The main source of calcium for humans is dairy products, including milk, cheese, and yogurt. These foods are rich in calcium, essential for building and maintaining strong bones and teeth, and play a crucial role in muscle function, nerve transmission, and blood clotting. For individuals who are lactose intolerant or prefer non-dairy options, there are alternative sources of calcium such as leafy green vegetables, fortified plant-based milks, tofu, almonds, and fish with edible bones. It is important to obtain adequate calcium through diet or supplements to prevent deficiency and support overall health, particularly during growth and aging.