Soy is the go-to protein source for many vegetarians and vegans, but it also contains lots of calcium. Just 1 ounce of tofu (which usually comes in 12.5-oz. packages) has 105 mg. And depending on which brand you buy, soymilk usually has between 200 and 500 mg. of calcium per cup. Like spinach, soy contains a compound that inhibits calcium absorption, but manufacturers typically use additives to give their products a calcium boost.
If you're still having trouble meeting the recommended 1,000 to 1,300 mg. of calcium each day, you can always reach for a supplement that offers your day's worth. Food manufacturers are also making this goal easier by adding calcium to many of their products (including flour and breakfast cereals) in a way that maximizes absorption. Calcium-fortified orange juice has 500 mg. in each cup, so a few glasses each day should be all you'll need.