Do Tomatoes Boost Happiness?
People who eat more tomatoes have less depression. At least that's what the headlines say. Is it true? Here's what you need to know.
There are two major types of scientific research: observational studies and randomized controlled trials (RCTs). Observational studies are often the starting point – they allow us to form hypotheses based on tons of data and lots of people.
Of course, observational studies show correlations, not causation, so we have to run RCTs to weed out confounding variables, reverse causality, and selection bias.
Here's an example: Let's say an observational study found that people who take yoga classes have far less depression than people who don't. The conclusion: Yoga prevents or treats depression. But does it?
Maybe people who take yoga classes also have less financial stress, eat healthier diets, do other types of exercise too, and take more supplements. Those are confounding variables. Is yoga preventing depression, or is it the clean diet, financial security, active lifestyle, or lack of nutritional deficiencies? Those things fight off the sads, too.
What about reverse causality? People with lower depression levels might be more motivated to do stuff like yoga, while those with depression might lack the energy or interest to do downward dogs in a social setting. So, lower depression could lead to more yoga classes, not the other way around.
You get the idea. We'd need several good RCTs to show causation.
So, what about all the mainstream headlines we're seeing about tomatoes and depression? Does eating tomatoes prevent depression? Let's take a look using both types of studies.
Lycopene and Depression: The Science
Observational studies tell us that people who eat more tomatoes and related products have a lower prevalence of depressive symptoms. For example, one Japanese study using almost 1000 people found that a tomato-rich diet, high in lycopene (thought to be the depression-fighting component), was independently associated with less depression.
Another meta-analysis of 12 observational studies involving over 33,000 participants found the same thing. A third study of 7,000 adults found that higher blood levels of carotenoids, including lycopene, were also linked to a lower risk of depression. Those who consumed the most tomato products (including tomato sauce and paste) were the least likely to be depressed. Tomato haters were the most likely to suffer from depression.
All very cool, but all observational. Something could be happening, but we need more info. So, let's break out the RCTs.
One randomized, double-blind, placebo-controlled clinical trial on men found that 25 mg of supplemental lycopene daily for 12 weeks significantly improved depression, anxiety, and stress scores compared to the placebo group. (This study also measured fertility and found that the lycopene takers had higher sperm counts and more ejaculate volume after taking the supplement.)
Animal studies also help researchers remove human biases and ethical concerns with testing. In one mouse study, depressed mice treated with lycopene had a complete reversal of depression-like behaviors.
How could lycopene do this? Through several biological mechanisms, primarily based on its antioxidant, anti-inflammatory, and neuroprotective properties. By calming brain inflammation, lycopene normalizes serotonin and dopamine signaling. At the molecular level, lycopene enhances synaptic plasticity and upregulates the BDNF–TrkB signaling pathway in the hippocampus. It also lowers out-of-whack cortisol levels.
How to Use This Info
The lycopene research followed a smart path. First, the observational studies led to a hypothesis: maybe the lycopene in tomatoes helps prevent or reduce depression. Then, the more precise RCTs showed that it does.
In short, eat more cooked tomatoes. Heating tomatoes releases lycopene and makes it more bioavailable. The more concentrated the tomato product, the more lycopene it has. So, tomato paste is better than tomato sauce, which is better than whole tomatoes. Or, as the human study did above, you can supplement with lycopene.
The successful study on men used 25 mg of lycopene daily. Our P-Well (Buy at Amazon) formula contains 30 mg. This supplement is mainly for prostate and sexual health (also improved by lycopene), but it happens to contain enough lycopene to reap the potential depression-fighting benefits, too.
