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Correspondence to Dr Evelina Liljeberg; evelina.liljeberg@ikv.uu.se Background Disease-related malnutrition is increasingly recognised as an unwanted consequence of acute and chronic disease.1 A range of guidelines within different clinical fields and settings recommend the use of oral nutritional supplements (ONS) as part of nutrition therapy for disease-related malnutrition, when food-based strategies alone are insufficient.2–7 Using ONS within nutrition therapy has also proven to be cost-effective.8–10 A common approach in most guidelines is to state that ONS should be initiated without focusing much on how best to do this.4 5 There are guidelines that include some descriptions on how to prescribe ONS,2 3 7 for example, to take patient preferences into account,2 but these guidelines focus on the broader concept of malnutrition treatment and do not comprehensively cover all aspects of ONS adherence. [...]guidance is needed on how ONS should be prescribed to optimise ONS consumption and adherence, to support clinical practice. Adherence is defined as ‘The extent to which a person’s behaviour—taking medication, following a diet and/or executing lifestyle changes—corresponds with agreed recommendations from a healthcare provider’ (Sabaté, p3).12 The terms adherence and compliance are often used interchangeably in the literature.11 Adherence can be difficult to achieve, especially in chronic conditions where therapy is needed for longer periods.12 Optimising adherence to ONS is important, since beneficial effects on nutritional intake and nutritional status are dependent on patients’ consumption of ONS.13 14 The WHO recognises the need for a systems approach when addressing adherence to long-term therapies.12 This system approach looks beyond the individual patient and addresses aspects of the healthcare system, including incentives for healthcare professionals. Individually tailored ONS prescription includes providing ONS samples, offering a variety of flavours, planning the timing of ONS intake and deciding on the type of ONS product and the amount to be taken daily.17–19 Previous research suggests that liquid format and ready-made ONS17 in a small volume/with high energy density13 17 26 may facilitate adherence, whereas excessive volume may be a barrier.17 19 Previous research further supports ‘in between meals’ as the preferred time for taking ONS.26 To further support adherence, the ONS prescriber should discuss and inform patients on the optimal serving style and preferred consumption method for the ONS, for example, to inform patients that ONS can be served chilled, or mixed with other ingredients to alter/enhance flavour, or served in small doses (eg, together with medication administration rounds for inpatients) (Step 4).17 18 27 Identifying preferred personal consumption methods may be important for all patients, but perhaps most important for older adults.18 For example, previous research has found mixed results regarding older adults, with some preferring to drink the ONS from the bottle using a straw,28 while others prefer it served in a glass or beaker.29 The practice pattern further recommends supporting patients with strategies to counteract any ONS-related side effects (Step 5), since this has been described as a central barrier to ONS adherence in previous research.17 The ONS prescriber should also consider any age-related physiological changes such as olfactory impairments or sensory decline that can alter the perception of ONS in older adults.18 The last step (Step 6) of the individual-level recommendations highlights the importance of meeting the patient regularly —by phone, face-to-face or during home visits—to follow-up on the ONS prescription (reassessing and revisiting steps 1—5, if needed).17 The evidence also confirms that adherence to ONS often declines over time, especially among patients with cancer.17 Consequently, a long treatment duration should be avoided if possible.

The aim of this systematic mixed-studies review is to summarise barriers/facilitators to adherence to and/or consumption of oral nutritional supplements (ONS) among patients with disease-related malnutrition. In March 2022, the Cochrane CENTRAL, PUBMED, PsycINFO (Ovid) and CINAHL were searched for articles with various study designs, published since 2000. Articles were identified on the basis of ‘population’ (patients ≥18 years with malnutrition/at nutritional risk), ‘intervention’ (ONS with ≥2 macronutrients and micronutrients), ‘comparison’ (any comparator/no comparator) and ‘outcome’ (factors affecting adherence or consumption) criteria. A sequential exploratory synthesis was conducted: first, a thematic synthesis was performed identifying barriers/facilitators; and second, the randomised controlled trials (RCTs) were used to support these findings. The five WHO dimensions of adherence guided the analysis. Study inclusion, data extraction, analysis and risk-of-bias assessment (MMAT 2018) were carried out independently by two researchers. From 21 835 screened articles, 171 were included with 42% RCTs and 20% qualitative studies. The two major populations were patients with malignancies (34%) and older adults (35%). In total, fifty-nine barriers/facilitators were identified. Patients’ health status, motivation, product tolerance and satisfaction as well as well-functioning healthcare routines and support were factors impacting ONS consumption. Few barriers/facilitators ( n = 13) were investigated in RCTs. Two of those were serving a small ONS volume and integrating ONS into ward routines. Given the complexity of ONS adherence, non-adherence to ONS should be addressed using a holistic approach. More studies are needed to investigate the effect of different approaches to increase adherence to ONS.

