Calcium supplements linked to dementia risk in women with certain health conditions

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According to a new study, calcium supplements may be associated with an increased risk of dementia in older women who have had a stroke or other signs of cerebrovascular disease. The research is published in the August 17, 2016, online issue of Neurology, the medical journal of the American Academy of Neurology.

18 aug 2016--Cerebrovascular disease is a group of disorders that affect blood flow in the brain. These diseases, including stroke, are the fifth leading cause of death in the United States and increase the risk of developing dementia.
"Osteoporosis is a common problem in the elderly. Because calcium deficiency contributes to osteoporosis, daily calcium intake of 1000 to 1200 mg is recommended. Getting this recommended amount through diet alone can be difficult, so calcium supplements are widely used," said study author Silke Kern, MD, PhD with the University of Gothenburg in Sweden. "Recently, however, the use of supplements and their effect on health has been questioned."
The study involved 700 dementia-free women between the ages of 70 and 92 who were followed for five years. Participants took a variety of tests at the beginning and end of the study, including tests of memory and thinking skills. A CT brain scan was performed in 447 participants at the start of the study.
Scientists also looked at the use of calcium supplements in the participants and whether they were diagnosed with dementia over the course of the study. A total of 98 women were taking calcium supplements at the start of the study and 54 women had already experienced a stroke. During the study, 54 more women had strokes, and 59 women developed dementia. Among the women who had CT scans, 71 percent had lesions on their brains' white matter, which is a marker for cerebrovascular disease.
The study found that the women who were treated with calcium supplements were twice as likely to develop dementia than women who did not take supplements. But when the researchers further analyzed the data, they found that the increased risk was only among women with cerebrovascular disease. Women with a history of stroke who took supplements had a nearly seven times increased risk of developing dementia than women with a history of stroke who did not take calcium supplements. Women with white matter lesions who took supplements were three times as likely to develop dementia as women who had white matter lesions and did not take supplements. Women without a history of stroke or women without white matter lesions had no increased risk when taking calcium supplements.
Overall, 14 out of 98 women who took supplements developed dementia, or 14 percent, compared to 45 out of 602 women who did not take supplements, or 8 percent. A total of six out of 15 women with a history of stroke who took supplements developed dementia, compared to 12 out of 93 women with a history of stroke who did not take supplements. Among the women with no history of stroke, 18 out of 83 who took supplements developed dementia, compared to 33 out of the 509 who did not take supplements.
"It is important to note that our study is observational, so we cannot assume that calcium supplements cause dementia," said Kern. The author also noted that the study was small and results cannot be generalized to the overall population, and additional studies are needed to confirm the findings.
Kern noted that calcium from food affects the body differently than calcium from supplements and appears to be safe or even protective against vascular problems.


Provided by American Academy of Neurology

Study: Calcium supplementation does not clog arteries

Heart diagram. Credit: Wikipedia

Contrary to recent reports, consuming calcium supplements is not likely to cause heart problems or heart attacks, according to a study from Purdue University.

