Date of Award

Summer 6-8-2017

Degree Type


Degree Name

Master of Science (MS)



First Advisor

Anita Nucci

Second Advisor

Teresa Douglas

Third Advisor

Sarah Henes


Objective: The primary aim of this retrospective cohort study was to determine the association between the source of dietary protein intake and the sum of plasma concentration of large neutral amino acids (LNAA) in patients with Phenylketonuria (PKU). A secondary aim of the study was to examine the effect of dietary compliance on plasma concentration of LNAA. Methods: The analysis included combined participant data from two previous studies conducted at the Emory University School of Medicine. Subjects are males (n=34) and females (n=43) with PKU ages 4-50 years. A Student t-test was used to compare total combined plasma LNAA (excluding tryptophan and phenylalanine) by dietary compliance status (alpha=0.05). Correlation statistics were used to determine the association between the ratio of reported intact food protein to medical food protein on plasma levels of LNAA. Multiple regression analysis was used to examine the contribution of intact protein to medical food protein ratio and other variables to plasma LNAA. Results: The median ratio of intact protein to medical food protein reported was 0.354 (IQR: 0.188, 0.914). Median percent of PHE intake over the PHE intake recommendation was 31.64 (Interquartile range [IQR]; 7.44, 104.98). Plasma concentration of LNAA did not differ significantly between those with plasma PHE levels within the therapeutic range μmol/L (compliant; 611.7 μmol/L [n=19]) vs levels above the therapeutic range (non-compliant; 595.3 μmol/L [n=47]); p=0.613). There was an inverse marginal correlation between the ratio of intact protein to medical food protein and plasma concentration of LNAA for those who were compliant (r = -0.436, r = 0.1) although the association was not statistically significant (p=0.08). No correlation was found for patients who were non-compliant. Regression analysis revealed that plasma concentration of LNAA was not significantly affected by the ratio of intact protein to medical food protein ratio, age, or gender. Conclusions: Although not statistically significant, a negative trend was observed between plasma LNAA concentration and the intact protein to medical food protein ratio in patients compliant with the PHE prescription. This suggests that the ratio of intact dietary protein to protein coming from medical food, as reported by patient diet records, may promote increased plasma LNAA levels in the effective treatment of PKU. The majority of the sample (74%) were non-compliant with diet based on plasma PHE levels. Future studies are needed to determine the consequences of non-compliance by decreased intake of medical food protein or increased intake of intact protein on plasma LNAA concentration and downstream health effects.