Egg shell composition is mostly made up of Calcium, Calcium Carbonate to be precise.Hence eggshells are a natural source of Calcium (and acts as an antacid). I personally feel that given the choice, we should try and opt for the naturally occurring supplements rather than the synthetic ones. This is not to say that you avoid store bought supplements if you need them (although some might strongly advocate against them) but naturally sourced supplements, especially as part of a healthy and balanced diet, will be assimilated more efficiently by the human body whereas synthetic compounds are hard to recognize and hence metabolise and often leave residues .If you'd like to learn more take a look at this article.
To use eggshells as Calcium supplements I recommend using free range chicken eggs. The composition of the egg shell is closely related to the diet of the chicken; the healthier and more wholesome the diet, the healthier the egg shell.
Once you've got your eggs,it is of utmost importance to properly clean them.Wash them with warm water and vinegar and let them dry.After using up the egg's contents, place the shells on a sheet of paper and let them dry.
Once they've dried, chop them in a grinder.
After chopping, you will notice that some particles are larger than others;the membrane of the shell doesn't get chopped as finely as the crust so you must pass the powder through a sieve.
And discard the large membrane bits.
You may consume 1/2-1 tsp of this powder daily with any food or drink you like or just by itself.It is recommended to discontinue course after 2 weeks.
Another use for this Calcium loaded powder is in an all natural dental powder. Check out this simple and all natural DIY DENTAL POWDER recipe to learn how to make your own.
NOTE: When administering/ taking supplenets (commercial or homemade) caution and sensibility is advised , based on general health status and/or pre-existing conditions or known sensitivities.Please consult your doctor before starting or changing any traditional medical course to a natural alternative, i am not a doctor and I only speak of what I've experienced and researched on the topic.