Diet History Is a Reliable Predictor of Suboptimal Docosahexaenoic Acid Levels in Adult Patients with Phenylketonuria.

BACKGROUND

Omega-3 long-chain polyunsaturated fatty acids (n3LCPUFA) levels are reduced in phenylketonuria (PKU). Recent care guidelines recommend essential fatty acid status is monitored in patients with PKU but access to such testing is limited. We hypothesized that information obtained on diet history would identify PKU adults with suboptimal levels of n3LCPUFA.

METHODS

A 12-month single site prospective study was completed including 35 adults (age 18-46) attending a clinic for adults with inborn errors of metabolism. Levels of n3LCPUFA were correlated with estimated intake using a published food frequency questionnaire. n3LCPUFA levels were tested at a commercial laboratory and values > one SD below the laboratory mean value were considered suboptimal.

RESULTS

Mean levels of docosahexaenoic acid (DHA) were lower and levels of eicosapentaenoic acid (EPA) and alpha-linoleic acid (ALA) higher in subjects with PKU than in laboratory controls. n3LCPUFA levels correlated with estimated intake (p <0.002). Diet history had a positive predictive value of 93% and negative predictive value of 90% to identify subjects with suboptimal n3LCPUFA levels.

CONCLUSIONS

Diet history is sufficient to predict adult subjects who may have low DHA levels and can be used to target testing or supplementation to those at risk. DHA levels are low despite high levels of ALA suggesting that supplementation, if indicated, should be with preformed DHA rather than with its precursors.