May 2, 2010

USA: Zinc Linked to Prostate Cancer Survival

LITTLE FALLS, New Jersey / MedPage Today / May 2, 2010

By Ed Susman, Contributing Writer, MedPage Today

Reviewed by Robert Jasmer, MD;
Associate Clinical Professor of Medicine, University of California, San Francisco and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner

WASHINGTON -- Men diagnosed with early stage prostate cancer have an increased chance of surviving the disease if they have eaten a diet rich in zinc, researchers said here at the annual meeting of the American Association for Cancer Research.

"Those men with high zinc intake were 74% less likely to die of prostate cancer than those with the lowest zinc intake," Mara S. Meyer, MS, a doctoral candidate at the Harvard School of Public Health, said during a poster presentation (95% CI 0.10 to 0.68, P=0.005).

Researchers also reported a trend indicating that men who consumed high levels of marine omega-3 docosahexaenoic acid were 30% less likely to die of prostate cancer than men who consumed the lowest levels of the fatty acids (95% CI 0.47 to 1.03, P=0.26).

Meyer found no apparent associations between prostate cancer-specific mortality and death from other causes involving dietary intake or saturated, monounsaturated, or omega-6 polyunsaturated fatty acids.

The researchers accessed data from the Örebro Swedish Cohort, including 525 confirmed prostate cancer cases among men living in Örebro County who were diagnosed from 1989 to 1991.

At the time of diagnosis, dietary data was collected by a food frequency questionnaire specific to the Swedish diet. Use of dietary supplements was negligible in this population, which was assembled before the introduction of PSA testing.

The researchers studied intake of zinc and fatty acids -- dividing intake into quartiles. They also noted time to death and whether death was caused by prostate cancer of some other illness.

Meyer noted that 218 men died from prostate cancer, and 257 men died from other causes. Fifty of the men in the cohort are still alive.

She said most of the men in this group ingested dietary zinc through consumption of grains.

"We did not see a relationship between zinc and mortality or disease specific mortality except among those patients who were diagnosed with an early stage prostate cancer," she said.

Twenty percent of the men diagnosed with Stage II cancer or a lower grade died of the disease, while 58% percent of these men died of some other cause.

Men in the highest quartile of daily zinc consumption averaged about 15.7 mg or more of the trace metal; those in the lowest quartile consumed 12.8 mg or less, Meyer reported.

"The role of diet in cancer is always difficult to study," commented Charles Rabkin, MD, senior investigator in the Infections and Immunoepidemiology Branch in the Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, Md.

"It can be challenging to tease out what is real in these studies and what is not," he told MedPage Today. "But studies such as this one by Meyer and her colleagues definitely give us some clues to pursue." [rc]

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