ORIGINAL ARTICLE
A review of reviews: A new look at the evidence for oral nutritional supplements in clinical practice

https://doi.org/10.1016/j.clnu.2007.04.004Get rights and content

Summary

Decisions about the treatment of disease-related malnutrition should be guided where possible by evidence. Increasing numbers of systematic reviews and meta-analyses have reviewed the efficacy of oral nutritional supplements for treating disease-related malnutrition.

In order to consolidate this evidence, an overview of systematic reviews and meta-analyses (‘review of reviews’) in which oral nutritional supplements were compared with routine care was undertaken, focussing primarily on clinical outcomes. Thirteen systematic reviews and meta-analyses were reviewed (up to August 2006), either of trials in adults, including the elderly, with a variety of conditions (6 reviews), or in specific groups, including chronic renal disease, diabetes, cancer, chronic obstructive pulmonary disease (COPD), hip fracture and gastrointestinal surgery (7 reviews).

This review of reviews found largely consistent clinical benefits with oral nutritional supplements in meta-analyses of trials across patient groups. Benefits included significant reductions in mortality and complications (e.g. infections, pressure ulcers), particularly in acute settings and acutely ill geriatrics. In some specific groups there were reductions in complications (in gastrointestinal surgery, hip fracture) but in other groups (e.g. COPD, chronic renal disease) more research is needed to assess relevant clinical outcomes. Across reviews of all patient groups, oral nutritional supplements consistently improved total nutritional intake, with little suppression of food intake. In general, reviews indicated improvements in weight (weight gain or less weight loss) with oral nutritional supplements. The only systematic review comparing oral nutritional supplements with dietary advice showed greater intakes and weight gain with oral nutritional supplements.

In summary, there is increasing evidence to support the use of oral nutritional supplements in clinical practice, particularly in acutely ill and older patients. Future research must be well designed in order to ascertain the most effective ways of using oral nutritional supplements and other dietary strategies to optimally treat disease-related malnutrition.

Introduction

In the current healthcare environment, there is pressure to promptly identify conditions and to treat them in an ethical and clinically effective way using limited resources. This applies to the treatment of disease-related malnutrition, a condition that is widespread in hospitals, community health care settings (outpatients, care homes, general practice) and in free living older people.1, 2, 3, 4 Figure 1 highlights the widespread prevalence of disease-related malnutrition (identified with the Malnutrition Universal Screening Tool ‘MUST’, www.bapen.org.uk) across healthcare settings and in free living elderly people.1, 2

Disease-related malnutrition is detrimental physiologically and clinically, impairing quality of life and delaying recovery from illness. Recent data suggests disease-related malnutrition doubles the risk of mortality in hospital patients and triples mortality in elderly patients in hospital and after discharge.5, 6 Disease-related malnutrition increases use of healthcare resources (hospitalisations, GP visits)1, 3, 4, 5, 7, 8 and latest estimates suggest that this condition costs the UK more than £7.3 billion (∼10.9 billion euro) annually.3, 9

Considering the widespread prevalence and adverse consequences of malnutrition, a condition that is largely treatable, prompt identification is required with screening, followed by the most appropriate, effective and ethical treatment. Most patients who have (or are at risk of) malnutrition can be managed with a variety of oral dietary approaches including dietary modification (fortification, extra snacks, etc.), counselling by a dietitian and/or commercially available oral nutritional supplements. With the rise of evidence-based practice, there is a need to demonstrate the effectiveness of these different treatment strategies. A systematic review (type I in the hierarchy of evidence10), which may or may not include a meta-analysis, is considered the best way of assessing the evidence base for interventions particularly when undertaken by those with a good understanding of the clinical use of the treatment.

An increasing number of systematic reviews have been undertaken to review the effectiveness of oral nutrition support strategies in the management of malnutrition. The majority of these systematic reviews have focussed on trials of oral nutritional supplements (ONS), the strategy for which there is the greatest number of individual trials available.4 Such reviews are often used as a basis for the production of guidelines by national and international professional bodies, such as the National Institute for Health and Clinical Excellence (NICE) in the UK.11 Indeed, there are already a substantial number of guidelines and standards referring to the use of ONS, and examples from the British Association for Parenteral and Enteral Nutrition (BAPEN) and the European Society for Clinical Nutrition and Metabolism (ESPEN) are summarised in Table 1.

