Nutrition Hotline
By Reed Mangels, PhD, RD
QUESTION: I just noticed that the amount of calcium in my supplement has increased to 600 mg per pill. Should I look for a new supplement? L.A., via email.
ANSWER: Calcium supplements are typically used by people who aren't sure they're getting enough calcium from their diet. Health care professionals have promoted calcium supplements as a way to reduce the risk of bone loss and fracture that often goes along with getting older. Recently, however, some concerns have been voiced about these supplements. Several studies of large groups of people have found that those people who took calcium supplements, especially those taking a high dose of supplemental calcium, had an increased risk of dying from heart disease or of having a heart attack or stroke. Results have not been one-hundred-percent consistent. Some studies only saw increased risk in men1, other studies only looked at women2,3, and some saw no increased risk4,5. Most studies that did show increased risk with calcium supplement use did not see an increased risk with dietary calcium. We don't know why this is. Some researchers theorize it may be because calcium supplements provide a relatively large amount of calcium at one time while dietary calcium may arrive in the body at varying times because of different rates of absorption and because calcium-containing foods are eaten throughout the day6.
We also don't know exactly how calcium supplements might increase the risk of heart-related problems. One possibility is an increased build-up of calcium in the blood vessels around the heart, which makes these blood vessels more likely to become narrow, thus reducing blood flow to the heart1,6. Calcium may also increase blood clotting and make blood vessels stiffer1,6, both of which could affect heart function. Use of calcium supplements may also increase the risk of kidney stones7.
Calcium is an important nutrient for bone health. While there is debate about when in life calcium intake is most important and even about how much calcium we need, the best recommendations we have come from the Food and Nutrition Board who developed the RDAs. Recommendations call for adults to get 1000 mg of calcium per day; 1200 mg per day is recommended for women age 51 and older and men after age 70.
Because of concerns about the increased risk of heart problems and kidney stones associated with the use of calcium supplements that have been seen in some studies, it seems sensible to get most or all of your calcium from food. Good sources include vegetables such as kale and collards, calcium-set tofu, and calcium-fortified plant milks. Our website — http://www.vrg.org/nutrition/calcium.php — can help you make plant-based choices. If you are concerned about the amount of calcium in your diet, a registered dietitian can help you sort this out. If your dietary calcium intake is low and you can't meet the RDA through your food choices, a low-dose calcium supplement can help to make up the difference. So, for instance, if your dietary calcium intake hovers around 700 mg per day and you need 1000 mg of calcium, a calcium supplement that provides 300 mg does not seem excessive. Ideally, however, you would meet your calcium needs from food.
Of course, if you already have osteoporosis or have a medical condition that affects your calcium needs, you should discuss calcium supplementation with your health care provider.
1 Xiao Q, Murphy RA, Houston DK, Harris TB, Chow WH, Park Y. 2013. Dietary and supplemental calcium intake and cardiovascular disease mortality: the National Institutes of Health-AARP Diet and Health Study. JAMA Intern Med. 173:639-46.
2 Bolland MJ, Grey A, Avenell A, Gamble GD, Reid R. 2011. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis. BMJ. 342:d2040.
3 Bolland MJ, Barber PA, Doughty RN, et al. 2008. Vascular events in healthy older women receiving calcium supplementation: randomized controlled trial. BMJ. 336:262-6.
4 Lewis JR, Radavelli-Bagatini S, Rejnmark L, et al. 2014. The effects of calcium supplementation on verified coronary heart disease hospitalization and death in postmenopausal women: a collaborative meta-analysis of randomized controlled trials. J Bone Miner Res. 10.1002/jbmr.2311. [Epub ahead of print]
5 Spence LA, Weaver CM. 2013. Calcium intake, vascular calcification, and vascular disease. Nutr Rev. 71:15-22.
6 Reid IR. 2014. Should we prescribe calcium supplements for osteoporosis prevention? J Bone Metab. 21:21-8.
7 Wallace RB, Wactawski-Wende J, O'Sullivan MJ, et al. 2011. Urinary tract stone occurrence in the Women's Health Initiative (WHI) randomized clinical trial of calcium and vitamin D supplements. Am J Clin Nutr. 94:270-7.
