Coffee, Cortisol, and the Internet

Apparently, drinking coffee has become a very complicated morning activity.

You can't drink it when you wake up because of cortisol. You shouldn't drink it on an empty stomach. You're supposed to wait exactly 90 minutes. You need to eat protein first. Don't add sugar. Don't drink it too late. And somewhere in the middle of all of this, your peaceful morning cup of coffee has turned into a hormonal obstacle course.

Your morning coffee probably doesn't need this much supervision.

That doesn't mean caffeine has no effect on your body. It absolutely does. Caffeine can influence cortisol, sleep, anxiety, digestion, and even short-term glucose metabolism. How much you drink, when you drink it, what else you've eaten, how well you're sleeping, and how sensitive you are to caffeine can all matter.

But there's a big difference between saying caffeine has physiological effects and saying your morning coffee is wrecking your hormones.

Let's separate the two.

First, Cortisol Isn't the Bad Guy

Cortisol has developed a terrible reputation online.

It's often discussed as though the goal of good health is to keep cortisol as low as possible at all times. But cortisol is an essential hormone. It helps regulate metabolism, blood pressure, immune function, and your response to stress, and it follows a natural daily rhythm.

One of the most noticeable parts of that rhythm happens in the morning.

Around waking, cortisol naturally rises. Researchers call the increase that occurs shortly after waking the cortisol awakening response. In healthy people, cortisol secretion is concentrated around the morning waking period, with a rapid increase typically occurring during the first 30 to 45 minutes after waking. Researchers believe this response helps prepare the body for the demands of the day.

So if you've heard that cortisol is higher in the morning, that's true. But that's not evidence that something has gone wrong. Your body isn't having a hormonal emergency every morning. It's doing something it's supposed to do.

And Yes, Caffeine Can Affect Cortisol

Here's another part of the internet claim that has some truth behind it.

Caffeine can stimulate cortisol secretion.

In controlled research, caffeine has increased cortisol levels, although habitual caffeine consumption appears to reduce some of that response through tolerance. In one crossover study involving both men and women, regular caffeine intake reduced the cortisol response to the first morning caffeine dose, while responses later in the day were still observed.

So I'm not going to tell you that coffee has absolutely no relationship with cortisol. It does.

What I am going to question is the leap from “caffeine can temporarily increase cortisol” to “drinking coffee in the morning is destroying your hormones.”

Those are not the same statement. Hormones are supposed to change in response to what's happening around you. A temporary hormonal response isn't automatically harmful, and cortisol itself isn't a toxin we need to avoid. Context matters.

The 90-Minute Coffee Rule Is Not a Biological Deadline

One of the most specific pieces of advice floating around online is that you should wait 60 to 90 minutes after waking before having caffeine.

Usually, cortisol gets blamed.

The argument goes something like this: cortisol is naturally high when you wake up, so drinking coffee during that period interferes with your natural cortisol rhythm, increases tolerance to caffeine, or sets you up for an afternoon crash.

It sounds very scientific because it involves a hormone and an exact number of minutes. But an exact recommendation requires evidence for that exact recommendation.

We know cortisol changes after waking. We know caffeine affects alertness and can affect cortisol. What we don't have is strong evidence showing that every healthy person needs to wait precisely 90 minutes after waking before drinking coffee to protect their hormones.

That doesn't mean waiting is bad. If you wake up, drink water, eat breakfast, get ready, and enjoy your coffee an hour later, wonderful. If you prefer coffee with breakfast 30 minutes after waking, there isn't good reason to assume you've sabotaged your endocrine system because the clock didn't reach 90 minutes.

I'd much rather look at how caffeine is affecting you than have everyone follow an arbitrary countdown.

I Still Like Eating Breakfast Before Coffee

This is one place where I don't want the pendulum to swing too far in the opposite direction.

I've talked before about eating breakfast before drinking coffee, and I still think that can be a useful habit.

Just maybe not for the dramatic reasons you've seen online.

For some people, coffee on an empty stomach feels terrible. They may notice nausea, shakiness, anxiety, reflux, stomach discomfort, or an urgent trip to the bathroom.