23 AUG 2015--"Our study found that consuming a high-calcium diet, which is defined as not exceeding 2,000 milligrams of calcium a day, is not a risk factor for heart attacks," said Connie Weaver, distinguished professor and head of the Department of Nutrition Science. "The recent concern that calcium supplements were a risk factor led people to stop supplementing their diets. This is a great concern because supplementation is essential to fill a void to meet the daily recommended amount of calcium for strong bones."
"We're already at epidemic levels for osteoporosis as one in two women older than 50 will get a fracture in her lifetime, and 20 percent of hip fractures occur in men," said Weaver, who is an expert in mineral bioavailability, calcium metabolism, botanicals and bone health.
The research is published online in the Journal of the American Heart Association. The project was funded by Pharmavite LLC, the Dairy Research Institute, Dairy Australia, Fonterra Cooperative Group Limited, Kraft Foods Inc., Nestle and grants from the National Institutes of Health. Weaver serves on the scientific advisory board for Pharmative LLC. Collaborators included Scott Radcliff, Meryl Wastney, Bill van Alstine and George Jackson from Purdue; Mike Sturek from the Indiana University School of Medicine; and Sean Newcomer from California State University.
"It had been reported that there is a 30 percent higher chance of heart attack from consuming calcium supplements," Weaver said. "In 2011, 22 percent of the population consumed calcium supplements, and that decreased in 2012 to 17 percent. The research supporting such a risk has been based on self-reports or from correlations or secondary analysis rather than primary causes. And this would be too hard to study in humans in such a way to control their diet and identify concerns prior to having a heart attack."
In Weaver's study, three groups of pigs were fed a normal diet, a high-calcium diet from supplements or a high-calcium diet from dairy products over a six-month period. The high-calcium diets were equivalent to 2,000 milligrams of calcium consumed one time each day. Neither high-calcium group had an increase of calcium in the arteries.
"The speculation was that calcium deposited in the soft tissue of the arteries and that a big dose of calcium from a supplement would cause it to precipitate in the blood," Weaver said.
The researchers determined this by using the calcium 41 technology, an isotope measure to trace calcium deposits through accelerator mass spectrometry. It can measure atomic quantities and determine whether any of the calcium 41 is deposited in the arteries' soft tissue. The researchers also used CT imaging and ultrasounds, as well as other biological measures.
"There is no cause for concern, and for every serving of low-fat dairy you miss, take 300 milligrams of calcium to get what you need for bone health," she says.
More information: "Effect of High‐Calcium Diet on Coronary Artery Disease in Ossabaw Miniature Swine With Metabolic Syndrome." J Am Heart Assoc. 2015;4:e001620, originally published August 13, 2015, DOI: 10.1161/JAHA.114.001620

Provided by Purdue University

Making sense of conflicting advice on calcium intake

In recent years, studies have reported inconsistent findings regarding whether calcium supplements used to prevent fractures increase the risk of heart attack.

18 oct 2013--Now, in an assessment of the scientific literature, reported as a perspective piece in the October 17, 2013 issue of the New England Journal of Medicine, a UC San Francisco researcher says patients and health care practitioners should focus on getting calcium from the diet, rather than supplements, when possible.

"Osteoporosis may result from inadequate calcium intake and it's quite common for certain segments of our population, such as the elderly, to consume less than the recommend amount," said Douglas C. Bauer, MD, UCSF professor of Medicine, Epidemiology and Biostatistics. "But a high calcium diet should be the preferred method to receive adequate amounts of the nutrient. The Institute of Medicine's recommended dosage for post-menopausal women over the age of 50 and men over 70 is 1,200 mg per day.

"If it is not possible to consume enough calcium from the diet, the use of calcium supplements is most likely safe and not associated with cardiovascular outcomes," he said.

Calcium supplements are known to have several side effects, the most common being indigestion and minor constipation, and kidney stones are a rare complication. However, several recent studies have suggested that calcium supplements can also lead to an increase risk of heart attacks.

A 2010 British Medical Journal study, which pooled nearly a dozen randomized trials, concluded that calcium supplements "are associated with an increased risk of myocardial infarction [heart attacks]" and went on to say, " As calcium supplements are widely used, these modest increases in risk of cardiovascular disease might translate into a large burden of disease in the population."

A 2013 JAMA Internal Medicine non-randomized study examined 11,778 cardiovascular-related deaths and found an increased risk with calcium supplement use. The authors concluded, "high intake of supplemental calcium is associated with an excess risk of CVD (cardiovascular disease) death in men but not in women."

However, several other studies have shown no relationship between the use of calcium supplements and cardiovascular events.

For example, a 2010 meta-analysis that included all of the Women's Health Initiative (WHI) trial participants showed "no significant relationship between supplementation and cardiovascular events" in three trials of calcium supplements alone.

Bauer recommends consuming dairy products to increase one's dietary intake of calcium as well as food products that are fortified with extra calcium, such as kale, broccoli and Bok Choy.

Dr. Bauer has received research support from Amgen and Novartis in the past for his work on independent adjudication of endpoints in clinical trials unrelated to calcium, which ended two years ago.

Provided by University of California, San Francisco

Calcium supplements linked to longer lifespans in women

Taking a calcium supplement of up to 1,000 mg per day can help women live longer, according to a recent study accepted for publication in The Endocrine Society's Journal of Clinical Endocrinology & Metabolism (JCEM).

