Girodon 1997.

Methods	Randomised, double‐blind, placebo‐controlled trial with parallel group design.
Participants	Country: France. Number of participants randomised: 81 elderly participants, 20 males and 61 females, aged 65 to 102 years, with an average age of 84 years. Inclusion criteria: at least 65 years of age, only age related diseases (osteoarthritis, hypertension, residual stroke etc.), that required chronic care. Exclusion criteria: history of cancer, taking medication that might interfere with nutritional status, immunocompetence, or vitamin or mineral supplements.
Interventions	Participants were randomly assigned to receive: group 1: placebo (n = 20); group 2: trace elements (zinc 20 mg in a form of zinc sulphate; selenium 100 µg in a form of selenite) (n = 20); group 3: vitamins (vitamin C 120 mg; beta‐carotene 6 mg; vitamin E 15 mg) (n = 20); group 4: combination of trace elements and vitamins at equal doses (n = 21); daily (one capsule a day) for a period of 2 years. Mean duration of follow‐up was 730 days.
Outcomes	The primary outcome measure was impact of a trace element and vitamin supplementation on infectious morbidity.
Notes	Compliance with treatment was checked by measuring the plasma vitamin levels and counting of the returned capsules. Compliance was good. After 6 months of supplementation, a significant increase in vitamin and trace element serum levels was obtained in the corresponding treatment groups: a plateau was then observed for the whole study. No changes appeared in the placebo group. There were no losses to follow‐up. Study agents were provided by Produits Roche SA.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The trial is described as randomised, but the method of sequence generation was not specified.
Allocation concealment (selection bias)	Unclear risk	The trial was described as randomised but the method used to conceal the allocation was not described, so that intervention allocations may have been foreseen in advance of, or during, enrolment.
Blinding (performance bias and detection bias) All outcomes	Low risk	The trial was described as blinded, the parties that were blinded, and the method of blinding was described, so that knowledge of allocation was adequately prevented during the trial.
Incomplete outcome data (attrition bias) All outcomes	Low risk	The numbers and reasons for dropouts and withdrawals in all intervention groups were described.
Selective reporting (reporting bias)	Low risk	Pre‐defined, or clinically relevant and reasonably expected outcomes are reported on.
Other bias	Low risk	The trial appears to be free of other components that could put it at risk of bias.