The Owner's Manual  For Your Skeleton!

Calcium in the Body
Calcium is crucial to maintain life; without it we would die. Just about every cell in the body, including those in the heart, nerves and muscles, relies on calcium to function properly. Bones require calcium to maintain their strength. In the body, calcium is found in three places:

     in the skeleton;
     in the cells;
     in the blood.

The levels of calcium in the blood determines the availability of calcium to the various organs and the skeletal structure.

Hormones control the amount of calcium in the blood. Everyone constantly loses calcium through urine, sweat, and feces, and it is renewed with calcium from the bones. In the process, the body constantly breaks down and rebuilds bones. Ultimately, the body's calcium is replaced by calcium from food or mineral supplements.

Absorbing Calcium
The body carefully regulates its calcium absorption. The body does this in three ways:

    It absorbs calcium directly from the food that you eat. This is the preferable way for the body to get calcium.

    It takes calcium from your bones if there is not enough available when it is needed.  This makes the bones thinner and  fragile, and is the major cause of osteoporosis.

    It slows down the amount of calcium leaving via the urine, returning some to the blood stream where it remains available to organs and cells.

The average person absorbs 30 to 70 percent of the calcium she or he eats.  While milk is a source of calcium, it certainly is not the ideal way to get your daily dose. Dairy products, with the exception of skim products, are loaded with saturated fat. Fat is directly related to heart disease and cancer. Dairy products are also high in protein. There are other reasons to worry about milk, too. Cows are routinely fed antibiotics. These are then passed directly on to the milk drinkers; antibiotics are detectable in one out of three cartons of milk. Many people are also allergic to milk, and over three-fourths of the world's population is lactose-intolerant, which means their bodies lack the enzymes necessary to digest milk.

The Need for Calcium
Throughout life, people's calcium needs change. Until about age 35, people consume more calcium that their bodies lose. But around age 45, the body begins to slip into "negative calcium balance", slowly the body loses more calcium than it takes in. As shown above, how rapidly calcium is lost depends, in part, on how much protein is in the diet, and the kind of protein it is. The loss of too much calcium can lead to "soft bones," or osteoporosis.

 Reducing Calcium Loss
Since the 1920's researchers have known that diets that are high in protein, especially animal protein, cause calcium to be lost through the urine. In nations with high rates of osteoporosis, protein intake is generally high, usually more than twice the U.S.
recommended daily allowance. Vegetarians have lower rates of osteoporosis than meat eaters. This may be due to the lower protein intake of vegetarians. Different types of protein also affect this loss.

Caffeine and sodium also increase the rate at which calcium is lost through urine. Alcohol inhibits calcium absorption and may also be toxic to bone.  Vitamin D, copper, zinc, manganese, fluorine, and boron are all essential for good bone formation, and weight-bearing exercise also increases bone mass and helps to prevent osteoporosis. Boron appears to help stop the loss of calcium. The best way to get boron is through fruits, vegetables, and beans.

Calcium and Aging
Calcium is essential to bone health for a number of reasons. In childhood, it is necessary to grow a healthy skeleton to support a growing body.

By age 20, bones typically stop growing in length. It is the current scientific thinking that peak bone mass is reached around this time. The density of your bones at this point will depend, in part, upon the extent of your calcium intake as a child. The greater this peak bone mass, the less likely your bones are to become porous and fragile later on.

Bone is living tissue, constantly renewing itself. Although bone is strong and relatively flexible, everyday wear and tear causes tiny structural defects, much like those that occur in the specialized cells that perform the work of a "maintenance crew." The first group excavates the defects to remove any crumbling or weakened bone, then leaves the "site."

Once they have left, the second group moves in to fill the crevices. The material that they deposit calcifies to form new bone. This two-part process is called bone remodeling. Remodeling is an ongoing, natural process and the cycle is completed every three to four months in a healthy young adult.

As you age, several things happen that make good calcium nutrition just as important. First of all, the remodeling process changes. The two groups of cells that form the maintenance crew become less efficient in working together — the ones that fill in the crevices are not able to rebuild the bone as quickly because they are having trouble keeping up with the excavators.