23 may 2013--Calcium, an essential nutrient for bone health, is commonly found in dairy products as well as vitamins. Although calcium is an essential nutrient for bone health, past studies have linked calcium supplements to heart disease risk. Researchers analyzing data from the large-scale Canadian Multicentre Osteoporosis Study (CaMos) sought to clarify this issue and found moderate doses of calcium supplements had a beneficial effect in women.

"Our study found daily use of calcium supplements was associated with a lower risk of death among women," said the study's lead author, David Goltzman, MD, of McGill University in Montreal, Canada. "The benefit was seen for women who took doses of up to 1,000 mg per day, regardless of whether the supplement contained vitamin D."

The longitudinal cohort study monitored the health of 9,033 Canadians between 1995 and 2007. During that period, 1,160 participants died. Although the data showed women who took calcium supplements had a lower mortality risk, there was no statistical benefit for men. The study found no conclusive evidence that vitamin D had an impact on mortality.

"Higher amounts of calcium were potentially linked to longer lifespans in women, regardless of the source of the calcium," Goltzman said. "That is, the same benefits were seen when the calcium came from dairy foods, non-dairy foods or supplements."

More information: The article, "Calcium and Vitamin D Intake and Mortality: Results from the Canadian Multi-centre Osteoporosis Study," will appear in the July 2013 issue of JCEM.

Provided by The Endocrine Society

Vitamin D with calcium shown to reduce mortality in elderly

A study recently published in the Endocrine Society's Journal of Clinical Endocrinology and Metabolism (JCEM) suggests that vitamin D—when taken with calcium—can reduce the rate of mortality in seniors, therefore providing a possible means of increasing life expectancy.

22 jun 2012--During the last decade, there has been increasing recognition of the potential health effects of vitamin D. It is well known that calcium with vitamin D supplements reduces the risk of fractures. The present study assessed mortality among patients randomized to either vitamin D alone or vitamin D with calcium. The findings from the study found that the reduced mortality was not due to a lower number of fractures, but represents a beneficial effect beyond the reduced fracture risk.

"This is the largest study ever performed on effects of calcium and vitamin D on mortality," said Lars Rejnmark, PhD, of Aarhus University Hospital in Denmark and lead author of the study. "Our results showed reduced mortality in elderly patients using vitamin D supplements in combination with calcium, but these results were not found in patients on vitamin D alone."

In this study, researchers used pooled data from eight randomized controlled trials with more than 1,000 participants each. The patient data set was comprised of nearly 90 percent women, with a median age of 70 years. During the three-year study, death was reduced by 9 percent in those treated with vitamin D with calcium.

"Some studies have suggested calcium (with or without vitamin D) supplements can have adverse effects on cardiovascular health," said Rejnmark. "Although our study does not rule out such effects, we found that calcium with vitamin D supplementation to elderly participants is overall not harmful to survival, and may have beneficial effects on general health".

More information: The article "Vitamin D with calcium reduces mortality: patient level pooled analysis of 70,528 patients from eight major vitamin D trials", appears in the August 2012 issue of JCEM.

Provided by The Endocrine Society

Older women should not take calcium, vitamin D: task force

Recommendations say evidence doesn't support benefit of low daily doses to prevent fractures.

