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Healthier equals happier ... exercise and a healthy diet can help regulate mood.

There's no argument that the right food and exercise help keep our bodies in good nick, but do they matter for our mental health too?

Last month Spanish researchers put the food-mood link on the table again with a study of 8964 people that found that those eating the most junk -  meaning commercial baked goods like croissants and doughnuts, and fast food like burgers and pizza - were more likely to be depressed than those who ate little or none. It's one of a few studies now suggesting that too much over-processed food could be bad for our mood, while a more Mediterranean-style menu with fish, fruit, vegetables, legumes, nuts, olive oil and grains may improve it. Still, it's hard to know what comes first - does eating junk contribute to a low mood, or do we eat junk because we're feeling bad?

But if croissants get the thumbs down for mental health, weight loss approaches emphasising low-carb, high-protein diets aren't helpful either - they can affect levels of the feel good hormone serotonin, says Tara Diversi, an Accredited Practising Dietitian.  Diversi, who has a special interest in both mental health and sports nutrition, will challenge the high protein message – popular with some personal trainers - when she speaks at the fitness industry's annual convention, FILEX, in Sydney next weekend.

"Depression can be an issue for some people who are trying to lose weight, but promoting diets low in carbohydrates and high in protein may lower their mood even more," she says. "Increasing protein in the diet reduces the availability of an amino acid called tryptophan which is important for making serotonin."

As for keeping blood sugar levels steady – another mood stabiliser - regular meals combining both protein and healthy carbs like whole grains are also important, she says.

Although there's a lot to learn about nutrients that might protect mental health, the key players so far are omega 3- fatty acids found mainly in fish, antioxidants – from food, not supplements, Diversi emphasises – and the B vitamin folate found in leafy vegetables, avocado, legumes and liver.

"Like vitamin C, folate can be unstable in food – when vegetables are getting old, for instance, or in cooking or reheating. On top of that folate can be depleted by alcohol and the contraceptive pill," she says. "I always suggest including fresh, uncooked leafy vegetables every day."

As for exercise, it deserves a higher profile as a mood disorders treatment and should be in the mental health toolkit, along with prescribed drugs, psychotherapy and food, says exercise therapist, Lisa Champion. But when it comes to persuading people to exercise for a better mood, she favours a gentle approach – a message that she's emphasising to the fitness industry at the same convention.

"If you're someone who just wishes they could pull the doona over their head, you don't need some fitness instructor bouncing in like the energizer bunny, saying 'let's do boot camp'," says Champion, the executive director of Fit for Good, the fitness industry's charity that makes fitness training available to people in need. "For anyone with a mood disorder the idea of committing to regular gym sessions may be daunting.  Instead we need more awareness that if you're feeling down, a walk, swim or bike ride can help shift your mood. We know you don't have to exercise at an intense level to get benefits for mental health so it shouldn't be seen as having to be strenuous."

What exercise is best for improving mood?

"So far it looks like anything that involves moving at moderate exertion. That means that if you use a perceived exertion scale where 1 equals standing still and 10 equals exercising so hard that you can't go on, you should aim to walk at a pace that's around 5 to 8," Champion says.

Exercise may also work as an antidote to panic attacks.

"Anxiety and exercise are both stressors and have similar effects – both can increase the heart rate and make you break out in a sweat. But exercise is a form of stress that's planned and there's now some evidence that exercise can train you to better tolerate the symptoms of anxiety and help decrease the frequency of panic attacks."

Do you think food and exercise make a difference to mental wellbeing?