In people who have relatively healthy bones, adequate calcium intake can help the remodeling process stay balanced. This means that replacement of new bone will remain more efficient, thus preventing a rapid decline in density.

Calcium is less efficiently absorbed as you age. You need to be even more vigilant about your calcium intake to protect your bones. Despite the slowdown of calcium absorption and less efficient remodeling, studies of older adults show that adequate calcium intake can slow bone loss and reduce the risk of fracturing.

Vegetarians and Osteoporosis
There are two types of vegetarians: vegans, those who do not eat any animal products whatsoever, and lacto-ovo vegetarians, those who do not eat animal flesh (meat, poultry or fish) but do eat animal products such as dairy foods.

Studies on the relationship between vegetarianism and osteoporosis have been done on lacto-ovo vegetarians; some studies with lacto-ovo vegetarians with high calcium intake have shown that this type of vegetarian has better bone density than meat eaters on a low calcium diet. However, these vegetarians are generally health conscious so it is difficult to determine whether it is the diet-related aspect alone that is responsible for these findings.

Vitamin D for Calcium Absorption
Vitamin D is crucial to calcium absorption. In fact, it increases calcium absorption by as much as 30% to 80%. Adults should receive 400 IUs of vitamin D per day (older adults should receive between 400 and 800).

The easiest and most natural way to get Vitamin D is from exposure to sunlight, which causes the body to manufacture its own. Just 15 minutes a day of summer sun exposure, even if only on the arms, face and hands, will greatly enhance Vitamin D production.

In Canada, where there is little sun intensity in the winter months, Vitamin D production in the skin ceases from early October until the end of March. If you are house-bound and don't get out into the sunlight much, you are not able to produce Vitamin D.

To make up for a lack of sunlight, you must try to find other sources. Although there are few food sources of Vitamin D, milk does contain significant amounts. (Fortified with Vitamin D, it contains 100 IUs per 250 ml glass). Foods such as margarine, eggs, chicken livers, salmon, sardines, herring, mackerel, swordfish, and fish oils (halibut and cod liver oils) all contain small amounts.

Since it may be difficult to get enough Vitamin D from food alone, you may wish to consider supplementation. Most multivitamins provide 400 IUs of Vitamin D.

It is not necessary to have vitamin D added to your calcium supplement as long as you have the recommended daily intake sometime during the day.

Minerals and Bone Health
Minerals like manganese, copper, and magnesium are important for bone health as they play a part in bone remodeling. Each has different activities, but deficiency in any of them can lead to stunted growth and bone deformity. However, you do not need a lot of these minerals every day and they are widely available in many foods. Deficiency in those with a varied diet would be quite unlikely.

Zinc also is available in the food that you eat and a serious deficiency would be unlikely. There is no evidence to support a role for zinc supplementation in the maintenance of good calcium absorption in otherwise healthy adults. In fact, high doses of zinc have been shown to inhibit calcium absorption when calcium intake is low.

There has been some research to show that the mineral boron may play a role in bone metabolism but there is currently not enough information to define just what that role is. Eating a varied, healthy diet that provides adequate calcium intake will usually ensure that your body gets the minerals that it needs.

  Bone Loss

To maintain strong, healthy bones, you need to make a "lifetime commitment" to getting enough calcium, warn experts from the US Department of Agriculture (USDA). They report that bone loss associated with aging climbs to pre-therapy levels soon after calcium supplements are abandoned.

Nutrition and osteoporosis experts have long advocated that individuals meet recommended dietary allowances (RDAs) for calcium — preferably from food — in order to build and maintain healthy bone density. Calcium is especially important for adolescents, who are building bone density to peak levels, and for post-menopausal women, who lose bone density at about 1% per year. Loss of bone density can cause osteoporosis and increase the risk of fractures in the elderly.

 In a special study, doctors examined calcium intake and bone density in nearly 300 men and women over the age of 65 for a period of 2 years. All of the subjects had taken calcium supplements for 3 years previous to the study.

 A large number of subjects told the researchers that they had stopped calcium supplementation. The doctors reported that "by 1 year after they stopped treatment," women who had stopped the therapy "had no residual benefit in terms of bone density."