14 jun 2012-- A leading U.S. government advisory panel has proposed that postmenopausal women not take low-dose calcium and vitamin D supplements daily to ward off bone fractures.
But the jury is still out on higher doses of these supplements, stated the U.S. Preventive Services Task Force (USPSTF), which issued the draft recommendations Tuesday. Public comment on the draft recommendations is invited until July 10.
The news was a bit of a bombshell, given that women have been told for so long to take calcium and vitamin D, said Dr. Suzanne Steinbaum, director of women and heart disease at Lenox Hill Hospital in New York City and a spokeswoman for the American Heart Association. "What we're really seeing is no role for calcium for the prevention of osteoporotic fractures. At this point, there's no reason to be taking calcium," she noted.
But, the issue of which women should take which supplements is a complicated one and these preliminary recommendations are unlikely to change practice immediately, said Dr. Shiri Levy, service chief of endocrinology at West Bloomfield Henry Ford Hospital in Michigan, who already tells her patients to get calcium from food sources as much as possible.
"Taking calcium naturally in the diet is probably the best way for patients who don't have lactose intolerance and can drink milk and eat dairy products," she said. "For those not able to take dairy products regularly, then we would supplement to the degree that we can. I would individualize it for patients."
And, Levy pointed out, data from the landmark Women's Health Initiative study did indicate that women on supplements showed a decreased risk for fractures.
As Steinbaum noted, millions of women take vitamin D supplements with or without calcium in the hopes of diminishing the risk of fractures as they age.
According to previous research, half of postmenopausal women will suffer such a fracture in their postmenopausal years.
The USPSTF said there was no evidence to support using the low-dose supplements -- defined as 400 IU of vitamin D with 1,000 milligrams of calcium carbonate -- as protection against fractures.
There was "inadequate evidence" as to how higher doses -- meaning more than 400 IU of vitamin D paired with 1,000 milligrams of calcium -- might affect bone fracture risk, the task force noted.
And it's not clear at this point if vitamin D/calcium supplementation could help fight cancer and fractures in men and younger women, the recommendations added.
There can be a downside to taking such daily supplements, given that there may be a slightly heightened risk of kidney stones, the USPSTF stated.
Both supplements have garnered plenty of evidence for and against their use.
For instance, vitamin D might lower the risk of colorectal and other forms of cancer, according to some studies, while calcium recently has been linked to an increased risk of heart attacks.
The USPSTF recommendations say that vitamin D could still be useful in preventing falls in people aged 65 or older who are already at increased risk for falling.
Women at average risk for osteoporosis should have a baseline bone density scan at age 65, Levy said.
Women who have risk factors for the condition such as celiac disease, a family history of osteoporosis or premature menopause should have a baseline bone density test taken earlier, when they go through menopause, she added.
"If there is an increased risk, we do recommend a healthy lifestyle, appropriate diet including foods rich in calcium and vitamin D and weight-bearing exercise," Levy said.
In addition to natural food sources, many foods are now fortified with vitamin D and calcium.

More information: The draft recommendations can be viewed at the USPSTF website.

Before you start bone-building meds, try dietary calcium and supplements: study

Has a bone density scan placed you at risk for osteoporosis, leading your doctor to prescribe a widely advertised bone-building medication? Not so fast! A University of Illinois study finds that an effective first course of action is increasing dietary calcium and vitamin D or taking calcium and vitamin D supplements.

09 may 2011--"For many people, prescription bone-building medicines should be a last resort," said Karen Chapman-Novakofski, a U of I professor of nutrition and co-author of a literature review published in a recent issue of Nutrients.

The study reported that adults who increase their intake of calcium and vitamin D usually increase bone mineral density and reduce the risk for hip fracture significantly. These results were often accomplished through supplements, but food is also a good source of these nutrients, she said.

"I suspect that many doctors reach for their prescription pads because they believe it's unlikely that people will change their diets," she noted.

The scientist said that prescription bone-building medications are expensive, and many have side effects, including ironically an increase in hip fractures and jaw necrosis. They should be used only if diet and supplements don't do the trick.

"Bisphosphonates, for instance, disrupt normal bone remodeling by shutting down the osteoclasts—the cells that break down old bone to make new bone. When that happens, new bone is built on top of old bone. Yes, your bone density is higher, but the bone's not always structurally sound," she said.

A bone density test measures quantity, not quality, of bone. "Although the test reports that you're fine or doing better, you may still be at risk for a fracture," said Chapman-Novakofski.

A woman in midlife can get enough calcium in her diet without gaining weight, said lead author Karen Plawecki, director of the U of I's dietetics program.

"Menopausal women should consume 1,200 milligrams of calcium a day. Three glasses of 1 percent to skim milk will get you up to 900 milligrams. The rest can easily be obtained through calcium-rich and calcium-fortified foods," Plawecki said.

According to Plawecki, the number of foods fortified with calcium and vitamin D is increasing exponentially. Examples are soy milk, orange juice, yogurt, crackers, cereal, bread, breakfast bars, and even pancakes.

The researchers also looked at the effects of dietary protein, vitamin K, soy, and sodium in their literature review. The new USDA food pyramid guidelines recommend that Americans decrease their sodium intake.

"Following a low-sodium diet does seem to have a positive effect on bone density. Some people have the habit of adding a generous sprinkle of salt to most foods before eating, but there's more involved here than learning not to do that. You have to choose different foods," Plawecki said.

