betty July 10, 2022

SINGAPORE – Military servicemen, athletes and outdoor workers should watch what they eat – not only to stay healthy – but also to prevent heat stroke caused by exertion.

The common nutrition, health supplements and diets of these highly active individuals can make them more at risk of exertional heat stroke, if taken inappropriately, said researchers from the National University of Singapore’s Yong Loo Lin School of Medicine (NUS Medicine), in a recently published review paper.

Those food choices, if over-consumed, mainly lead to gastrointestinal complications, leading to fluid loss and higher risk of exertional heat stroke.

One example is carbohydrate, which is a staple for many, including sportsmen, who may take it in the form of energy bars, gels and energising drinks in between training and workouts.

But if taken in large amounts – more than 90g of the carbohydrates per hour – those foods can cause vomiting and diarrhoea.

“One possible reason is that large doses of carbohydrates may not be adequately absorbed – the carbohydrates left sitting in the gut can subsequently lead to gastrointestinal symptoms,” said Dr Beverly Tan from NUS Medicine’s Human Potential Translational Research Programme, and one of the two co-leads of the paper.

Scientists from Britain and the United States were also part of the team.

Exertional heat stroke happens with a spike in the core body temperature to above 40 deg C at times – due to strenuous exercise – often in hot and humid environments. Key symptoms are disturbances to the central nervous system, such as delirium, and unconsciousness. Organ and tissue damage are also common, which can lead to multiple-organ failure. 

In Singapore, exertional heat injuries are more common, compared with classic heat injuries during heatwaves in temperate regions.

These exertional heat injuries are more common among people who do intensive physical activities for long hours under the sun, including marathoners, construction workers and those in the military.

A doctor from Khoo Teck Puat Hospital previously told The Straits Times that it sees up to three times more patients with heat-related injuries during the hotter months which fall around mid-year than in the cooler months.

And with temperatures and humidity expected to rise due to climate change, the risk of exertional heat stroke will be even greater, said Associate Professor Jason Lee, deputy director of the Human Potential Translational Research Programme and the other co-lead of the paper.

Beyond carbohydrate bars and gels, performance-enhancing supplements containing caffeine and sodium bicarbonate do their job by helping consumers reduce their perception of effort and fatigue.

But those effects can increase the consumers’ risk of exertional heat stroke when they end up over-estimating their abilities while doing strenuous work in the heat.