 In other words, they resumed losing bone density at pre-treatment rates. Men who abandoned supplements took a little longer to see treatment effects vanish, but after 2 years of not taking extra calcium, they, too, saw levels of bone loss rise to pre-treatment levels. The bottom line,  is that there appears to be "no sustained benefit from calcium" once treatment stops.

 Similar results were found in adolescents. Dr. Steven Abrams, a pediatric researcher at the USDA/ARS Children's Nutrition Research Center, in Houston, Texas, reviewed findings from four 1-to-2-year trials in girls and boys aged 6 to 14 years.

 "The benefit from calcium supplementation wasn't really held once you stopped it," Abrams said, with bone development (that is, increases in bone density) in adolescents who stopped supplementation slowing to levels similar to those seen in untreated children.

Current US government RDAs for calcium are 800 mg for children aged 4 to 8, 1300 mg for children aged 9 to 18, 1000 mg a day for adults aged 19 - 49, and 1200 mg per day for adults over age 50. Calcium is found in dairy products and in produce such as collards, turnip greens, rhubarb, broccoli and kale.

  Calcium Reduces Bone Loss, Fracture Rate for Older People

By The National Institute on Aging 
September 3, 1997

Supplements of calcium and vitamin D can significantly reduce bone loss and the risk of fractures in older people, according to a new report from scientists at Tufts University. The research, the first to show that these supplements can help older men fight osteoporosis, also demonstrates that the benefits of these low cost and easily available supplements can be maintained over several years.

The findings by Bess Dawson-Hughes, M.D., and colleagues of the Jean Meyer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University appear in the September 4, 1997, The New England Journal of Medicine. The research was funded by the National Institute on Aging (NIA) as part of its STOP/IT (Sites Testing Osteoporosis Prevention/Intervention Treatments) initiative.

"Older people can benefit from this therapy at essentially no risk and at low cost," said Dawson-Hughes. "Our research underscores the importance of calcium and vitamin D supplementation in helping healthy and active older people stay that way."

NIA scientists noted the importance of the finding for older men. "Until recently, osteoporosis has been considered to be a women's problem," said Sherry Sherman, Ph.D., Director, Clinical Endocrinology and Osteoporosis Research, NIA, and project officer for the study. "We know that older men do experience considerable bone loss over time. With people living longer than ever, increasing the intake of calcium and vitamin D can be an important lifelong strategy for both sexes."

The researchers chose a combination of calcium and vitamin D to take advantage of the vitamin's influence in helping the body absorb and utilize calcium. As people age, the absorption of calcium and, it is believed, vitamin D, declines, as does production of vitamin D by the skin. This reduced ability to absorb calcium contributes to bone loss as people age, and low bone density is an underlying cause of increased hip fracture among the elderly.

The amounts of calcium and vitamin D used in the study are in keeping with recent recommendations of a National Academy of Sciences (NAS) panel, which recommended changes in current dietary requirements for calcium and related nutrients. The NAS group suggested that people over 50 increase their daily intake of calcium to about 1,200 milligrams and found that about 400-600 International Units of vitamin D (cholecalciferol) would be adequate.

Dawson-Hughes followed 389 men and women age 65 and older for 3 years. The study participants kept to their usual diets, in which they were generally getting the old recommended dietary allowances of calcium and vitamin D. At bedtime, about half of the study participants took placebo pills of no nutritional value. The other half took two separate pills, one containing 500 milligrams of elemental calcium (calcium citrate malate) and the other 700 International Units of vitamin D. All participants visited Tufts every 6 months for measurements of bone mineral density and other tests. Researchers also noted the number of fractures that occurred during the study period.

Over the 3 years, the calcium/vitamin D group lost significantly less total body bone, and, in some areas, gained bone mineral density. In men, where the findings were more pronounced, those taking placebos lost about one percent of their bone density at the hip over 3 years. Men taking the calcium/vitamin D combination increased their bone density by about 1 percent. The benefit at the hip for men, therefore, totaled a 2 percent improvement in bone density for the supplemented group. For women, the positive effects were most notable in the total body bone density, with lesser effects at the hip and spine.

In addition, the supplements may be effective in maintaining the skeleton over the long term, Dawson-Hughes said. The researchers found that the supplements were beneficial to bone density at the hip, spine, and total body in the first year, and further improved bone density of the total body during the second and third years of the study. The initial effects of supplementation at the hip and spine during the first year held steady, but did not change appreciably, over the next two years.

