Federal health officials recommend 1,000 milligrams of calcium per day for people younger than 50, but some are overdoing it.

RENEE MONTAGNE, HOST:

And when it comes to a healthy diet - especially for women - nutritionists and doctors will tell you, you need calcium. The question is, how much is enough? Here's NPR's Patti Neighmond.

PATTI NEIGHMOND, BYLINE: It's a fact most people know well - calcium helps build bones and keeps them strong, which is why people like 26-year-old Vera Yakovchenko eat lots of calcium-rich foods.

VERA YAKOVCHENKO: I eat yogurt - probably excessively - and cheese. I drink almond milk which has fortified calcium.

NEIGHMOND: And people who think they don't get enough calcium in their diet, often take supplements - like 62-year-old Marcia Hughes.

MARCIA HUGHES: About 1,500 to 2,000 milligrams a day.

NEIGHMOND: Federal health officials recommend women and men under the age of 50, consume 1,000 milligrams of calcium a day. The recommendation goes up to 1,200 after the age of 70, for men; and after menopause, for women, when a major drop in estrogen causes bone loss.

So if 1,200 milligrams is good, is taking more better? No, says Dr. Ethel Siris.

DR. ETHEL C. SIRIS: You need enough. You don't need extra.

NEIGHMOND: Siris directs the Osteoporosis Center at Columbia University Medical Center.

SIRIS: Extra calcium does you no good. And there is a small risk that if you take too much, you might get a kidney stone.

NEIGHMOND: The body can only handle 600 milligrams at once. And if too much calcium builds up in the bloodstream, it's excreted through the kidneys - which can cause a kidney stone. That's been known for awhile. But recently, Siris says, there's another concern.

SIRIS: There have been some studies which have suggested that calcium - and perhaps it's excess calcium - may calcify the coronary arteries in susceptible people - which is not good; it may precipitate heart attacks.

NEIGHMOND: One study showed people who take calcium supplements had a slightly higher risk of having a heart attack. Endocrinologist Robert Eckel, with the American Heart Association.

DR. ROBERT ECKEL: And so this has raised the question as to whether there's, potentially, some danger in using over-the-counter calcium supplements - which, of course, go beyond, simply, our usual dietary intakes of calcium. So there's, at this point in time, a bit of a signal in this direction. But still a controversial area, and I don't think anyone has stepped forward yet, to say that calcium supplements should be abandoned.

NEIGHMOND: Particularly since calcium is so critical for bone health. Even so, the heart studies do raise questions, says Eckel, that need to be answered. But even if it turns out there's only a very small, increased risk of heart attack, why take that risk? Osteoporosis expert Siris says, just don't take excess calcium. How do you do that? Count your calcium - starting, first, with the foods you consume every day.

SIRIS: If you're somebody having a glass of milk with your breakfast, that's 300 milligrams of your needed 1,200. A container of yogurt will give you 2- to 300 milligrams - and you can read the label. A couple of ounces of cheese will give you about 300 milligrams.

NEIGHMOND: Three servings a day of dairy, pretty much meets the calcium requirement for an adult under 50. And if you don't eat dairy, you can find calcium in other foods as well.

SIRIS: Lots of the foods we eat have little bits of calcium. So even if someone is not consuming any dairy at all, they're probably still getting somewhere between 200 and 400 milligrams a day of calcium, from the average American diet.

NEIGHMOND: Vegetables like broccoli, bok choy and turnip greens have lots of calcium. So do oranges, figs, salmon and sardines. Cereals and soy milk often have added calcium as well as vitamin D, which is needed to help the body absorb calcium.

So after estimating your daily intake of calcium from food, then you can calculate whether you need to take an extra supplement. You may just need 300 or 600 milligrams extra, and maybe not every single day.

Patti Neighmond, NPR News. Transcript provided by NPR, Copyright NPR.