A Cochrane review included 62 trials with a total of 10 187 participants. Most participants (71%, 26 studies) were hospitalised in-patients with acute conditions. Other participants were either in long-stay / care of the elderly / continuing care wards or nursing homes (14%, 15 studies), or at home in the community (15%, 21 studies). The trials aimed to provide between 175 and 1350 additional kcal/day. Additional protein was between 10 g and 50 g/day. Thirty-five trials used supplements with at least some vitamins and minerals. Maximum duration of interventions was 18 months. The pooled weighted mean difference (WMD) for percentage weight change showed a benefit of supplementation of 2.2% (95% CI 1.8 to 2.5; 42 trials). There was no significant reduction in mortality in the supplemented compared with control groups (RR 0.92; CI 0.81 to 1.04) from 42 trials. However, mortality results were statistically significant when limited to trials in which participants were defined as undernourished (RR 0.79; 95% CI 0.64 to 0.97; n = 2461). The risk of complications was reduced in 24 trials (RR 0.86, 95% CI 0.75 to 0.99). Few trials were able to suggest any functional benefit from supplementation. The difference in length of stay from 12 trials also showed no statistically significant effect.
Comment: The quality of evidence is downgraded by study quality (inadequate allocation concealment) and inconsistency (heterogeneity in patients, treatments and outcomes).