Emerging evidence suggests a link does exist, with a healthy balanced diet, particularly one high in fruit, vegetables and wholegrains, seeming to boost mood and even fight depression. Highly processed food or "junk" food also seems linked with lower mood.
After Radio National's 'All In The Mind' looked at this topic recently, we asked you about your experience of links between food and mood — with some fascinating results.
"If I've fallen off the [healthy eating] wagon, my tell-tale sign is if I start crying over television ads." — Kirsten.
"If I eat heaps of steamed veggies for supper, my feeling the next day is so much better. If I eat junk food for supper I feel down in the doldrums." — Eddie.
You should bear in mind mood is highly subjective, and so our perception of how we feel is easily influenced by beliefs we might hold.
It's also hard for us to sift out the influence of other factors that might sway how we feel.
It's worth noting too that most of the studies in this area have monitored effects over longer periods of time — at least weeks or months.
And scientists stressed it's your diet as a whole that seemed to matter most, rather than homing in on single foods.
Here's a selection of your feedback, with some expert comments as well.
Sugar Many of you linked sugar with your mood — particularly processed white sugar.
"If I consume products that contain white sugar it transforms me into an irritable, depressed, totally negative person who thinks life isn't worth living. Once it wears off around the 24hr mark I'm fine." — Helen.
"As a rule of thumb I avoid processed foods if I can and sugary things … I am 68 years old, walk and cycle every day and have never had even one day off work through illness in my whole working life." — Edward.
"I manage it [depression] by eating healthy, avoiding sugar and looking on the bright side of life … it is not easy and pleasant at times." — Terry.
Sarah Dash, who is doing a PhD in food and mood at Deakin University, said the idea increased sugar consumption was linked with low mood did have some science behind it.
What you eat could help manage depression and anxiety
There's growing evidence for the idea that our brains and our guts are intimately linked.
Habitual sugar consumption can prevent the lining of our gut from doing its job of stopping harmful substances passing into the body, she said.
When this happens, small molecules can escape from the gut into the bloodstream, causing inflammation.
While our understanding of the processes involved is still developing, "this low level of inflammation is a risk factor for depression".
"If you have a leaky gut, you can actually induce depression-like behaviours in animals — things like they socially withdraw or don't want to eat anything," Ms Dash said.
She added that high and low blood sugar levels could also influence your mood over very short time frames.
But Dr Paul Bertrand, head of the Gut Neuroscience Laboratory at RMIT, was surprised it took Helen 24 hours to feel her 'sugar low' wore off.
"Normally we associate sugar with relatively quick effects" — 30 to 60 minutes, he said. A prolonged response could indicate something other than sugar might be to blame.
Dr Bertrand stressed if a person's feeling depressed or down, diet could be one small part of a larger issue — and that it's vital to seek medical advice as a first port of call. And dietary change should complement rather than replace antidepressants if they are needed.
Processed foods Another thing many of you noted was a big boost to your mood when you started to avoid processed foods.
"If I've eaten foods that contain additives, my brain starts self-talk that results in depression. Even as recently as a few days ago, lying in my bed my brain starts to talk about how no-one likes me; how people don't treat me well." — Rob.
"I'm 10 pounds lighter, I've been incredibly productive, I'm out of bed and seeing flashes of my old energetic self." — Weez.
There are so many things in processed foods it's very hard to pin down if there's a particular component affecting your mood, Dr Bertrand said.
What has shown to be beneficial, though, is a general shift away from processed foods and towards whole foods in a person's diet, improving your overall gut health.
"The nerves in your gut directly communicate with the brain," he said.
"So if the gut's unhappy, it can be communicated up to your brain and really start to lower your mood."
Deakin University's Dr Felice Jacka said there was "very extensive data from animal studies" showing certain unhealthy food components affect the brain directly, with important negative impacts on a region called the hippocampus, involved in many things, including mood regulation.
There is also new evidence that "common emulsifiers in many processed foods have a very noxious impact on the gut" which in turn affects mood.
Gluten According to Coeliac Australia, one in 70 people had coeliac disease — meaning they could not consume gluten without risking diarrhoea, nausea, pain, fatigue, and other symptoms.
