Researchers examined survey data on dietary habits and vitamin and supplement use collected between 1999 and 2014 from 42,038 adults.
About one in 20 adults got a substantial portion of their daily calcium from supplements, the study found.
In the study’s first year, 2.5% of supplement users got more than the estimated daily amount of calcium necessary. This peaked at 6.7% of supplement users from 2003 to 2004, then dipped to 4.6% by 2013 to 2014.
“Supplemental calcium has potential benefits, particularly in relation to bone health; however, it may also put people at increased risk of kidney stones, cardiovascular disease, and adverse gastrointestinal symptoms,” said senior study author Pamela Lutsey of the School of Public Health at the University of Minnesota in Minneapolis.
“This is in contrast to calcium consumed from dietary sources, which is generally well-tolerated and has been associated lower risk of fractures, colon cancer, kidney stones, and hypertension,” Lutsey said by email
Americans get most of their dietary calcium from dairy products, such as milk, yogurt, and cheese, all of which are rich natural sources of calcium, Lutsey added. Non-dairy sources include cruciferous vegetables, such as Chinese cabbage, kale, and broccoli.
For women up to age 50 and men up to age 70, total daily calcium intake from all sources of 800 milligrams is recommended to meet the estimated average requirements of most people, researchers note in the journal Bone. After age 50 for women and 70 for men, the suggested figure rises to 1,000 milligrams a day. These intake estimates are based on the amount of calcium needed to promote bone health.
The upper tolerable limit of calcium supplementation is 2,500 milligrams a day for adults up to age 50, and 2,000 milligrams a day after that. Larger doses are linked to an increased risk of soft tissue damage.
By the end of the study period, only 0.3% of supplement users were taking more than the upper tolerable limit, down from 1.2% in 2007 to 2008.
Women and older adults, especially those who were white, were more likely than other individuals to take too much calcium.
The study wasn’t a controlled experiment designed to prove whether or how calcium supplements might help or harm health. Another limitation is that researchers relied on survey participants to accurately recall and report what they ate, or to show all of the vitamins, minerals, and supplements they took.
Still, results add to the evidence that use of calcium supplements is declining, in part out of safety concerns, said Dr Kurt Kennel, a nutrition researcher at the Mayo Clinic in Rochester, Minnesota, who wasn’t involved in the study.
One persistent problem is that supplement users often get a lot of calcium in their diet, Kennel said.
“Since those who take supplements are more likely to have higher dietary intake of calcium, one can surmise that they are getting too much calcium because of the supplementation,” Kennel said.
Older men and women should discuss calcium supplements with their healthcare provider to determine if they need them or not.
“For most people, following a healthy diet to obtain calcium from their diet is sufficient,” Kennel added. “For healthy persons, taking calcium supplements will not decrease the risk of osteoporosis or fractures but may cause side effects.”
However, certain medical conditions like ulcerative colitis and kidney failure, diuretic medications, and weight-loss surgery can all lead to calcium deficiencies, and these patients in particular may need supplements, said Dr Neelum Aggarwal of Rush University Medical Center in Chicago.
“Rarely is diet alone going to help persons come back from a calcium-deficient state,” Aggarwal, who wasn’t involved in the study, said by email.