Your mother always said drink your milk. Strong bones, strong teeth … we’ve all heard the litany.
These days calcium in the diet is said to reduce colon cancer, lower blood pressure and ease the symptoms of PMS. If you believe all the hype, calcium could be called a miracle mineral, yet if you dig deeper you’ll find the scientific community does not always agree.
For years it was thought a diet high in calcium contributed to the development of kidney stones since calcium is a major component in about 80 percent of all stones. Doctors routinely told their patients with kidney stones to limit their calcium intake. The stones, which can cause severe pain, often become lodged in the kidneys or in the ureters, the tubes that carry urine to the bladder.
However further research, which started in 1993, challenged those previous assumptions. A large study found that men who ate the most dietary calcium were actually the least likely to develop stones. A later study showed comparable results in women.
Experts suspect calcium prevents stone formation by binding with oxalate, a substance also found in many kidney stones. Oxalate is found in fruits and vegetables such as spinach, and other foods such as peanuts and chocolate. In some people, excess oxalate in the urine stays in the kidney and starts accumulating into a stone. But when oxalate is consumed with calcium, the mineral binds to the oxalate and the two are excreted in the stool, before they can contribute to stone formation. Test results differed when calcium supplements were taken. Because supplements are often taken between meals, there is no available oxalate in the stomach to bind with the calcium.
Not every scientist agrees with this evidence. Skeptics stress the difficulty of establishing calcium as the factor in this reduction in risk.
Calcium is the major player in another controversy. While calcium is essential to building strong bones, does it help prevent osteoporosis later in life, as some nutrition experts insist? The experts disagree. Osteoporosis is characterized by a gradual thinning and weakening of the bones. In the disease’s advanced stages, vertebrae can become so fragile they easily collapse, which can lead to a debilitating curving of the spine. This increasing fragility can also mean greater risk of fractures.
A professor at the Harvard School of Public Health conducted a 12-year study which challenged the assumption that additional calcium could prevent this illness. In this test, close to 80,000 women ages 30-55 were studied. They found no evidence that women who consumed one to three servings of dairy of milk or other calcium-rich foods, reduced the risk of hip fractures, the standard measure for osteoporosis. These results contradict earlier trials.
Calcium has long been theorized to reduce the risk of colon cancer by protecting the cells within the colon. The colon’s interior is lined with a layer of cells called epithelial cells, which are similar to cells that make up the outer layer of skin. Recent findings published in the New England Journal of Medicine add to this earlier evidence. In a four-year trial, 843 adults at high risk due to a history of colorectal tumors were randomly assigned to take either 1,200 milligrams of supplemental calcium per day, or a placebo.
Overall, those in the calcium group were about 20 percent less likely than the others to be diagnosed with at least one tumor.
Various trials have shown low-calcium diets can go hand in hand with the risk of high blood pressure. Roughly 50 million Americans have high blood pressure, also called hypertension.
Called the “silent killer” this ailment often does not produce symptoms for years, secretly damaging arteries and organs throughout the body.
Researchers in Argentina found women might influence their children’s risk of high blood pressure in the future by taking calcium during pregnancy. Other studies done in California showed teen-agers significantly lowered their blood pressure by taking 1,500 mg of calcium, equal to five cups of milk, a day.
In one of the largest-ever studies of PMS, researchers gave one group of women calcium and other group placebos. The calcium group reported a 50 percent drop in four major PMS symptoms, pain, water retention, mood swings and food cravings. The leaders of this study believe PMS may be a signal that women are not getting enough calcium.
The medical experts do agree on one thing. Adequate calcium is important for maintaining strong bones.
Experts recommend drinking calcium-fortified beverages, such as soy milk and orange juice.
Broccoli and kale also contain calcium.
Another key to keeping calcium levels high is through retention, since smoking, coffee and physical exercise all deplete calcium stores.