Skeleton Crew - sources of calcium to maintain good health

Vegetarian Times, July, 1999 by Mary Jane Horton

Calcium is necessary for much more than just healthy bones. Are you sure you know how to get enough?

As the most abundant and active mineral in the body, calcium is the ultimate utility player: It regulates blood pressure, enzyme activity, muscle contraction and heartbeat; helps blood clot; controls the release of neurotransmitters (chemicals that send nerve impulses); and is believed to reduce symptoms of PMS and the risk of colon cancer. And a new study conducted at Purdue University in Indiana found that 1,000 milligrams (mg.) of calcium a day helped prevent weight gain and actually promoted weight loss in women aged 18 to 31.

Think of your bones as the body's calcium bank. Because the mineral is deposited and withdrawn by the body as needed, it's essential for us to get sufficient amounts to build up and maintain these stores. But that can be trickier than it sounds. According to experts, most people don't get the amount of calcium they need. Research from the Framingham Nutritional Studies, published in the Journal of the American Dietetic Association in 1997, estimates that only about half of Americans get the recommended levels (see "Your Magic Number," p. 85, for dosages). Even people who are vigilant about consuming enough calcium may not be absorbing enough. Factors such as lifestyle habits (smoking, poor diet, prescription medication) and nutrient interactions (e.g., iron blocks calcium uptake) play a huge role in inhibiting absorption and, in some cases, actually cause calcium to be leached from the bones.

The main risk associated with a calcium deficiency is osteoporosis, a disease characterized by low bone mass and the structural deterioration of the bones. Yet osteoporosis isn't caused by a lack of calcium, but by its poor absorption in the body and accelerated excretion rates. Nor is osteoporosis an "old woman's" disease. Men and women of all ages are at risk, if not equally so. According to the National Institutes of Health, osteoporosis affects 28 million Americans, 20 percent of whom are men. And every year 80,000 men and 200,000 women suffer a hip fracture due to osteoporosis, translating into a 20 percent increased risk of death within the year.

ABSORB IT, STORE IT

Since almost all the calcium in your body is stored in the bones (the rest circulates throughout the body or is stored in your teeth), it's important to get a lot of it when your bones are still building rather than deteriorating--which starts happening earlier than you might think. "In adulthood, women's and men's bones get more porous and start breaking down as early as age 20," says Kathy McManus, M.S., R.D., manager of clinical nutrition at Brigham and Women's Hospital in Boston.

The stockpiling of calcium is an ongoing process, but building your bones to full capacity early in life is your best defense against osteoporosis. Keith Block, M.D., clinical assistant professor at the University of Illinois at Chicago's College of Medicine, explains that building our bone mass up to 100 percent is crucial since we lose about 20 percent of it as we age. He notes that the people at the greatest risk of a deficiency are teenagers in the process of building their stores; pregnant or lactating women, whose bodies use and therefore require more calcium; people who don't get enough vitamin D (which is critical for calcium absorption); and those with generally poor diets.

"It's always best to get calcium from food," says Block. "That's the way nature intended for it to be used as part of a total package. The challenge is making sure you get enough from food." The first step toward building up your stores is eating plenty of calcium-rich foods. Look at your diet and examine the average amount of calcium you get daily (see "Beyond Milk," below, for some of those amounts). Of course, the trick is getting it absorbed by the small intestine, from which it enters the blood, circulates and is eventually deposited into the bones. Poor eating habits can literally rob your bones of calcium, making a healthy diet more important than singling out calcium intake. "Americans have overly acidic diets because of the amounts of meat, salt, alcohol [and caffeine] they eat and drink," says Susan Lark, M.D., author of The Chemistry of Success (Bay Books, 1999). She explains that once an acidic environment is created, the body naturally seeks to neutralize that condition and does so by drawing calcium, an alkaline mineral, out of the bones and into the bloodstream. This leaching process leaves less of the mineral available to maintain bone strength.

There are other factors that affect calcium absorption. "People who eat a very high fiber diet may have lower absorption rates," says McManus. "Phytic acid, found in wheat bran, and the phosphates found in brown rice decrease absorption. But as long as you get calcium from green leafy vegetables, soy and other vegetarian sources, your intake should be sufficient." Iron is another inhibitor. It's important to take iron and calcium supplements separately and not to eat iron-rich foods (lentils, kidney and lima beans) with your calcium sources.