12/8/2012 9:16:00 AM Dr. K for Dec. 9, 2012 Calcium is found in many foods other than milk and cheese
DEAR DOCTOR K: I need to get more calcium, and I'd like it to come from foods rather than supplements. I'm a vegan, so dairy products aren't an option for me.
DEAR READER: When most people think of food sources of calcium, they think of milk and cheese. Vegans can't eat food that comes from animals, so those sources of calcium aren't available to you. But getting calcium from food sources is becoming easier for vegans. There are many vegan foods that are naturally rich in calcium, and more foods than ever are fortified with calcium, including some cereals and orange juices.
Current recommendations are that adults aim for between 1,000 and 1,200 milligrams (mg) of calcium per day. (The exact amount varies depending on your age and gender.) Many foods besides dairy products can help you meet your daily requirements.
I've put a table on my website, AskDoctorK.com, that shows how much calcium is found in common foods. For example, just a cup of fortified orange juice supplies about 300 mg of calcium. And three-quarters of a cup of some fortified cereals, such as Whole Grain Total, offers 1,000 mg of calcium.
The plant kingdom is also calcium-rich. Spinach, dried beans and nuts are among the best sources. However, the calcium content can't always be accepted at face value; some vegetables and grains contain substances that undermine calcium absorption. For example, the oxalic acid in spinach and rhubarb combines with the calcium in these plants so that it isn't readily absorbed. Insoluble fiber, such as that in wheat bran, also reduces calcium absorption. But soluble fiber, such as that in fruit pectins, does not affect calcium absorption.
If you're still struggling to get enough calcium, try making some smart substitutions. For example, choose firm tofu (258 mg of calcium per 1/2 cup serving) over soft tofu (130 mg of calcium per 1/2 cup serving).
Your body has a hard time absorbing large amounts of calcium all at once, so don't try to get most of your calcium in one meal. Instead, get it in doses of 500 mg or less, a few times throughout the day.
You can, of course, take calcium in the form of supplements. For most people, calcium carbonate is well absorbed and inexpensive; you should take the supplements with meals. If you take a medicine to reduce stomach acid (like a proton pump inhibitor or an H2 blocker), it's better to take calcium citrate, because it is better absorbed than calcium carbonate.
Finally, a note about calcium. There is strong evidence that the combination of calcium (through dietary sources or supplements) combined with vitamin D can protect against the thinning of bones. However, the evidence that calcium supplements without vitamin D can prevent bone fractures is not very strong. Whether you're a vegan or not, and regardless of your gender, if you're over age 50 I'd recommend you talk with your doctor about a vitamin D supplement to go along with the calcium in your diet.
(Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.)