Diana likes her caffeine, as many of us do. And she doesn't like milk. She puts 1/4 cup of coffee in her milk to "get it down in the morning." Later throughout the day, it's usually 3 Diet Pepsi's. Diana wants to know if the caffeine in her coffee and soda prevent the calcium from being absorbed. Great question!
The easy answer is yes, but only to a degree. Caffeine has been shown to reduce the absorption of calcium from the foods we consume. It also increases the excretion of calcium already in the body. But, this does not prevent all of the calcium from being used. Drinking one cup of brewed caffeinated coffee or 2 cups of tea essentially creates a loss of 2-3 mg of calcium. Studies conclude that drinking caffeine at these levels does not impact bone health in premenopausal women. Of course, the more caffeine you consume, the less calcium your body has available to use. And the older we get, the amount of calcium we absorb decreases (I hate all of these things on the list of "As You Get Older...!")
My advice is to keep getting those calcium sources in! If you consume more than 2 cups of caffeinated beverages a day, try to have your high calcium foods at another time at least once a day. For example, I love to have a yogurt just before bed. It's yummy and I'm not consuming any caffeine to interfere with its absorption. And late yesterday afternoon, I had a skinny decaf latte.
Don't forget, Diana, if you really don't like milk, look for other sources of calcium you really do enjoy: yogurt, low-cheese, fortified soy milk, sardines, tofu, salmon, spinach, kale...