The Caffeine Effect: How can caffeine affect our health and vision?

For many of us, the morning hasn’t started until we’ve had our first cup of coffee for the day. 

From tea, chocolate, a can of Coke or energy drink, caffeine is in many of the food and drinks we consume, and with many health benefits such as lowering your risk of Type 2 Diabetes, protecting you from Alzheimer’s and Dementia and even helping burn fat, it is a great addition to our diet.

But are we drinking too much caffeine, and what can too much do to our health? 

Lenstore has analysed the short and long-term symptoms we could experience from consuming too much caffeine, from blurry vision, muscle aches and insomnia. In addition, the analysis looks at the coffee capitals of the world to show who is consuming the most and how much it costs for a cup in each city. We also use search volume to determine the most popular coffee style in every country.  

Could drinking too much coffee see you looking like Steve in 50-100 years?

A healthy adult is recommended to have no more than 400 milligrams (mg) of caffeine each day, which works out to roughly four cups of coffee. 

With people in the UK consuming 2.71 cups of coffee a day on average, and almost one in five of us drinking five or more (19%), we wanted to visualise Steve, who is representative of just what we might look like and the symptoms we could experience if we don’t curb our caffeine habits. 

Anxiety

It’s no surprise almost half of us (49%) admit that we can’t start our day without a cup of tea or coffee, however almost one in five of us (18%) admit that caffeine gives us anxiety.

Caffeine triggers the release of adrenaline, which is the ‘fight or flight’ hormone associated with increased energy. When we overdose on caffeine, these effects become heightened and can cause us to feel nervous, anxious, and jittery. Both increased and modest doses have been shown to cause increased stress levels. 

Insomnia

Many of us have caffeine to stay awake, but that also means it can make it difficult to get a decent night’s sleep with a third (33%) admitting that caffeine makes it difficult for them to fall asleep at night. 

It’s important to be conscious of the time you are having caffeine to ensure it doesn’t interfere with your sleeping patterns and recovery, with research showing it can stay in your system for up to nine hours. Signs of insomnia can see you experience dry eyes, which if this is the case is important to lubricate your eyes with eye drops and avoid wearing contact lenses if possible until the symptom reduces.

Headaches

Interestingly, caffeine can both cause and cure a headache with more than one in five (22%) of our respondents saying it gives them a headache, however, more than two fifths (43%) said it doesn't. With caffeine featuring in over-the-counter pain-relief medications, it can in fact help reduce inflammation which, as a result, can bring relief. 

Unfortunately, it is what makes caffeine so effective at reducing a headache that can also cause it. With caffeine narrowing the blood vessels around your brain, when you stop taking it, these vessels expand again and your pain will come back. Headaches are often a symptom people experience from the withdrawal of coffee. 

Dizziness/ lightheadedness

Like other stimulants such as tobacco, caffeine reduces blood flow to the brain, which may see you experiencing sensations of light-headedness or wooziness from overconsumption of coffee. 

Muscle tremors

As a stimulant, too much caffeine can cause your muscles to twitch or spasm and can occur in different forms, from an eye twitch to trembling hands. While this is often only a fleeting feeling, it may be a sign that you need to reduce your caffeine consumption. 

High blood pressure

Whilst caffeine overall does not appear to increase your risk of heart disease, it has been shown to raise your blood pressure according to several studies. Many of our respondents agree with more than a quarter (26%) revealing caffeine increases their heart rate.

Therefore, you should carefully monitor your caffeine intake if you already suffer from high blood pressure, as high levels can put you at a greater risk of a heart attack or stroke. 

High blood pressure and your eyes

High blood pressure can damage the tiny blood vessels that supply blood to the eyes, which as a result can cause a number of eye problems, including retinopathy (where your retina becomes damaged and can lead to blurred vision, bleeding in the eye and even complete sight loss). High blood pressure can also cause nerve damage which can impact your ability to see, as well as a fluid buildup in the retina known as choroidopathy, which can impair your vision as well. 

Studies are also now showing a connection between those consuming large amounts of caffeine each day and their risk of glaucoma (this is being seen as a risk for those with a genetic predisposition to higher eye pressure). Glaucoma can have a number of symptoms including red eye, eye pain, seeing rings around lights, blurred vision and blindness if left untreated. 

