If you've been reluctant to take calcium supplements for fear of heart problems, it's time to cast that worry aside.
In the latest back and forth between researchers, new study findings offer assurance that people who take calcium at recommended levels for bone health can continue to do so safely.
The study, published last week in the American Journal of Clinical Nutrition, was conducted in almost 1,300 older men and women and found no link whatsoever between calcium intake – from diet or supplements – and coronary artery calcification, a strong predictor of heart attack.
These findings come after two controversial studies from New Zealand researchers sparked concern that calcium supplements could raise the risk of heart attack, particularly in older women. Their proposed theory: Calcium ingested from supplements increases blood calcium and deposits in artery walls, building up in fatty plaques. Over time, calcified fatty plaques can harden and narrow blood vessels, hindering blood flow to the heart.
Many women stopped taking calcium pills, attempting to meet daily needs from diet alone.
Yet several concerns about the research methods used in these earlier reports have been actively debated in scientific journals, leading scientists to seriously question their conclusions.
The latest study set out to determine if calcium intake from diet and supplements was, in fact, associated with coronary artery calcification in participants enrolled in the Framingham Heart Study, the longest-running medical study to date. The investigators examined 1,278 men and women, average age 60, who were asked about their diet and supplement use and underwent CT (computed tomography) scans of their coronary arteries four years later.
After accounting for cardiovascular disease risk factors such as age, body weight, smoking and alcohol use, the researchers found no link between calcium intake and coronary artery calcium scores. Participants with the highest calcium intake from diet or supplements (1,558 to 2,821 milligrams in women and 1,047 to 3,050 milligrams in men) had the same calcium scores as those with the lowest calcium intakes.
These findings add to the weight of the evidence that calcium supplements do not have adverse effects on cardiovascular disease risk. In fact, previous studies have shown that calcium has beneficial effects on blood pressure and blood cholesterol levels. There's also preliminary evidence to suggest that calcium plus vitamin D supplementation may improve blood glucose (sugar) control in people with type 2 diabetes.
While coronary artery calcification is indeed a risk factor for heart attack, there's not a stitch of evidence that consuming calcium causes this condition. Calcification in arteries is the result of events happening in damaged arteries, not simply because calcium is circulating in your bloodstream.
Furthermore, experts contend that the small increase in blood calcium that occurs after taking a supplement is unlikely to be large enough to cause calcification in artery walls, or any tissue in the body.
The appropriateness of inferring from study findings that calcium supplements – or any dietary factor, for that matter – causes harm should be based on four criteria: a strong association between calcium and heart attack, consistent findings from earlier studies, a dose-response relationship (e.g., as calcium intake increases, the risk of heart attack increases) and a biologic mechanism that makes sense.
According to an expert review of research on the link between calcium use and cardiovascular disease published this month in Advances in Nutrition, An International Review Journal, the earlier reports that raised fears among women and their doctors met none of these criteria.
The Institute of Medicine Food and Nutrition Board – the organization that establishes nutrient recommendations for North Americans – also concluded that the evidence to date does not support a link between calcium and cardiovascular disease.
An adequate intake of calcium – from food and supplements – has repeatedly been shown to preserve bone density in older adults. Studies have revealed that age-related bone loss is more pronounced when dietary calcium is low, which is the case for many Canadians.
Meeting daily calcium requirements goes beyond bone health. Evidence suggests that calcium supplementation can help reduce the risk of precancerous colon polyps, maintain a healthy blood pressure, prevent pregnancy-induced high blood pressure (pre-eclampsia) and ease symptoms of premenstrual syndrome.
Women and men, aged 19 to 50, need 1,000 milligrams of calcium each day; older women require 1,200 milligrams. After age 70, men's daily calcium requirements increase to 1,200 milligrams. The safe upper daily limit for calcium (from food and supplements) is 2,500 milligrams for adults 19 to 50 years and 2,000 milligrams for older adults.
Get the calcium you need from your diet first since calcium-rich foods provide many other nutrients important to health. If your diet falls short, make up the difference with a calcium supplement. (Most multivitamins do not contain enough calcium to suffice as a supplement.) That said, it's always important that you discuss with your health-care provider whether calcium supplements are appropriate for your health profile. People with chronic kidney disease, for example, should only take calcium as prescribed by their doctor.
Where to find calcium
Selected foods – dairy and non-dairy – that are rich in calcium:
Milk, 1 cup, 305 milligrams (mg) of calcium
Yogurt, plain, ¾ cup, 336 mg
Yogurt, fruit flavoured, ¾ cup, 254 mg
Cheese, cheddar, 1 oz., 204 mg
Fortified plant beverages (e.g. soy, rice, almond), 1 cup, 300 to 330 mg
Baked beans, 1 cup, 154 mg
Soybeans, cooked, 1 cup, 261 mg
Tofu, firm, with calcium sulfate, ½ cup, 253 mg
Almond butter, 2 tbsp., 112 mg
Bok choy, cooked, 1 cup, 158 mg
Collard greens, cooked, 1 cup, 266 mg
Rapini (broccoli raab), cooked, 1 cup, 200 mg
Spinach, cooked, 1 cup, 245 mg
Swiss chard, cooked, 1 cup, 102 mg
Blackstrap molasses, 1 tbsp., 180 mg
(Source: USDA Agricultural Research Service)
Leslie Beck, a registered dietitian, is the national director of nutrition at BodyScience Medical. She can be seen every Thursday at noon on CTV News Channel's Direct. www.lesliebeck.com
Leslie Beck