29 Feb 2020

High sugar diet may impair metabolic health & maternal care after pregnancy

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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