Study turns the spotlight on to shift workers' heart health

John Kapiris, 35, looked around his workplace and didn’t like what he saw.

Some of his colleagues, he noticed, were growing more generous of girth by the year, and he was determined not to follow them down that path.

John's a night-shift worker in the fruit and vegetable wholesale industry and starts work between 2am and 3am, five days on, two days off. He’s been doing it now for about 15 years.

“Most of the guys over a certain age, say about 40, are all pretty fat, and I don’t want to fall into that category,” he said.

So when he heard about a Monash University pilot study investigating night-shift workers’ eating habits and their cardiovascular risk, he quickly signed up.

“I figured the more I know about my health, the better,” he said.

Increased disease risk

Associate Professor Maxine Bonham, a senior academic in the Department of Nutrition, Dietetics and Food at Monash, is leading the study.

She said many workers who live to a schedule that's out of sync with their circadian rhythms have poor health outcomes.

“Epidemiological evidence shows increased disease risk in shift workers for conditions related to cardiovascular health and diabetes, and in 2007, the World Health Organisation declared shift work as a probable carcinogen,” she said.

According to the Australian Bureau of Statistics, there are more than 1.4 million shift workers in Australia, who are defined as “people who work rotating shifts, irregular shifts, evening shifts, afternoon shifts, morning shifts or split shifts”.

The study elaborates on research in 2017, by dietitian and PhD student Gloria Leung, which found that when we eat (not just what we eat) had a significant effect on blood sugar levels.

Leung is involved in the new study, too, along with Dr Catherine Huggins, a researcher in the Department of Nutrition, Dietetics and Food, and another PhD student, Rochelle Davis.

“In [the 2017] study, we fed participants the same meal (a low glycaemic index meal) at 8am, 8pm and at midnight on three separate days,” Leung said.

“What we found was that when they ate the meal at night-time, their blood glucose was up to six times higher.”

The latest study, Shifting the Risk: A study investigating meal timing and heart health in shift workers,  is collecting data from 20 shift workers aged 18 to 60 over a 13-week period.

Leung and Associate Professor Bonham hope it will pave the way for a much bigger study into the effects of meal times on the health of shift workers.

“What we're hoping from our study is that it may, in the long term, be able to provide some guidance to shift workers on when to eat during the night, and what to eat,” Associate Professor Bonham said.

Two intervention types

In the first four weeks of the study, participants are randomised into one of two dietary interventions. They either continue with their usual diet, or they're asked to change their meal times, but not the types of food they eat. This is based on Leung’s recommendations, who reviews each participant’s food diary when they start, rearranges the times that they should eat their standard meals, and asks them to avoid eating between 1am and 6am.

After four weeks, there's a two-week break, and then the study resumes for a further four weeks, when participants either go back to eating as they usually would during the night, or move onto the meal timing intervention. Each participant visits the research facility three times – once at the beginning, middle and the very end.

During these visits, their blood glucose and lipids are tested, which tells the researchers whether the changes in meal times have had any effect on the participants’ cardiovascular health.

“We’re trying to find out if it’s actually feasible for people who work shifts to eat like this,” Leung said.

“Each shift worker has a different lifestyle from their work hours, break times at work and when they catch up on sleep – it all varies.

“What this study ultimately aims to prove is that health improvement is possible through small changes in meal times, which are also cost-effective and convenient.”

“We’re trying to find out if it’s actually feasible for people who work shifts to eat like this.”

For John Kapiris, who finished his 13 weeks with the study on Easter Saturday, it was initially difficult to adjust to the changed eating regime, but he said he learnt some valuable lessons from the experience.

“I now realise that being hungry for a few hours is not a big deal – nothing will happen to you. We’re just not used to being hungry any more, ever.”