Calcium supplements may increase heart risk in women

April 21, 2011 in Heart Health, Nutrition Topics in the News, Women's Health

Calcium supplements may increase heart risk in women

New study findings from New Zealand researchers suggest that calcium supplements may increase the risk of heart attack in postmenopausal women.

To investigate, researchers used data from the Women's Health Initiative (WHI), a seven year study on calcium and vitamin D supplementation that involved more than 36,000 women.  The study was designed to see if calcium plus vitamin D reduced the risk of hip fracture. 

Overall the study found no increased risk of cardiovascular events from taking calcium combined with vitamin D. But half the participants were already taking personal calcium supplements upon entering the study, whether they were assigned to calcium plus vitamin D or the placebo, which might have obscured the results.

That's why the Auckland, New Zeland team re-analyzed the WHI results to investigate the link between calcium supplements, with or without vitamin D. They wanted to provide the best current estimate of the effect of calcium supplements on heart disease risk.

When looking at the 16,718 women who were not taking personal calcium supplements at the start of the study, they found that those allocated to calcium plus vitamin D supplements were at increased risk of cardiovascular events, especially heart attack.

Conversely, women who were already taking a personal calcium supplement had no greater risk of heart attack or stroke.

The authors speculate that a sudden increase in blood calcium which remains high can cause calcium to settle in the artery walls, thereby increasing plaque thickness. This could explain why women who already had calcium in their blood due to prior personal supplement use did not experience an increased risk of heart problems.

The researchers estimate that treating 1000 women with calcium supplements for 5 years would lead to six additional heart attacks while preventing three hip fractures. While the risk to an individual is very small,  when you look at millions of people the risk adds up.

When the researchers combined these results with data from 13 other studies, they saw a trend of calcium supplements, with or without vitamin D, increasing risk the risk of heart attack and stroke.

Leslie's Note:  It's important to know that studies have revealed that dietary calcium does not pose an increased risk of heart disease or stroke; nor do vitamin D supplements.  We continue to recommend that people meet calcium and vitamin D requirements for bone health. Calcium also helps keep blood pressure in check and may help reduce the risk of colorectal cancer.

It's possible that calcium is a "threshold" mineral meaning that some calcium is good for you, but too much may put you at risk.

Adults to age 50 require 1000 milligrams of calcium each day; older adults require 1200 milligrams. Calculate what you are already getting from your diet on a daily basis, then make up the difference with a calcium supplement.  There is no need to take more than 1200 milligrams of calcium per day.

One cup of milk, ¾ cup plain yogurt and 1.5 ounces of cheese all contain roughly 300 milligrams (mg) of calcium.  Other sources include fortified soy beverages (300 mg per 1 cup), sardines with bones (3 ounces = 325 mg), canned salmon with bones (3 ounces = 188 mg), cooked Swiss chard (1 cup = 102 mg), cooked broccoli (1 cup = 62 mg) and almonds (1/4 cup = 92 mg).

Osteoporosis Canada recommends a daily vitamin D3 supplement of 400 to 1000 IU for adults under age 50 who don't have osteoporosis. After 50, a daily supplement of 800 to 2000 IU is recommended.  If you're over 50 - or have osteoporosis - take vitamin D year round.

Click here to learn more about calcium requirements and souces.

All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.