The United Kingdom holds the title of the world’s largest consumer of instant coffee, with a staggering 54% of the population favoring it over other types of coffee, as reported by Deloitte this year.

However, could this beloved beverage be harboring a hidden danger to our health? Recent research has uncovered a potential connection between instant coffee consumption and age-related macular degeneration (AMD), the leading cause of blindness in the UK. This condition gradually deteriorates central vision, making daily tasks like reading and driving increasingly challenging.

AMD comes in two varieties: wet and dry. The dry type accounts for 90% of the UK’s 700,000 AMD cases. It occurs when minute protein deposits accumulate on the macula, the part of the retina responsible for sharp central vision.

In contrast, wet AMD results from abnormal blood vessel growth in the eye’s back, which harms the macula.

Certain genetic factors are known to elevate the risk of developing AMD. The study further revealed that individuals carrying these genes who consumed more than the typical two cups of instant coffee daily faced an increased risk. Doubling their intake from two to four cups raised their risk nearly sevenfold.

So, should we consider switching to brewed coffee? The researchers behind this study suggest that might be a wise choice.

The team from Hubei University in China analysed data from more than half a million people in the UK and Finland which included genes, coffee consumption and health status.

Instant coffee is made by brewing concentrated extracts and then spray-drying (where droplets of hot coffee extract are sprayed through hot air to dry them)

They found a ‘significant’ genetic correlation between those who consumed instant coffee and those who developed dry AMD. (No such links were found with other types of coffee or with wet AMD.)

‘Instant coffee may increase the risk of AMD and reducing its intake could help prevent dry AMD,’ wrote the researchers in the journal Food Science and Nutrition.

‘People at risk for AMD should avoid instant coffee. Clinicians can advise patients to reduce instant coffee intake based on genetic risk profiles. These interventions may significantly contribute to AMD prevention and treatment.’

One theory is that the manufacturing process generates high levels of compounds that can damage the retina, researchers said.

Denise Voon, a clinical adviser at The College of Optometrists

As Denise Voon, a clinical adviser at The College of Optometrists, explains, instant coffee is made by brewing concentrated extracts and then spray-drying (where droplets of hot coffee extract are sprayed through hot air to dry them).

‘This process generates higher levels of acrylamide, advanced glycation end-products [when sugar sticks to body components such as proteins, creating a sticky layer] and other by-products that can cause inflammation and other damage to cells in the retina than when manufacturing other types of coffee.’

In other words, it’s not caffeine that’s the problem but by-products of the manufacturing process of instant coffee.

The industrial manufacturing process means instant coffee is an ultra-processed food (UPF), says Sheraz Daya, an eye surgeon at the private Centre for Sight in London.

‘That means it’s produced industrially, using processes such as spray drying,’ he explains. ‘We all know about problems with UPFs, particularly acrylamide which is really toxic.’

A study of more than 150,000 people aged 50-plus, published in the European Journal of Nutrition last year, found that every 10 per cent increase in UPFs in a person’s diet was associated with an 8 per cent increase in their risk of AMD.

Illustration of macular degeneration, which slowly destroys central vision, the part of the eye that controls sharp forward vision, making it difficult to read and see fine details

A family history of AMD increases your risk – having a parent or sibling with AMD means you have a 50 per cent risk of developing it, too.

‘If I had a relative with a history of macular degeneration, I’d avoid instant coffee – and other UPFs as much as possible,’ adds Mr Daya.

While the study was thorough, it didn’t prove that instant coffee is harmful and it’s important not to panic, says Denise Voon.

Nevertheless, she advises: ‘If you are at particular risk, such as having a first-degree relative with AMD, you may wish to limit your instant coffee intake, or switch to other forms of coffee – and have a rich diet of green, leafy vegetables and oily fish twice a week.’

Yet other experts are more sceptical about the findings. A spokesman for the Macular Society raised questions about the researchers’ methodology, including the decision to combine data from ‘two different countries with very different habits around coffee consumption’.

They added: ‘The statement about stopping instant coffee to stop people developing AMD isn’t backed by robust evidence. AMD is caused by many factors – one single factor, such as drinking instant coffee, is not the cause of AMD.’

Professor Dan Reinstein, an eye surgeon at the London Vision Clinic concurs, saying that while the study makes an ‘eye-catching claim’, the evidence is too weak to suggest that instant coffee damages vision.

It’s possible that the other lifestyle factors, such as smoking and drinking, are behind the link, he says – and not instant coffee at all.

‘There’s no prior reliable evidence that instant coffee harms your eyes,’ explains Professor Reinstein, ‘and this study does not change that.’

He adds: ‘The real ways to protect your sight are to avoid smoking; eat a balanced diet that’s rich in green vegetables and fish; control blood pressure; and get regular eye checks.

‘Coffee choice doesn’t belong on that list.’