Why is alcohol dangerous in a heatwave, and should I cut it out completely?

As Europe endures a record-breaking heatwave, countries are taking steps to keep people safe and prevent health services from becoming overstretched. Parisians face a temporary ban on drinking alcohol in public to reduce the pressure on the hospitals after a four-fold rise in cardiac arrests in a 24-hour period.We look at why drinking alcohol can be dangerous in a heatwave.What does alcohol do to the body?A cold beer in the sun need not be a problem, but strong drinks and large volumes can be dangerous. Alcohol is a diuretic, and estimates suggest every 1ml of alcohol stimulates the body to produce about 10ml of urine. If you have a 25ml nip of 40% whisky, that amounts to 10ml of alcohol and 15ml of water. The 10ml of alcohol will cause you to produce 100ml of urine, leading to a net water loss of 85ml. There’s a smaller effect with beer. A pint (568ml) of 5% beer contains about 28ml of alcohol, which stimulates about 280ml of urine, but the body gains about 260ml of water.“You’re better off with that pint of beer, you are more hydrated than you would be if you didn’t drink it,” said Prof Ron Maughan, an honorary professor at the University of St Andrews who has worked with the British Olympic Association. But drinking pint after pint can be a problem because the sheer volume stimulates urination. “When you drink not one pint of beer but many pints of beer, you run into difficulties,” he said.Why is there a risk of heart attack?Heat and alcohol can put immense strain on the heart. People sweat more in hot weather and the loss of water causes a drop in blood volume. At the same time, blood vessels near the skin widen to help the blood lose more heat as it is pumped around the body. Alcohol magnifies this effect, causing the blood vessels to widen even further. Together, this drives a drop in blood pressure, so the heart has to work to harder to ensure enough oxygen reaches the brain and other organs. If the heart cannot match the demand, people can feel dizzy and collapse because too little oxygen reaches the brain.Losing sodium, potassium and magnesium through dehydration can make matters worse. The loss of electrolytes can cause arrhythmias or irregular heart beats. In the most severe cases, the heart itself receives too little blood to work properly, which can lead to a heart attack. “If there is too little blood and the pump function is not good and you have arrhythmia, you may have a problem in supplying your own heart with blood,” said Prof Helmut Seitz at the University of Heidelberg in Germany.What about heatstroke?Drinking alcohol in a heatwave dramatically raises the risk of heatstroke, where the body fails to regulate its core temperature. dehydration and the effects of alcohol on the brain make it harder for the body to keep within a safe temperature range, but people are also less likely to spot the warning signs such as slurred speech, headache, feeling sick and a racing heart.Do alcohol bans help?Seitz said there was a lot of sense behind the Paris ban. Beyond the risky physiological effects of consuming alcohol in a heatwave, alcohol impairs people’s judgment, makes them more aggressive and leading to more risk-taking. “You risk more than you should do. You jump into the water and break your neck, or jump in and have an infarction [heart attack] because of the shock,” he said.Is it best to have no alcohol?Not necessarily. “There’s a danger the advice can be counterproductive,” said Maughan. Having the odd pint of weak beer can help with hydration, but if people are warned off all alcohol, they may not replace it with water, juice or other drinks.He suggests that people who want to drink stick to a couple of pints of weak beer or shandy. “You reduce the alcohol content, but maintain the volume,” he said.