His research interests center on dietary polyphenols. Within the field of polyphenols, he studies polyphenol chemistry and levels in foods; bioactivities against chronic diseases such as diabetes, bioavailability, and pharmacokinetics; and analytical methods such as HPLC-mass spectrometry. Currently, Neilson’s group studies apple, cocoa, and grape polyphenols. He is also collaborating with Amanda Stewart and Gregory Peck to investigate the impact amongst orchard practices, apple varietals, and fermentation dynamics on apple polyphenols in apple juices and hard cider.