Confusion & hallucinations

Caffeine can trigger a number of emotions, from irritability to anger and confusion. Both consuming it and having withdrawal from it can cause a number of reactions from finding it difficult to concentrate and even feeling depressed. If you are noticing that your mental health is being affected, it is important to speak to your GP. 

Overconsumption of coffee can see the body become more stressed, and as a result of high adrenaline levels, can cause you to become confused or even hallucinate. Brain fog is also a common symptom people experience from the withdrawal of caffeine, and whilst it is experienced by many, it is still unhealthy and maybe a sign you need to cut back. 

Blurred vision 

Excessive consumption of caffeine can see a sudden increase in your blood sugar levels, which can lead to blurred vision, eye spasms and potentially a burning or tingling sensation in your eye area. 

The Coffee Capitals of the World 

Lenstore also wanted to look into coffee consumption across the world to find out where the most caffeinated cities are. Looking at the number of coffee shops per square mile, the country’s annual consumption and the average cost of a cup, the study crowns the most caffeine-addicted locations. 

The top 10 countries that consume the highest amount of coffee each year

When it comes to who is drinking the most coffee, the Nordic countries dominate the top 10, with Finland, Iceland, Sweden and Norway all featuring in the top five consumers. Finland ranks top, with each person consuming 9.6kg of coffee each year, which is triple the number of individuals across 20 other countries, including the UK (1.7kg), New Zealand (1.3kg), the USA (3.1kg) and France (3.2kg). 

Turkey consumes the least coffee of all countries analysed at just 0.4kg per person each year. Surprisingly the USA consumes less coffee than most countries at 3.1kg, and the UK the seventh lowest amount in the analysis.

The top 10 cities for affordable coffee include:

Columbia’s Bogotá takes the crown as the cheapest city to buy a cup of coffee at just £0.93, which is shockingly nearly five times less than a cup of coffee in Copenhagen, which comes to a staggering £4.47. Europe and South America dominate the top 10 cheapest cities list for a cup of coffee, with Rome, Italy sitting in third at £1.09, a city and country known for its fantastic-tasting coffee. 

The top 10 cities with the highest number of coffee shops per square mile

There’s nothing better than grabbing a cup of coffee when exploring new cities, but how easy is it to get your hands on one? Athens takes the crown with the highest number of coffee shops per square mile at a whopping 17.4. Next is Seoul, where the South Korean capital has over 9 coffee shops per square mile. London ranks in the top 10 with just under 3 coffee shops per square mile, meaning you’re spoilt for choice whilst exploring.

The cappuccino crowned as the world’s most popular coffee according to search interest

For the final part of the study, Lenstore analysed search interest to determine the most popular coffee drink in every major city. From espresso to a flat white, these are the most popular coffees in each location.

Based on the research above, how bad is your caffeine obsession?

Methodology

Lenstore’s study has researched the long and short term effects of the high intake of caffeine, looking at what it can do physically and psychologically. In addition, Lenstore has analysed the caffeine consumption of countries around the world, the average cost of a coffee in major global cities and the number of coffee shops per square mile in these locations to find out the most coffee-addicted destinations. Finally Lenstore analysed a seedlist of the most popular coffee’s and used Google Keyword Planner to determine the most searched style in 38 countries.

Sources used include:

1. https://www.healthline.com/health/caffeine-and-anxiety#caffeine-and-anxiety
2. https://silversteineyecenters.com/blog/2017/02/does-caffeine-affect-vision/
3. https://www.healthline.com/health/caffeine-effects-on-body
4. https://www.healthline.com/nutrition/caffeine-side-effects#TOC_TITLE_HDR_11
5. https://iris.ca/en/blog-post-detail/how-does-caffeine-affect-your-eyesight
6. https://www.bbcgoodfood.com/howto/guide/how-much-caffeine-tea
7. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/caffeine/art-20045678#:~:text=Up%20to%20400%20milligrams%20(mg,two%20%22energy%20shot%22%20drinks.
8. https://www.numbeo.com/
9. https://www.tripadvisor.co.uk/
10. https://en.wikipedia.org/
11. https://www.caffeineinformer.com/caffeine-what-the-world-drinks
12. https://public.knoema.com/hvfyqyb/world-coffee-consumption?country=1000370-chile 
13. Google Keyword Planner