Zinc Linked to Prostate Cancer Survival. What are Good Zinc Food Sources?
April 22, 2010
* In this study, men diagnosed with early stage prostate cancer had an increased chance of surviving the disease if they adhered to a diet rich in zinc.
* Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered preliminary until published in a peer-reviewed journal.
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 …rebro Swedish Cohort, including 525 confirmed prostate cancer cases among men living in …rebro 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."
Primary source: American Association for Cancer Research
Meyer M, et al "Diet, inflammation and prostate cancer survival in the Orebro Prostate Cancer Survivors Cohort" AACR 2010; Abstract 5747.
What are Good Zinc Food Sources?
An important mineral for the body for various functions
Zinc is one of the most important minerals used by the body for various functions and fortunately, there is a wide variety of zinc food sources available naturally for you to take advantage of. To give you an idea just how important it is, zinc helps in the production of about 100 enzymes in your body, builds you a healthy immune system, maintains your senses of smell and taste and is needed for DNA synthesis.
Foods Containing Zinc
Zinc is very much associated with protein foods. Thus, you may assume that most foods high in zinc are protein-rich as well. The best sources of zinc include beef, lamb, pork, crabmeat, turkey, chicken, lobster, clams and salmon.
If you are a vegetarian, you will most probably intake less zinc that those who have meat-based diets. Good zinc food sources aside from meats are dairy products such as milk and cheese, yeast, peanuts, beans, and wholegrain cereals, brown rice, whole wheat bread, potato and yogurt. Of all these vegetarian zinc foods, pumpkin seeds offer one of the most concentrated non-meat food sources of zinc.
Zinc Foods: Foods Rich in Zinc Content
Many foods contain some amounts of zinc, but to be considered a good zinc food source, the food must contain a substantial amount of the mineral relative to the calorie content. It should also contribute at least about 10% of the Recommended Dietary Allowance in one standard serving size.
Recommended Dietary Allowances for Zinc
For adults, the RDA for zinc should be about 11 milligrams per day for adult men and 8 milligrams for women. If you are lactating or pregnant, you need to put in about 3 mg more. For children, about 5 mg is needed for 4-8 year olds, and 8 mg for 9-13 year olds, while infants need only about 3 mg.
The Truth about Zinc Nutrition
The downside of taking these high zinc foods is that no matter how much of them you take in, only a mere 15%-40% of the zinc actually gets absorbed by your body overall. This is especially true for non-meat zinc food sources. Dietary fibers and phytic acid in brain prevents the absorption of zinc in your body. Phytic acid found in your brain forms a complex with the zinc that you take in, and this compound is insoluble so that it cannot be absorbed readily by your body. Whole grains are a better source of zinc than refined grains as they have the ability to produce enzymes that can destroy phytic acid. On the other hand, the zinc you get from eating meat is four times more bio-available than in grain foods.
It has been found that increasing intake of vitamins such as Vitamin C, E and B6 and minerals such as magnesium can increase zinc absorption in the body. So, it will be a good idea to add these to your daily vitamin and mineral intake.
Risks in Taking Too Much Zinc
If you are healthy and you eat a well-balance diet, you will rarely need supplements to complete your body's zinc needs. You should be careful in taking zinc supplements because too much of zinc can be potentially harmful to your body. It has been reported that intake of more than 50 milligrams of zinc (both from diet and from supplements) can lead to improper copper metabolism, altered iron function, reduction of HDL's (good cholesterol) and reduced immune function.
Zinc is very important to your body and you should make sure that you have enough zinc food source intake to complete your dietary needs. However, as always, taking too much can lead to harsh consequences, so make sure that you only take what is needed.