Are Calcium Supplements Bad For Your Heart?

It is well known that adequate calcium intake is important for bone health at all ages.  Calcium supplementation is common, with 43% of American adults (and 70% of postmenopausal women) regularly taking calcium supplements.  However, there is a lot of confusing information out there, with some studies suggesting that calcium supplements may increase the risk of heart disease.

A recent article in the New England Journal of Medicine provides an excellent discussion around the controversies of calcium supplementation and heart health.   Here are some key points:

1.  The recommended daily calcium intake for Canadian adults:

• age 19-50: 1,000 mg of elemental calcium per day (see #4 below re the meaning of 'elemental' calcium)
• men age 51-70: 1,000 mg
• women age 51-70: 1,200 mg
• adults over 70 years: 1,200 mg

2.  The evidence suggesting that calcium supplements may increase the risk of cardiovascular disease is inconsistent - in other words, we still don't have a definitive answer to this question.  Compiled data from several studies pooled together (called 'meta-analyses') have suggested increased risk, while a large randomized controlled trial called the Women's Health Initiative (WHI) did not show an increased risk.  (Randomized controlled clinical trials provide more trustworthy evidence than meta-analyses do, so the fact that the WHI didn't show an increased risk carries weight.).  

It has been speculated that a sharper increase in blood calcium levels after eating a calcium supplement may result in increased cardiovascular risk, but this has not been proven. 

3.  Given that it is still not clear whether calcium supplements increase cardiovascular risk or not, getting the recommended calcium intake from food and beverages is the preferred approach.  

We consume about 300mg of elemental calcium per day from non dairy sources.  Here are some examples of dairy and non-dairy calcium sources: 

• 1 cup of milk: 300 mg
• 1 serving of yogurt (100g): 100 mg
• 1 oz cheddar cheese: 200 mg
• 1 cup low fat cottage cheese: 200 mg
• 1 cup raw broccoli: 43 mg
• 1 cup raw kale: 100 mg
• 1 slice bread (commercially prepared): 30-70 mg
• fortified breakfast cereal - varies widely - check the label!

4.  If you need to use calcium supplements over and above dietary intake to reach your recommended calcium intake, check the label for the mg of elemental calcium, as this is the value that is important.  Calcium supplements come in many different forms (calcium carbonate, calcium gluconate, calcium citrate etc), and each type of calcium supplement contains a different percentage of elemental calcium.  If your supplement doesn't say how many mg of elemental calcium it contains, here is a guide: 

• calcium carbonate: contains 40% elemental calcium (so, if your supplement is 750mg of calcium carbonate, it contains 300 mg of elemental calcium)
• calcium citrate: contains 21% elemental calcium
• calcium gluconate: contains 9% elemental calcium

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