Evaluating calcium's complexities

Researchers interested in the relationship between calcium and heart attacks and stroke risk collected information on diet, supplement use, and other health habits from 23,980 German men and women. The participants were 35 to 65 years old at the start of the study, and none had a history of heart disease or stroke.

The study authors followed the group for approximately 11 years, and accounted for other factors that can affect heart disease and stroke risk, such as age, gender, exercise habits, body weight, diabetes, and smoking and alcohol use, finding that:

• Adequate dietary calcium is heart healthy: People who averaged 820 mg of dietary calcium per day were 31% less likely to suffer a heart attack compared with those averaging less than 513 mg. (When men and women were analyzed separately, there was no observed heart attack risk reduction in men, and the reduced risk of heart attack was stronger for women.) People who averaged 466 mg of calcium per day from dairy were 32% less likely to suffer a heart attack compared with those averaging less than 188 mg of dairy calcium daily.
• More does not equal better: Dietary calcium intakes above an average of 1,130 mg per day did not reduce heart attack risk compared with an average of 513 mg per day.
• Supplements may not be the best source: Calcium supplement users were 1.86 times more likely to suffer a heart attack compared with non-supplement users, and people who took only calcium supplements were 2.39 times more likely to suffer a heart attack compared with people who did not use supplements of any type.

Food for thought

This study is observational and cannot prove cause and effect. Still, the findings agree with two other large studies, suggesting something about calcium supplements may be problematic for the cardiovascular system.

Calcium supplements may increase risk in part because they result in large, short-term increases in blood calcium levels, which may harm the heart and blood vessels. This is very different than getting calcium from food, which delivers smaller amounts of calcium throughout the day. Additionally, large calcium doses may lower tissue levels--though blood levels may remain the same--of nutrients that are believed to be important for heart health, such as magnesium. "Many studies have shown that magnesium is beneficial for the heart. If taking large amounts of supplemental calcium has an adverse effect on heart function, that effect might be preventable by taking magnesium along with calcium," says Alan Gaby, MD, Chief Science Editor of Aisle7.

Slow and steady = smart steps to healthy nutrition

Keep these simple tips in mind to help you find the right calcium balance for good health.

• Eat food first. Try to get your calcium from food. Good sources include low-fat dairy, green leafy vegetables, canned fish (sardines or salmon) with the bones, and fortified foods such as calcium-fortified orange juice and cereals, which deliver smaller amounts of calcium per serving than supplements.
• Ask the doc. You may not need supplements. Consult a doctor or a dietitian to determine if you get enough calcium from food.
• Divide doses. If you don't get enough calcium from food, take calcium in divided doses. For example, a supplement that provides 300 to 400 mg calcium per pill can be taken with breakfast, lunch, and dinner, rather than in one large dose of 900 to 1,200 mg.
• Supplement with savvy. Only supplement what you need, to keep total calcium intake from food and supplements combined around 800 to 1,200 mg per day.
• Master magnesium. Magnesium appears to play an important role in heart health, and levels of this nutrient may be reduced by eating too much calcium. Maintain a balance between these important nutrients by noshing on magnesium-rich foods such as spinach, pumpkin seeds, beans, Brazil nuts, low-sodium tomato products, dark chocolate (65% or greater cocoa content), and whole grains--especially buck wheat, bulgur wheat, and oat bran.

(Heart 2012;98:920-5)