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How I found out the ‘two drinks and drive’ belief is now a dangerous myth

Lucy Denyer enjoys a bottle of red at home, monitored by a home breathalyser
Lucy Denyer enjoys a bottle of red at home, monitored by a home breathalyser - Lorne Campbell/Guzelian

My husband breathes slowly and regularly into the plastic tube, a wry grin on his face. A few seconds later, the screen flashes red. 0.44 mg/L, it says. That’s 0.80 per cent blood alcohol content – which puts him bang on the legal alcohol limit to drive, should my husband wish to get behind the wheel. His face falls. He’s only had one beer.

It’s a Friday night and I’m entertaining my family. There’s roast chicken, with cranberry torte for pudding. Then cheese. Plenty of booze will, of course, be on offer: celebratory fizz to kick off the evening, red wine for dinner and beer and G&T for those who want it. At the end of the evening, my folks will drive home – as we would do were we going to theirs.

Because it’s fine to have a couple of glasses of wine with dinner if you’re driving, right?

Well, possibly not. Last week, Sir Ian Gilmore, the president of the British Medical Association (BMA) – who is also chair of the Alcohol Health Alliance – said the idea of “getting away with” two drinks and then driving home “has always been dangerous”, calling for Brits to have no alcohol at all if they’re planning to get behind the wheel this Christmas.

Drunk-driving offences are on the rise. The latest Office for National Statistics figures show a 27 per cent increase in alcohol-related deaths between 2019 and 2021, and the latest data suggest around 260 drink-driving deaths annually in the UK, or almost one in five of all deaths on our roads.

Enforcement of drink-driving laws has also declined during this time: the number of dedicated roads policing officers reduced by 27 per cent between 2011/12 and 2015/16, and there were 25 per cent fewer breath tests in 2015 than 2011.

Wines and beers have increased in ABV in recent decades, making it difficult to calculate a "unit" of alcohol
Popular wines have increased in ABV in recent decades, from 9 per cent in the 1960s to around 14 per cent now, making it difficult to calculate a "unit" of alcohol - Lorne Campbell/Guzelian

In the UK, we also have one of the highest drink-drive limits in the world, at 80mg/100ml – compared to the majority of Europe, at 50mg/100ml (at its annual conference in the summer, the BMA passed a motion to lobby the Government to lower the drink-driving limit to this level). In Hungary, it’s illegal to drink and drive. In France, you’re obliged to carry two breathalysers with you in the car at all times.

Hence our mission this evening to investigate – complete with digital breathalyser – how much or how little we have to drink to wander over the limit. The results are – if you’ll excuse the pun – sobering.

Britain’s current drink-driving laws were devised in the 1960s. Though it had been an offence to be found drunk in charge of any mechanically propelled vehicle on any highway or public place since 1925 (punishable by £50, the removal of a driving licence and a possible prison sentence), it was not until 1967 that a legal drink-driving limit was set, at 80mg of alcohol per 100ml of blood, after an American study found that this was the level at which the chances of being involved in a car crash rose sharply. This was also when it became an offence to fail or refuse to supply a breath, blood or urine sample.

The law has basically remained the same ever since. As a basic guide, men are advised not to drink more than three units of alcohol before driving (one unit of 10ml, or 8g of pure alcohol, is around the amount the average adult can process in an hour), while women should stick to two – although the RAC warns there is “no hard-and-fast rule” for how many units a person can safely drink without exceeding the 80mg limit.

This is commonly interpreted as it being OK to drive after a couple of drinks (although one friend insists that, in the country, it’s “five and drive”, while another south-western acquaintance claims “seven in Devon”. They’re joking. I hope).

In 1967, the most popular drink was Liebfraumilch, which has an ABV (alcohol by volume) of 9 per cent, and would have been served in a pub in a 125ml glass – totalling one unit. Today, you’d struggle to get a wine with an ABV of anything less than 12 per cent, and a standard-sized serving is 175ml – or 2.5 units. Little wonder, perhaps, that after a glass of red on top of my initial glass of fizz, my blood alcohol content has soared to 0.82 per cent. Luckily I’m not driving anywhere.

“The perceived wisdom is, two glasses and you can drive,” says wine consultant Karen Hardwick. “People don’t realise how much they’re having. But how are you going to metabolise that alcohol?”

