As the UK swelters through its increasingly frequent heatwaves, staying hydrated is becoming an urgent health concern for households across the country. Temperatures soaring above 30°C can push our bodies to their limits, and it's not just extreme heat that's a problem – even mild dehydration can have serious consequences. So, what do you need to know about keeping cool and staying healthy during the hottest months?
Dr Lewis James, a lecturer in sport, exercise and health sciences at Loughborough University, explains that our bodies constantly generate heat as cells convert fuel into energy. Approximately 75-80% of this energy manifests as heat, which is usually dissipated through convection and radiation when external temperatures are cooler. However, when air temperatures rise above skin temperature (typically around 35-36°C in the UK), sweating becomes the body's main defence to lose heat.
While an average person might lose less than 500ml of water through sweat on a normal day, this volume increases significantly in hotter conditions. In fact, when air temperatures surpass skin temperature, sweating is virtually the only way to lose heat – which means we need to replace lost fluids to maintain bodily functions. According to NHS sources, even mild dehydration can lead to noticeable impairments such as headaches, fatigue, reduced concentration, and poorer physical performance.
But how do you know if you're dehydrated? Experts recommend monitoring urine colour as a more reliable indicator than feeling thirsty. Producing small amounts of dark yellow to brown urine suggests dehydration, and for the majority of people, simply drinking plenty of plain water at regular intervals throughout the day will be sufficient to avoid the dangers of dehydration during a heatwave.
The economic impact of heat-related health issues, including dehydration, can also be significant. The NHS may experience increased pressure due to heatstroke and other heat-related illnesses, leading to longer waiting times for other medical services. For businesses, a workforce experiencing reduced concentration and fatigue due to dehydration can see a dip in productivity, affecting various sectors from office-based roles to outdoor labour. Ensuring employees have access to water and promoting regular hydration breaks are simple measures that can make all the difference.