Yes, but it will be difficult. Dairy foods are the richest source of calcium and contribute 73% of the calcium in the U.S. food supply. Other foods contain smaller amounts of calcium and may contain components (such as phytates and oxalate) that reduce calcium absorption . For example, a person would need to eat 8 cups of spinach, 2 1/2 cups of broccoli, 7 cups of red beans, or 6 ounces of dry roasted almonds to get the amount of calcium absorbed from an 8 ounce glass of milk.