About one in five Americans takes a calcium supplement, often along with vitamin D, even if they're getting enough of these nutrients in their diet.
Doctors have been recommending the pills for years, either to prevent bone breaks or cancer. But a panel of experts said they're not sure the supplements are actually helping with Americans' health.
After reviewing studies of whether daily calcium and vitamin D supplements do as promised a government advisory panel said, doctors said postmenopasual women should not take anything lower than the standard 400 international units of vitamin D and 1,000 milligrams of calcium.
"That level of Vitamin D supplementation to the diet is not effective for preventing fracture," said Kirsten Bibbins-Domingo with the U.S Preventive Services Task Force.
Experts said there's not enough evidence to conclude whether higher doses might be beneficial for women who've gone through menopause or if any dose would prevent a bone break in men and younger women.
They did find a small increased risk for kidney stones among people taking the supplements.
The report also looked at whether the supplements could lower the risk for cancer and came up with very little.
Experts said eating foods like leafy greens, yogurt and milk can boost your calcium and vitamin D levels naturally.