Background: Oral nutritional supplements (ONS) are often recommended as part of a nutritional intervention for malnutrition. However, adherence to ONS prescription is challenging and there is a lack of knowledge about how ONS should be included in the nutritional care to maximise benefits for the patient and healthcare system. Research Objective: The objective was to identify barriers and facilitators of ONS adherence related to healthcare team and system-related factors among patients with malnutrition or at risk. Methods: This mixed-studies systematic review includes studies identified in the Cochrane Central Register of Controlled Trials, PUBMED, PsycINFO, and CINAHL in March 2022. Study inclusion (title/abstract screening, full text reading) and risk of bias assessment were performed according to systematic review standards. A sequential exploratory synthesis of data was conducted with a qualitative phase (thematic analysis) followed by a quantitative phase (descriptive statistics). The World Health Organization's five dimensions of adherence was used as a framework for categorizing the data and this preliminary analysis focuses on the healthcare team and system-related dimension. Results: In total, 21835 articles were screened, 507 articles were read in full text, and 171 articles were included in the review (RCT n = 71, non-RCT n = 41, Descriptive n = 21, Qualitative n =34, Mixed methods n = 4). Six analytical themes were identified. Within the theme 'Continuity of (ONS) care', well-functioning organizational routines and structure e.g., 'Integrate ONS into daily routine' (Facilitator) and 'Lack of communication in healthcare transitions' (Barrier) were key factors to achieve adherence to ONS. Discussion: The findings highlight the central role the healthcare team and system play for ONS adherence and suggest that healthcare professionals should adopt a holistic approach when ONS are included in the nutritional care. Future experimental studies investigating the effect of different healthcare approaches to adherence to ONS are needed.

ABSTRACT Research on disease‐related malnutrition and adherence to oral nutritional supplements (ONS) has increased in recent years. To guide future studies, it is important to identify trends in terminology use and intervention characteristics. This review aimed to map characteristics of research investigating adherence to ONS in patients with disease‐related malnutrition and explore changes over time. This review is a secondary analysis of quantitative studies from a systematic mixed‐studies review. Online databases, including PubMed, Cinahl, Cochrane Central Register of Controlled Trials, and APA PsycInfo, were searched to identify studies published from 2000 to March 2022. A quantitative content analysis of extracted data was performed, and the Mixed Methods Appraisal Tool (MMAT) was used to assess methodological risk of bias. This review includes 137 articles, over half of which are randomized controlled trials (52%). The term “oral nutritional supplements” was used in 40% of the studies. Adherence to ONS was mainly described by the term “compliance” (69%). It was most common to offer ready‐made milk‐based ONS (56%) and ONS as a sole intervention (51%). The prescribed dose of ONS was fixed in 64% of studies and individualized in 22% of studies. There was variation in the methods used to assess adherence to ONS, and adherence was not reported in nearly a fifth of studies. There was an increase in methodological quality over time (p = 0.024). To ensure better understanding and increase the rigor and reproducibility of ONS intervention research, it is crucial to standardize the terminology used and to describe the interventions clearly. This review, encompassing 137 articles, mapped the characteristics of research on adherence to oral nutritional supplements (ONS) in patients with disease‐related malnutrition and explored changes over time. Key findings reveal a diverse range of terms used to describe ONS and adherence to this nutrition therapy. The ONS interventions frequently deviated from appropriate prescribing descriptions in nutrition guidelines, and there was a modest improvement in methodological quality over time.