Amy Lanou, PhD, has written a book called "Building Bone Vitality" that recommends that you eat a low acid diet that will allow you to maintain sufficient calcium for bone health.
Foods that are less acid, or more alkaline, can prevent calcium from being pulled out of your bones. This can ultimately prevent osteoporosis. A low acid diet can also reduce the need for calcium in the form of supplements.
A low acid diet will put a strong emphasis on fruits and vegetables, and less on animal proteins and dairy products.
"The low-acid approach to maintaining bone health also helps explain why Asian countries that consume much less calcium in their diets have a much lower rate of osteoporosis than in the west. Western countries with the highest rates of osteoporosis not only consume the most dairy products, but also consume the most meat, poultry and fish, and eat fewer fruits and vegetables."
http://www.thirdage.com/osteoporosis/low-acid-diet-prevention