Refractory malnutrition: Does every patient respond to nutrition? 

Standardized malnutrition criteria were published in 2012, and ever since, dietitians have been keenly looking for and diagnosing malnutrition. Since the appearance of these standards, a joint effort from the American Society for Parenteral and Enteral Nutrition (ASPEN) as well as the Academy of Nutrition and Dietetics (AND), malnutrition has been a driving force to shape nutrition care. After diagnosing malnutrition, a registered dietitian may increase calorie or protein goals or advocate for early nutrition support in an effort to improve their malnutrition criteria.  

Studies have shown that malnutrition results in poor patient outcomes. One question that has not been answered, and is currently being researched, remains – will a malnourished patient adequately respond to nutrition interventions? The term refractory malnutrition has been used to describe individuals who remain “malnourished” via defined clinical standards despite maximum, and oftentimes increasing, nutrition efforts. Likewise, refractory malnutrition may be used to describe an individual who is “malnourished,” but resolution of malnutrition will not improve clinical outcomes.   

The influence of inflammation 

Several studies have shown the positive benefits of nutrition interventions for malnourished patients. However, some studies have pointed to negative outcomes. This elucidates the idea that not all patients have the same response to nutrition. One key factor could be inflammation. Inflammation has several metabolic effects, which may lead to a diagnosis of malnutrition under the ASPEN/AND criteria. Inflammation increases insulin resistance and can lead to a loss of appetite. Together, this inhibits nutrients from entering the cell for utilization. Furthermore, an inflammatory response can lead to a sustained catabolic response where fat and muscle stores are utilized rather than exogenous sources. This can lead to the fat and muscle wasting that are identified during a nutrition focused physical exam. 

In response to a lack of clinical data investigating whether the inflammatory response of a patient influences treatment response to nutrition support, Merker et al began studying nearly 2,000 patients for more information. These researchers collected baseline C-reactive protein as a marker of inflammation and evaluated nutrition’s role on 30-day mortality. Patients were categorized as having a low, moderate, or high level of inflammation. They found a strong effect of nutrition support on patients with low to moderate levels of inflammation. Conversely, among patients with a high level of inflammation, no significant benefit of nutrition support was seen. This study may highlight the need to evaluate the degree of inflammation on admission as a contributing factor to nutrition response.   

Age and mobility 

Furthermore, when considering the diagnostic criteria for malnutrition, there are also confounding variables such as mobility status or age. When diagnosing malnutrition, it may be pertinent to consider if resolution of typically defined “malnutrition” will result in improved outcomes? For example, is it reasonable to assume that resolution of a patient’s age-related wasting will improve clinical outcomes?  

All together, these concepts demonstrate that perhaps not all patients who are malnourished according to the current diagnostic criteria will see an improvement in clinical outcomes with provision of adequate nutrition. Looking forward, more research is likely to surface to better understand the role of confounding variables, such as inflammation, on nutrition response and how this may impact nutrition interventions. 

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References:

Merker M, Felder M, Gueissaz L, et al. Association of baseline inflammation with effectiveness of nutritional support among patients with disease-related malnutrition. JAMA Network Open. 2020;3(3). doi:10.1001/jamanetworkopen.2020.0663  

White JV, Guenter P, Jensen G, Malone A, Schofield M. Consensus statement of the Academy of Nutrition and Dietetics/American Society for Parenteral and Enteral Nutrition: Characteristics recommended for the identification and documentation of adult malnutrition (undernutrition). Journal of the Academy of Nutrition and Dietetics. 2012;112(5):730-738. doi:10.1016/j.jand.2012.03.012  

Seres D. Response to Nourishment is Not Predicted by Current Malnutrition Diagnostic Schema: Moving Past the Terminology of “Malnutrition.” Presented at ASPEN 2023 Nutrition Science & Practice Conference. April 2023. Accessed June 30, 2023.