It was when Russia was USSR and soviet state was pushing hard to become at par with US. A top erstwhile spy told that Russian Soviet dictator Stalin, used to spy on the visiting world leaders like Mao to know their hidden personality traits. They even used scientific methods for this. Soviets used to analyze the excreta for Potassium and Amino acid tryptophan to know the state of mind of the leaders. Tryptophan is used by animals for synthesis of proteins essential for growth. Studies indicate that it acts as an antidepressant.
For example, if they detected high levels of amino acid Tryptophan,“ he explained, “they concluded that person was calm and approachable”. On the other hand, potassium ion regulate the blood pressure. The diets rich in Potassium help reduce the high blood pressure. But a lack of potassium in poo was seen as a sign of a nervous disposition and someone with insomnia.