Mother always said, "Drink your milk," but what she really meant was that your growing body needed calcium and that three glasses of milk a day efficiently delivered the amount needed to stay strong and healthy.
Today, some question the health benefits of milk but what remains clear is that calcium -- a mineral found in nuts, beans, fortified foods and leafy, dark-green vegetables, as well as dairy products -- is necessary to build strong bones and guard against a host of diseases.
In fact, the National Academy of Sciences Institute of Medicine, the federal agency that sets nutritional standards, in 1997 raised the recommended dietary intake for calcium for adults 19 to 50 from 800 milligrams a day to 1,000 milligrams a day.
Thanks to widespread publicity, the disease of osteoporosis, in which the bones shrink, grow fragile and become vulnerable to fractures, has become the best-known threat to people who don't ingest enough calcium during their growing years.
What's less-well known is that calcium is also necessary for the heart, muscles and nerves to function properly, for blood to clot and to ward off periodontal disease, since the mineral is a large component in the teeth and jawbone.
Consumption Less Than Recommended
National nutrition studies have shown that many women and young girls consume less than half the amount of calcium recommended to grow and maintain healthy bones. Seniors, especially post-menopausal women, are also at risk, because many elderly aren't milk drinkers and suffer from decreased appetite, which makes it hard for them to meet their nutritional needs.
"It's really important to get enough calcium, because it plays a big part in blood pressure regulation and it helps control many metabolic processes in your body," says Becky Roach, a registered dietitian at the University of Illinois McKinley Health Center in Urbana.
In addition to consuming enough calcium, nutritional experts say it's important to lead a healthy lifestyle, because certain habits can leach calcium right out of our bones. Smoking is one offender; excessive alcohol is another. Likewise, medication such as steroids can strip the body of calcium and lead to bone loss.
That's because 99 percent of the calcium in the human body is contained in the bones. The remaining 1 percent circulates in the blood and soft tissues. Without enough calcium in the diet, the body begins breaking down the bones, which contain our emergency supply of calcium. Over the years, if the body breaks down more than it replaces, osteoporosis can set in.
Calcium is especially important during childhood, adolescence and early adulthood because this is the period when the bones form, grow and reach their maximum weight and density. By the time a person reaches 30, bone size peaks and soon after that, the body begins to lose bone mass.
There is some evidence that a calcium-rich diet, regular weight-bearing exercise, abstaining from smoking and keeping alcohol intake moderate help keep bones strong and prevent bone loss. After menopause, when a woman's body produces less estrogen, many women, especially those considered to be at risk for osteoporosis, opt for estrogen replacement therapy, which makes bones stronger and aids in the absorption of calcium.
Men, too, are vulnerable to osteoporosis, especially as they age, and doctors may recommend testosterone for those found to be at risk. With growing awareness about the calcium needs of older Americans, the National Academy of Sciences Institute of Medicine in 1997 recommended that adults 51 and older consume 1,200 milligrams of calcium a day.
The Calcium-Vitamin D Connection
Like many vitamins and minerals, calcium doesn't work independently in the body. It is closely connected with Vitamin D, which is found in foods such as fortified dairy products, egg yolks, fish and liver and is absorbed through the skin after direct exposure to sunlight.
Without a daily intake of 400 to 800 international units of vitamin D daily, the body is unable to absorb enough calcium from food, experts say. People who live in northern climates with long winters, the elderly and the housebound are especially at risk.
"Vitamin D. is necessary for calcium to metabolize in your body, and that's why we fortify food with both vitamin D and calcium," explains Roach, of the University of Illinois at Urbana.
She also points out that unlike vitamin D, which can build up in the fatty tissues, it is virtually impossible to ingest too much calcium. The water-soluble mineral is metabolized in the kidneys, which means any excess will simply be excreted.
Fortifying Food With Calcium
Today, increased awareness about the importance of calcium has led many food manufacturers to fortify a wide variety of foods with this crucial mineral. It is now possible to buy orange juice, apple juice, soy products, frozen waffles, breakfast cereals, graham crackers, other grains and a variety of snack foods that have been fortified with calcium.