Smoked or processed meats, bacon, lunch meat, and processed foods all contain a lot of sodium and could sabotage bone health. "Cheese is also very high in sodium so try to get your calcium some other way more often," Plawecki said.

She recommends a "portfolio diet" that contains a number of nutrients, not just extra calcium and vitamin D. For bone health, the researchers also encourage consuming adequate protein, less sodium, and more magnesium and potassium.

"That can be done by following a diet that's high in fruits and vegetables, has adequate calcium and protein, and is light on salt," she said.

Chapman-Novakofski noted that the National Osteoporosis Foundation recommends more physical activity. She suggests a combination of aerobic, strength, balance, and flexibility exercises with a focus on improving your core muscles so you can catch yourself if you start to fall.

Whatever sort of exercise you're doing, you have to introduce new forms of activity every so often because your bones will stop responding to the same old routine and rebuilding will slow, she said.

Plawecki and Chapman-Novakofski set out to determine the impact of dietary, supplemental, and educational interventions over the last 10 years and reached their conclusions after reviewing 219 articles in scientific journals.

More information: For more information, visit their website about osteoporosis at http://urbanext.il … steoporosis/

Provided by University of Illinois at Urbana-Champaign

Study adds weight to link between calcium supplements and heart problems

New research published in the British Medical Journal today adds to mounting evidence that calcium supplements increase the risk of cardiovascular events, particularly heart attacks, in older women.

The findings suggest that their use in managing osteoporosis should be re-assessed.

22 april 2011--Calcium supplements are often prescribed to older (postmenopausal) women to maintain bone health. Sometimes they are combined with vitamin D, but it's still unclear whether taking calcium supplements, with or without vitamin D, can affect the heart.

The Women's Health Initiative (WHI) study - a seven-year trial of over 36,000 women – found no cardiovascular effect of taking combined calcium and vitamin D supplements, but the majority of participants were already taking personal calcium supplements, which may have obscured any adverse effects.

So a team of researchers, led by Professor Ian Reid at the University of Auckland, re-analysed the WHI results to provide the best current estimate of the effects of calcium supplements, with or without vitamin D, on the risk of cardiovascular events.

They analysed data from 16,718 women who were not taking personal calcium supplements at the start of the trial and found that those allocated to combined calcium and vitamin D supplements were at an increased risk of cardiovascular events, especially heart attack.

By contrast, in women who were taking personal calcium supplements at the start of the trial, combined calcium and vitamin D supplements did not alter their cardiovascular risk.

The authors suspect that the abrupt change in blood calcium levels after taking a supplement causes the adverse effect, rather than it being related to the total amount of calcium consumed. High blood calcium levels are linked to calcification (hardening) of the arteries, which may also help to explain these results.

Further analyses - adding data from 13 other trials, involving 29,000 people altogether - also found consistent increases in the risk of heart attack and stroke associated with taking calcium supplements, with or without vitamin D, leading the authors to conclude that these data justify a reassessment of the use of calcium supplements in older people.

But in an accompanying editorial, Professors Bo Abrahamsen and Opinder Sahota argue that there is insufficient evidence available to support or refute the association.

Because of study limitations, they say "it is not possible to provide reassurance that calcium supplements given with vitamin D do not cause adverse cardiovascular events or to link them with certainty to increased cardiovascular risk. Clearly further studies are needed and the debate remains ongoing."

Provided by British Medical Journal

Calcium Supplements May Increase Heart Attack Risk

Meta-analysis reveals significant increase in risk in those taking calcium versus those on placebo

31 july 2010-- Calcium supplementation is associated with an increased risk of myocardial infarction, according to a meta-analysis published online July 29 in BMJ.

Mark J. Bolland, Ph.D., of the University of Auckland in New Zealand, and colleagues searched the medical literature for randomized, placebo-controlled studies of calcium supplementation (500 or more mg/day) involving more than 100 subjects (mean age, over 40). The reviewers analyzed 15 studies with an aggregate of more than 20,000 subjects.

In five studies with patient level data, the investigators found that 143 subjects taking calcium had myocardial infarctions compared to 111 on placebo (hazard ratio, 1.31). There were also increases in risk for stroke; the composite end point of myocardial infarction, stroke, or sudden death; and all-cause mortality; however, these were considered nonsignificant. In a meta-analysis of trial level data, 166 subjects taking calcium had myocardial infarctions compared to 130 on placebo (pooled relative risk, 1.27).

