When it comes to calcium-fortified drinks, new research shows that the amount of calcium listed on the label is not the same amount of calcium that ends up in your glass. That’s because in drinks where calcium must be added, such as soy and rice beverages and orange juice, the calcium settles to the bottom of the container.

In addition, the study, which was published in the latest issue of “Nutrition Today,” states that simply shaking the beverage before drinking doesn’t really help. In fact, the researchers report they had to use really vigorous shaking, like from a shaker used to shake paint in a hardware store, to suspend the calcium enough to drink.

As part of the study, they also looked at milk to see if each glass of milk contained the amount of calcium listed on the label. And the result was a resounding yes.

Researchers gave each of the beverage products tested a score based on how well the calcium stayed suspended, and therefore drinkable, in the beverage. Milk scored higher than all four soy or rice beverages, and higher than eight of 10 orange just products. Two of the orange juice products scored similar to milk.

The researchers concluded that due to the inconsistent results of calcium-fortification in other beverages that milk is the most reliable calcium source of those beverages tested.

The research was conducted at the Osteoporosis Research Center at Creighton, University in Omaha, Neb. Robert P. Heaney was the team leader.