Eating eggshell to prevent calcium deficiency
From BearWiki
Claim: It's not worth it in the wilderness to risk your life for a little extra calcium.
Bear often seems to have his survival priorities all wrong and always feels the need to make some unreasonable climb. In the Moab Desert episode, Bear decides to scale a cliff to get a two small bird eggs (perhaps the size of quail eggs)[1], despite the fact that such a climb only does more harm than good.
However, one tip that he advises is that you eat the eggshells for the calcium. Eating anything imposes digestive costs (calories, and water), and the harder to digest it is, the more the imposed cost. So, is it worth it for the calcium?
Hardly. The human body has massive stores of calcium -- the bones and teeth. Depleting these stores enough to cause noticable problems takes years (as does replenishing them, so always eat enough calcium in your diet!). In fact, if you eat *too much* calcium at once, you increase your risk of constipation and kidney stones.[2]
Furthermore, you don't have to eat things like eggshells to get your calcium. Many common weeds contain calcium, such as purslane, lambsquarter, and amaranth; green leafy vegetables and legumes are one of the main sources of calcium in human diets after dairy. Cooking bones also leeches calcium into the broth.[3]
Calcium is a long-term need. Wilderness survival is a short-term situation. Unless you have plans to become a hermit and live out the rest of your life in a secluded part of the world, don't worry about it when lost. What you want to eat most is things that give you calories, energy, and/or are easy to digest -- fats, simple carbohydrates, and sugars.