Caffeine can also suppress appetite for some people. If your routine is coffee at 7:00, another coffee at 9:00, suddenly realizing you're starving at noon, and then spending the rest of the day trying to catch up on food, I'd rather work on the morning routine than blame your willpower later.

Having breakfast first also gives us an opportunity to start the day with actual nutrition: protein, carbohydrates, fiber, fat, vitamins, and minerals.

Coffee is lovely. It is not breakfast.

So my preference for eating before or alongside your morning coffee isn't because I think one cup on an empty stomach is going to “break” your cortisol. It's because fueling your body before asking caffeine to make you feel energized is often a pretty sensible foundation.

Those are two very different messages.

What About Blood Sugar?

This is another place where coffee advice gets oversimplified.

Caffeine can acutely affect glucose metabolism. Controlled studies have found that caffeine can temporarily reduce insulin sensitivity, and short-term studies of caffeinated coffee have sometimes found higher glucose responses. Interestingly, longer-term observational and clinical research on habitual coffee consumption doesn't tell the same simple story, which suggests that caffeine's immediate effects and coffee's long-term health associations shouldn't be treated as interchangeable.

Does that mean every woman needs to eat a perfectly balanced breakfast before a sip of coffee because otherwise her blood sugar will “spike”?

No.

If someone has diabetes, prediabetes, symptoms suggestive of glucose problems, or is actively monitoring blood glucose for a medical reason, caffeine may be one variable worth paying attention to. For everyone else, we don't need to turn every normal fluctuation in glucose into an emergency.

This is another reason I like breakfast, though. If your morning currently consists of sweetened coffee and nothing else until lunchtime, the bigger conversation may not be whether coffee caused a tiny change on a glucose graph. The bigger conversation may simply be whether you're adequately fueling yourself in the morning.

Your Stomach May Have Opinions About Coffee Too

If you've ever taken three sips of coffee and suddenly needed to know where the nearest bathroom was, you're definitely not alone.

Coffee can stimulate activity in the colon, and interestingly, caffeine doesn't appear to explain the entire effect. Coffee contains many biologically active compounds besides caffeine, and research suggests it can influence gastric secretions and gastrointestinal motility.

Some people also report that coffee worsens reflux or heartburn.

The research here isn't perfectly tidy. A recent meta-analysis found a small association between coffee consumption and GERD, but the authors noted that the clinical importance of the difference was unclear and that universal coffee avoidance for GERD still needs further study.

That's actually a great example of why individualized nutrition matters. If coffee reliably gives you heartburn every morning, I don't particularly care that someone on Instagram says coffee is healthy. Your pattern matters.

But if you drink a cup every morning with no reflux, no stomach pain, and no digestive problems, I'm also not going to remove it from your diet because someone else reacts poorly to it.

Coffee Can Absolutely Make You Feel More Anxious

This one deserves attention because caffeine is a stimulant.

If you've ever had one cup too many and felt jittery, shaky, restless, or like your heart and brain were both trying to win a race, you've experienced that firsthand.

Research supports an association between caffeine and increased anxiety, particularly at higher doses, although sensitivity varies considerably from person to person. A 2024 meta-analysis found greater anxiety after caffeine consumption in healthy participants, with larger effects at higher doses. A newer systematic review similarly found evidence of a dose-dependent anxiety effect and noted differences related to habitual caffeine consumption.

That individual variability matters. One woman can drink two cups of coffee and feel completely normal, while another drinks half a cup and feels like she can hear colors. Neither person's response tells us what everyone else should do.

If you're already dealing with anxiety, palpitations, shakiness, or feeling chronically wired, your caffeine intake is absolutely something I'd want to discuss. And that includes more than coffee. Energy drinks, pre-workout products, tea, soda, chocolate, certain medications, and other products can contribute caffeine too.

The Coffee Habit I'd Pay More Attention to Is the Afternoon One

The internet spends a lot of energy debating whether you should drink coffee at 7:00 or 8:30 in the morning.

Meanwhile, your 3:00 p.m. coffee may be much more relevant to how you feel tomorrow.

