People who eat a diet laden with processed and
high-fat foods may put themselves at greater risk of depression,
according to new research.
But eating a ‘whole food’ diet with plenty of
fresh vegetables, fruit and fish could help prevent the onset of
depressive symptoms in middle age.
The
study, published in the November issue of British Journal
of Psychiatry, is the first to examine the association between
overall diet and depression. Previous studies have focused on the
effect of individual nutrients.
Researchers from University College London
studied 3,486 participants from the Whitehall II Study. The
participants had an average age of 55, and worked in civil service
departments in London. Each participant completed a questionnaire
about their eating habits, and a self-report assessment for
depression.
The researchers found that people with the
highest intake of ‘whole food’ were less likely to report having
symptoms of depression. In contrast, high consumption of processed
food was associated with increased odds of depression.
These associations between diet and onset of
depressive symptoms remained after the researchers controlled for
other indicators of a healthy lifestyle, such as not smoking,
taking physical activity and a healthy body mass.
The authors said: “Our results suggest that
consuming fruits, vegetables and fish may afford protection against
the onset of depressive symptoms, whereas a diet rich in processed
meat, chocolates, sweetened desserts, fried food, refined cereals
and high-fat dairy products would increase people’s
vulnerability.”
The researchers put forward several
explanations for their findings. First, the high level of
antioxidants in fruits and vegetables could have a protective
effect, as previous studies have shown higher antioxidant levels to
be associated with lower risk of depression. Folate, which is found
in large amounts in vegetables such as broccoli, cabbage and
spinach, and dried legumes such as lentils and chickpeas, may have
a similar protective effect.
Second, eating lots of fish may protect
against depression because of its high levels of long-chain
polyunsaturated fatty acids, which are a major component of neuron
membranes in the brain.
Thirdly, it is possible that a ‘whole food’
diet protects against depression because of the combined effect of
consuming nutrients from lots of different types of food - rather
than the effect of one single nutrient.
The researchers say further research is needed
to explain why eating processed food is associated with higher risk
of depression. But they suggest it could be because a processed
food diet is associated with a higher risk of coronary heart
disease and inflammation, which are known to be involved in the
development of depression.
The researchers concluded: “The deleterious effect of a
processed food diet on depression is a novel finding. Our research
suggests that healthy eating policies will generate additional
benefits to health and well-being, and that improving people’s diet
should be considered as a potential target for preventing
depressive disorders.”