Humans suffer the highest burden of chronic disease in every age group ever in human history. Why? While many theories have been proposed, presented here are thoughts on a unified theory of disease to understand causes and provide guidance for health restoration and disease prevention. My thesis is that the combination of high and increasing body load of heavy metals, meta-metals and persistent and non-persistent environmental chemicals; multiple nutrient deficiencies and insufficiencies and loss of "unimportant" molecules from the food supply; dis-synchronization with the environment; and genetic susceptibility combine to disrupt physiology and cause disease.