Decay of Food DNA in the Gastrointestinal Tract: Implications for Molecular Dietary Records

Background/Objectives: The widely recognized potential for biased responses to food frequency questionnaires and non-compliant self-reporting is motivating the search for alternative food intake records. The analysis of fecal DNA has been investigated as a potentially less biased and technically manageable method to replace or complement oral or written dietary surveys. The accuracy of fecal-DNA-based recalls critically depends on the persistence of ingested DNA of dietary origin during digestion. Methods: To inform the implementation of alternative molecular dietary inventories, we quantified the concentration of dietary DNA in the small intestine and in the feces of dogs, and in several sections of the mouse gastro-intestinal tract. Results: Using PCR assays specific for five ingredients used in commercial dog food and in mouse chow, we observed that fish DNA was most sensitive to digestion in the canine GI tract. In both species, DNA from corn and wheat was detectable in intestinal and in fecal samples. Perturbation of the mouse intestinal microbiota with antibiotics delayed the dietary DNA degradation in the GI tract. Conclusions: These results illustrate the limitations of DNA-based dietary recalls, underscoring their potential for generating biased information.