Relevance of RNIs (DRVs) to Nutritional Support Alan Shenkin Department of Clinical Chemistry University of Liverpool

The Glib Answer Not much

DRVs provide the guidelines for oral nutritional requirements in health Of particular relevance to populations rather than the individual.

The individual and population reference values Relationship between requirement, intake,and likelihood of deficiency

Different requirements at different stages of disease Stabilise - rehydrate/electrolytes -vitamins/trace elements -antibiotics/disease control Repair -slow correction of deficiencies -concern about refeeding syndrome Replete - increased requirements Chronic depletion

Different requirements at different stages of disease Acute disease If hypermetabolic, minimise extent of negative nitrogen balance How much energy/protein? EAR for energy based on health, activity and age ? REE plus a stress factor

Predicting energy requirements Schofield/Harrison Benedict BMR + 10% - 50% Stress + Fever (10%/degree C) + 10% Thermic effect of feeding Activity -10% ventilated +10% lying in bed +20% Bed to chair +40% up around ward +20% for anabolism

Leads to excess energy provision At best, fat synthesis At worst fatty liver, glucose intolerance

Benefits/safety of hypocaloric feeding Maintains a supply of energy substrate

Benefits/safety of hypocaloric feeding Maintains a supply of energy substrate Does not overload the liver with non-oxidised substrates

Benefits/safety of hypocaloric feeding Maintains a supply of energy substrate Does not overload the liver with non-oxidised substrates Does not overload the lungs

Benefits/safety of hypocaloric feeding Maintains a supply of energy substrate Does not overload the liver with non-oxidised substrates Does not overload the lungs More likely to be balanced to micronutrient supply.

Different requirements at different stages of disease Acute disease If hypermetabolic, minimise extent of negative nitrogen balance How much energy/protein? As hypermetabolism settles, meet requirements, with extra for anabolism Benefits/safety of hypocaloric feeding

Protein requirements Protein RNIs- male- 55g/d i.e 0.75 g/kg/d female- 45g/d i.e 0.75g/kg/d It is prudent for adults to avoid protein intakes of more than twice the RNI (DoH) In catabolic disease, net protein catabolism is lowest when 1.5-2g/kg/d protein is supplied with adequate energy.

RNIs and ETF Comparable in some patients- especially long-term NS Depends on status on starting ETF- ?depletion ??general/specific nutrients On going requirements - ?catabolic/anabolic - losses - digestion/absorption - bioavailability - proportion from EN/IVN

mg/μg RNIs and two typical tube feeds (1500Kcal)

RNIs and TPN Bypass the regulating role of the gut Generally, lower requirement by IVN than by EN Continuous intake rather than bolus Probably only relevant for home IVN Effects of disease- lower/higher requirements

RNIs and IVN mg/ μg X10

RNI approach to supply in Nutrition Support-the underlying problem What outcome are you trying to achieve ? Maintenance of body composition? Positive nitrogen balance? Optimal tissue function?

Different objectives in different patients Maintenance in long term home EN Reduction in complications and optimal speed of recovery in acutely ill patients

NS and reduction in complications Wound healing Improved immune function Improved mobility Improved mental state

What is the optimal intake for vitamins/trace elements/protein –energy in short term and long-term NS ?

The challenge for PENG in the next 21 years To become seriously research active To undertake studies that matter in terms of patient outcome To characterise optimal intakes in disease

Conclusions DRVs/RNIs are of little value in deciding the nutritional requirement of individual patients Requirements vary with disease type/severity/ phase/duration/complications, and the balance of EN to IVN The skill of the nutritionist is to apply knowledge, clinical assessment, and understanding of nutrition and metabolism to the individual patient More research is needed on optimal intakes in relation to outcome