Anyone who suffers from depression is likely to be fed up with advice from otherwise well-meaning friends who send them all sorts of online articles promising yet another secret to curing depression.

As someone who has experienced the inner workings of this condition, I can assure you of an interested but honest approach to a topic that is usually the subject of heated online debate—diet—and, this time, its role in depression.

You can count the ways to cure depression on one hand. Jonathan Haidt, one of the best-known contemporary American social psychologists (he studies individual behaviour in a social context), is passionate about the subject of happiness, which he has been studying for years, and is a man who has been searching for his own way out of depression. In his book, The Happiness Hypothesis, he concludes that the solution to today’s increasingly common mental health problems, such as anxiety and depression, lies in changing the way we think—not by sheer willpower alone, but by using one or a combination of cognitive behaviour therapy, meditation, and medication, solutions for which there is already a scientific consensus on their effectiveness.

Can diet help with depression?

All three methods mentioned above have their pros and cons. Treatment with selective serotonin reuptake inhibitors (SSRIs), drugs such as Prozac, Paxil, Zoloft, Celexa, Lexapro, etc., is by far the fastest and most radical way out of depression. Treatment with this class of drugs must be taken under the strict supervision of a psychiatrist, and the results experienced by the patient are in some cases characterised by a real change in personality for the better, more self-confidence, more determination in the face of obstacles, and more joy in general, which inevitably leads to significant changes in personal relationships and career. Unpleasant personality traits and lifelong habits disappeared after four to five weeks of use in patients (not just those with depression) where years of psychotherapy had failed.

Haidt himself says that he would have taken Paxil for the rest of his life if it hadn’t had such severe side effects. Prozac, on the other hand, is a shortcut, says Haidt, who warns that “if you believe in the Protestant work ethic and the maxim, ‘No pain, no gain’, then you might be disturbed by Prozac.”[1] There are many unknowns about Prozac and its cousins—especially how it works—but what is known is that it works (only as long as you take it).

Cognitive therapy and meditation can help you make lasting changes, but the road is long and arduous. Meditation is a quintessentially Eastern solution to life’s problems, but it is now being recommended in the Western medical world as a natural, free and side-effect-free alternative to reduce anxiety and increase life satisfaction. The aim of meditation is to change automatic thought processes and to achieve liberation from the attachments that cause many negative thoughts, by focusing attention in a non-analytical way, by paying attention to the breath, a word, an image, and so on. The problem is that meditation is very difficult at first and people lack the patience and humility to deal with repeated failures. Once learned, meditation can be practised daily.

Cognitive therapy is the expensive and analytical alternative to meditation. If people with depression seem to be caught in a feedback loop in which distorted thoughts produce negative feelings that further distort thinking, Haidt describes cognitive therapy as teaching them to become aware of these thoughts, to define the distortions, and then to find alternatives to their way of thinking. Over time, patients’ thoughts become more realistic, the feedback loop is interrupted, and depression and anxiety are reduced.

“When cognitive therapy is done very well it is as effective as drugs such as Prozac for the treatment of depression, and its enormous advantage over Prozac is that when cognitive therapy stops, the benefits usually continue,” explains Haidt.[2] Yet this is a process that can take years, with slow progress or setbacks that frustrate the patient, who has to use his or her willpower to apply what they’ve learned in therapy to everyday life. In many cases, therapy is combined with SSRIs.

There is no mention of diet in the solutions to depression that Haidt explains and that therapists widely recommend. Therefore, it’s only natural to gasp when we see the case the Wall Street Journal cites: Loretta Go, a 60-year-old woman who had tried cognitive therapy (we don’t know for how long) and several antidepressants (we don’t know what class they were) began looking for alternative treatments on the Internet and as a result made some dietary changes. She gave up processed and fried foods, sugar, and fizzy drinks (we don’t know how much she consumed before) and started eating fruit and vegetables, eggs, lots of tofu, and lots of cashews. In just a few weeks she’d cured herself of the insomnia and depression she’d suffered for years. There is no source for the WSJ article that we can check. This raises questions about the way in which the media in general promote diets, even beneficial ones, that the public then goes on to follow.

Happiness goes through the stomach

The reality is that there are no sure answers at the moment. There is no study to prove that an unhealthy diet causes depression, and no study to prove that a healthy diet cures depression. What is happening, however, is the development of what is known as “nutritional psychiatry,”  a name that should give legitimacy to psychiatrists who are beginning to ask patients not only how they feel and what they think, but also what they eat. Given that as far back as the 1900s doctors were proposing theories linking gut microbes, which are directly influenced by diet, to symptoms such as “fatigue, melancholia, and the neuroses…total lack of ambition so that every effort in life is a burden, a mental depression,” one might wonder why the holistic approach to the patient has not penetrated the field of psychiatry sooner.

