Posted June 25, 2021
A meta-analysis examines the link between depression and dietary/serum zinc.
- Zinc is an essential mineral needed for growth. It plays a key role in many physiological processes, such as healthy immune function.
- Lower zinc intake and blood levels have been linked with symptoms of depression.
- Zinc supplementation may be advisable for depressed patients who do not get sufficient zinc in their diet or have trouble absorbing zinc.
Source: stecks05/Pixabay (modifications: Arash Emamzadeh)
What is Zinc?
Zinc is a micronutrient (an essential mineral needed for growth and development). Zinc plays a role in many physiological processes, such as DNAsynthesis, protein production, cell growth, healthy immune function, sense of taste and smell, and the functioning of countless enzymes. Food sources of zinc include animal proteins (e.g., chicken, red meat, and seafood, particularly oysters), but also whole grains, nuts, and legumes.
Zinc supplements have been used for the treatment of a variety of conditions (e.g., colds, wound healing, diarrhea). However, consuming too much zinc can be harmful, so zinc supplements are not usually recommended for healthy people unless they do not get sufficient zinc from food sources or have trouble absorbing zinc.
For example, zinc supplements are sometimes recommended for vegetarians and vegans, individuals with alcohol problems and certain digestive conditions (e.g., inflammatory bowel diseases), and pregnantwomen.
Low zinc levels have been linked with a variety of health conditions (e.g., skin conditions, infections), including mental illness, especially depression. The review by Yosaee et al., described below, investigated the relationship between zinc and depression.
A Review of the Link Between Depression and Zinc Levels
The review began with a search of several databases (e.g., PubMed) for keywords “depression” and “zinc.” Original observational studies and randomized controlled trials (RCTs) in adult populations were included if they used depression as an outcome and zinc as an intervention or exposure factor.
The search resulted in 4,245 articles, from which 13 observational investigations (four cohort and nine cross-sectional designs) and seven RCTs met the final criteria.
- Characteristics of the RCTs: 319 participants; 2-12 weeks in duration.
- Characteristics of the observational research: 27,296 participants in cross-sectional investigations and 15,852 in cohort investigations.
The meta-analysis of the seven RCTs showed zinc supplementation was associated with a reduction in depression [weighted mean difference (WMD) = −4.15 point; 95% confidence intervals (CI): −6.56, −1.75 point; P < 0.01)].
Furthermore, zinc supplementation reduced depression scores in patients with depression who were not receiving antidepressants.
The results from the four cohort studies showed the highest zinc intake was linked with a nearly 28 percent reduction in the risk of depression [Relative Risks (RR): 0.66; 95% CI: 0.50, 0.82)].
And an analysis of the nine cross-sectional studies found having high zinc levels (serum zinc concentration combined with dietary zinc) was inversely linked with the risk for depression [RR: 0.61; 95% CI: 0.51, 0.70].
In summary, data from different types of studies showed an association between zinc levels and depression.
So, why might zinc be related to a lower risk for depression? The potential mechanisms are speculative and complicated—involving a variety of factors, like oxidative stress, N-methyl-D-aspartate (NMDA), brain-derived neurotrophic factor (BDNF), neurogenesis, cortisol, neural plasticity, and the endocrine and immune system.
Concluding Thoughts on Zinc for Depression
Here is a summary of the main findings of the meta-analysis:
- Many depressed individuals appeared to have zinc insufficiency or zinc deficiency (determined by the amount of zinc in their blood and diet).
- In cohort investigations, a 28 percent reduction in the risk of depression was seen in those with the highest zinc intake.
- In patients with depression who were not treated with antidepressants, zinc supplementation significantly reduced depression.
- The antidepressant effects of zinc supplementation were most pronounced in patients with mild to moderate depression.
The researchers note their findings may not be generalizable to healthy individuals (e.g., those without depression). Furthermore, most of the studies used in the analysis were limited in geographical location. Though some of these came from multiple countries (e.g., Germany, Finland, the U.S.), the majority were conducted in Iran and Australia. Therefore, one must await the replication of these findings. And given the correlational nature of the data (i.e. correlation does not mean causation), firm conclusions regarding the effects of zinc on depression cannot be drawn.
Nevertheless, this is not the first review to have observed a link between zinc and depression.
For instance, a 2013 meta-analysis noted depression correlated with lower blood concentration of zinc. That review, based on data from 1,643 depressed patients, concluded, “zinc concentrations were approximately −1.85 mmol/L lower in depressed subjects than control subjects,” and “greater depression severity was associated with greater relative zinc deficiency.” A more recent meta-analysis also found dietary zinc intake was linked with a lower risk for depression. In short, the relationship between zinc and depression is worthy of further research.
If you are depressed and are considering taking zinc supplements—especially if you are not getting enough zinc in your diet or have trouble absorbing zinc—please consult your physician first. As noted earlier, taking too much zinc is harmful, so it is important to determine how much zinc your body requires.
Arash Emamzadeh attended the University of British Columbia in Canada, where he studied genetics and psychology. He has also done graduate work in clinical psychology and neuropsychology in the U.S.