Do zinc supplements increase the risk of prostate cancer?

Double Blind

As usual, the sound bites and headlines have it all wrong (or at least partly wrong) as they deliver their latest provocative copy along the lines of: “Zinc Supplements Increase Risk of Prostate Cancer.”

The study that prompted these warnings actually contradicts the scare headlines. And, as usual, we’ll cut through the hype to get the real news. Because there is some important new information about zinc that men should be aware of.

Going overboard

Researchers at the National Cancer Institute used data from the Health Professionals Follow-Up Study (involving more than 50,000 men for over 14 years) to specifically examine 434 cases of advanced prostate cancer. They found that a “chronic zinc oversupply” may raise the risk of prostate cancer.

So if you look only at the superficial details, the news can be made to sound dire: compared to men who took no zinc supplements at all, men who took more than 100 mg per day for more than 10 years had almost THREE TIMES greater risk of prostate cancer.

And who takes more than 100 mg of zinc daily? Very few people, I would guess. Certainly no one who is paying attention to the widely-published warnings that zinc may be potentially toxic over a prolonged period at daily doses of more than 100 mg. At that level, research shows heart problems and anemia can occur.

But here’s the real clincher: the authors of the study stated that zinc intake from supplement doses of 100 mg per day or less was “not associated with prostate cancer risk.” Which is in complete contradiction to the headline: “Zinc Supplements Increase Risk of Prostate Cancer” (reported on Ivanhoe Newswire). Furthermore, the researchers stressed that other factors may have combined with the high zinc dosage to create the cancer risk.

All of a sudden, this dire warning doesn’t sound so dire.

Call off the dogs

Unless you go out of your way to add extra zinc to your vitamin regimen, chances are you’re not getting anywhere close to 100 mg. Most multivitamin supplements provide well under 50 mg of zinc. And you would need to eat dozens of oysters and a few servings of beef every day to even approach 100 mg of dietary zinc.

Meanwhile, the zinc that you are getting is very useful. In addition to enhancing the immune system, zinc helps repair damaged tissues, inhibits the abnormal clotting that contributes to cardiovascular disease, and is one of the key nutrients needed for DNA reproduction and repair. Zinc also helps keep your vision healthy. In the e-Alert “Feast Your Eyes” (9/5/02) I told you about the Age-Related Eye Disease Study (sponsored by the National Eye Institute), which recommends a daily intake of 80 mg of zinc for anyone in a high-risk group for age-related macular degeneration (AMD).

So once again we see scare headlines doing a disservice to consumers who might easily be led to believe that taking any zinc at all is dangerous. Obviously, nothing could be further from the truth.

A pinch of copper

One final note for those of you who do include zinc in your daily supplement intake: it’s a good idea to add a little copper as well.

In the e-Alert “Aim High” (5/7/03), HSI Panelist Allan Spreen, M.D., noted that zinc can create a copper deficiency, and vice versa. And Jonathan V. Wright, M.D., agrees, stating that, “Zinc supplements should usually be offset by a small amount of copper, 1-2 mg daily.” Fortunately, many multivitamins already take care of the dual zinc/copper need with a low dose of copper.

I hope there aren’t any men out there that saw these inaccurate reports about prostate cancer and tossed out their multivitamins that contained zinc. Because unless you’re taking way too much, the zinc you’re getting is doing plenty of good, and virtually no harm.

To Your Good Health,

Jenny Thompson
Health Sciences Institute

Sources:
“Zinc Supplement Use and Risk of Prostate Cancer” Journal of the National Cancer Institute, Vol. 95, No. 13, 1004-1007, 7/2/03, jncicancerspectrum.oupjournals.org
“Zinc Supplements Increase Risk of Prostate Cancer” Ivanhoe Newswire, 7/3/03, Ivanhoe.com
“Zinc – a Prostate Cancer Risk?” Health Daily News, 7/4/03, health24.co.za
“Large Zinc Doses may Raise Prostate Cancer Risk” NutraIngredients, 7/2/03, nutraingredients.com
“Preventing Colds, Flu, and Infection” Jonathan V. Wright, M.D., Nutrition & Healing, April 2001, wrightnewsletter.com