An unhealthy diet is the main factor in premature mortality, so why should we think that it only affects the heart, leading to cardiovascular disease, and not the brain? For so long, depression has been approached solely from the point of view of an emotional or biochemical imbalance. However, we now know that depression can be caused by a wide range of factors, and there are still not enough convincing studies to point to a single major cause or to pinpoint exactly why biochemical imbalances occur.

The list of factors only keeps diversifying. Among the latest theories is that inflammation in the body can cause reactions in the brain that, over time, lead to neurological diseases such as depression and Alzheimer’s, although a causal link between inflammation and the two diseases has not yet been established. Nevertheless, for those who are moving in the direction of “nutritional psychiatry,” such a link would make sense.

The brain is like an expensive car. If we fuel it with quality fuel (i.e. food rich in vitamins, minerals, and antioxidants that nourish the brain and protect it from oxidative stress) then we can expect the car to run well for many years. If, on the other hand, we feed it a diet high in refined sugars and trans fats, which predispose the body to inflammation and oxidative stress, then just as we might expect to develop diabetes and cardiovascular disease, we might as well expect to develop brain disorders such as depression, explains Eva Selhub, a physician at Harvard Medical School.

At the same time, let’s not forget that 95% of the body’s serotonin—the neurotransmitter that regulates sleep and appetite, stabilises mood and inhibits pain—is produced in the gastrointestinal tract, which is lined with millions of neurons that process and extract the substances our bodies need from food. Jonathan Haidt calls the digestive system the body’s “second brain,” which has a high degree of autonomy and is designed to function very well even when the vagus nerve, which connects the stomach to the brain, is severed.[3] This “brain” reacts in unexpected ways to anything that affects its neurotransmitters, such as acetylcholine and serotonin, which is why many of the initial side effects of Prozac and other SSRIs interfere with the activities of the digestive system.

Some researchers and doctors, such as Selhub, argue that the production and activity of these neurotransmitters is strongly influenced by the billions of microorganisms that make up the gut microbiome, which researchers are increasingly studying. The “good” bacteria in the microbiome act as a protective barrier against “bad” bacteria, help absorb nutrients, limit inflammation, and activate neural pathways that run directly between the stomach and the brain. Studies showing that a Mediterranean or Japanese diet could help cure depression suggest that replacing a diet high in sugar and trans fats with one rich in unprocessed foods, which act as natural probiotics, affects levels of “good” bacteria, which in turn have a positive effect on neurotransmitters.

What do studies say about the link between depression and diet?

At the moment, these are just speculations. So far, there have been no trials in which people with a diagnosis of depression have been treated solely with a change in diet. The most relevant and widely-cited study, published in the journal BMC Medicine, took 67 people who had already started treatment for depression—either therapy alone or therapy and antidepressants—and gave half of them nutritional counselling to help them eat more healthily (Mediterranean diet). After 12 weeks, those who had changed their diet were rated as having a better mood than the others.

The limitations of the studies are obvious, and the researchers’ conclusion that “dietary improvement may provide an efficacious and accessible treatment strategy” is premature and not supported by scientific consensus, say critics. At the same time, changing your diet, like changing any ingrained habit, is very difficult to do without professional help when you have depression. So, at best, the study shows that diet can improve the symptoms of a patient who’s already receiving treatment.

Eating healthily makes a lot of sense in many ways, but preventing or treating depression would not be high on the list of reasons. Apart from a placebo effect, trying to cure yourself through diet would be an ineffective distraction from treatment. By comparison, there is substantial evidence that exercise is effective, points out Allan Frances, former director of the Department of Psychiatry at Duke University.

If diet alone could prevent depression, it would mean that no one who eats a healthy diet (i.e. the Mediterranean, Japanese, or Nordic diets, or some variation of them), according to studies, should suffer from depression. However, I can argue from my own experience that this is not the case, and articles in the press that completely ignore these cases do a disservice to a vulnerable group of people. If for those who have depression and an unhealthy diet the studies seem to offer the good news that changing to a healthy diet can improve their condition, what about those who have depression and follow a healthy diet? What is the good news for them? Probably the only good news would be that if they hadn’t had a healthy diet, they might have had an even more severe depression.

We don’t know what we will learn from studying the human microbiome in detail. Perhaps one day depression will be cured with a cocktail of prebiotics and probiotics. For now, treatments that have been shown to be effective should not be discarded in favour of a diet, but neither should a healthy diet be discarded just because we are following a treatment that has started to work. Some people need to be led into therapy before they can think about making other positive changes in their lives, while others will desperately try all sorts of alternative methods just to avoid ending up in the therapist’s office.

We are different, we suffer differently, and we heal differently. And from that point of view, we should be glad that more and more options are being added to the solution of this endemic disease.

Eliza Vladescu is a communication specialist and previously was part of the permanent ST Network team. She currently works as an online communication consultant.

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[1]“Jonathan Haidt, ‘The Happiness Hypothesis’, Basic Books: 2006, p. 41.”

“Jonathan Haidt, ‘The Happiness Hypothesis’, Basic Books: 2006, p. 41.”