A study conducted by researchers in Argentina, found that only half of a large egg shell can provide the full amount of calcium recommended daily, which is about 700 mg.
The crusts must be thoroughly sterilized before eating them, to prevent the risk of salmonella, sometimes carried by raw eggs.
The researchers said this could be easily achieved by soaking them in boiling water or roasting them in a hot oven, then crushing them and adding them to food and bread to boost calcium.