Melange

Throughout the novel the Children of Dune, there is a physical substance which the entire story is based off of. This substance is called Melange. It's a drug which prolongs the life of those who live among it, is in almost all materials created on "Dune", and is only created on one planet, in this novels entire universe (dune). Once the melange is in your diet, there is no returning. It becomes a necessity for the body, an addiction.
I believe there is a modern day substance which can be related to this 'Melange'; Sugar. It is contained in our every day diet, and there is a monopoly over the industry. Once sugar has been introduced into your everyday diet, you need small amounts of it to satisfy your urges. Hence the creation of desserts, sweets, treats, malts, soda-pops, ect. Everyone on the planet requires this substance in small amounts in order to survive, but when we overuse it, it can become deadly (just like the spice Melange on Dune).

I find it surprising how many similarities I can find between this highly fictional world created my Frank Herbert, and the modern day wolrd we know today.