Peppermint is a herb traditionally used in cooking or as a digestive aid. The essential oil is produced from the plant's leaves, stems and shoots. Holland and Barrett's peppermint capsules are enteric coated capsules forming a protective barrier to allow the oil to be absorbed providing the best benefits. Peppermint is a herb traditionally used in cooking or as a digestive aid. The essential oil is produced from the plant's leaves, stems and shoots. Holland and Barrett's peppermint capsules are enteric coated capsules forming a protective barrier to allow the oil to be absorbed providing the best benefits.