Even small losses of bone mass each year are important, scientists say. The losses are cumulative and add up to significant decreases in bone mineral density over time. "If we could retard bone loss in older people, we could make a lot of headway in preventing the devastation of osteoporosis and the fractures that commonly come with it," said Sherman.

The group taking supplements did considerably better in avoiding fractures. Some 5.9 percent of the participants taking the calcium and vitamin D suffered fractures, compared with 12.9 percent who did not take the supplements. Most of the fractures occurred in women.

Some 28 million middle-aged and older people are at risk of osteoporosis, and hip fractures related to low bone mass are a leading cause of nursing home entry for the elderly.

The NIA leads the Federal effort conducting and funding basic, clinical, social, and behavioral research aimed at maintaining independence and improving lives of older people and their families. For more information on NIA and aging in general, visit the NIA website .    

Calcium and Osteoporosis

Calcium supplementation to prevent bone loss in post menopausal women has been the subject of intense scrutiny. Since 1988, 43 studies have been published on the relationship between calcium intake, bone mass, and bone loss. Results have been confusing, in part because actual calcium intake cannot be determined. In 19 of the 43 studies, however, the investigators were able to control calcium intake, and in 16 of the 19, calcium slowed or stopped bone loss.

Another reason for conflicting data is failure to segregate data for women within 5 years of menopause. According to endocrinologist Robert Heaney, during this period bone loss is due predominantly to estrogen withdrawal, not to whatever calcium insufficiency may also be present. In 12 of the 19 studies in which calcium intake was controlled, women were excluded who were within 5 years of menopause; all 12 studies showed that calcium conferred a significant benefit. A final problem with clinical studies is that follow-up is usually too short to provide meaningful data.

Recently, Reid et al. reported the results of their long-term (more than 2 years) placebo-controlled study of calcium intake and bone mineral density in 122 normal woman (average age, 58 years) at least 3 years after they had reached menopause. Mean dietary calcium intake was 750 mg a day, and the supplemented group received an additional 1000 mg elemental calcium (5.24 g calcium lactate-gluconate and 800 mg calcium carbonate, formulated as an effervescent tablet).

The control group received an identical-appearing placebo. Subjects were evaluated 3 and 6 months after beginning therapy and then every 6 months for 2 years. Bone densitometry (total body, lumbar spine, and proximal femur) showed that calcium supplementation had a beneficial effect on bone loss that was consistent and statistically significant throughout the skeleton.

The placebo group lost bone at a rate of about 1% a year at most sites. On average, the rate of loss of total- body bone mineral density was reduced by almost half (43%) in the calcium group, and loss was eliminated entirely in the trunk. The only adverse event was the development of a kidney stone in one patient at 6 months. (Reid IR et al. N Engl J Med. 1993; 328: 460-464.)

How much calcium is enough to prevent postmenopausal bone loss? The 1984 Consensus Conference on Osteoporosis recommended a total intake of 1500 mg per day for women with estrogen deficiency. This is about the average amount of calcium required to keep a post menopausal woman in calcium balance. This intake is probably two or three times that of most adult women in the United States. The data from Reid et al. indicate that a higher daily calcium intake -- 1750 mg total -- may be more effective for reducing bone loss. And, as Heaney noted, studies suggest that it is never too late to start treatment; reductions in fracture rates can occur in as little as 18 months. Vitamin D levels are commonly low in this age group, and supplementation promotes calcium absorption. Preventing osteoporosis is a worthy goal. A reduction of just 20% in the US hip fracture rate would reduce the number of hip fractures by 40,000 to 50,000 annually, for an average saving of $1.5 to $2 billion.

Recent studies have determined that the quality of the calcium supplement, the times taken throughout the day, and adherance to continued supplementation far outweigh the amount taken om individual doses..

In other words, if you take a high quality calcium supplement several times throughout the day (not one mega dose per day), and continue with this treatment indefinatly, your benifits would be far greater then a hit or miss treatment.

 
Back to Calcium FAQ
Return to the main A to B CALM Calcium page