If you ask any parent in my generation what influence sugar has on their kids, it’s likely they’ll say with deep conviction that sugar makes their children certifiably crazy. We see it time and time again after birthday parties and special holiday outings. Shortly after filling up on candies, cookies and cake our little darlings transform into wailing, complaining, fractious beasts.  

So you can imagine my surprise when I sat down this week to review the research connecting sugar consumption to poor mood and discovered that there is no compelling evidence to prove this “known fact.” Indeed meta-analysis published in the highly reputable Journal of the American Medical Association, considered the results of 16 of the highest quality studies on the sugar-mood link and concluded that the sweet stuff doesn’t impact behaviour for better or for worse in any significant way.

Of course, this is not to say that sugar is health food. The evidence linking excess sugar to concerning problems such as obesity and dental decay is compelling. But this raises an interesting issue about the complexity of nutrition science. On any given day, there are a multitude of causes and conditions that may conspire to inspire a volcanic eruption in my kids. For example, on the same day that we overindulge at a party, it’s also likely that my kids will be super-excited and over-stimulated. They’re also likely to have skipped their usual afternoon nap or to be coming down with another flu virus courtesy of their friends at childcare.

As a journalist who places great value on scientific evidence whenever I’m drawing conclusions about health, it was clear after my deep-dive into sugar science that I can’t blame it for our post-party mental meltdowns. But something still wasn’t adding up. I’ve witnessed the mood crash just one too many times in my kids and in myself to conclude that there’s no link between food and mood. So I kept digging.

It turns out that although thousands of published studies have considered what determines our happiness and psychological health, little is known about the direct influence of what we eat on how we feel. There is one particularly compelling theme emerging though. Rather than being the decadent delights that we are eating on “special occasions,” the problem may actually be related to we are not eating.

In recent years data has begun pouring in linking a lack of fruit and vegetables to poor mood. For example, adults who don’t eat enough servings of fruit and vegetables daily have higher odds of being depressed. It’s a similar story with kids. Conversely, a new meta-analysis of 18 high-quality studies involving a total of 289,018 people revealed that high intake of fruit and vegetables is associated with a 20 percent reduced risk of depression.

We all know that fruit and vegetables are rich sources of health-giving fibre, vitamins and minerals, antioxidants, flavonoids and phytochemicals. I suspect that when my kids and I fill up on highly-processed, low-nutrient foods at celebrations and special events, we’re not refuelling with premium quality nutrients that our bodies need for optimum performance. We are running on empty, and emotionally crashing and burning.

I confess that there is not a randomised clinically controlled trial to prove my suspicion, but it is interesting that a recent study involving 12,389 people found that a shift from “low” to “high” intake of fruit and vegetables over two years resulted in significant improvements in happiness, life satisfaction and well-being. The mood boost was comparable to going from being unemployed to employed. Other research shows that happiness rises in a dose–response way with the number of daily portions of fruit and vegetables. The more you eat, the better you feel. Another study looked at the correlation between what we eat today and how we feel tomorrow and found that eating high levels of fruit and veg was predictive of greater emotional wellbeing on the following day.

All this packs a powerful punch when you consider the rising prevalence of mental ill-health globally. At a time when depression affects hundreds of millions of people and psycho-pharmaceuticals are at an all-time high, we desperately need low-cost, high-impact strategies to tackle the mental health epidemic. At the same time, here in Australia only five percent of us are eating enough fruit and vegetables daily. It’s a similar story in the US, UK, Canada and all over the world really.

Although we still need more high-quality randomised controlled trials, I believe this new evidence showing the food-mood link represents a potentially important new direction in mental health. Imagine going to your shrink and being prescribed steamed vegetables instead of anti-depressants. Imagine thinking of your local green grocer as your pharmacist. Imagine coming home from a birthday party and tucking your sweet little angels into bed without a care or complaint. It’s certainly food for thought.