7. Fungus

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Yep, whether we like it or not, certain fungi are essential to our health. Included on that list is one called Candida albicans, a fungus that resides in the intestines. This particular fungus has a tendency to get a bit ambitious where reproduction is concerned so a healthy balance is maintained with the help of beneficial bacteria, more commonly referred to as probiotics. If your probiotic army gets decimated by antibiotics or some other chemical attack, Candida albicans can run wild and make you feel depressed, irritable, confused, dizzy, manic, delusional, psychotic and even suicidal or violet.