"Calcium supplements (without coadministered vitamin D) are associated with an increased risk of myocardial infarction. As calcium supplements are widely used, these modest increases in risk of cardiovascular disease might translate into a large burden of disease in the population. A reassessment of the role of calcium supplements in the management of osteoporosis is warranted," the authors write.

One study author disclosed receiving research support from and acting as a consultant for the dairy company Fonterra, while four authors reported receiving study drugs for clinical trials of calcium supplementation from pharmaceutical companies.

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UC Davis research confirms benefits of calcium and vitamin D in preventing fractures

Calif., 15 jan 2010— Taking both calcium and vitamin D supplements on a daily basis reduces the risk of bone fractures, regardless of whether a person is young or old, male or female, or has had fractures in the past, a large study of nearly 70,000 patients from throughout the United States and Europe has found.

The study included data published in 2006 from clinical trials conducted at UC Davis in Sacramento as part of the Women's Health Initiative (WHI). It appears online in this week's edition of the British Medical Journal.

"What is important about this very large study is that goes a long way toward resolving conflicting evidence about the role of vitamin D, either alone or in combination with calcium, in reducing fractures," said John Robbins, professor of internal medicine at UC Davis and a co-author of the journal article. "Our WHI research in Sacramento included more than 1,000 healthy, postmenopausal women and concluded that taking calcium and vitamin D together helped them preserve bone health and prevent fractures. This latest analysis, because it incorporates so many more people, really confirms our earlier conclusions."

Led by researchers at Copenhagen University in Denmark, Robbins and an international team of colleagues analyzed the results of seven large clinical trials from around the world to assess the effectiveness of vitamin D alone or with calcium in reducing fractures among people averaging 70 years or older. The researchers could not identify any significant effects for people who only take vitamin D supplements.

Among the clinical trial results analyzed was Robbins' WHI research, which was part of a 15-year, national program to address the most common causes of death, disability and poor quality of life in postmenopausal women such as cardiovascular disease, cancer and osteoporosis. Those trials were primarily designed to study the effect of calcium and vitamin D supplementation in preventing hip fractures, with a secondary objective of testing the supplements on spine and other types of fractures, as well as on colorectal cancer. The results were published in the Feb. 16, 2006 edition of the New England Journal of Medicine.

Fractures are a major cause of disability, loss of independence and death for older people. The injuries are often the result of osteoporosis, or porous bone, a disease characterized by low bone mass and bone fragility. The National Osteoporosis Foundation estimates that about 10 million Americans have osteoporosis; 80 percent of them are women. Four of 10 women over age 50 will experience a fracture of the hip, spine or wrist in their lifetime, and osteoporosis-related fractures were responsible for an estimated $19 billion in health-related costs in 2005.

"This study supports a growing consensus that combined calcium and vitamin D is more effective than vitamin D alone in reducing a variety of fractures," said Robbins. "Interestingly, this combination of supplements benefits both women and men of all ages, which is not something we fully expected to find. We now need to investigate the best dosage, duration and optimal way for people to take it."

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UC Davis Health System is an academic health center that includes a top-ranked school of medicine, a 613-bed acute care hospital, the Betty Irene Moore School of Nursing, a National Cancer Institute-designated cancer center, the unique MIND Institute for the study of neurodevelopmental disorders, a comprehensive children's hospital, a level 1 trauma center and outpatient clinics in communities throughout the Sacramento region. Consistently ranked among the nation's top medical schools and best hospitals, UC Davis has established itself as a national leader in telehealth, rural medicine, cancer, neurodevelopmental disorders, vascular medicine, and trauma and emergency medicine. Other areas of research strength include clinical and translational science, regenerative medicine, infectious disease, neuroscience, functional genomics and mouse biology, comparative medicine and nutrition, among many others.