Others may report a sensitivity to gluten — that it makes them feel unwell — and avoiding gluten has also become a popular health trend.
Some of you linked gluten to anxiety, depression, and bad mood:
"I made food changes and used key nutrients and no longer have any anxiety — unless I'm exposed to certain foods like gluten-containing grains" — Trudy.
"Often I cannot speak as I know I will explode and probably regret what I say — so I choose not to speak if I am having a 'gluten moment'. Eating gluten also makes me feel like I have a hangover for days." — Sophie.
The notion that non-coeliacs can be sensitive to gluten is controversial, and Ms Dash said another reason someone who avoids gluten could experience an improved mood is if the shift means they replace processed foods with more whole foods.
Both Ms Dash and Dr Bertrand said those who tended to avoid gluten should be careful about what they were missing out on.
"Not having gluten in your diet because it sounds trendy is not a good idea, because it's a good source of many nutrients," Dr Bertrand said.
"[If it's happy] your gut's more likely to be functioning better and not sending signals to your brain saying: I'm diseased, I'm unhappy, I'm inflamed."
MSG This naturally-occurring amino acid, used as an additive to give foods a stronger savoury flavour, has received its fair share of criticism when it comes to health.
A common belief is that foods heavy in MSG will give someone a headache and flushed skin.
No evidence has been found to prove that connection despite rigorous testing, and both the US and Australia consider MSG a safe food additive.
Rob writes that after he has lots of MSG:
"I have the most weird and exhausting dreams at night. Some are so bad that I have a sense, in my dream, that I want to get out of my dream, and I can wake up in a state of mild terror relieved I survived whatever it was." — Rob.
While it is impossible to rule out some sort of MSG sensitivity in Rob, Dr Bertrand said it could just as easily be another component of the meal that affects Rob's dreams — like its fat content, spices, or its overall size.
"I often seem to have crazy bad dreams after a heavy, fatty meal — like a big duck dinner," Dr Bertrand said.
"It's delicious, but there's probably too much fat, causing a bit of an overload, and the gut's unhappy and tells you about it."
Mushrooms and chocolate: Dorothy said that for the past 40 years, she has noticed a link between mushrooms and her mood — after eating them, she becomes sad and weepy.
The same thing also happened with white chocolate — so much so that she said if she is ever put in a nursing home, she wanted the staff to be told not to feed her those foods.
"Of course I still indulge on occasions, but weigh up the risk and think — 'Ok ... for those few moments of pleasure I will have two days of sadness!'" — Dorothy.
Dr Bertrand and Ms Dash were at a loss to explain this.
Mushrooms are a good source of fibre — and associated with good health effects, rather than mood change, they said.
"Often mushrooms can make you farty, which is an indication the gut bacteria are digesting them," Dr Bertrand said. This is generally considered a good thing.
And chocolate, particularly dark chocolate, is in good favour in research relating to food and mood because it often has anti-inflammatory properties, Ms Dash said.
Shakes and smoothies: You love your shakes too — especially if they're green. Samantha combined a shake diet with exercise to feel better, while Jennifer became a convert to smoothies containing fruit with some greens.
"In between shakes, I was eating little tins of flavoured tuna and salmon, nuts and smoothies. I was feeling so alive" — Samantha.
"I kid you not, within three days I was feeling slightly better ... by the end of the fortnight I was one of those glowy, 'high on life', colours seem brighter, 'hey you should try this' converts" — Jennifer.
Both our experts said smoothies and shakes that contained green ingredients and fruits usually had lots of fibre, which is very good for your gut — and thus your mood.
Ms Dash said the shakes and smoothies could be replacing less healthy foods, also helping you to feel better.
But Dr Bertrand said it was good to still have some whole fruit and vegies in your diet, rather than getting them solely in smoothies. Among other reasons, chewing is good for your jaws and teeth.
If you need urgent assistance, see Need help now For mental health information, guidance and referrals, see the SANE Help Centre SANE Forums is published by SANE Australia with funding from the Australian Government Department of Health SANE Australia ABN 92006533606 PO Box 226 South Melbourne 3205 Australia