Because tryptophan is present in milk and warm milk helps some people feel drowsy, tryptophan became a much sought-after item for the treatment of insomnia at natural food stores. Yet some people who took tryptophan as a natural supplement developed a syndrome called eosinophilia-myalgia syndrome. Some people died. Scientists later believed the deaths were the result of taking the amino acid tryptophan. Not everyone who took tryptophan, however, experienced these side effects. In addition, not everyone who took tryptophan received help for insomnia. The influence of tryptophan on sleep continues to be studied in major sleep laboratories across the nation. While this amino acid is not available as a natural dietary supplement or sleep remedy, you can easily include tryptophan in your diet through food sources such as turkey, cheese, nuts, beans, eggs, and milk.