Even primary school children know a good diet and proper nutrition is important if you want to be physically healthy.
Eat the wrong things or insufficient of the good things and chances are you’re destined to develop heart problems, diabetes or cancer.
But what about a person’s psychological health? How important is diet and nutrition in mental health? And is there any evidence that people treat or prevent mental illness by taking particular nutrients, supplements or vitamins?
So that’s what at least 15 international researchers sought to find out. Their quest was to look at all the latest evidence from the randomised controlled trials done since 2012 on nutrition and mental health and determine what, if anything, worked and for what condition.
Published in the most recent edition of the journal World Psychiatry, these researchers ended up doing a meta-review of 33 meta-analyses of placebo-controlled randomised controlled trials involving almost 11,000 patients worldwide.
What did they find?
“The strongest evidence was found for polyunsaturated fatty acids (PUFAs), particularly as eicopentanoic acid, as an adjunctive treatment for depression,” the study authors wrote.
They said these PUFAs, administered as omega-3 fatty acids had been the most investigated nutritional supplement and had the most significant effect of all the supplements in helping reduce symptoms when for major depressive disorder. The data suggests the PUFAs help via reductions in oxidative stress and they work best in those patients with raised inflammatory markers and no reported comorbidities. Similarly they were found to be ineffective in pregnant women. It is important to note that the greatest benefit was seen when these supplements were used as an adjunctive treatment.
“As a monotherapy, the data are less compelling for omega-3,” they said.
Folate-based supplements were the most commonly investigated vitamin supplement in terms of looking for a benefit in mental illness. And even though folic acid is the most commonly taken form of the supplement, it was high dose methylfolate (the most bioactive metabolite of folic acid) that was found to have moderate-to-large benefits for depressive symptoms when used as an adjunctive treatment.
Interestingly, folate-based supplements also helped reduce the negative symptoms in schizophrenia, but once again this benefit appeared only with high dose methylfolate (>15mg/day), which may be explained by the fact that methylfolate is more readily absorbed than other formulations in patients who have a genetic predisposition to folic acid malabsorption.
As for the other vitamins, it seemed there is only good evidence for vitamin D.
“Vitamin D was found to significantly reduce depressive symptoms in patients with clinical depression,” they concluded. And even though the best evidence was from trials using intramuscular injections of the vitamin, the benefit was still evident when the researchers just looked at trials using oral supplements.
There was some suggestion that zinc could be of use in depression, however the researchers questioned some aspects of the trials and therefore could not say for certain there was a benefit.
Finally, the meta-review found evidence that the amino acid supplement N-acetylcysteine was potentially effective for reducing depressive symptoms and improving functional recovery when used as an adjunctive therapy in patients with schizophrenia.
As for any of the other vitamins, minerals, amino acids or antioxidants, there was no evidence of any benefit in their use in patients with mental illness either alone or as an adjunctive treatment.
And even though there has been increasing interest in the role the gut microbiome plays in mental health, to date there is no evidence that either pre or probiotics make a difference, although this review did include only one meta-analysis of trials that showed conflicting results.
In their conclusion, the researchers warn against losing sight of the bigger picture when investigating the role of supplements in treating mental illness.
‘The poor physical health of people with mental illness is well documented, and excessive and unhealthy dietary intake appears to be a key factor involved. Improved diet quality is associated with reduced all-cause mortality whereas multivitamin and multimineral supplements may not improve life expectancy,” they said.
Firth J, Teasdale SB, Allott K, Siskind D, Marx W, Cotter J, et al. The efficacy and safety of nutrient supplements in the treatment of mental disorders: a meta-review of meta-analyses of randomized controlled trials. World Psychiatry. 2019 Oct; 18(3): 308-24. DOI: 10.1002/wps.20672