February 9, 2025, 10:42 pm | Read time: 4 minutes
In order to alleviate the symptoms of depression, those affected are often prescribed medication: antidepressants. However, patients are often critical of this and ask themselves whether there is an alternative. Researchers investigated this question – with success. FITBOOK editor Janine Riedle discusses the study.
Depression is one of the most common mental illnesses worldwide. In Germany, 8.2 percent of people were affected in 2016. In other words, 5.3 million adults (aged 18-79) in Germany are affected.1 While antidepressants are frequently used, their effect is limited, and side effects are problematic. Scientists are, therefore, increasingly looking for natural alternatives that have fewer undesirable effects. The key to a different treatment for depression may lie in tomatoes.
Overview of the Study
What the Researchers Investigated
However, this does not mean eating kilos of tomatoes. What is more important is the lycopene it contains – the pigment that gives tomatoes their red color. It has strong antioxidant and anti-inflammatory properties and can have neuroprotective effects.
In this study, researchers, therefore, investigated whether lycopene can alleviate depressive symptoms in mice exposed to chronic social stress. The focus was on the mechanism via the so-called BDNF-TrkB signaling pathway, which is crucial for synaptic plasticity – i.e., the adaptability of neuronal connections.
Tests on Mice
The scientists carried out the study with 84 male mice.2 24 mice served as a control group. The other 60 mice were repeatedly exposed to social stress over a period of ten days by bringing them together with larger and more aggressive conspecifics. This created a model for social defeat stress. After this stress phase, the stressed mice were divided into two groups: one received daily lycopene (20 milligrams per kilogram), and the other received a placebo.
The researchers carried out four behavioral tests to assess the depression-like symptoms:
- Social interaction test: assesses avoidance behavior toward other mice.
- Sucrose preference test: measures the ability to experience pleasure from sweet water (an indicator of anhedonia).
- Tail suspension test: measures hopelessness by the duration of immobility.
- Open-field test: examines the general activity of the mice.
In addition, the researchers analyzed brain samples to assess neuronal structures and measure protein and gene expression.
Lycopene Improved the Mood of the Mice
The results showed that mice with chronic stress had significantly reduced social interactions, a lower preference for sweet water, and a prolonged inability to move in the swimming and tail suspension tests – typical signs of depression.
After lycopene treatment, these scores improved: the mice showed significantly improved social behavior and spent more time with their conspecifics, in contrast to the stressed animals. In addition, they showed a greater preference for sweetened water, which indicates that they feel better pleasure. The inability to move in the swimming test was also reduced in the lycopene group, symbolizing less despair.
On a cellular level, it was shown that lycopene increased the density of nerve cells in the hippocampus. In addition, increased expression of BDNF and TrkB was found, indicating improved synaptic plasticity.
What Is the Significance of the Results?
The study provides evidence that lycopene may have an antidepressant effect by improving synaptic plasticity in the brain. The increased BDNF expression suggests that lycopene activates the BDNF-TrkB signaling pathway – a mechanism that already plays a role in established antidepressants.
One advantage of lycopene could be its high safety. In the study, the dose used was equivalent to around 1.62 milligrams per kilogram for humans – an amount that could theoretically be achieved through dietary supplementation. However, a fresh tomato contains only three to five milligrams of lycopene, so a therapeutic dose for depression would probably require a concentrated form.
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Classification of the Study and Possible Limitations
Although the study provides new insights into the antidepressant effect of lycopene, there are some limitations. The studies were only carried out with mice, which does not guarantee that the results can be transferred to humans. In addition, only male mice were used – but as women often react differently to stress, it remains unclear whether lycopene has the same effect on both sexes. The short study period is also a cause for concern, as the long-term effects of lycopene remain unclear.
Another point of criticism is that no comparison was made with antidepressants. It is, therefore, not clear whether the lycopene contained in tomatoes can help with depression just as well.
Future research should include clinical studies on humans and investigate whether lycopene is effective as a dietary supplement or in combination with classic antidepressants.