The identification of chemicals with statistically higher levels in the MCI compared to the ND (e.g., galacturonic acid, IAA, 4-HPLA) shows the importance of this group for the early identification of individuals at risk. However external factors, including diet, medication, and exercise, may account for some of the observed chemical differences across groups, such that more information about these factors would enhance the interpretation of findings. Notably, one AD patient exhibited high outlier levels for NfL and BHBA compared with the other patients in the group (Figure ), and it would be interesting to investigate whether this is due to AD pathology or to environmental factors such as a ketogenic diet, as previously discussed.