Calcium tied to lower cancer risk in older people

By LINDSEY TANNER
CHICAGO, 24 feb 2009-- – A study in nearly half a million older men and women bolsters evidence that diets rich in calcium may help protect against some cancers. The benefits were mostly associated with foods high in calcium, rather than calcium tablets.
Previous studies have produced conflicting results. The new research involved food questionnaires from participants and a follow-up check of records for cancer cases during the subsequent seven years. This research method is less rigorous than some previous but smaller studies.
But because of its huge size — 492,810 people and more than 50,000 cancers — the new study presents powerful evidence favoring the idea that calcium may somehow keep cells from becoming cancerous, said University of North Carolina nutrition expert John Anderson, who was not involved in the study.
The study was run jointly by the National Institutes of Health and AARP. The results appear in Monday's Archives of Internal Medicine.
National Cancer Institute researcher Yikyung Park, the study's lead author, called the results strong but said more studies are needed to confirm the findings.
Duke University nutrition researcher Denise Snyder said the results support the idea that food rather than supplements is the best source for nutrients.
Participants were AARP members aged 50 to 71 who began the study in the mid-1990s. A total of 36,965 men and 16,605 women were later diagnosed with cancer. There were more than 10 different kinds of cancer, the most common being prostate, breast, lung and colorectal.
Compared with people who got little calcium, those who consumed the most had the lowest chances of getting colon cancer. Those in that highest category got on average 1,530 milligrams a day among men and 1,881 milligrams daily among women. The recommended amount for older people is 1,200 milligrams, and getting much more than that didn't result in any greater protection. Adults can get that amount from four cups of milk or calcium-fortified orange juice.
Men who got the most calcium from food were about 30 percent less likely to get cancer of the esophagus, about 20 percent less likely to get head and neck cancer and 16 percent less likely to get colon cancer, when compared to men who got low amounts of calcium.
Among women, those who got the most food-based calcium were 28 percent less likely to get colon cancer than low-calcium women.
In men, calcium supplements only seemed to help protect against colon cancer; for women, supplements meant a lower risk for liver cancer, which is rare.
Some previous studies have linked diets high in calcium with prostate cancer but the current study found no such risk.
Adults who ate the most calcium also tended to be healthier overall than the others.
Northwestern University preventive medicine instructor Patricia Sheean called the results impressive. But she noted that all those in the study, AARP members, may have been healthier and wealthier than the general U.S. population so it's not clear if the results would apply to the wider population.

Calcium Supplements Increase Vascular Events?

