How Much Calcium Do You Really Need?

A major medical panel suggests that many women don’t need calcium and vitamin D pills to protect against bone fractures. Not all experts agree

by Leslie Pepper
Photograph: Christopher Silas Neal

The promise is appealing: If you’re religious about taking calcium supplements, you can fend off the bone thinning known as osteoporosis and prevent the debilitating fractures that often come with the condition. That’s why in 2012, Americans spent $1.2 billion on calcium supplements and $652 million on vitamin D pills, which can boost thebody’s absorption of calcium.

But recently the effectiveness of those supplements has been questioned. Last year, after reviewing 16 randomized, controlled studies as well as 28 observational studies, the U.S. Preventive Services Task Force concluded that daily supplementation with calcium and vitamin D does not protect healthy postmenopausal women from experiencing fractures and therefore cannot be recommended. The group also said that while data are sparse, there’s no evidence that supplementation will benefit premenopausal women either.

Does this mean we should toss our calcium and vitamin D supplements in the garbage? To answer that question, you first need to understand the reasons these supplements were recommended in the first place.

Why Your Body Needs Calcium and D
Bones seem solid, but their structures are continuously being broken down and renewed. During the breakdown phase, bone cells called osteoclasts dissolve old bone, explains Ethel S. Siris, MD, director of the Toni Stabile Osteoporosis Center at the Columbia University Medical Center. In the renewal phase, cells called osteoblasts pull calcium and other minerals from the blood. These minerals join with collagen (a protein that provides structure) to re-form bone tissue. The activities of the osteoclasts and osteoblasts are balanced so that the right amount of bone is always being created and destroyed.

When we reach our thirties, however, that balance begins to shift. The -breaking-down process becomes dominant, and women lose slightly more bone tissue than they build. That loss really accelerates for a few years after menopause, when estrogen levels plummet. Estrogen regulates the activity of the osteoclasts, and “in its absence, the osteoclasts become too aggressive and they suck in too much bone,” says Siris. This is why -osteoporosis—which affects 7.4 million women over 50—becomes such a significant danger after menopause.

But the bones aren’t the body’s only customer for calcium; the mineral is also essential to the functioning of the heart, muscles and nerves. “The body tries to maintain a constant level of calcium in the blood, so if you’re deficient, your body is going to take it from your skeleton, which is the biggest storage house for this mineral,” says Andrea Sikon, MD, chair of the department of internal medicine and geriatrics at the Cleveland Clinic. For this reason, an insufficient intake of calcium can speed up the weakening of bones.

A shortfall in vitamin D, which your body can manufacture if you’re exposed to sunlight, may also lead to brittle bones. That’s because you need a derivative of vitamin D called calcitriol to facilitate the intestine’s absorption of calcium.

The conventional recommendations for a daily intake of 1,000 milligrams of calcium and 600 international units of D (from all sources—food and possibly supplements) are intended to avert shortages that would end up weakening bones and leading to osteoporosis.

Preventing osteoporosis is a way to head off the fractures that often have terrible consequences. For instance, for a year after a hip fracture, women over 65 are twice as likely to die as they would have been without the injury. Since fewer than one in four American women get the recommended doses of calcium from food and many don’t spend enough time in the sun to get sufficient D (one study estimates 42 percent of Americans are deficient), most medical experts have urged the use of supplements to make up the difference.

The Controversy Over Supplements
It has been well documented that sufficient calcium and vitamin D are necessary for strong bones. But whether supplementation translates into fewer fractures is open to dispute. In 2005 two British studies concluded that calcium pills didn’t prevent fractures, even when taken in combination with vitamin D. The next year, the Women’s Health Initiative, a large American trial, found that postmenopausal women ages 50 to 79 who took a combination of 1,000 milligrams of calcium and 400 milligrams of vitamin D for seven years were no less likely to break their hips than women who took a placebo. While several studies haveshown fracture reductions with supplementation, the task force still felt the bulk of the evidence militated against taking the typical doses of vitamin D and calcium.

However, leading experts on osteoporosis (including the National Osteoporosis Foundation and almost all the specialists Morecontacted) are not convinced that calcium and vitamin D supplements are useless. “We can’t make calcium, your body loses some every day, and if you don’t get it from food, you’re going to rob it from bone,” says Connie M. Weaver, PhD, director of the Women’s Global Health Institute at Purdue University. “So how are you going to replace the loss if you don’t have enough in your diet?”

In addition, studies considered by the task force generally did not address the possibility that some participants might not have taken their pills every day. When the Women’s Health Initiative researchers reanalyzed their data, looking only at the women who claimed they faithfully took the supplements, the outcome was much different. The compliant subgroup had a 30 percent reduction in hip fractures.

What’s more, vitamin D is important for muscle synthesis. Among its good effects: boosting strength in the lower body and decreasing body sway and instability. Perhaps for that reason, research shows that taking a D supplement of 700 to 1,000 IU a day reduces the risk of falling (which of course is a precursor to fractures), a benefit that calcium alone does not bestow.

The Bottom Line
Most experts agree that the safest and probably most effective source of calcium for strong bones and overall health is diet, not supplements. “The nutrients in our diets are like the instruments in a symphony orchestra. They play together, and one depends upon the other for the total impact,” says Robert P. Heaney, MD, an endocrinologist at Creighton University Medical School.

How do we ensure we’re getting enough? Women 50 and under need 1,000 milligrams of calcium a day, which translates to about one eight-ounce container of plain yogurt and two eight-ounce glasses of milk. Women over 50 would need to add about an ounce of hard cheese to get to the recommended 1,200 milligrams. 

If you’re not getting enough calcium in your diet, that doesn’t mean you should take a daily 1,000-milligram pill. Instead, figure out how much you’re getting in a typical day, then supplement that amount only enough to make up the shortfall. (See “Calculate the Calcium in Your Diet” on page 114.) Or, suggests Weaver, think in terms of having three servings of milk-based products a day. For every one you miss, you need a 300--milligram supplement of calcium. Those supplements are available in two main forms: calcium carbonate and calcium citrate. “Either is fine,” says Siris. 

You also need 600 international units of vitamin D (if you’re over 70, up that to 800). While we get some vitamin D from foods like fatty fish and fortified orange juice and milk, we manufacture most of it in our bodies when the ultraviolet rays from the sun strike the skin. Which means many of us are deficient.

Speak to your doctor about getting your vitamin D levels checked. The best measure is your blood level of a D form known as 25-hydroxyvitamin D. Have the test done in April or May, when levels tend to be lower, advises Miriam Nelson, PhD, professor of nutrition at the Friedman School of Nutrition Science and Policy at Tufts University.

And remember that vitamins and minerals are only part of the story. Engaging in weight-bearing activity—anything that forces your bones and muscles to work against gravity—is crucial to strengthening bones. Aim to exercise for 30 minutes at least five days a week by, say, walking or gardening. Exercise also helps maintain muscle
strength, coordination and balance, which in turn help prevent falls and related fractures.

Next: More's Ultimate Anti-Aging Meal Plan

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First Published Tue, 2014-02-04 12:15

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