To answer this eternal conundrum, we turn to the Chinese. Generally speaking, Chinese philosophy has it that the universe and all living things are constantly at play between the extremes of the yin and yang principles. Yin represents the passive, female, fluid, dark, cold, dispersing forces and yang the active, male, fiery, light, hot and concentrating forces. Any time there is an excess of either principle in the body, the body's natural tendency toward homeostasis, or balance, takes over and restores health. When this drive toward balance fails, disease results.
When we drink alcohol, we are ingesting one of the most yin substances on Earth. We know it is yin because of the mental state it puts us into: blissful, spacy, sleepy, comatose. In response to this attack of excess yin, the body begins to throw off its own yin forces to compensate—a process we experience as peeing a lot and being thirsty.
In excreting our own yin, we deplete the yin, and the yang (fire)—which was always there but held in balance by our yin—comes to the fore. The yang in the body, also known by its effects, is seen most easily in the passions, especially sexual lust. Because we have depleted the yin, the yang comes bursting out, and as a result, we feel the urge to get it on.
—Peter Sutherland, visiting fellow,OC Weekly DataLab