Calcium: How to Make It Add Up
For: How to Sell a 5¢ Supplement
for $1, February 2003
Readers ask many questions about calcium supplements. Here are some answers to your latest queries.
How much calcium do I need?
Your goal should be at least 1,000 milligrams (mg) a day from food and supplements, or 1,200 to 1,500 mg if you are a woman over 50 or a man over 65. The average American woman consumes only 625 mg; the average man, 865 mg.
Is it okay to get all of it from supplements?
Don't rely exclusively on supplements. Get as much calcium as you can from foods. Foods contain other important nutrients, some of which promote calcium absorption. Best sources: an eight-ounce serving of plain yogurt has 300 to 400 mg of calcium; a cup of milk, 300 mg (stick to low-fat or nonfat dairy products). A three-ounce serving of sardines with bones contains 370 mg; a cup of kale, 95 mg; and a cup of broccoli, 70 mg. Some kinds of tofu and soy milk contain added calcium, though this isn't as well absorbed as the calcium in cow's milk.
Which form of calcium supplement is best?
It makes little practical difference, as long as you take enough. Read the labels: check the milligrams of "elemental calcium" you're getting per pill, not the amount of calcium gluconate, for instance, or calcium citrate. No pill is pure calcium. The mineral has to be combined with something else: carbonate, citrate, gluconate, etc. Plain calcium carbonate, as found in some antacids, is most common and least expensive, and contains the highest concentration of calcium per pill. Thus, to get a given amount of calcium, you can take smaller pills, or fewer of them.
What does USP mean?
These letters on a label mean that the product is supposed to meet the U.S. Pharmacopeia's standard for dissolution and for dosage. Buy a supplement labeled "USP."
When should I take a supplement?
It's best to take most calcium supplements with meals. The acid secreted by the stomach during digestion enhances absorption of most calcium supplements, especially calcium carbonate. And the presence of other nutrients may also promote absorption. Calcium citrate is an exception: it doesn't need stomach acid to be absorbed, so you can take it any time (this makes it good for people who have disorders in which the stomach produces less acid).
If calcium needs stomach acid in order to be absorbed, will the calcium in antacids be absorbed?
This isn't a problem, especially if you take the tablets with meals, when the stomach secretes lots of acid. The real problem is antacids containing aluminum, since that mineral can impair calcium absorption substantially.
How much calcium should I take at a time?
Not more than 500 milligrams from supplements. The body absorbs larger amounts less efficiently. If you're taking 1,000 milligrams a day, take it in two or more doses over the course of the day.
How much is too much?
Up to 2,500 milligrams daily from food and supplements is considered safe. More and more foods are fortified with calcium today. If you consume those and also drink milk and take calcium pills, you may be getting too much calcium.
Is the calcium in fortified orange juice well absorbed?
Yes. Fortified OJ is a good option.
If I'm prone to kidney stones. Should I avoid calcium?
It depends what kind of stones you get, so talk to your doctor. Stone formers were once told to avoid calcium, but research now suggests that getting the recommended amounts of calcium may actually help prevent stones in many people (see WELLNESS LETTER, March 1998). But some stone formers may reduce their chances of recurrence by cutting down on calcium.
Do calcium pills contain lead?
In the past many supplements contained significant amounts
of lead, but action by manufacturers and the government have resulted
in lower lead levels. A recent study in the Journal
of the American Medical Association found that some brands of calcium
carbonate do contain some lead, but far below the federal limit. Lead
is mainly of concern for children and pregnant women taking calcium supplements.
Lead occurs everywhere, and it's not possible to guarantee absolutely
lead-free food or supplements.
Does fiber interfere with calcium absorption? What about oxalates in spinach and other foods?
Some kinds of fiber do reduce calcium absorption somewhat. If you eat a large amount of wheat bran cereal for breakfast, for instance, you might wait and take your supplement at lunch. Oxalates are substances that bind calcium. In foods rich in them (such as spinach and beans), oxalates can decrease absorption of the calcium in those foods, since the oxalates are bound with it. If you consume the recommended 1,000 to 1,500 milligrams of calcium a day, however, such dietary interactions shouldn't be a problem.
Why do women on hormone therapy need less calcium?
If you're on hormones, it's likely that your body will better utilize the calcium you consume. But it's still safest to aim for at least 1,200 milligrams a day.
Our bottom line
• Get as much calcium as possible from food. Make up any shortfall with supplements.
• Buy supplements by price. Calcium carbonate is cheapest. If it gives you gas, take smaller doses or switch to another form.
• Look for "USP" on the label.
• Take your supplement with meals to aid absorption.
• Take no more than 500 milligrams in supplements at a time.
• Keep taking the supplements. If you stop taking them, any gains in bone strength will fade.
• Get enough vitamin D, which is essential for bone health, especially if you're over 50. Normally your body makes enough D when it's exposed to a little sunlight, but after age 50 your body produces less. Get at least 400 IU a day (that's the amount in a quart of fortified milk or most multivitamin/mineral pills), 800 IU if you're over 65. Some calcium pills also contain D.
• If you are taking thyroid hormones, the antibiotic tetracycline, corticosteroids, or iron pills, talk with your doctor or pharmacist. Calcium can interfere with these and some other drugs or minerals.
UC Berkeley Wellness Letter, May 2001