Preparations comprising probiotic strains and l-tryptophan

A preparation comprising:

• at least one probiotic strain belonging to the genus Lactobacillus paracasei (Lacticaseibacillus paracasei):
• Lactobacillus brevis (Levilactobacillus brevis):
• Lactobacillus delbrueckii:
• Lactobacillus crispatus:
• Lactobacillus plantarum (Lactiplantibacillus plantarum):
• Lactobacillus plantarum subspecies argentoratensis:
• Lactobacillus reuteri (Limosilactobacillus reuteri):
• or Lactobacillus hilgardii (Lentilactobacillus hilgardii);
• and
• L-tryptophan or a dipeptide containing L-tryptophan:
• or
• a foodstuff, fruit or plant or meat extract containing L-tryptophan.