You may know someone who seems to be able to drink all of the caffeine they want and sleep like a baby each night.
For others, a sip of coffee taken after lunch could give them insomnia all night.
Caffeine is metabolized by a liver enzyme coded by the gene CYP1A2. If you carry 1 or two "bad" copies of this gene, it will slow your ability to process your caffeine intake - and you may be more sensitive than someone else.
Chris Kresser, LAc recently made an excellent review of how coffee can be good or bad for you based on whether you are a fast or slow metabolizer of caffeine. According to Kresser, slow metabolizers of caffeine may be at higher risk of heart disease, high blood pressure, impaired fasting glucose, and possibly some cancers. Fast metabolizers of caffeine may experience benefits for heart disease, obesity, exercise and more.
We have an enormous amount of genetic information at our fingertips. While not available in some states like New York, a simple 23andMe.com test can give you a wealth of information of how you metabolize certain nutrients, including caffeine.
But what happens if you are a so-called "fast metabolizer" of caffeine (carry two "good" copies of the gene), yet still find yourself extra-sensitive to the stimulating effects of caffeine?
The Role of COMT, Stress Hormones, and Caffeine Sensitivity
The reason fast metabolizers of caffeine can still be sensitive to a cup of coffee or black tea comes back to the interplay of other genes that help you metabolize your catecholamine hormones - specifically epinephrine and norepinephrine (adrenaline and noreadrenaline). Even those switching to a substitute like yerba mate may still experience issues.
Like caffeine, you may be a "fast" or "slow" metabolizer of your catecholamine hormones.
One of the major group of genes involved with metabolism of these hormones is known as COMT (catechol-O-methyltransferase). If you carry "bad" copies of COMT, you are more likely to hold on to your production of the "catecholamine" class of hormones - which includes hormones like dopamine, epinephrine and norepinephrine.
Slow metabolism of catecholamine hormones is not always a bad thing.
For instance, slow metabolizers of catecholamines tend to have an easy time focusing, and report a generally pleasant mood. Dopamine helps individuals focus for long periods of time and is involved in pleasure pathways. They can read for hours at a time and often find careers as writers, scientists, statisticians, engineers and doctors.
It does come at its costs, however.
A slow metabolizer of catecholamines could focus at a high level for a number of hours but then fall off a cliff where they can quickly become irritable, tired, and require some time to refresh and recharge their batteries. During these periods they can be socially distant and sometimes act depressed or engage in addictive behaviors.
Carriers of a faulty version of the COMT gene sometimes walk a delicate balance as their "addictive" tendencies can be expressed in positive and negative ways. Faulty copies of COMT can make you more susceptible for various forms of addiction - both drug-related such as alcohol, and behavior-related such as gambling due to the potential for excess dopamine to linger and enhance reward-seeking behaviors. It can also give you the patience and work ethic to complete important medical research, write detailed books, and be a talented craftsman.
So Why Does Coffee Still Make Me Irritable?
When you drink a cup of coffee, the caffeine stimulates you in part by triggering the release of the catecholamine hormones epinephrine and norepinephrine. It "steals" future energy by dipping in to your adrenal reserves of these hormones.
You may be a fast metabolizer of the caffeine, you may be a slow metabolizer of the extra epinephrine and norepinephrine that the caffeine helped release.
Bonus Tip: Mold in coffee can also cause excitability in those who are sensitive.
To minimize mold, use single estate and/or single origin beans for your coffee. Ask your barista, read your labels, and call the company to find out.
Bulletproof coffee is a great place to start.
When your coffee shop uses a mix of beans, the beans are often pulled from a different areas of the globe - or from different coffee growers in a region.
Blends of beans will be much more likely to sit around in bags or bins for longer periods of time. They're traveling more & are more likely invite contamination - I find single origin beans taste fresher and yield richer flavors.
Companies that make blends are also trying to maximize margins based on pricing. So you may get poorer quality beans thrown into a blend for the sake of maximizing profitability.
For decaffeinated coffee, look for the Swiss Water Method and consider Bulletproof Decaf.
Sometimes blends may dilute a high quality bean with poorer quality beans. You'll pay the price of the higher quality bean - meanwhile it may be blended with less quality beans.
As a result of COMT, adrenal fatigue, & mold, that second cup of java can leave you irritable and jittery even if you're a fast metabolizer of caffeine.
If you are an everyday coffee drinker, it is recommended that every 2-3 weeks, take a week off of coffee or switch to decaf for 7-10 days in order to re-sensitize your system and minimize feelings of caffeine withdrawal or dependence.