those with serum <13 ng/ml. This serum level corresponds to intake of 4000 IU/day. This exceeds the National Academy of Sciences upper limit of 2000 IU/day. A 25(OH)D level of 52 ng/ml could be maintained by intake of 2000 IU/day and, when appropriate, about 12 min/day in the sun, equivalent to oral intake of 3000 IU of Vitamin D(3).

CONCLUSIONS: Intake of 2000 IU/day of Vitamin D(3), and, when possible, moderate exposure to sunlight, could raise serum 25(OH)D to 52 ng/ml, a level associated with reduction by 50% in incidence of breast cancer, according to observational studies.

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