Caffeine can interfere with sleep even when you don't feel like it does. A systematic review and meta-analysis found that caffeine reduced total sleep time, reduced sleep efficiency, increased the time it took to fall asleep, and reduced deep sleep. The researchers estimated that a typical coffee containing about 107 mg of caffeine would need to be consumed roughly nine hours before bedtime to avoid a measurable reduction in total sleep time, although individual responses and caffeine doses vary.

A newer randomized trial helps show why dose matters too. In that study, 100 mg of caffeine didn't significantly affect sleep even when consumed four hours before bed, while a much larger 400 mg dose disrupted sleep when consumed considerably earlier.

So I'm not going to give everyone an exact universal caffeine cutoff. Instead, look at the pattern. If you drink coffee at 3:00 because you're exhausted, can't fall asleep easily at night, wake up tired, and then require a lot of caffeine to function the next morning, we may have created a cycle worth interrupting.

Sometimes the answer to needing more caffeine isn't more caffeine. Sometimes we need to look at the sleep underneath it.

How Much Coffee Is Too Much?

Again, there isn't one number that tells us everything about an individual.

For most healthy adults, the FDA cites 400 mg of caffeine per day as an amount not generally associated with negative effects. But the FDA also specifically notes that sensitivity varies depending on factors such as medications, medical conditions, body weight, and individual sensitivity.

And 400 mg isn't a goal. You don't earn a prize for reaching your caffeine allowance.

If 100 mg makes you feel anxious and disrupts your sleep, your useful limit may be much lower. If you tolerate caffeine well, sleep beautifully, eat regularly, and enjoy a couple cups of coffee in the morning without any problems, we don't need to manufacture one.

Pregnancy is also a separate conversation with lower recommended caffeine limits, so general adult caffeine guidance shouldn't simply be applied during pregnancy.

Look at Your Coffee Habit in Context

Instead of trying to decide whether coffee is universally “good” or “bad,” it makes more sense to look at what your coffee habit is doing in the context of the rest of your day. Someone who eats breakfast, enjoys a cup or two in the morning, sleeps well, and feels good is in a very different situation from someone who uses coffee to avoid eating until noon, needs another cup every few hours to stay awake, feels jittery all afternoon, and then struggles to fall asleep at night.

Your own symptoms can give us useful information too. If coffee consistently aggravates reflux, sends you running to the bathroom, makes you shaky or anxious, or seems to affect you very differently when you drink it without food, those patterns are worth paying attention to. Likewise, if your caffeine intake has slowly climbed because you're constantly exhausted, I want to know why you need that much stimulation to get through the day rather than simply finding a way to squeeze in another cup.

That's much more useful information than asking whether coffee “spikes cortisol.” Of course caffeine can affect cortisol. The better question is whether your overall coffee habit is supporting you or compensating for something else that needs attention.

Keep the Breakfast. Lose the Fear.

I'm still a fan of eating breakfast before or with your coffee. Eating regularly, getting enough protein and overall nutrition, and not relying on caffeine to replace food are solid foundational habits. If having breakfast first also leaves you feeling less jittery, less nauseous, or more steadily energized through the morning, that's even more reason to keep doing it.

And if you genuinely feel better waiting a little while after waking before drinking coffee, you can keep doing that too. You just don't need to believe that 89 minutes is dangerous and 90 minutes is magical. The goal isn't to build the most hormonally perfect morning routine possible. It's to find habits that support your nutrition, energy, digestion, stress, and sleep without creating unnecessary fear around normal physiology.

That's an important distinction in functional health. We can take hormones, blood sugar, digestion, and nervous-system health seriously without turning every normal response into a problem that needs fixing. Sometimes the most useful thing we can do is step away from the viral rule and look at what's actually happening in the individual person.

If you're exhausted despite relying on caffeine, struggling with blood sugar or digestive symptoms, skipping meals, sleeping poorly, or wondering whether your daily habits are actually supporting how you want to feel, you can book a Free Discovery Call with me. We'll look at the whole pattern rather than blaming one cup of coffee for everything.