How eating your vegies can make you feel calmer
A fast-track way to feeling better may be to stock up on your fruit and vegetables, a study has found.
In recent years, there has been growing interest in the link not only between diet and our physical health but diet, mood and mental health.
A good quality diet (which comes in many forms, with a common denominator of abundant fruit and vegetables) is considered to reduce your risk of depression, while a poor diet (abundant in processed and sugary foods) is considered to increase your risk.
Earlier this year, a study from Deakin University found that people with moderate depression who worked with a clinical dietitian had a greater reduction in their symptoms over a three-month period compared with those who were provided social support over the same time.
Meanwhile, researchers from the University of Sydney explored whether fruit and vegetable intake affected stress levels, an experience that was "a lot more common in our day-to-day lives", said lead researcher, Melody Ding of the University of Sydney's School of Public Health.
Ding and her colleagues analysed the fruit and vegetable intake, as well as the lifestyles and "psychological distress", of more than 60,000 Australians aged 45 years and older between 2006 and 2008 and then again in 2010.
After adjusting for other factors (including "reverse causality" where less stressed people are likely to eat better), they found that people who ate three to four daily serves of vegetables had a 12 per cent lower risk of stress. Similarly, those who ate five to seven daily serves of fruit and vegetables had a 14 per cent lower risk of stress than those who ate between zero and four serves daily.
Interestingly however, the results, published in the British Medical Journal Open, were more significant for women than men (for men there was no significant association) and there was a threshold for receiving benefits.
"Most of these associations remained significant at medium levels of intake but were no longer significant at the highest intake levels in fully adjusted models," the authors said.
"Especially with the recent media craze around 800 grams of fruit and vegetables, we were expecting, possibly, the more the better – it doesn't do any harm but it seems to level off," Ding said, suggesting that a possible explanation was that if people were consuming large quantities of fruit and vegetables, they might be eating too much of all types of food.
As for the gender discrepancy, Ding said it was baffling.
"This one really gave us a lot of headache," she said. "We don't really know why – we thought one of the reasons was that maybe women were better at reporting their fruit and vegetable intake – women are more involved in food preparation so they recognise how much fruit and veg they're eating."
She insisted that it was still important to include men in this message.
Why fruit and vegetable intake helped to relieve stress was "the million-dollar question", Ding said.
Deakin University's Food and Mood Centre may provide some insight into the why.
"Researchers now believe that depression, in particular, is not just a brain disorder, but rather a whole-body disorder, with dysfunction of the immune system (chronic, low-grade systemic inflammation) as a very important risk factor," they explain. "This 'systemic inflammation' arises as a result of many of the environmental stressors that are common in our lives: poor diet, lack of exercise, smoking, being overweight and obesity, lack of sleep; lack of vitamin D etc. as well as stress.
"Many of these factors influence gut microbiota, which in turn profoundly influence the immune system. In fact, gut microbiota affect more than the immune system – they seem to be critical to almost every aspect of health including our metabolism and body weight and brain function and health. Each of these factors is highly relevant to depression, reinforcing the idea of depression as a whole body disorder."
The suggestion is not that food can or should replace other treatments, rather that diet ought to be considered as part of treating stress and even depression.
While researchers continue to try and understand the relationship, Ding said their findings were yet another reason to nourish from the inside-out.
"These findings are really similar to our previous 'two and five' message – it's important to encourage the public to to watch their fruit and vegetable intake, not only for the sake of longer life and gut health but potentially for the benefit of being less stressed."