Indolepropionic acid increases with increasing fiber intake and is associated with lower levels of the inflammatory biomarker, CRP. The study measured serum metabolites of 110 randomly selected participants at baseline and at a 5-year follow-up. Indolepropionic acid was also associated with better preservation of β-cell function. The study also found that several forms of phosphatidylcholine were also inversely associated with type 2 diabetes.