Coffee *drool* is arguably the most widely consumed drug in western society. I’ve never met anyone (that I respect) who doesn’t love a well-made cup of coffee. I’m joking, of course. But on a serious note, who doesn’t love coffee? Most of us are even addicted to it. It’s a massive part of many cultures around the world. We kickstart our day with a coffee, we socialise over a coffee, we use it as a pick-me-up in the afternoons, and some cultures even drink it after dinner with dessert. But when it comes to the health effects of coffee, many people argue whether it is good or bad. The truth is, coffee has an array of proven health benefits but it also has some potentially negative side-effects. So, the question is: How can we mitigate the potential downsides and still capitalise on all of the wonderful things coffee has to offer? In this article, I’m going to cover how to turn the cost-benefit ratio in your favour.

Coffee consumption has been shown to have multiple health benefits. It’s rich in antioxidants/flavonoids which give it anti-cancer properties, it’s linked to lower body weight, it helps you feel energised and focused, and it also tastes amazing! So, at the very least, it will flood your body with feel-good endorphins. But like most things in life, just because some is good doesn’t mean more is better.

The Impact of Coffee on Blood Glucose Levels

The cool thing about living with type 1 diabetes is that it’s like a window into human physiology. I get objective, measurable insights into my health through the lens of glucose monitoring and insulin requirements which means I can test all kinds of experiments on myself and bounce my findings off the scientific literature to confirm or deny my hypotheses. Over the last ten years living with diabetes, I’ve been able to consistently measure the direct impact of coffee on my insulin and blood glucose levels.

I first discovered the relationship between coffee and blood glucose shortly after my diagnosis. I quickly realised that my morning coffee was causing my blood glucose to spike. Initially, I thought it was the carbohydrate content in the almond milk that was causing this, so I started drinking black coffee but nothing changed. I then started giving a little bit of insulin before my coffee but it wasn’t always effective. In fact, it felt like the coffee was making me insulin resistant.

As part of my experiment, I stopped drinking coffee for a few days and guess what happened? Just like that, my blood glucose levels stabilised.

I knew that there had to be another mechanism going on inside my body that was causing my blood glucose to spike, so I set out to find a solution. I began doing some research and I made many interesting findings. It turns out, it’s not the carbohydrate in the milk causing my blood glucose to rise, rather it’s the caffeine in coffee that triggers numerous physiological processes.

Caffeine induces a stress hormone response (cortisol and adrenaline). One of the many roles of these hormones is to mobilise hepatic glucose. In other words, these hormones tell your liver to turn on the glucose tap and dump a load of glucose into the bloodstream to be used for rapid energy. Imagine you’re being chased by a lion. Adrenaline will surge and your liver will supply you with stored energy so that you can run away. Well, unfortunately (or fortunately, depending on what way you look at it), coffee does the same thing! Our primal physiology can’t tell the difference between the adrenaline induced by a predator or a cup of coffee.

What does the science say?

The effects of coffee are well-documented in the scientific literature. In a 2016 meta-analysis and systematic review, acute caffeine ingestion was shown to reduce insulin sensitivity in healthy subjects. Furthermore, a study looking at the effects of caffeine on men with type 2 diabetes showed that caffeine ingestion before an oral glucose tolerance test (OGTT) impairs blood glucose tolerance. Similar findings were shown in a study looking at the effects of caffeine on fasting glucose and insulin levels, as well as glucose and insulin responses to a mixed-meal tolerance test (MMTT) in people with type 2 diabetes. There is also evidence that caffeine ingestion is associated with a reduction in glucose uptake independent of obesity and diabetes status. This is supported by findings showing that acute caffeine ingestion impedes insulin-mediated glucose disposal. So, it is evident that this phenomenon is not just related to diabetes, but is apparent and demonstrable in healthy, non-diabetic subjects too.

Interestingly, there is also evidence, as seen in a 2018 meta-analysis and systematic review, that long-term coffee consumption is associated with reduced incidence of type 2 diabetes. I know, it sounds confusing but that’s because coffee does have numerous health-promoting effects such as antioxidative, anti-inflammatory and gut microbiome benefits. So let’s not throw our hand up in the air just yet.

