If a strong cup of coffee helps you function first thing in the morning, you are in good company. Most adults rely on some form of caffeine to start their day; however, scientific studies show that caffeine does not impact all people in the same way.
This is especially important if you are like me, reaching for a cup of coffee every afternoon at work yet never feeling a burst of energy afterward. Ironically, while afternoon coffee did not give me energy, it made falling asleep many hours later quite challenging!
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What I Learned
It took two whole decades to figure out why. I hope to spare you that same hassle, but of course, must note that this article should not substitute for the advice of your health care provider.
In short, I surprisingly learned that our individual response to caffeine is determined largely by our genetics. Click here if you want to skip down and quickly learn how to test your own caffeine genetics.
How Caffeine Affects Your Body
Not just in coffee, caffeine occurs naturally in many plants and fruits, including of course coffee beans, but also tea leaves, cacao pods, and kola nuts (the ingredient in cola sodas). It is also chemically synthesized and added to foods, beverages, and even medications. While caffeine does not have any nutritional value, it can cause powerful physical and psychological effects that have created whole new markets: think energy drinks, pre-workout supplements, and even caffeinated water!
- Caffeine is a central nervous system stimulant that can help you feel more alert and prevent drowsiness. However, in large amounts or due to genetics, it can make you feel anxious, jittery, and disrupt sleep. (Tip: Closely read labels of food, drinks, and supplements to make sure there is no hidden caffeine you are unintentionally consuming)
- Caffeine temporarily increases heart rate and blood pressure, which increases the amount of oxygenated blood circulating throughout the body. This can temporarily improve endurance and reflexes similar to the body’s natural “fight or flight” response.
- Caffeine has a complicated connection to headaches in that it can both cause and treat them. Individuals who drink lots of caffeine may experience withdrawal headaches if they quit suddenly or miss a “dose.” It may also trigger headaches in those who are particularly sensitive to its effects. Yet, caffeine is also a common ingredient in both over-the-counter and prescription migraine headache medicine.
- One more note about caffeine withdrawal is that it can trigger mood changes, including irritability, drowsiness, and anxiety. So, if you want to cut down it is generally a good idea to reduce gradually to prevent the unpleasantness associated with stopping suddenly.
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The Reason Why Caffeine May Not Affect You
If you don’t get your desired effects on energy from caffeine, don’t worry, there may be a few explanations.
The Caffeine Genes
What I found is that how our unique body responds to caffeine is determined by our genetics.
That’s right, your DNA may determine whether that afternoon cup of coffee wakes you up and helps you finish the day strong…or gives you the jitters…or does nothing at all!
A team from the Harvard School of Public Health looked at the results of approximately 24 studies involving more than 120,000 people. They were able to locate eight genetic variants connected to caffeine consumption. Six of the variants were connected to genes that control how caffeine is metabolized by the body or how caffeine stimulates the body. Two genes connected with cholesterol and blood sugar may also play a role in how you respond to caffeine, but it is unclear why.
Two genes, CYP1A2 and ADORA2A, appeared to have the largest impact on how caffeine affects us:
CYP1A2, this gene determines how your body metabolizes (or breaks down) caffeine.
- If you metabolize it fast, you are more likely to receive the desired energy boost without jitters or nervousness
- If you metabolize it slowly, it stays in your system longer and may cause more jitters or negative effects
ADORA2A, this gene determines how caffeine acts on your brain.
- Different variants of this gene impact whether that afternoon cup of coffee help you become more alert or explain why it has no effect
- This gene also influences the effects of caffeine on your sleep quality, and even if its consumption makes you anxious
By now you are probably thinking, this science lesson is great but what you really want is…
The Simple Genetic Test to Understand How Caffeine Affects You
When I first found out I was a slow caffeine metabolizer it was through the popular 23andme genetic test. Unfortunately, this testing service stopped reporting on caffeine metabolism in 2016.
Luckily, there are newer (and more useful) tests to help you understand your genes and the influence they have on how caffeine affects you. The one that specifically provides insight into caffeine is the MyDNA Personalized Nutrition & Fitness Plus Caffeine test kit (amazon link also in the image below).
It tests CYP1A2 and ADORA2A which may finally help you understand why caffeine has a different effect on you. As a bonus, the test provides a whole list of other actionable health insights, including:
- Your immune system
- Optimal foods to eat for your unique genetics
- The best workouts to achieve your fitness goals
For the cost of going out for coffee for a few weeks (that may not even work!), you get an impressive amount of insights and tools that can help improve your overall health and well-being.
The Effects of Excess Consumption
A study conducted by researchers from the University of Bristol in Great Britain looked at the effects of caffeine on alertness in heavy, low, and non-caffeine users after going without caffeine for 16 hours. Both the low and heavy caffeine users reported feeling more alert after taking caffeine pills; however, their level of alertness was no higher than the non-caffeine users that had received placebos. Heavy caffeine users taking the placebo were the least alert of those studied.
The researchers concluded that these results showed that caffeine actually did not raise overall alertness. The effect that the low and heavy caffeine users felt was actually a reversal of withdrawal symptoms brought on by going without caffeine for so long. The caffeine simply restored them to a normal level of alertness experienced with regular caffeine use.
The heavy caffeine drinkers receiving the placebo also reported headaches. In some cases, the headaches were so severe that the individuals had to drop out of the study. These results highlight that caffeine is not a “one size fits all” compound to improve alertness and that in some cases it may have a negative effect through dependence and withdrawal symptoms.
Finally, other factors, including body mass, age, and other health conditions can affect tolerance to caffeine. So, if you also experience side effects from the use of (or lack of use of ) caffeine, in addition to exploring your genetics, a discussion with a healthcare provider can be useful to develop a plan on how to best consume caffeine safely.