A perfect example of how a dietary supplement can actually cause disease is calcium carbonate, which is the most common form of calcium supplement on the market today. This form of calcium is very toxic and not readily absorbed by your body--and can lead to a significant increased risk of heart disease:
http://preventdisease.com/news/16/11011 ... ease.shtmlThe best non-dairy source of dietary calcium, without any negative side effects, is actually green vegetables, or even oranges (not pasteurized commercial orange juice, which is basically orange-flavored sugar water):
https://www.healthaliciousness.com/arti ... tables.phpThe problem with relying on commercial milk--and milk products--for your calcium intake is that the pasteurization process--exposure to high heat--can actually transform the natural calcium complex in milk into toxic calcium carbonate, which your body cannot readily absorb. Raw milk, of course, does not pose this problem, and is always the best form of dairy you can consume for dietary calcium.
As far as Oregano Oil goes, as Acrimonious correctly points out, it does have very powerful anti-bacterial, anti-viral, and analgesic benefits. However, you have to be very careful with it because it comes in different concentrations--and if you try to ingest or put pure oregano oil on your skin, it can cause severe burns--even to your esophagus. It's best to dilute the pure oregano oil with olive oil--or just buy diluted oregano oil, which is much cheaper--and safer.