It’s a pertinent question – and one that varies from person to person, which is also what makes knowing your limits tricky. After swallowing an alcoholic drink, about 25 per cent of the alcohol is absorbed straight from your stomach into the bloodstream. How quickly you absorb it depends on a number of factors, including the concentration of alcohol in your drink, whether your stomach is full (my husband hadn’t had lunch, which is likely why his beer sent him soaring) and whether your drink is carbonated (champagne, for example, is absorbed more quickly than non-sparkling drinks, which is why we all feel more tipsy after a glass of fizz).

Once the alcohol has entered the bloodstream, it remains in the body until it is processed – largely by the liver, which breaks down about 90-98 per cent of the alcohol, with the rest removed by breathing, sweating and peeing. Your body mass and the size of your liver are factors in how much alcohol you can metabolise in an hour, but it’s mostly down to genetic makeup, and how efficiently your ADH and ALDH enzymes, which break down alcohol, work. All of which means it can take longer than you think to flush the booze out of your system, dinner or no dinner. “If you’ve had a heavy session, you shouldn’t really get in the car the next morning either,” says Hardwick.

But the measurement system in place in Britain doesn’t really help. For a start, while we all think we know what a unit is, it’s likely we don’t really. A pint of beer, for example, comes in at around 2.3 units, and can be up to 3 units if it’s a strong 6 per cent ale. One of those fishbowl-sized glasses that a standard pub G&T comes in these days racks up a couple more. Three large glasses of wine equals a bottle – which equals 10 units, when it’s the standard 13.5 per cent ABV of a decent red. And when it comes to having friends round for dinner, none of us are measuring our drinks out, we’re just sloshing it straight into the glass.

ABV percentages are also getting higher. “Even 15 years ago, it wasn’t unusual to find a Bordeaux at 12 per cent,” says Hardwick. “Now, that would typically be 14 or 14.5 per cent.” Anything under 12.5 per cent is now classified as a low-alcohol wine. When it comes to beer, meanwhile, drinks trends mean we’re now much more likely to be sipping a Spanish or Greek lager at 4.6 per cent ABV than a traditional British bitter with an ABV of some 1 per cent lower. According to a recent YouGov survey, San Miguel, with an ABV of 5.0 per cent, is now the nation’s most popular beer, compared to Stella Artois in 2014, at 4.8 per cent.

These two factors combined – an ignorance of genuine unit size combined with increasingly alcoholic drinks – mean that we’re fairly clueless when it comes to our limits. This is not helped by the fact that the UK has no mandatory labelling laws for alcohol products – unlike alcohol-free beers or mixers, there’s no requirement to include any nutritional information in terms of calories and so on. Dr Katherine Severi, chief executive of the Institute of Alcohol Studies (IAS) is categorical in her disdain for this state of affairs. “It’s really unfair on consumers to allow drinks companies to withhold information about a product that is carcinogenic.”

Lucy Denyer checks her alcohol levels with a home breathalyser after half a large glass of red wine
Lucy Denyer checks her alcohol levels after half a large glass of red wine - Lorne Campbell/Guzelian

There are, perhaps, signs of change: research suggests that when it comes to the younger generation, people are drinking less, or not at all compared to their baby-boomer predecessors. There are also fewer drivers in that age group: barely more than one in four people aged 17 to 20 now have a full driving licence, according to the Department for Transport, down from almost one in two young adults in 1989.

My children aren’t old enough to drive yet. But even our lighthearted experiment with the breathalyser has made me rethink my attitude to alcohol and driving. I’m not a big drinker – I rarely exceed the Chief Medical Officer’s low-risk drinking guidelines of 14 units a week. But I do like a glass or two of wine if we’re having dinner out, and confess to having driven home after a couple more times than I care to remember.

My father’s experience was perhaps the most salutary. At 76, he’s hale and hearty, and has always enjoyed a decent glass of wine in the evening. After three glasses of champagne and one of red, however, his blood alcohol content had soared to 1.43 per cent – nearly double the legal limit. Though he said he felt completely clear-headed, he was obviously shocked at the results. Luckily for him, my mother had just the one glass, and was well under the legal limit – so she drove them home. This Christmas, I’ll be trying to follow her example.