As he manoeuvres his taxi through the barely moving traffic of downtown Yangon, Myo Min Htaike's jaw methodically pounds a pulpy mass of nuts and tobacco, his teeth stained a dark blood-red.
Plying his trade in the seemingly eternal gridlock of Myanmar's now booming commercial hub, he is more than used to spending long days on the roads and "kun ja" - better known as betel nut or quid - is the one thing that keeps him going.
"I'm so sleepy when I start driving the taxi," the 32-year-old tells AFP. "So I eat kun ja to help me stay awake."
Kun ja is an enormously popular stimulant chewed throughout Myanmar.
But it comes with a long list of serious health downsides including addiction, deeply stained gums and a high risk of mouth cancer.
The small parcels of tobacco, areca nuts, slaked lime and optional spices, wrapped in the vivid green leaves of the betel plant, are ubiquitous across the former junta-run nation.
Users sing its praises as a pick-me-up that increases alertness, boosts energy and freshens the breath.
"When I started eating betel quid for my tooth pain, I didn't like it much. But it made my toothache go away and I came to like it," Myo Min Htaike says, the tell-tale red stains visible on his lips.
'It's Myanmar's habit'
Yangon is a city in a constant state of change since decades of brutal junta rule gave way to a reformist government in 2011 that resulted in the lifting of most western sanctions.
Cranes jostle for space on an increasingly crowded skyline as locals furiously tap away on mobile phones that just a few years ago were far beyond their reach.
But some things have not changed, as the vivid red splashes of spat out betel on virtually every pavement and wall testify.
Chewers queue up at small kiosks across the city selling the wraps for 200 kyats (S$0.22). Hawkers carry them in trays hung around their necks and sell them to passing motorists at busy junctions.
For sellers, feeding the national habit can provide a good living. Myo Myint Tun rises at 3:00 am every morning to sell quids to commuters at a city train station.
On top of his 20 regulars, he estimates another 80 people stop by each day, earning him around $40 - a good living in a country where the average wage in 2012 was less than $100 a month.
"Most of the people in Myanmar eat betel quid - it's Myanmar's habit. It's been that way since long ago," he says.
But doctors warn that the national appetite for the stimulant is damaging health in a country with a threadbare medical system.
"Myanmar has one of the highest (number of) users of smokeless tobacco globally, especially among males," Dr Dhirendra Narain Sinha, a specialist at the World Health Organisation (WHO) told AFP.
His research has found just over half of Myanmar's men use the substance, in addition to 16 per cent of its women.
Both tobacco and areca nut are known carcinogens, with mouth-related cancers accounting for a fifth of all of Myanmar's cases of the illness.
Those who chew betel quids without tobacco, Sinha says, have a 250 per cent greater chance of having oral and oropharyngeal cancer than non users. For those who chew tobacco as well the risk jumps 770 per cent.
But doctors say the message to stop chewing is not getting through.
"People do not know what are the side effects or the health effects of eating betel quids in Myanmar," warns Dr Than Sein of local advocacy group the People's Health Foundation (PHF).
Low healthcare spending
According to the latest WHO figures, Myanmar spends the lowest proportion of its GDP on healthcare in the world - just 0.5 per cent in 2013, lower than South Sudan and Haiti.
By comparison, the military budget accounted for 4.3 per cent of GDP in 2014, say defence analysts from the Stockholm International Peace Research Institute. The onset of mouth cancer is often a slow and avoidable death sentence.
In common with neighbouring countries, cigarette packs in Myanmar now carry gory photographic warnings of the health risks, but betel is free of any packaging.
The PHF has produced leaflets and posters aiming to get its message across, and wants warnings placed at betel kiosks. The health ministry says it is studying the proposal.
But helping Myanmar kick the habit will not be easy. Betel-chewing is a deeply-rooted cultural practice throughout south and southeast Asia, thought to date back several centuries.
Nonetheless, Dr Than Sein says he takes inspiration from neighbouring countries.
"If you go to Thailand, you will not see much of the people eating betel quid anymore, even in the rural areas. If you go to Malaysia, the same way. So why do our people still keep the tradition?" he asks.
Sitting behind the wheel of his taxi, Myo Min Htaike says he is more than aware of the health risks, but after 12 years sees no prospect of quitting.
"I'm afraid (of suffering health problems)," he admits.
"But I can't live without it."