Instead of drinking milk or taking supplements to get adequate amounts of calcium, calcium-rich mineral water is an equally good source, researchers say.

“The special feature of mineral water as a source of calcium is as a calorie-free alternative to milk and dairy products,” Theresa Greupner of Leibniz University Hannover in Germany said in an e-mail. “In a world with a steadily growing number of overweight and obese people, it is important to reduce the energy intake and to promote alternatives to satisfy the calcium demand apart from high caloric milk and dairy products.”

Her team’s study, funded by the Association of German Mineral Water Bottlers, looked at how well the body absorbed calcium in five different products, each containing 300mg calcium: three types of calcium-rich mineral water, milk and a calcium supplement.

Twenty-one men and women participated in the study. There was no difference in how calcium from the five different sources was absorbed, the researchers report in the Journal of the American College of Nutrition.

Other minerals in the water did not affect calcium absorption.

Most mineral waters list mineralisation on the label, and the higher the amount of calcium, the better the water is as a calcium source, Greupner said.

A person would need to drink two litres of 500mg/L mineral water per day, or more than three cups of milk, to meet the German standard daily requirement of 1,000mg calcium. In the US, 1,300mg/day of calcium is recommended for adults. It’s well known in Italy that mineral water can be a good source of calcium, Maria Luisa Brandi of the University of Florence in Italy said in a phone interview.

Brandi, who was not involved in the current study, and her colleagues showed in a 2004 study that calcium in mineral water was as well absorbed as calcium in milk.

“The concept is well established in medicine,” Brandi said. “We recommend water with high calcium content for osteoporotic patients.”