Let’s take a deeper look into the physiological mechanisms of caffeine ingestion…

The Metabolic Effects of Caffeine

Caffeine stimulates the release of glucocorticoids such as cortisol, and catecholamines such as adrenaline, which have many widespread metabolic actions in the human body:

1. Caffeine Releases Glucose Into The Bloodstream
Adrenaline and cortisol are key hormones in the ‘fight or flight’ response. They stimulate the liver to release glucose into the bloodstream via two physiological processes; glycogenolysis and gluconeogenesis. This basically means that the liver breaks down stored glucose in the form of glycogen, and it also breaks down non-glucose sources of energy such as fat sources. Interestingly, insulin inhibits these exact two processes from taking place.
 We’ll come back to why this is so important later.

2. Caffeine Increases Lipolysis
That’s just a fancy way of saying that it increases fat burning. It breaks down fat tissue and releases free fatty acids into the bloodstream to be used for energy. This is also interesting because one of the must-know properties of insulin is that it inhibits lipolysis. In other words, insulin is like a metabolic switch that ‘turns off’ fat burning. No, that doesn’t mean insulin ‘makes you fat’ like many ‘experts’ are claiming in the blogosphere. Insulin levels in the normal physiological range are perfectly healthy. Let’s stop vilifying insulin.

3. Caffeine Causes Temporary Insulin Resistance
This might seem like a bad thing considering we are always striving for increased insulin sensitivity, but it’s actually beneficial in this context. If insulin levels are high, it inhibits the exact mechanisms of fuel mobilisation that caffeine is stimulating. So as a result, our body finds a way to allow energy burning to occur by becoming temporarily insulin resistant. In a state of impaired insulin sensitivity, insulin can’t do its job properly on a cellular level, which prevents it from triggering it’s storage properties and allows nutrients to be mobilised from the liver and used for energy.

Insulin vs Adrenaline

It is important to understand that insulin and adrenaline have opposite actions in the human body

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Adrenaline releases nutrients.
Insulin stores nutrients.

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Therefore, if consuming coffee promotes the release of adrenaline, it would make sense to limit our insulin levels at this time.

So When Is The Best Time to Drink Coffee?

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The timing of coffee intake, as well as the combination with other nutrients, is the key to optimising blood glucose control.

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My Coffee Intake Recommendations:

1. Drink coffee in the absence of carbohydrates and/or in a fasted state
   Taking into consideration that coffee causes temporary insulin resistance and glucose intolerance, adding carbohydrates (sugars) to an already compromised system will make for even higher blood glucose levels. Moreover, the extra carbohydrate will require more insulin to get the job done which will counteract the beneficial metabolic effects of coffee i.e releasing stored nutrients for energy.TIP: If you drink coffee first thing in the morning, try having it in a fasted state rather than with a carbohydrate-rich breakfast. That means the coffee-croissant combo is a no-go. Sorry guys!
2. Drink Coffee Pre-Workout or Before Physical Activity
   Exercise has many beneficial physiological effects; it improves insulin sensitivity, increases fat burning, and opens the glucose gateway to the cells of the body – all of which allow for better blood glucose regulation. Therefore, exercise will help mitigate the effects of caffeine on insulin resistance as well as soak up any excess blood glucose. There is scientific evidence showing that even exercise does not completely mitigate the increased insulin resistance caused by caffeine, but it certainly reduces the extent of it. Furthermore, the caffeine will help fuel a more productive workout by increasing adrenaline output which makes more glucose and free fatty acids available in the blood to be used for energy – both of which result in feeling more energised and focused.
3. Drink Coffee Between 10 and 11 a.m
   Our body functions on a circadian rhythm which is like an internal body clock that regulates your sleep-wake cycle and ultimately your energy fluctuations throughout the day. But that’s just one part of a complex equation. Your circadian rhythm is part of a biological system that dictates many critical physiological processes such as your core body temperature, hormonal levels, metabolism, blood pressure, and even the way your genes are expressed (epigenetics). The stress hormone, cortisol, has its own circadian rhythm. It is elevated in the early hours of the morning to help wake you up from your sleep. Like caffeine, cortisol has energy-boosting properties. Most people drink coffee first thing in the morning which might be suboptimal. Caffeine stimulates adrenalin and cortisol which gives you energy, but the body’s cortisol levels are naturally highest in the morning to wake you up. Caffeine and cortisol have similar awakening effects on the body. Adding caffeine on top of the already elevated cortisol levels is not optimal. Instead, let cortisol do it’s thing naturally, then later in the morning at around 10 a.m when your cortisol levels naturally drop, you can reach for the coffee and get the most bang for your buck.
   

