Zinc and your bones

Zinc ‘Em

Your bones enjoy getting zinced.

In the e-Alert “Waiting to Exhale” (9/13/04) that I sent you earlier this week, I told you about a study that showed how the use of an inhaler – also known as inhaled corticosteroids (ICS) – to treat asthma or chronic obstructive pulmonary disease may contribute to fracture risk due to weakened bones.

That study was conducted at a Veterans Administration hospital, so nearly all the subjects were men. Now I’ve come across a study that shows how an adequate intake of dietary zinc may help men maintain a healthy bone mass density (BMD).

Researchers at the University of California, San Diego, recruited nearly 400 men between the ages of 45 and 92. The BMD was measured for each subject at the outset of the study, and again four years later. Dietary habits were assessed with food-frequency questionnaires, and zinc levels were measured with blood tests. Analysis of the data showed that both dietary zinc intake and plasma zinc both had a positive association with BMD in men. (Previous studies have already associated low zinc intake with osteoporosis in women.)

In this study, the average dietary zinc intake was just over 11 mg per day, which is the recommended daily allowance (RDA) for males over the age of 19. The best source of zinc is animal protein. Oysters deliver the highest amounts of zinc, followed by red meat and chicken. Other sources include fish, whole grains, nuts and beans.

But men, don’t let anyone tell you that the RDA of zinc – or even triple the RDA – will cause prostate cancer.

In the e-Alert “Double Blind” (7/9/03), I told you about a study that warned of elevated prostate cancer risk for men who had a daily zinc intake of 100 mg or more. But the study also found that
an intake of zinc less than 100 mg per day had no association with the 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 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 along with 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.

And for those of you who already 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), Dr. Spreen 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.

To Your Good Health,

Jenny Thompson
Health Sciences Institute

Sources:
“Zinc Intakes and Plasma Concentrations in Men with
Osteoporosis: The Rancho Bernardo Study” American Journal of
Clinical Nutrition” Vol. 80, No. 3, September 2004,
ncbi.nlm.nih.gov