Rats on a high sugar diet during
pregnancy have altered levels of sex steroid hormones (e.g. progesterone) and
dopamine in their brains, which may lead to behavioural changes that can affect
care of offspring and motivation, as well as increasing the risk of diabetes
and liver disease, according to a study published in the Journal
of Endocrinology. Pregnant rats on a high sugar diet, equivalent to
a typical Western diet, had increased progesterone levels, a hormone important
for healthy pregnancy and lactation, and changes in the dopamine system, a
neurotransmitter key in motivation, reward and mood. They also showed signs of
prediabetes and fatty liver disease. The study findings suggest that sugar
consumption during pregnancy may have serious, long-term health risks for the
mental health of both mothers and pups, beyond the established risks for
diabetes and heart disease.
The World Health
Organisation advises limiting added sugars in our diet to 5-10% of our daily
calories. However, The Western diet typically contains 15-25%. It is well
established that high sugar consumption increases the risk of diabetes, heart
and liver disease. Chronic sugar consumption has also been reported to affect
learning, memory and goal-directed behaviours in rats. The mechanisms
underlying these brain effects are poorly understood and the majority of
studies have been performed on male rats. Since important hormone and metabolic
changes occur during pregnancy and lactation, the current study aimed to
investigate how high sugar intake may affect the health rats after giving
birth.
In this study,
Dr Daniel Tobiansky and colleagues, working in the lab of Prof Kiran Soma at
The University of British Columbia in Canada, investigated the effects of a
high sugar diet on hormone levels and markers of metabolic function in female
rats. The rats were maintained on a high sugar diet (equivalent to 25% of their
total calorie intake) covering a period 10 weeks prior to mating, as well as
throughout pregnancy and lactation. Markers of metabolic health indicated that
their glucose regulation was impaired and that they had fatty livers, although
their body weight was not different from rats on normal diet. Levels of
progesterone were increased whilst markers of dopamine function indicated that
its activity in the brain was altered.
Dr Tobiansky
states, “Beyond the established metabolic effects of high sugar intake, our
data suggest that it may also have long-term harmful effects on mental health
and maternal care. Progesterone is important for healthy pregnancy and
lactation, whilst dopamine signalling is key for reward, learning and
motivational behaviours. Taken together, these findings suggest that maternal
behaviour, such as pup grooming and feeding could be negatively affected.”
Dr Tobiansky and
his team are planning to publish data from the offspring of these female rats.
He remarks, “Our yet to be published data also indicate that maternal high
sucrose diet can impact offspring behaviours and food preferences in profound
ways.”
Dr Tobiansky comments,
“We suggest that public and health professionals follow the recommendations
from the World Health Organization and the American Heart Association. They
both suggest limiting added sugars to <10% of daily calories, and for
maximum benefit, to 5%. This likely has benefits for metabolic health, as well
as hormone and brain health. That translates to ~25g or 6 teaspoons of sugar
per day, based on a diet of 2,000 kcal per day.”
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