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My Personal Approach

After making these changes to the timing of my coffee consumption and my insulin protocol, I no longer experience blood glucose spikes. I am now able to make the most of the energy that the coffee provides by using it to fuel activity.

Recently something very unusual and frustrating happened to me. Every morning after taking my dog for a walk, I go for a swim in the ocean and then I grab a coffee from my local cafe by the beach. I usually take 0.5-1 unit of insulin with my morning coffee to mitigate the natural glucose elevation that occurs after caffeine ingestion, but on this particular day, when I took out my insulin pen to give my injection – it was empty! I didn’t have time to go home and get a new insulin pen so I just used it as an experiment to see what would happen. As predicted, my blood glucose spiked! It was 5.6 mmol/L when I arrived at the cafe. After my coffee, it was 12mmol/L.

This is the second time in ten years that this has happened to me (running out of insulin). I tried not to let it bother me but I have to admit, it did. As soon as I got home I gave a correction dose and within two hours I was back in the normal range. Sometimes diabetes really sucks. It’s kind of crazy to think that people living with type 1 diabetes have to be a manual pancreas. A normal pancreas responds to elevations in blood glucose, however people with type 1 diabetes have to predict glucose elevations before they happen so that we can administer insulin appropriately in the right dose.

Most people take for granted the fact that they can simply eat or drink whatever they want without hesitation or a second thought. Diabetes is like a full-time job. It requires hundreds of daily decisions to ensure that you can tightly manage a complex system designed to be automatic. One of the many invaluable lessons that diabetes has taught me is how to be ok with being imperfect. I’ve always been attracted to the pursuit of perfection when it comes to managing my condition but I have to constantly remind myself: “Don’t let perfection get in the way of progress”.

The Take-Home Messages

• Caffeine in coffee promotes the release of cortisol and adrenaline.
• Adrenaline and cortisol turn on energy mobilisation pathways whilst making you temporarily insulin resistant.
• Adrenaline and insulin have opposite metabolic actions.
• High insulin levels will counteract the energy-burning effects of the coffee, so we want low insulin levels when we consume coffee.
• To achieve this, drink coffee in a) a fasted state, b) in the absence of carbs, and c) at a time when you are most insulin sensitive.
• Perform some kind of movement or exercise around coffee ingestion to improve glucose tolerance and insulin sensitivity
• Drink coffee between 10 and 11 a.m when the body’s natural circadian cortisol levels are lowest. This will also make the energy-boosting effects of coffee more impactful.
• Exercise will help mitigate the state of temporary insulin resistance by improving insulin sensitivity as well as soaking up any excess glucose from the bloodstream.
• Exercise will also help utilise the free fatty acids in the bloodstream caused by adrenaline-induced lipolysis (fat burning) – ultimately allowing you to burn some extra fat.

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That’s it for today’s Daily Dose of science. I hope this information has given you a new perspective on coffee drinking. I’d love to hear from you, so please leave a comment on this post or send me a message. Enjoy your coffee!

REFERENCES:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6544578/

https://pubmed.ncbi.nlm.nih.gov/11151742

https://care.diabetesjournals.org/content/25/2/399.short

https://care.diabetesjournals.org/content/25/2/364

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2257922/

https://academic.oup.com/jn/article/134/10/2528/4688344

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1464218/

https://care.diabetesjournals.org/content/27/8/2047

https://pubmed.ncbi.nlm.nih.gov/24150256/

https://care.diabetesjournals.org/content/29/2/398

https://care.diabetesjournals.org/content/27/12/2990

https://academic.oup.com/jn/article/134/10/2528/4688344