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Super-sized study proves link between carb-loaded lunch and afternoon drowsiness

Health & Medical

A high intake of saturated fats and carbohydrates increases the risk of daytime sleepiness while protein might reduce drowsiness, South Australian researchers have found.

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Flinders University researcher Dr Yohannes Adama Melaku said the study was an opportunity to take a theory of out of the laboratory and see if it applied in the general population, which it did.

“We looked at the effect of changing nutrients in the diet without changing the amount of calories consumed, allowing us to demystify the interplay and complex interaction among macronutrients in predicting daytime sleepiness,” he said.

The study was based on a 2010 questionnaire in which 1590 South Australians aged between 18 and 90 years provided their average 24-hour food intake.

The research, which was published in the journal Nutrients last month, was part of the North West Adelaide Health Study (NWAHS).

The broader study followed 4033 participants aged 18 and 90 years between 1999 and 2018.

Dr Melaku said the researchers found, on average, people were eating the recommended calories for their age and weight.

He said drowsiness was occurring when participants’ carbohydrate and saturated fat intake was excessive and their protein diminished.

“We saw a great opportunity to examine daytime sleepiness outcomes within a much larger sample size,” Dr Melaku said.

“The link between nutrition and sleep is becoming increasingly recognised.

“Especially for people in certain industries, for example heavy truck drivers, it’s important to know the foods they eat are an important factor for preventing accidents.

“It’s this consistency from the lab showing excessive saturated fats and carbohydrates cause excessive daytime sleepiness and could be a risk factor with work place injury.”

According to The Sleep Foundation, 29 per cent of Australians report making errors at work due to sleepiness. Feeling sleepy is also associated with a number of risks from work-related injuries to cardiovascular diseases.

On the other hand, Dr Melaku said an increased protein intake was inversely associated with excessive daytime sleepiness – but more research was needed to confirm if dietary interventions would alleviate daytime drowsiness.

“Cutting excessive saturated fat and carbohydrate and increasing protein could be a good solution for daytime sleepiness,” he said.

“Currently we are collecting data about the timing of eating food. We know it’s not only the quality of food but timing of food is very important, so we are tracing that.”

The study was funded by the Hospital Research Foundation, Freemason’s Foundation Centre for Men’s Health and the University of Adelaide.

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