Calcium is found naturally in animals and plants. In animals and humans, calcium is found naturally in bones and teeth.
Calcium-rich foods
In addition to choosing foods from the following list, you should 
learn to look at food labels and choose foods that have a higher% DV for
 calcium and at least 20% or more. You can find large differences in the
 calcium content of foods, even among different brands of the same foods
 such as cheese, juice and bread.
Plain yogurt
Yogurt, fruit
Milk, low fat or fat-free
Whole milk
Cheese, including American, ricotta, mozzarella and cheddar cheese
Milk shakes
Eggnog
Check the nutrition label to make sure the cheese has a lot of 
calcium. Also look for foods made with these calcium-rich foods as 
ingredients, such as macaroni and cheese (cheese), pudding (milk) and 
nachos (cheese).
Limestone: Limestone is the most widely used source 
of natural calcium. It is used in the manufacture of fertilizer to the 
soil and also taking calcium supplements for calcium deficient people. 
Limestone is simply calcium carbonate is known for its ability to reduce
 acidity in the stomach. Due to this reason, calcium carbonate derived 
from limestone, marble and chalk is used in making high quality, 
effective calcium tablets.
Milk: In the animal sources, milk is the most 
abundant natural source of calcium. 1 cup of pure milk provides 400 mg 
of calcium. Dairy products, including low-fat products such as cheese, 
yoghurt and cream are rich sources of calcium.
Vegetarian diet: vegetables, beans
 and nuts are another natural source of calcium. Kale, broccoli, 
spinach, cabbage, mustard, turnip and dandelion greens are good sources 
of calcium and provide up to 400 mg of calcium in 1-3 portions.
Coral Calcium: Coral calcium is essentially calcium 
carbonate is another natural source of calcium. Coral calcium is 
obtained from fossilized coral reefs and is used in making calcium 
supplements of high quality. It has an absorption rate higher than 
normal calcium carbonate and therefore provides the most basic of 
calcium (up to 40%).
Coral calcium is a refined shape of calcium carbonate and offers many
 health benefits including long-term prevention of degenerative diseases
 and overcome calcium deficiency. Tablets made with coral calcium are 
recommended to be consumed immediately after meals. They reduce stomach 
acid and help proper digestion of food.
Daily calcium needs
It is also important to understand how children really need calcium. 
The Food and Nutrition Board of the National Academy of Sciences 
recommends:
500 mg daily for children who are 1 to 3 years
800 mg daily for children who are 4 to 8 years
Non-dairy foods with calcium
Getting enough calcium can be an especially difficult if your 
children are allergic to milk. These non-dairy foods are good choices 
for children with milk allergies who need calcium:
Salmon, tofu, rhubarb, sardines, kale, spinach, turnip greens, okra, 
white beans, baked beans, broccoli, peas, Brussels sprouts, sesame 
seeds, bok choy, almonds
Calcium-fortified foods
In addition to the large number of calcium-rich foods that are 
naturally present, such as milk and cheese, many foods are now fortified
 with calcium. Calcium-fortified breakfast cereal, including General 
Mills Whole Grain Total, Total Raisin Bran, Total Cranberry Crunch, and 
total honey clusters, which have all 100% DV of calcium per serving!
- Calcium-fortified orange juice
- Calcium-fortified soy milk
- Sunny D with Calcium (the sunniest D products have calcium, so look for one that does if your child needs extra calcium in their diet)
- Instant Oatmeal
- Calcium-fortified bread or English muffins
- Calcium-fortified beverages such as Pediasure or Carnation Instant Breakfast
- Other breakfast cereals fortified with calcium, including General Mills Golden Grahams (350 mg)
- Learning to read food labels, you may be able to find other foods that are fortified with calcium.
- Talk to your pediatrician if you do not know if your child has enough calcium in their diet.
Most varieties of vitamins for children do not have a lot of calcium 
in them and you may need a calcium supplement to the special place.
Choose from a combination of calcium-rich foods to get more calcium 
in the diet of your child, like a grilled cheese sandwich with 
calcium-fortified bread and cheese or breakfast cereal fortified with 
calcium d a half cup of low fat milk.
In addition to getting enough calcium in your diet, regular exercise is also important for healthy bones.
 
 
 
 

 
 
Among the calcium-rich food on the list, I think coral calcium is one of those that are extracted naturally. This means harvesting it does not harm the habitat of animals. It also has one of the highest dosages of calcium. Thus, taking it daily will provide the calcium needed by the body to fight off diseases.
Yulanda Mccargo
Yulanda, Thank's for your explanation. Hopefully, your explanation could be useful for other readers. :)