The dietary management of PROP consists of limiting complete (intact, natural) protein containing the propiogenic amino acids; valine (VAL), isoleucine (ILE), methionine (MET) and threonine (THR) to lessen the toxic accumulation of propionic acid. VAL, ILE, MET and THR are indispensable (essential) amino acids, necessary in adequate quantities for protein utilization, anabolism for growth and tissue repair. Early case reports of individuals with PROP treated with restriction of complete protein intake alone, showed poor growth outcomes and clinical signs of inadequate total protein intake. PROP medical foods (formulas) provide protein equivalents restricting propiogenic amino acids while still providing other essential amino acids and nutrients. Cohort studies over the past decades have elucidated ranges of total protein intake with variable proportions of complete protein (including human breastmilk) and PROP medical food protein equivalents. Individuals with more severe forms of PROP require greater restriction of complete protein and rely on additional PROP medical food protein equivalents in order to meet their daily total protein needs. Individuals with milder forms of PROP may tolerate their age-appropriate DRI AI/RDA from complete protein without requiring the addition of PROP medical food protein equivalents. Should an individual's plasma concentration of ILE and/or VAL fall below the desired range, first consider an increase of complete protein due to a lack of evidence for the efficacy of adding single L-ILE and/or L-VAL amino acid supplements.
Limited data relating energy intake to protein intake and outcomes in PROP have been reported in case studies. In general, energy intake should meet the age-appropriate DRI EER. Energy intake should be adequate under all circumstances to prevent catabolism and the release of propiogenic amino acids from endogenous protein and odd-chain fats from lipid stores. Non-ambulatory individuals and/or those with decreased physical activity due to hypotonia or other neurological complications may need some caloric restriction to prevent obesity. There is no evidence that the recommended intake of fluids, essential fatty acids, vitamins, minerals, and other micronutrients for individuals with PROP differs from that for the general population. Careful and frequent monitoring of dietary intake, adherence to recommendations, and nutritional, clinical and biochemical markers that are essential for adjusting an individual’s PROP medical nutrition therapy is discussed in Question #2. Additional information about supplementation is discussed in Question #3 and monitoring of nutrition therapy in Question #4.
Definitions of the protein terminology used throughout this guideline are listed in Appendix B.
Guided by individual tolerance, disease severity and clinical status, aim for normal blood concentrations of ILE, VAL, MET and THR by providing 60-100% of the age-appropriate recommended total protein requirement from sources of complete (intact) protein. See TABLE #3, Recommended Intakes of PRO and Energy for Well Individuals with PROP.
Insufficient Evidence | Consensus | Weak | Fair | Strong |
Conditional | Imperative |
For individuals tolerating less than 100% daily protein requirement from complete (intact) protein, add PROP medical food to meet 100-120% of total protein requirement. See TABLE #3, Recommended Intakes of PRO and Energy for Well Individuals with PROP and TABLE #4, Classification of Medical Foods for the Nutrition Management of PROP .
Insufficient Evidence | Consensus | Weak | Fair | Strong |
Conditional | Imperative |
Provide additional sources of complete (intact) protein, rather than supplementing single L-amino acids, to individuals who have clinical or biochemical evidence of low plasma propiogenic amino acids.
Insufficient Evidence | Consensus | Weak | Fair | Strong |
Conditional | Imperative |
For infants with PROP, consider human breast milk as a source of complete protein if used with careful monitoring.
Insufficient Evidence | Consensus | Weak | Fair | Strong |
Conditional | Imperative |
Provide 80-120% of total energy requirements for age to spare protein catabolism while individualizing energy goals for physical activity, clinical status and to support normal growth and weight management. See TABLE #3, Recommended Intakes of PRO and Energy for Well Individuals with PROP.
Insufficient Evidence | Consensus | Weak | Fair | Strong |
Conditional | Imperative |
Meet the DRI for age for intake of essential fatty acids, fluids, vitamins, minerals, and micronutrients; consider supplementation when insufficient intake is determined by clinical, biochemical, nutritional and/or adherence monitoring. See TABLE #5, Nutrient Sources in the Nutrition Management of Well Individuals with PROP.
Insufficient Evidence | Consensus | Weak | Fair | Strong |
Conditional | Imperative |