My apologies to the British, don’t drink your milk with your tea

Fortified milk is a great source of calcium and vitamin D, making it a powerhouse for bone health. However, sometimes, just drinking it is not enough. Calcium is a tricky nutrient that can chelate - or chemically bind - to other substances, making it virtually worthless to the body. Consider these points when planning your calcium intake:

• Tannins in tea (and to a lesser extent coffee) chelate with milk calcium reducing the amount bioavailable to you.
• Attention vegans: Oxalic acid found in spinach, collard greens, sweet potatoes, rhubarb, and beans binds with calcium and prevents its absorption. Try kale instead. It is low in oxalic acid and delivers about 200mg calcium per cooked cup.
• If your diet is rich in high-fiber, whole-grain cereal, legumes and nuts/seeds, you likely need more calcium. The phytic acid and fiber in these foods bind with calcium making it less available. Examples: cheese on a bean burrito, milk on cereal, or yogurt with lentils. If these are your sources of calcium, think about adding a supplement.

http://cals.arizona.edu/pubs/health/az1042.pdfhttp://ods.od.nih.gov/factsheets/calcium.asp#h5