Calcium is the most essential element for strong bones, and the best source of calcium is undoubtedly milk. Milk also contains potassium, magnesium, riboflavin, phosphorus, and vitamins D and B12. All these nutrients are important for healthy bones.t the same time, strong bones are required for good posture, balance and strength. To enjoy strong bones, certain key nutrients are required, such as calcium, magnesium, potassium, vitamins, beta-carotene, and protein.