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When it comes to physical health, mountains of evidence will tell you that a healthy diet is important. And it is.

But a growing body of research is showing that diet is important for mental health, too. And before you click away, no, I'm not about to show you 10 superfoods to cure your depression! or anything. Mental health is way more complicated than that, and everything from your genetics to your environment can affect it.

But there is some evidence that diet also plays a role here. Studies have found a link between what people eat and their risk of mental illness — even when it comes to the severity of their symptoms. And if diet contributes to these conditions, well, maybe it can help treat them, too.

There are all kinds of studies showing how diet and mental health are related. Some focus on food in general — like a 2013 meta-analysis, which found that diets high in fruit, vegetables, fish, and whole grains may be associated with a reduced risk of depression. But other studies have found something more specific.

They've reported that, when it comes to mental health, it's not just about having a generally “healthy” or “unhealthy” diet. Instead, specific nutrients are sometimes involved. For example, in a 2017 paper, researchers used data from a long-term health study to look at older adults diagnosed with depression.

And they found that participants' levels of vitamins B12, B6, and folate all decreased in the year leading up to their diagnosis. Several other studies have also found that participants with depression and schizophrenia tended to have lower levels of folate than the general population. Admittedly, this relationship is based on correlations, which means they don't say a nutrient caused anything.

But it seems like there could be something going on here. And if so, there's a pretty good explanation for why: Those nutrients all act as antioxidants. During daily life, chemical reactions in your body can split oxygen molecules into atoms with unpaired electrons, which are called free radicals.

Without a second electron, these free radicals are unstable, so they scavenge other cells to find an electron to pair with. That puts the body under stress and can ultimately cause inflammation or other damage. Antioxidants are molecules that fight that stress by handing over their own electrons without becoming unstable themselves.

What does that have to do with mental health? Well, there's a lot of evidence for a link between certain mental health symptoms and inflammation. The link is especially strong for depression, but papers have found some support for this connection with ADHD, schizophrenia, and bipolar disorder as well.

The research is ongoing, but the general idea seems to be that inflammatory molecules may affect how chemicals are released in the brain. In any case, the relationship has come up enough that some researchers have wondered if giving a patient nutrient supplements that fight inflammation could help ease their symptoms. And amazingly, it might — at least, in some cases.

In September 2019, a huge meta-review was published in World Psychiatry, and it took a big-picture look at nutritional supplements and mental health conditions. Now, a meta-review is a re-analysis of the data from a bunch of meta-analyses, which themselves are re-analyses of the data from a bunch of individual studies. So suffice it to say, this paper looked at a ton of data.

And what it found was kind of encouraging. For one, it found that folate — which fights inflammation — was helpful for depression symptoms when it was used as an add-on to existing treatment. It also found emerging evidence that a kind of antioxidant amino acid could be a useful treatment for depression, schizophrenia, and bipolar disorder.

The big stars of the paper, though, were omega-3s, which are types of fatty acids with anti-inflammatory properties. There are a bunch of them, but the most effective one in this review was EPA. In the paper, there was some evidence that omega-3 supplements helped with ADHD.

And there was a bunch of evidence that they helped with depression. Like, these supplements were demonstrated to reduce depressive symptoms in people with major depressive disorder over 13 studies involving more than 1200 participants. That's a lot of participants!

Especially for psych research! Now, one thing this review didn't say was that all supplements are effective all the time. Like, it didn't find that omega-3s were helpful for schizophrenia or other mental illnesses.

And despite what smaller studies have found, the review found little evidence for the effectiveness of zinc, magnesium, or vitamin C or E supplements. Vitamin D even fell short, although the authors noted that there is some growing evidence that it could help treat depression. Overall, the authors say we need more research examining individual nutrients and their effects on specific mental illnesses.

But the takeaway is that supplements could be really helpful for some patients, depending on their situation. Of course, there's also a big thing to keep in mind here: Even for the nutrients that showed promise, these supplements are not a cure-all. Diet is only one potential factor in someone's mental health, and it's completely possible to have a nutrient-rich diet and a mental illness.

Like I said earlier, mental health is complicated. And just because supplements could help doesn't mean they're the only way to get help. Ultimately, those kinds of decisions are up to a person and their doctor.

If nothing else, though, this kind of research does remind us that our brains aren't separate from the rest of our bodies. And eating a healthy diet is likely one way to take care of them both. If you want to learn more about mental health, you might enjoy our episode about how there's more than one type of bipolar disorder.

But as always, thanks for watching this episode of SciShow Psych! We know there's a lot of content online these days, and we're thankful you're spending some of your time getting smarter with us. [ ♪OUTRO ].