SUNDAY, Feb. 11, 2007 (HealthDay News) -- In the life of a human bone, it's all downhill after 30.
That's the typical cut-off point for bone-building, so experts say it's crucial that younger people take in enough calcium and another nutrient, vitamin D, to maximize the skeleton's potential.
After age 30, those same two nutrients are key to slowing the gradual bone loss that comes with age.
Calcium isn't just important to bones, though.
"It's also important to help prevent colon cancer and for good muscle contraction, including heart muscle," said Katharine Tallmadge, a Washington, D.C., dietitian and a spokeswoman for the American Dietetic Association. "It might even be important for lowering blood pressure and helping to burn off fat."
In fact, calcium is so important to so many aspects of health that "if we don't get enough in our diet, our body pulls it from the bones," Tallmadge said. "It's a critical mineral."
The U.S. Department of Agriculture's recommended daily allowance of calcium amounts to about 1,000 milligrams a day for adults ages 19 to 50 years of age and 1,200 milligrams a day for adults over 50. While many people turn to supplements for their calcium, Tallmadge said food is always a better bet.
"I encourage people to get three high-dairy foods per day, each containing about a third of the daily requirement" she said. "That could be a cup of milk, fortified soy milk, fortified orange juice, a cup of yogurt, one-and-a-half ounces of hard cheese." Lactose-intolerant individuals should still be able to consume skim or lactate-free varieties of milk, or they can turn to fortified non-dairy products.
There are also calcium-laden food sources besides dairy products -- such as grains and vegetables -- but it's tougher for the body to get enough of the nutrient from these foods, Tallmadge said.
Bone-building doesn't rely just on calcium, however.
"The really other important factor here is vitamin D -- it's just as important, if not more important, than calcium," Tallmadge said. Without this nutrient, the body's intestines simply cannot absorb dietary calcium.
There's one big hitch, though: Vitamin D isn't found naturally in most foods. Instead, human skin uses ultraviolet sunlight to manufacture the body's own supply of this nutrient.
That was a great system in prehistoric days, when humans spent most of their lives outside and poorly clad. But it's not so ideal today.
"People aren't out so much anymore and when they do go out, they cover themselves with sunscreen," Tallmadge said. "So, we are experiencing a rash of vitamin D deficiencies -- rickets -- in children. That causes a softening of bones that can lead to bow-legs."
The problem is more pronounced in black children because natural pigments in darker skin block out much of the sun's rays. The problem has gotten so bad, Tallmadge said, that "the U.S. National Academy of Sciences is now working on a new report on vitamin D, and I believe that, unofficially, we're going to double the daily requirement from 400 units to 800 or even 1,000 units per day."
Spending more time outside -- at least a half hour or an hour at midday -- is one way of boosting vitamin D levels. Foods and supplements can also help, according to Tallmadge. "In a cup of milk, you usually get 100 units, and in a multivitamin, you might get 300 or 400 units," she said. Makers of multivitamins are now formulating higher-dose supplements based on the expected change in daily requirements, she added.
The bottom line is that everyone needs to get adequate daily amounts of both of these "partners in health," calcium and vitamin D, beginning in childhood and continuing throughout the life span.
"After our 30s, that will really help to prevent bone loss," Tallmadge said. "And remember, those losses start to really accelerate after our 50s."
More information
For more on calcium and bone health, visit the U.S. National Institutes of Health.
