Because nuts are high in energy and fat, they’ve had a bad rap in the past.
But as nutrition science has moved on, we now recognize that they’re a welcome addition to a healthy diet.
Nuts are rich in vitamins, minerals, and fiber. And they contain a heroic dose of healthy fats.
Evidence of the physical health benefits of including nuts in your diet is mounting. There’s less evidence of any potential effects on your mental health.
In this article, we’ll dive into the existing research and figure out whether adding nuts to your diet might improve your mood.
The scale of the issue
In 2019, around 1 in 8 people worldwide had a mental health condition, with depression and anxiety being the most common.
Talking therapies and medication can be very effective for some people, but they’re not perfect.
For instance, not everyone has the time and resources for talking therapies, and drugs often have side effects. Plus, they don’t work for everyone.
Finding new ways to tackle this growing concern is urgent.
Food and mental health
Over recent years, the role of nutrition in mental health has entered the spotlight.
The Supporting the Modification of lifestyle In Lowered Emotional States, or "SMILES," trial in 2017 was one of the earliest intervention studies to investigate links between food and mood.
The study included participants with major depression. Some received a series of in-depth nutritional consultations, while the control group received social support.
After 12 weeks, 8% of the control group were in remission, compared with 32.3% of those in the nutrition group.
So, 1 in 3 of the participants who changed their diets no longer experienced significant symptoms of major depression — an almost miraculous result.
Although this was a relatively small study, it opened the floodgates to larger ones, which reached similar conclusions.
These and other investigations helped develop the field of research known as nutritional psychiatry.
Thanks to this work, it’s increasingly clear that having a healthy diet can influence your mental health. But much less is known about the roles of specific foods, like nuts.
Can nuts improve mental health?
Although the evidence is patchy, some research has shed some light on the question. In this section, we’ll look at a few of these interesting studies.
Mediterranean diet plus nuts
One study from 2013 explored three diets and their influences on the risk of developing depression:
Low-fat diet: This was the control group.
Mediterranean diet plus extra virgin olive oil: The scientists gave each participant 1 liter of oil every week.
Mediterranean diet plus nuts: The researchers gave each participant 30 grams of mixed nuts daily.
There were almost 4,000 participants, aged 55–80, and all had a high risk of developing cardiovascular disease. Around half the participants had type 2 diabetes.
The scientists followed up for at least 3 years to see how many people developed depression.
They found that those in the nut-heavy Mediterranean diet group were less likely to develop depression than the control group. But the difference wasn’t large enough to be statistically significant.
However, when the researchers analyzed the data further, they found that the difference was significant for one group of participants.
According to the authors, people with type 2 diabetes who “followed the nut-heavy Mediterranean diet had a 40% reduction in depression risk, compared with the control group.”
So, these results are encouraging, to a certain degree. But what about studies that focus on nuts alone?
Depression in China
A Chinese study from 2016 using data from 13,626 participants goes some way toward filling this gap.
Compared with people who ate nuts just once a week, those who ate nuts more frequently were significantly less likely to report symptoms of depression, the researchers found.
And for participants who ate nuts at least four times a week, the prevalence of depression symptoms was less than half that of the people who only ate nuts 1–3 times a week.
These findings are exciting, but as the authors explain, because of the type of study, they can’t prove cause and effect.
Also, the scientists didn’t take information about other foods the participants were eating. So, there’s a possibility that the participants who ate more nuts had healthier diets overall.
Another possible reason for the results is “reverse causation.” In other words, less healthy foods may not cause depression — it may be that when you have depression, you choose less healthy foods.
Overall, though, the authors are “convinced” that there's a meaningful link between nuts and depression.
What about other mental health conditions?
Anxiety in Iran
A 2020 study in Iran investigated whether consuming legumes and nuts might be associated with depression, anxiety, and psychological distress.
The study included more than 3,000 adults aged 18–55.
The scientists found that, compared with men who ate the fewest nuts and legumes, men who ate the most “were 66% less likely to be anxious.” They didn’t see any effect in women.
Like the Chinese study, this was cross-sectional, so we can’t tell whether nuts caused a reduction in anxiety.
And because this study looked at nuts and legumes, we can’t really tease out the effects of either.
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Zeroing in on walnuts
Some researchers have focused specifically on walnuts. For instance, one study used data from 26,656 people involved in the National Health and Nutrition Examination Survey.
As part of this survey, participants completed a questionnaire that helps doctors assess depression severity. A lower score means fewer symptoms.
They found that “Depression scores were significantly lower among nut consumers and particularly walnut consumers, as compared to non-nut consumers.”
After they accounted for a range of factors that might influence the results, the authors concluded that “Walnut users had scores significantly lower than other nut consumers. The difference was strongest among women, who are more likely than men to report higher depression scores.”
Once again, the researchers didn’t control for background diet — so walnut eaters may have had more healthy diets overall. And this can positively affect mental health, regardless of nut intake.
More walnut wrangling
As we’ve seen in some of the studies above, figuring out whether nuts actually influence mental health is challenging.
One problem is that it’s tough to tease nuts apart from the rest of a participant’s diet. And also, there’s the thorny issue of reverse causation.
The next study attempted to get around these issues. The scientists conducted a double-blind, randomized, placebo-controlled study — the “gold standard” of research.
They split 64 healthy participants aged 18–25 into two groups.
Group 1 ate three slices of banana bread with walnuts daily for 8 weeks. Then, they had a 6-week washout period without any banana bread.
Then, for another 8 weeks, they ate banana bread without walnuts three times a day. What a delicious experiment.
Group 2 did the same but in reverse, starting with the walnut-free banana bread.
The researchers used a questionnaire to measure participants' “mood disturbance” before the study started and after each 8-week phase.
Overall, they found that in males, there was “a significant, medium effect size improvement of the [total mood disturbance] score.”
One has to wonder whether receiving so much free banana bread might have helped lift spirits. However, the team didn’t find any effect in female participants.
Although the results are slightly underwhelming, the authors suggest that the effect might be more pronounced and meaningful in older populations, rather than the young, healthy participants in their study.
A recent review
A review published in 2022 looked at 10 relevant studies, which included data from more than 66,000 participants.
They found that in six studies investigating depression, nuts were associated with a lower risk of this condition. Although in three of these studies, the results weren’t statistically significant.
The authors of the review also looked at four studies that investigated links between eating nuts and mood more generally.
One of these studies did find an association between eating more nuts and having a better mood.
But the other three found non-significant links between higher nut consumption and increased negative feelings.
Overall, the authors conclude that "The available literature suggests that higher nut consumption could be associated with a lower risk of depression, fewer depressive symptoms, and better mood state in the general population.”
What’s the conclusion, then?
In a nutshell, if you’ll forgive the wisecrack, we don’t know whether nuts alone help protect against mental health issues.
To date, the evidence isn’t super strong, and scientists need to carry out more research.
So, if you like nuts, this is relatively good news. And if you don’t like nuts, well, perhaps you’ve just not found the right nut for you yet.
In general, rather than focusing on just one component of your diet, it’s best to aim for diversity. It’s all about your overall dietary pattern.
If you concentrate on eating a wide range of plants and limit ultra-processed foods when possible, you’re on the right path.
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A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED). Nutritional Neuroscience. (2019). https://www.tandfonline.com/doi/full/10.1080/1028415X.2017.1411320
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