Higher calcium intake associated with lower digestive cancer risk

A study of 492,810 men and women has found a protective effect for calcium against digestive system cancers in both men and women.

In the February 23, 2009 issue of the American Medical Association journal Archives of Internal Medicine, Yikyung Park, Sc.D., of the National Cancer Institute and colleagues evaluated data from 293,907 men and 198,903 women who participated in the National Institutes of Health-AARP Diet and Health Study. The participants' intake of calcium from food and supplements was determined from responses to dietary questionnaires completed upon enrollment. Forty-nine percent of the men and 57 percent of the women used multivitamins that contain calcium, and 14 percent of the men and 41 percent of the women used individual calcium supplements.

Over the seven year average follow-up period, 36,965 cancers occurred among the male participants and 16,605 in the women. Although calcium intake was not associated with the combined risk of all cancers in men, for women, cancer risk declined with an intake of up to 1,296 milligrams per day, after which there appeared to be no further reduction. Women at this level of calcium intake experienced a 7 percent lower risk of all cancers compared with those whose intake was 494 milligrams or less. Cancers of the digestive system, including esophagus, stomach, pancreas, liver, and colorectal cancer, were reduced in both men and women whose calcium intake was high. For men whose total calcium intake was among the highest 20 percent at 1530 milligrams or more, there was a 21 percent lower risk of colorectal cancer compared with men whose intake was lowest at 526 milligrams, and for women whose intake was in the top one-fifth at 1881 milligrams per day, the risk was 28 percent lower. No signficant association with prostate or other nondigestive system cancers was observed. Continue Reading

Higher vitamin E levels in smokers linked with reduced pancreatic cancer risk

The February, 2009 issue of the American Journal of Clinical Nutrition reported the finding of researchers at the National Cancer Institute, the University of Michigan, and the National Public Health Institute in Helsinki, Finland, of an association between higher concentrations of alpha-tocopherol (the most biologically active and plentiful form of vitamin E in most human tissues) and a lower risk of pancreatic cancer in smokers. Smoking, diabetes and obesity are among the known risk factors for this deadly form of cancer.

Rachel Z. Stolzenberg-Solomon and colleagues evaluated data from 29,092 men who participated in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, a double-blind placebo-controlled trial which sought to determine the effect of alpha-tocopherol and beta-carotene supplementation on the prevention of cancers in smokers between 1985 and 1988. Over up to 19.4 years of follow-up, 318 cases of pancreatic cancer were diagnosed.

For participants whose serum alpha-tocopherol levels at the beginning of the study were among the top 20 percent of participants, the risk of developing pancreatic cancer was 48 percent lower than those whose levels were in the lowest fifth. Among the 27,111 subjects for whom dietary questionnaire responses were available, for those who had the highest polyunsaturated fat intake at over 9.9 grams per day there was an even greater reduction in pancreatic cancer risk observed in participants with the highest vitamin E levels, a finding that could be explained by vitamin E’s ability to counteract polyunsaturated fats’ pro-oxidant effect.

While no protective association was observed between dietary intake of vitamin E and pancreatic cancer risk in this study, the authors note that dietary intake as estimated by questionnaire responses is not precise, and that serum vitamin concentrates may be more biologically meaningful due to their reflection of the combined effects of intake, absorption and utilization as well as depletion caused by oxidative stress. “Our results support the hypothesis that higher concentrations of serum alpha-tocopherol may protect against pancreatic carcinogenesis in smokers,” they conclude. “Further research is needed to evaluate our findings in other populations, particularly relative to exposure factors that influence endogenous oxidative stress.”

High dose vitamin C injections slash tumor growth in mice

An article published in the August 5, 2008, issue of the Proceedings of the National Academy of Sciences reported that injections of ascorbate (vitamin C) reduce the weight and growth rate of tumors by half in mouse models of ovarian, pancreatic and Brain cancer, while leaving normal cells unharmed.

Researchers at the National Institutes of Health (NIH) tested ascorbate in 43 tumor and 5 normal cell lines to determine a concentration that decreases cell survival in cancerous cells without resulting in toxicity to healthy cells. They subsequently injected a dose of 4 grams ascorbate (neutralized with sodium hydroxide) per kilogram body weight once or twice per day into immune-deficient mice with implanted ovarian, pancreatic and glioblastoma (brain) tumors. "At these high injected doses, we hoped to see drug-like activity that might be useful in cancer,” explained lead author Mark Levine, MD, who is the chief of the Molecular and Clinical Nutrition Section of the National Institute of Diabetes and Digestive and Kidney Diseases at the NIH.

Dr Levine’s team found that injecting the animals with ascorbate decreased tumor growth and weight by 41 to 53 percent. While metastases occurred in 30 percent of the mice with brain tumors, none appeared in animals injected with vitamin C. No adverse effects of vitamin C treatment were noted. Continue Reading