Three new studies from the Moores Cancer Center at the University of California, San Diego, have strongly linked vitamin D with lower risk for breast, colon, and kidney cancers.

In the breast cancer study, researchers analyzed the blood-fluid (serum) levels of vitamin D in 1,760 individuals and found that those who had the lowest levels of 25-hydroxyvitamin D had the highest rates of breast cancer, and that as the levels of vitamin D increased, breast cancer rates dropped.

In the colon cancer study, published in the February 2007 issue of the American Journal of Preventive Medicine, scientists reviewed findings from five different studies that took blood samples from healthy volunteer donors, and then followed up for 25 years. Researchers divided 1,448 participants into five equal groups according to the serum levels of vitamin D and found that those who had 34 nanograms of vitamin D per milliliter of blood (ng/ml) were 50 percent less likely to have colon or rectal (colorectal) cancer than were those with the lowest levels. In the studies, vitamin D levels ranged from below 13 ng/ml to 52 ng/ml. Doctors projected that those who get a total of 2,000 IU of vitamin D3 per day from diet, supplements, and sunshine will be 66 percent less likely to get colorectal cancer compared to those with the lowest vitamin D levels.

In the kidney cancer study, published in the International Journal of Cancer, researchers for the first time were able to use data from 175 countries and found that those who live closest to the equator—where sunlight is strongest—have the least kidney (renal) cancer.

Reference: Journal of Steroid Biochemistry and Molecular Biology; Feb., 2007, Vol. 103, No. 2.

A large, new Chinese study has found that calcium protects against cancer of the colon and rectum (colorectal). The Shanghai Women’s Health Study, from 1997 through 2000, enrolled 73,314 Chinese women aged 40 to 70, average age 55.5, who were living in urban Shanghai. Researchers followed up for an average of 5.7 years and, excluding the first two years of follow up, found that those with the highest amounts of calcium in the diet were 40% less likely to develop colorectal cancer than were those with the lowest dietary calcium. By the end of the follow up period, there were 129 reported cases of colon cancer, and 91 reported cases of rectal cancer.

     The study is significant because of the large number of participants, and because the Chinese diet typically includes less calcium than does the Western diet. Previous large U.S. studies: the 1991 Women’s Health Initiative with 161,808 women, the 1976 Nurse’s Health Study I with 122,000 women, and the 1989 Nurse’s Health Study II with 125,000 women, did not report any link between calcium and colorectal cancer.

Reference: International Journal of Cancer; 2006, Vol. 119, No. 12, 2938-42.

People with higher blood-fluid (serum) levels of selenium, the essential trace mineral, had significantly lower risk for bladder cancer, according to findings from a new Belgian study. Doctors conducted a case-control study that examined 178 persons with bladder cancer (cases) and 362 persons without bladder cancer (controls). The researchers took into account age, sex, smoking habits, and occupational hazards, and measured fruits and vegetables in the diet, as well as levels of vitamins A (retinol), C, and E, and total antioxidants in the blood.

After adjusting for these factors, scientists determined that those who had the highest levels of selenium—more than 96 mcg per liter of blood (mcg/l)—were 70% less likely to develop bladder cancer as were those who had the lowest levels of selenium; less than 82.4 mcg/l. Doctors also found that those in the middle group, whose selenium levels were between 82.4 mcg/l and 96 mcg/l, had 52% less risk of developing bladder cancer compared to those with the lowest levels. The researchers pointed out that, for each 10 mcg/l increase in the selenium level, the risk for bladder cancer dropped by 14%. The average person has about one liter of blood per 30 pounds of body weight.

According to the September, 2006, issue of Lancet Oncology, researchers first noticed the connection between selenium and cancer 40 years ago, when geographic studies reported lower death rates for cancer in regions of the U.S. with high levels of selenium. The first double-blind selenium-cancer study began in 1983 when researchers recruited 1,312 patients with histories of skin cancer at seven dermatology clinics located in low-selenium areas of the U.S. Doctors administered 200 mcg of selenium per day—about twice the average amount Americans consume—or a placebo, and followed up 10 years later. While results were not significant for skin cancer, there were 41% fewer total cancers, and 18% fewer deaths from cancer for selenium users compared to placebo.

Reference: International Journal of Urology; 2006, Vol. 13, No. 9, 1180-4.

Antioxidant supplements tended to increase cancer-survival rates, shrink tumors, and did not interfere with cancer chemotherapy treatments, according to a new review.

Researchers from the Institute for Integrative Cancer Research and Education in Evanston, Illinois, reviewed 19 randomized, clinically-controlled trials involving 1,554 participants, most of whom had advanced or relapsed cancer. Seven of the trials used glutathione, four trials used melatonin, two trials used vitamin A, two trials used an antioxidant mixture that included beta-carotene and selenium, and four additional trials used, individually, N-acetylcysteine, vitamin C, vitamin E, or ellagic acid, an antioxidant in fruits and nuts such as cranberries and walnuts.

Scientists concluded that chemotherapy treatments were at least as effective in participants who took antioxidant supplements as in those who took placebo, and that the antioxidant group had similar or better survival rates than did the placebo group. In 18 out of the 19 trials, tumors shrank and responded as well or better for those who took antioxidants compared to those who took placebo. In 15 out of 17 trials that analyzed the toxic effects of the chemotherapy—such as diarrhea, losing weight, damaging nerves, and low blood counts—the antioxidant group had similar or lower toxicity rates compared to placebo.

There has been a long-running debate in the medical community about whether or not antioxidant supplements alter the effect of cancer chemotherapy. One theory is that—because chemotherapy works by creating oxidants—antioxidants may diminish this effect. Another theory is that antioxidants reduce the toxic effects of chemotherapy. The study authors noted that, by reducing side effects from chemotherapy, antioxidant supplements may permit people to continue cancer chemotherapy treatment without stopping, interrupting, or reducing dosing, which may improve cancer health outcomes.

Reference: Cancer Treatment Reviews: March 28, 2007.