SMILES: 67 adults with depression, a dietician against social support, remission 32 percent versus 8 percent

The founding trial of nutritional psychiatry: 12 weeks, seven dietician sessions, MADRS d 1.16, remission 32.3% vs 8.0%, NNT 4.1 with a 95% CI of 2.3 to 27.8. Single blind, 56 of 67 with complete data, and a 2018 correction on recruitment.

moderate evidence63/100

Reasonable evidence with real limitations. how we score evidence

Caveat on this rating: n=67, 56 with complete data; single blind; 55 of 67 already on therapy or medication; control was social support, not treatment; NNT interval 2.3 to 27.8; remission counts of 10 versus 2. A 2018 correction disclosed an unreported recruitment channel.

Almost every headline about food and depression traces back to this trial. It is a real randomised trial with a real result, and it is small, unblinded and has a confidence interval that runs from excellent to nearly useless.

Significant findings

"'SMILES' was a 12-week, parallel-group, single blind, randomised controlled trial of an adjunctive dietary intervention in the treatment of moderate to severe depression. The intervention consisted of seven individual nutritional consulting sessions delivered by a clinical dietician. The control condition comprised a social support protocol to the same visit schedule and length."

"We assessed 166 individuals for eligibility, of whom 67 were enrolled (diet intervention, n = 33; control, n = 34). Of these, 55 were utilising some form of therapy: 21 were using psychotherapy and pharmacotherapy combined; 9 were using exclusively psychotherapy; and 25 were using only pharmacotherapy."

At 12 weeks "There were 31 in the diet support group and 25 in the social support control group who had complete data." The diet group "demonstrated significantly greater improvement between baseline and 12 weeks on the MADRS than the social support control group, t(60.7) = 4.38, p < 0.001, Cohen's d = -1.16."

"Remission, defined as a MADRS score <10, was achieved for 32.3% (n = 10) and 8.0% (n = 2) of the intervention and control groups, respectively"; "number needed to treat (NNT) based on remission scores was 4.1 (95% CI of NNT 2.3-27.8)." A sensitivity analysis found the result "robust to violations of MAR assumptions" about dropouts.

The correction

In December 2018 the journal published a correction: "The original version of this paper did not specify that a website was used in the final year of recruitment, in addition to the other stated recruitment methods." A recruitment channel, not a result, but it was not disclosed in the original.

The other direction

Sixty seven people, and 56 with data at the end. Single blind means participants knew which arm they were in, and a person who knows they are on the diet plan is a person rating their own mood. Fifty five of the 67 were already on therapy, medication or both, so this is diet added to treatment, not diet instead of it. The control was social support, so the finding is that diet beat company, not that diet beat treatment. An NNT interval of 2.3 to 27.8 is the honest width of a small trial. The remission counts are 10 people against 2.

What this does not show

It does not compare a diet with an antidepressant or with psychotherapy. It does not tell anyone to change what they eat, or what they take, and neither does this row. The Firth 2019 row in this set is what the effect looks like once the larger, duller trials are pooled.

Worth asking

Ten people against two: what would the same trial look like with ten times as many, and has anyone run it?

Source

Reputable peer-reviewed journal

Read the source: https://doi.org/10.1186/s12916-017-0791-y

DOI: 10.1186/s12916-017-0791-y

How this was scored

Study design: Randomised controlled trial
Funding: Funding not disclosed
Published in: Reputable peer-reviewed journal
Sample size: 67
Preregistered: Yes
Conflicts disclosed: not recorded
Independent of proponent: not recorded
Retracted: No

Read the full scoring rubric, including what it can't tell you.

Published September 29, 2026.

Questions

How strong is the evidence behind this?

veisund rates this source "moderate evidence". Reasonable evidence with real limitations. It scores 63 out of 100 on our published rubric. One caveat travels with that badge: n=67, 56 with complete data; single blind; 55 of 67 already on therapy or medication; control was social support, not treatment; NNT interval 2.3 to 27.8; remission counts of 10 versus 2. A 2018 correction disclosed an unreported recruitment channel. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.

What is the source for this?

A randomised controlled trial of dietary improvement for adults with major depression (the 'SMILES' trial) — Jacka FN, O'Neil A, Opie R, Itsiopoulos C, Cotton S, Mohebbi M, Castle D, Dash S, Mihalopoulos C, Chatterton ML, Brazionis L, Dean OM, Hodge AM, Berk M (2017). Published in: Reputable peer-reviewed journal. DOI: 10.1186/s12916-017-0791-y. The full source is linked on this page so you can read it yourself.

Who paid for this research, and does that matter?

Study design: Randomised controlled trial. Funding: Funding not disclosed. Independence from the proponent is not recorded. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.

Is this medical advice?

This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.

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