"In the last 10 to 15 years, more fortified products have become available and companies are putting it in to sell the product," says Reed Mangles, PhD, registered dietitian and nutrition adviser for the Baltimore, Maryland--based Vegetarian Resource Group. "There's just so much publicity about osteoporosis in this country, and women are looking for alternative sources of calcium."
Non-Dairy Sources of Calcium
Eating dairy products such as milk, cheese and yogurt is still probably the easiest way to meet your daily calcium requirement. Dairy is one of the four basic food groups, and products made from milk are widely available. Experts recommend three servings of dairy products daily, but be sure to seek out low-fat versions of these foods since they are high in fat, which can be unhealthy when consumed in large quantities.
However, "It's entirely possible to meet your calcium needs without using dairy products," Mangles says. "If you're going to drink a cup of milk, you can drink fortified soy milk."
According to the Vegetarian Resource Group, 4 ounces of tofu or three-quarters of a cup of collard greens contains as much calcium as a cup of cow's milk.
Dark green, leafy vegetables such as kale, broccoli, bok choy, mustard, turnip and other greens are all rich in calcium. Spinach, beet greens, rhubarb and chard are calcium-rich, but they also contain a substance called oxalic acid, which binds to the calcium and keeps it from being absorbed by the body, Mangles says.
Canned salmon, sardines and other fish are also high in calcium, provided you eat the bones. Almonds, Brazil nuts and sesame all contain high amounts of calcium, as does food made with these products, such as tahini and almond butter. Two tablespoons of almonds or Brazil nuts, for example, contain 50 milligrams of calcium. Ditto for beans, especially soybeans, navy beans and Great Northern beans. There are 100 milligrams of calcium in a cup of cooked beans.
Dried figs are also high in calcium, with five figs providing 250 milligrams. And tofu offers another calcium source. But the amount of calcium varies from brand to brand, and Mangles says consumers need to read labels carefully, choosing tofu products that are processed with calcium sulfate, and not nigari, which are the two substances commonly used to make soy curdle.
Still, the emergence of fortified food gives vegetarians and vegans a host of calcium options that didn't exist 15 years ago. Most grains today are fortified with vitamins and minerals including calcium. Even some junk food contains calcium, such as milkshakes that contain real milk products and hamburger buns made of calcium-fortified wheat.
"If you were just eating collard greens, you'd have to eat 2.5 cups a day to meet your calcium requirement," says Mangles. "My recommendation today is to eat some fortified food and some fruits and vegetables and nuts and beans."
Deciphering Food Labels
Roach, the University of Illinois dietitian, says that with the advent of fortified foods, consumers must become savvy interpreters of listed ingredients. The calcium content on packaged foods is generally listed as a percentage of the U.S. Recommended Daily Allowance. And because for most people that is 1,000 milligrams, consumers should multiply the USRDA by 10 to calculate the amount of calcium in one serving. For example, soy yogurt with 10 percent of the USRDA would have 100 milligrams of calcium in one serving.
"It's very confusing to see all the different terminology when you're reading labels, and you have to determine if what you're reading is for one serving of food or the entire container," says Roach.
For those who can't get enough calcium in their diets, experts recommend an over-the-counter calcium supplement that should be taken with meals in several doses throughout the day, which helps it absorb more readily into the system. Some doctors advise people to use antacids, such as Tums, which are relatively cheap as well as high in calcium, because they are pure calcium carbonate (or chalk). Others recommend that patients go directly to a calcium supplement. Either way, experts say the supplement should be used in conjunction with calcium-rich food, not as a substitute.
"People should try wherever possible to eat the foods," says Roach, "because they're getting other nutrients as well as calcium."
Denise Hamilton is a Southern California-based writer whose work appears in publications including Apria.com, the Los Angeles Times' Health section and New Times Los Angeles. Her first book, "The Jasmine Trade," is published by Scribner.
