Despite the nationwide popularity of milk advertisements featuring celebrities sporting white milk mustaches, milk consumption in the United States has been declining for the past 30 years. As a result, calcium nutrition among Americans of all ages has continued to deteriorate. Some experts point out that children and young people today drink so much soda, juice, and other beverages instead of milk that their calcium intake has fallen to half the level of the 1950s, raising concerns about a potential osteoporosis crisis.
The human skeleton reaches its peak at around age 20. Without sufficient calcium intake by that age, people enter their 30s—when bone density begins to decline—already at a disadvantage. Meanwhile, a growing body of research is reporting the remarkably varied functions of calcium, underscoring the importance of a calcium-rich diet for people of every age.
For those who consume plenty of dairy products, meeting the recommended calcium intake is not difficult. A child who drinks three or four glasses of milk a day, for example, gets enough calcium. But as the importance of calcium receives greater attention, confusion about how to consume it and which foods provide it has compounded the problem.
Getting Calcium Through Food Is Better
It is better to obtain calcium from food than from supplements. Foods provide not only calcium but also other nutrients that help the body absorb it. A 1994 National Institutes of Health conference concluded that achieving optimal calcium intake requires changes in dietary habits, including greater consumption of dairy products and calcium-rich vegetables.
Experts also point out that excessive salt and protein intake, particularly animal protein, causes calcium to be excreted in the urine. Eating a hamburger, for example, can result in the loss of as much as 23 milligrams of calcium. Coffee, by contrast, causes a loss of only about 2 to 3 milligrams per cup, less than initially feared.
Dairy Products
Milk remains the best source of calcium. It is not only rich in calcium but also contains lactose and added vitamin D, which help with absorption. People who cannot digest lactose can still obtain plenty of calcium by drinking lactose-free milk. By weight, plain nonfat yogurt contains more calcium than milk, but it lacks vitamin D. Among frozen dairy desserts, nonfat frozen yogurt is a better calcium source than ice cream or ice milk.
Hard cheeses are very high in calcium regardless of their fat content. Cottage cheese, however, provides less calcium than milk or yogurt unless it has been fortified.
For children who are allergic to milk or become constipated when they drink it, calcium-fortified soy milk or calcium supplements are alternatives.
Vegetables
Kale, collard greens, turnip greens, mustard greens, Chinese cabbage, chicory, and bok choy are excellent vegetable sources of calcium. Broccoli is a more widely recognized source, but its calcium content is lower.
Although spinach is high in calcium, its oxalic acid binds to the mineral and interferes with absorption, so only about 5 percent is absorbed. However, the oxalic acid in foods such as spinach and rhubarb does not prevent the absorption of calcium from other foods eaten with them. Another type of plant acid found in dried beans also interferes with calcium absorption to some extent, though less severely than oxalic acid.
Dietary fiber generally has little effect on calcium absorption. However, fiber such as wheat bran partially interferes with the absorption of calcium in foods consumed with it, including milk served with bran cereal.
Other Foods
Canned sardines with their bones intact are an excellent source of calcium. Three ounces of sardines contain as much calcium as eight ounces of milk. Canned salmon with the bones provides about half as much calcium as sardines.
Other good sources include dry-roasted soybeans, molasses, figs, beans, sesame seeds, almonds, oranges, and calcium-fortified orange juice. The acids in juice help calcium absorption, making it particularly beneficial for older adults whose stomachs produce insufficient acid.
Supplements
For people who cannot obtain enough calcium through food, or find it difficult to do so, supplements are the next best option. Calcium supplements can be considered safe as long as intake does not exceed 2,000 milligrams a day and the person is not at risk of developing calcium-containing urinary stones.
However, no one can say with certainty how much calcium taken in pill form will actually be absorbed. Calcium citrate is a better choice, particularly for older adults with low stomach acid. When taken with meals, however, calcium carbonate is an inexpensive and effective source.
Taking calcium supplements before bedtime is preferable because it gives them more time to remain in the stomach. If possible, avoid taking them with foods containing wheat bran. People who also take iron or an iron-containing vitamin supplement should take them at different times so that calcium does not interfere with iron absorption.
When buying a calcium supplement, check the amount of elemental calcium in each tablet, rather than its total weight. Tablets containing 500 milligrams or less of calcium are more readily absorbed.
Vitamin D must not be overlooked, either. Most people today do not get enough of this valuable vitamin, which helps the body absorb calcium. Recent research suggests that the recommended daily intake for adults should be 800 IU rather than the current recommendation of 400 IU. Although milk is now fortified with vitamin D, its actual content often falls short of the stated 400 units per quart.
People produce 90 percent of their vitamin D through skin exposed to ultraviolet rays from sunlight. It is therefore advisable to expose the skin to sunlight for at least 10 to 15 minutes a day. Alternatively, consume fatty fish, cod liver oil, or vitamin D supplements.