Lisa Nainggolan
January 17, 2008 (Auckland, New Zealand) – A new study has shown that calcium supplementation might increase vascular events in elderly women [1]. The findings are somewhat unexpected, because previous trials have shown that calcium improves blood cholesterol levels, senior author Dr Ian R Reid (University of Auckland, New Zealand) told heartwire.
Dr Mark J Bolland (University of Auckland, New Zealand) and colleagues published the findings online in BMJ January 15, 2008.
"This is quite controversial, given that the worldwide calcium-supplement market is worth $3 billion a year," says Reid. "The trial was primarily looking at what calcium supplements do to bone density, but we had a secondary hypothesis right from the outset that calcium might actually prevent heart attack. What we found, to our surprise, was that we didn't see a decrease but an increase, and the findings appear to be quite robust." Reid added, however, that there have been some clues from three other recent studies, including one from Women's Health Initiative (WHI) in the US [2]: "these three did not find significant increases in the number of heart attacks [with calcium], but they have found upward trends."
Dr Erin D Michos (Johns Hopkins University, Baltimore, MD), who was not involved with this new study but cowrote an editorial accompanying the publication of the WHI study on vitamin-D/calcium supplements last year [3], told heartwire: "This is a thought-provoking study, although not definitive, but further work should be done."
Others warned that it is premature to make any treatment decisions on the basis of this new study. British Heart Foundation spokesperson Judy O'Sullivan said more rigorous research was needed before any firm conclusions could be drawn. "Anyone who has been advised by their doctor to take calcium supplements to protect their bones should not stop doing so in light of this study alone without medical advice," she said.
Findings equivocal
The New Zealand team randomized 1471 postmenopausal women (average age 74 years) to either calcium supplementation (1 g/day calcium citrate) or placebo. As well as bone density, they looked at adverse cardiovascular events over five years: death, sudden death, MI, angina, other chest pain, stroke, transient ischemic attack, and a composite end point of MI, stroke, or sudden death.
Reid says the study collected data on MIs and strokes "in a much more careful way" than any other previous studies have done. "We got cardiologists and other people involved and audited all those things and went back to patients' hospital records and so on."
MI was more commonly reported in the calcium group than in the placebo group (45 events in 31 women vs 19 events in 14 women, p=0.01), and the composite end point was also reached more often in the calcium group (101 events in 69 women vs 54 events in 42 women, p=0.008). Even after adjudication, MI remained more common in the calcium group, as did the composite end point.But when unreported events were added from the national database of hospital admissions in New Zealand, the relative risk of MI was 1.49 in those taking calcium compared with placebo recipients (p=0.16) and that of the composite end point 1.21 in those taking calcium compared with those on placebo (p=0.32).
"Thus, the present study does not unequivocally show an adverse cardiovascular event of calcium but suggests that this matter needs to be considered carefully before calcium supplementation can be broadly advocated," the researchers note.
Michos told heartwire the results are somewhat difficult to interpret, because there appear to be some imbalances between the calcium and placebo arms at baseline, "which may have influenced the higher outcomes seen in the calcium arm."
Also, the New Zealand team did not report serum vitamin-D levels, except to say they excluded those with very severe vitamin-D deficiency, she notes. "While I still believe vitamin D is important and beneficial for cardiovascular health, supplementation with calcium alone (without vitamin D) may not be beneficial for CV health."
Age may play a role
Reid says that "there is a possibility that this was a chance finding, but what makes us believe that this is not the explanation is that there have been three other recent studies--one from the UK, one from the US, and one from Australia--that have found upward trends in the numbers of heart attacks with calcium, so we are showing the same sorts of trends."
"Taken together, these four studies raise major concerns about the cardiovascular safety of calcium supplementation, particularly with respect to MI in older postmenopausal women," say the researchers in their paper.
Reid says it is important to consider age. The women in the New Zealand study were quite old, those in the Australian study were similarly elderly, but those in the US--the WHI study--were more than 10 years younger, as were the ones studied in the UK.
"Most of the trials have been done in women in their 50s and 60s, and the signal hasn't come through as strongly in those younger women, so it's probably okay [to use calcium] in those younger women."
High calcium uptake might accelerate calcification of arteries?
The findings from his study may also be stronger, Reid said, because they used quite a high dose, 1 g per day, and a more soluble calcium preparation than others have done, which probably resulted in better compliance. "And our study is a bit longer than some of the others, so that may also explain why we've got a more powerful effect.
"The other thing that makes us think that this is not a chance finding is that it is now pretty well established that patients on dialysis using calcium supplementation are at increased risk of heart attack and death.
"What we think is happening is that the higher calcium intake--and particularly the bolus of calcium that supplementation provides--is somehow accelerating the laying down of calcium in the artery walls of the heart," he notes.
"The way I interpret this is that if you have preexisting heart disease--which probably most of our participants did, although they probably weren't aware of it--then the extra calcium appears to be bad. But if, on the other hand, you are 54 and you have nice clean arteries to your heart, then probably calcium is not going to cause you any major problems. That's my take on it. But I don't know if it can be proven."
He added that the advice they have been providing to women in New Zealand in the past few months, since they became aware of these findings, "is that if you are in the older age group and are known to have heart disease, it's probably not sensible for you to take a calcium supplement. In younger people, calcium supplements look reasonable, but it may be sensible to aim for a smaller dose, say 500 mg/day."
He noted that the study also showed--"in a more clear-cut way than any other"--that calcium substantially slows bone loss, "so going down to 500 mg/day is not going to achieve the same bone benefit, although it is probably a safer balance."
But for patients who really have major problems with osteoporosis, "it's much more sensible to focus on using specific osteoporosis drugs," he said. "If you've got osteoporosis, take other things, don't just rely on extra calcium."
What's next?
Reid says his team has a number of plans to look at this issue going forward. "We are going to try to access the radiographs from women in the study and see if we can quantify calcification in them." They also have another study that has just finished, this time in a few hundred men, in which they are looking at coronary artery calcium. "In the men's study, they are younger, and there is an adverse trend, but it's much smaller," he noted.
And he hopes to coordinate a meta-analysis of the UK, US, and Australian studies and his own "to see if we can use all the available evidence to determine whether there really is something solid here."
Reid has received research support from and acted as a consultant for Fonterra and Mission Pharmacal.
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