Different systematic reviews and meta-analyses can, however, sometimes produce conflicting and confusing results. One such example includes systematic reviews examining the effects of fish and fish oil on cardiovascular disease.12, 13 This may arise because the reviews and analyses are undertaken at different times, using different studies, inclusion criteria and statistical methods. The extent to which such discrepancies in findings exist with systematic reviews of clinical trials of ONS is unclear. Due to the increasing number of systematic reviews and meta-analyses of trials of ONS use in different patient groups and specific conditions, it was felt important to consolidate the findings and address any inconsistencies in results. Therefore, the aim of this review of reviews was to assess and consolidate the key findings from systematic reviews and meta-analyses of trials of ONS (compared with “routine care” in adults), focussing primarily on the effects on clinical outcome whilst also considering functional outcomes, nutritional status and intake.

Section snippets

Methodology

Systematic reviews and meta-analyses were identified using searches of electronic databases, including Pub Med and Cochrane (search terms: systematic review, meta-analysis, enteral*, oral*, supplement*, sip, feed, liquid, formula*), checking of bibliographies, hand searching of conference proceedings and discussion with experts in the field (completed August 2006). The pre-determined inclusion and exclusion criteria for selection of systematic reviews and meta-analyses are shown in Table 2.

Summary of search findings (all reviews)

Thirteen systematic reviews and meta-analyses of trials of ONS were identified for inclusion in this review of reviews.4, 11, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 Earlier versions of reviews by the same authors or duplicate reviews were not included.26, 27, 28, 29, 30, 31, 32 All systematic reviews were published4, 11, 15, 16, 17, 18, 19, 20, 21, 22, 23, 25 or available to the authors whilst in press24 at the time of the review (August 2006). The main characteristics of the included

Systematic reviews of ONS trials across patient groups

The systematic reviews and meta-analyses of trials across patient groups (Table 3) provided more data than the reviews of more specific conditions. These meta-analyses consistently suggested a reduction in mortality and complications in favour of ONS versus routine care, particularly in acutely ill patients.4, 11, 21, 23 The evidence relating to clinical outcomes (mortality, complications), function, nutritional intake and status is discussed below.

Systematic reviews of ONS trials in specific conditions

The effects of ONS in specific conditions were covered by systematic reviews and meta-analyses of trials of patients with cancer,22 chronic kidney disease,20 COPD,19 diabetes,18 gastrointestinal surgery16, 24 and hip fracture.17 In addition, the systematic review by Stratton et al. assessed the evidence for ONS use in a variety of specific conditions (see Table 4 and refer to4) and Milne et al.23 undertook meta-analyses of clinical outcome data in ONS trials in hip fracture and stroke.

For

Gastrointestinal tolerance and adverse effects of ONS

No significant detriments to clinical outcome from the use of ONS were identified in any of the systematic reviews and meta-analyses included in this review. Similarly, no individual RCTs have shown any significant adverse effects of ONS on clinical outcome.4

Some reviews assessed gastrointestinal tolerance and suggested some minor adverse gastrointestinal complaints, including nausea, bloating and diarrhoea, with supplementation.4 A significant increase in vomiting with the early use of enteral

Quality assessment

In all of these systematic reviews and meta-analyses, the quality of included studies was formally assessed by a variety of procedures, including the Jadad score42 the Quality of evidence Quality Assessment scale (Agency for Health Care and Policy Research43) and a 10-item quality assessment tool from the Cochrane organization.44 The main limitation of individual studies included in the reviews was the lack of blinding. Few studies, particularly older studies, used a placebo. This may lead to

Conclusion

Systematic reviews and meta-analyses are one of the tools that clinicians use alongside clinical judgement and experience to guide decisions about the best treatment to use for their patients. This review of reviews highlighted the breadth of evidence that now exists to support the use of ONS, especially liquid, multi-nutrient ONS, in the treatment of patients with a wide variety of conditions. The evidence is strongest in the acutely ill, in older patients and undernourished patients, with

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