coffee cup

Is Coffee Bad?

When I had the idea to write a blog about coffee consumption, I knew I had written one in the past.  But I thought I had it all wrong.  I just took a read of that blog and I’ll be damned if I’m not smarter than I thought!

It’s always nice when it works out that way 😝

So, what the hell am I going to talk about in reference to coffee?  Well, my last blog did a bang-up job of explaining my thoughts on coffee.  But there are a few areas I want to expand on.  I want to talk about the downsides to coffee.  Really, I’ll be focusing on the genetics of caffeine metabolism.

So, let’s jump to it, shall we?

The Basics

If you haven’t read the first blog yet, I’d definitely start there.  It will cover a lot of the information that I won’t be talking about in this blog.  In this blog, like I mentioned, we’ll be talking genetics.

Specifically, what gene dictates how quickly you metabolize caffeine.  And if there are any downsides to being a slow metabolizer.

Let’s talk terminology really quick.  When discussing genes, whether in this blog or other blogs, you’ll see some of the terms below.  I want to make sure you understand what they are.

Single Nucleotide Polymorphism (SNP; pronounced snip) – this means there’s a genetic variation on a gene

Homozygous – When both alleles on a gene are mutated or different than the norm

Heterozygous – When one allele on a gene is mutated or different than the norm


Okay…so let’s talk the caffeine gene.  The primary gene that controls caffeine metabolism is CYP1A2.  If you have Ancestry DNA raw data or 23andme raw data, you can search for this gene by using the RS number.  It is rs762551.

If you pull up your gene and you see “C;C” that means you’re in the majority of the population.  You metabolize coffee as a normal rate.  If you see “A;C” you have a heterozygous mutation but still likely metabolize coffee at a normal rate.  If you see “A;A” you’re a fast metabolizer…like me!

If you’re a fast metabolizer, you can drink coffee all day and have no adverse effects from the caffeine.  On top of that, you’ll experience increased athletic performance from consuming caffeine prior to working out.  When you metabolize it quick, you feel a boost in athletic performance!

If you’re a normal metabolizer, you don’t get these fun benefits…sorry.  You’ll likely feel jittery after a few cups.  If you have coffee in the afternoon or evening, you’ll find you’re awake all night.

You don’t need genetic information though to know if you’re a normal or fast metabolizer.  Have a few cups on an empty tum tum.  How do you feel?  Jittery?  Likely a normal metabolizer.  If you drink coffee late will you be up?  Then likely a normal metabolizer.  If none of that affects you, then you’re likely a fast metabolizer.

Associated Risks

So, why do you need to know if you metabolize coffee normal or fast?  Because too much coffee for a normal metabolizer can cause health concerns.

If you’re a normal metabolizer, the more coffee you drink in a day, the greater the risk you have for having a non-fatal heart attack.  For a fast metabolizer, there is no risk from coffee.

Referencing the image below, you can see the risk associated with having more than 1 cup (8 oz = 160 mg of caffeine) of coffee daily.

chart detailing health effects of caffeine consumption


You can see for those that are normal metabolizers, the more coffee the higher the risk for a non-fatal heart attack.

What Else?

Aside from increased risk of non-fatal heart attacks, normal metabolizers are also at an increased risk for high blood pressure and impaired glucose metabolism.

There are a lot of reasons we develop high blood pressures, but by and large, it’s due to inflammation.  Since some have a slower rate of clearing caffeine, it’s possible the longer the caffeine is in the body, the more inflammation it could be causing.  That’s just a theory on my part though.  Researchers aren’t really sure why blood pressure spikes in normal caffeine metabolizers.

Another point to think about is glucose metabolism.  This is specific to individuals with diabetes or insulin resistance.  Yes, you can have insulin resistance without having diabetes.  I see it frequently in my office.

How Much Are You Drinking?

If you know you’re a slow metabolizer or feel like you probably are, you should be sticking to a cup of coffee daily.  A second cup on occasion shouldn’t be an issue.  But bear in mind other caffeine you might be consuming throughout the day.

While coffee does have the largest concentration of caffeine, don’t forget about these other sources of caffeine:

Soda (about 75 mg per 12 oz)

Black tea (about 45 mg per 8 oz)

Chai tea (about 45 mg per 8 oz)

Chocolate (about 70 mg per bar)

Decaf coffee (Yup! – about 12 mg per 16 oz)

Coffee or chocolate flavored foods (ice cream, cereal, etc)

Medications like Excedrin (65 mg per two caps)

So, if an 8 oz serving of coffee contains 160 mg of caffeine, you’ll want to ensure you stay at or below that for slow metabolizers.

In the comments below, let me know how much caffeine are you consuming daily.

Sunny Brigham, MS, CNS

I'm Sunny! I'm a board-certified clinical nutritionist with an MS in Clinical Nutrition. I help individuals reduce fatigue, eliminate bloat, and lose weight by healing the digestive tract and balancing hormones. I provide individual and group nutrition consultations nationwide. Grab my metabolism boosting guide!

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