A week ago we sent out a health alert about the dangers of calcium supplements for men. That was because of an article in JAMA Internal Medicine (online, February, 4, 2013) reporting that men taking more than 1500 mg of calcium daily in the form of supplements were at increased risk for cardiovascular disease death. The size of the study (over 200,000 men) and the length of the follow-up (12 years) suggested that this was unlikely to be due to chance.
There was one confusing result, however. The women who participated in this National Institutes of Health-AARP Diet and Health Study were NOT at increased risk for death. The nearly 170,000 women who were included in the research seemed to avoid the small but significant risk that calcium seemed to pose for men. The authors concluded:
“We found a significant interaction by sex. Elevated CVD [cardiovascular disease] mortality with increasing supplemental calcium in-take was observed only in men; however, we cannot rule out the possibility that supplemental calcium intake may be associated with cardiovascular mortality in women.”
Now, a brand new study published in the BMJ (online, February 13, 2013) suggests that women may indeed be vulnerable to complications from high doses of calcium in supplements. The Swedish government has been tracking the health of all its residents since 1952. In this most recent research, investigators analyzed data from 61,443 Swedish women who were followed for an average of 19 years. (They were born between 1914 and 1948.)
Over the nearly two decades they were tracked, about 12,000 women died (17%). One third of the deaths were attributed to cardiovascular disease. Now here’s where it gets interesting. Women who consumed more than 1,400 mg of calcium from their diets had a higher risk of cardiovascular disease mortality (about 50% greater) than women who consumed 600 to 1000 mg of calcium from their food. If you add in calcium supplements (as pills) on top of dietary calcium (from food), however, the risk jumps dramatically. In their own words:
“Women who had a high dietary intake of calcium exceeding 1400 mg/day and additionally used calcium supplements had a higher mortality rate than women with a similarly high intake of calcium but without taking supplements. Thus, among calcium tablet users (500 mg calcium per tablet), a high dietary calcium intake (>1400 mg/day) conferred a multivariable adjusted hazard ratio of 2.57 for all cause mortality compared with a dietary calcium intake of between 600 and 999 mg/day.”
In the world of epidemiology, a greater than two-fold increased risk of death is considered serious and not likely to be caused by chance. Add this study to other research and a pattern starts to emerge.
• A study last spring involving nearly 24,000 German adults found that those taking calcium supplements were more likely to have heart attacks during the 11 years of follow-up (Heart, online May 23, 2012).
• A study of American women from the Women’s Health Initiative (WHI) involved 16,000 women over the age of 40. Those who were randomized to receive calcium and vitamin D (vs. placebo) were about 20% more likely to experience heart attacks or other vascular problems.
Speaking of vitamin D, many women have assumed that vitamin D would somehow protect them from the problems of too much calcium. Here is what the Swedish investigators found:
“Vitamin D intake did not significantly modify the associations between calcium intake and the rate of deaths from all causes, cardiovascular disease, or ischaemic heart disease.”
That said, the Swedish researchers propose that too much calcium in the diet plus supplemental calcium pills could suppress vitamin D levels, and lead to inflammation and hypertension as well as elevated triglycerides, hardening of arteries and atherosclerosis. They also suggest that too much calcium in the blood can increase the risk of clots due to a “hypercoagulable state.” Other researchers have also proposed that excess calcium might increase blood coagulation and lead to “stiffness” in the arterial wall. They have also proposed that:
“One plausible biological mechanism through which calcium may exert a harmful effect on cardiovascular health is vascular calcification–the deposit of calcium phosphate in cardiovascular structures…Emerging evidence has linked calcification of coronary arteries with increased atherosclerotic plaque burden, risk of coronary heart disease and mortality.”
Although calcium is crucial for good health, the body is well equipped to regulate levels of this essential element. For reasons that are not entirely clear, many health professionals hopped on the calcium bandwagon and started recommending very high doses in the form of pills. Commercials on TV also encouraged women to take extra calcium. It is not unusual for a woman to be told to take 1000 mg or more of elemental calcium on top of dairy products and other foods high in calcium. At last count nearly two-thirds of American women take calcium supplements.
Based on several recent studies and the most recent Swedish research, it would appear that this advice might well have been misguided. When women consume lots of calcium from their diets and add calcium supplements to that, there is a significant increase in the risk of cardiovascular death.
So, what’s a woman to do, given all the conflicting information of the last several decades? The Swedish researchers did NOT find any increased risk of death when daily dietary calcium intake ranged between 600 mg and 1,400 mg. That could well be the sweet spot. A glass of milk, a carton of low-fat (unsweetened) yogurt and lots of dark green leafy vegetables are likely to accomplish this goal. From where we sit, getting a moderate amount of calcium from food makes a lot of sense. Basically, we’re back to grandma’s wisdom: moderation in all things!
We welcome your comments below. Here are some that were posted to a previous link.
Twenty years ago at age 52, I decided to take calcium because of the bone loss associated with menopause. After several months, I developed large, painful, palpable lumps on my Achilles tendons making it painful to walk. My Dr. sent me to an arthritis clinic at a nearby teaching hospital. The first diagnoses was anklyosing spondolythyasis which was disproved with further blood work.
It took over a year to find out the lumps which were appearing around other joints by this time, were caused from taking calcium. This was not discovered by a Dr., but by accident in an article in a medical journal. The lumps disappeared in a couple of months when the calcium was stopped. The body does not seem to like the addition of minerals not ingested from food.
This situation is very confusing. What to do? What to do? Would you please do a program very soon devoted to the subject of calcium. My bone density is below what it should be. I stopped Foxamax because of its side effects and have been taking calcium regularly. Is it possible to get all the calcium we need from our diet? Thanks.
PEOPLE’S PHARMACY RESPONSE: You may be interested in a show we did a couple of years ago on Bone Vitality.
It’s great to see someone shedding light on health issues related to calcium supplements. Several years ago, a family member was suffering from kidney stones, and her doctor suggested that they were caused by too much calcium. That’s what prompted me to do extensive research into nutritional supplements. There’s no doubt in my mind that the best source of calcium is good old-fashioned food.
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