High-sugar diet is as 'damaging to your brain as extreme stress or ABUSE'
High-sugar diet is as 'damaging to your brain as extreme stress or ABUSE'
There has been a seismic shift in the dietary landscape in recent years.
Where once fat was the much maligned enemy, now scientists are turning their attention to sugar.
It is now widely accepted that more must be done to encourage people to reduce their sugar intake.
So much so that dietary guidelines in the UK and US have been altered to reflect the changing scientific evidence.
The
World Health Organization recommends no more than 10 per cent of a
person's daily energy should come from added sugars, or those found
naturally in juices and honey.
That equates to around 50g or 12 teaspoons a day.
While
the links between a high-sugar diet and obesity are well documented, in
light of the mounting evidence, experts are turning their attention to
the other ways sugar can affect the body.
In
a recent study, a team at the University of New South Wales in
Australia, found sugar is as damaging to the brain as extreme stress or
abuse.
Here research associate, Jayanthi Maniam and profressor of pharmacology, Margaret Morris discuss their findings.
We all know that cola and lemonade aren’t great for our waistline or our dental health.
But our new study has shed light on just how much damage sugary drinks can also do to our brain.
The
changes we observed to the region of the brain that controls emotional
behaviour and cognitive function were more extensive than those caused
by extreme early life stress.
It
is known that adverse experiences early in life, such as extreme stress
or abuse, increase the risk of poor mental health and psychiatric
disorders later in life.
The number
of traumatic events - accidents; witnessing an injury; bereavement;
natural disasters; physical, sexual and emotional abuse; domestic
violence and being a victim of crime - a child is exposed to is
associated with elevated concentrations of the major stress hormone,
cortisol.
There
is also evidence that childhood maltreatment is associated with reduced
brain volume and that these changes may be linked to anxiety.
Looking
at rats, we examined whether the impact of early life stress on the
brain was exacerbated by drinking high volumes of sugary drinks after
weaning.
As females are more likely to experience adverse life events, we studied female Sprague-Dawley rats.
To
model early life trauma or abuse, after rats were born half of the
litters were exposed to limited nesting material from days two to nine
after birth.
They then returned to normal bedding until they were weaned.
The limited nesting alters maternal behaviour and increases anxiety in the offspring later in life.
At
weaning, half the rats were given unlimited to access to low-fat chow
and water to drink, while their sisters were given chow, water and a 25
per cent sugar solution that they could choose to drink.
Animals exposed to early life stress were smaller at weaning, but this difference disappeared over time.
Rats consuming sugar in both groups (control and stress) ate more calories over the experiment.
The rats were followed until they were 15 weeks old, and then their brains were examined.
As
we know that early life stress can impact mental health and function,
we examined a part of the brain called the hippocampus, which is
important for both memory and stress.
Four
groups of rats were studied – control (no stress), control rats
drinking sugar, rats exposed to stress, and rats exposed to stress who
drank sugar.
We
found that chronic consumption of sugar in rats who were not stressed
produced similar changes in the hippocampus as seen in the rats who were
stressed but not drinking sugar.
Early
life stress exposure or sugar drinking led to lower expression of the
receptor that binds the major stress hormone cortisol, which may affect
the ability to recover from exposure to a stressful situation.
Another gene that is important for the growth of nerves, Neurod1, was also reduced by both sugar and stress.
Other
genes important for the growth of nerves were investigated, and just
drinking sugar from a young age was sufficient to reduce them.
The
rats were exposed to high sugar intakes during development, and the
impact of the sugar is worrying as it may affect brain development,
although further work is required to test this.
In
this study, combining sugar intake and early life stress did not
produce further changes in the hippocampus, but whether this remains the
case over time is unclear.
The changes
in the brain induced by sugar are of great concern given the high
consumption of sugar-sweetened beverages, with particularly high
consumption in children aged nine to 16 years.
If
similar processes are at play in humans to what was found in our rat
study, reducing the consumption of sugar across the community is
important.
The
fact that drinking sugar or exposure to early life stress reduced the
expression of genes critical for brain development and growth is of
great concern.
While
it is impossible to perform such studies in humans, the brain circuits
controlling stress responses and feeding are conserved across species.
People
who were exposed to early life trauma have changes in the structure of
their hippocampus. In humans, those consuming the most 'western' diet
had smaller hippocampal volumes, in line with data from animal models.
Taken
together, these findings suggest future work should consider possible
long-term effects of high sugar intake, particularly early in life, on
the brain and behaviour.
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