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The Truth About Caffeine: When It’s Good for You… and When It’s Not

July 14, 2025

Struggle to complete a full sentence before your first sip of coffee in the morning? 

For the vast majority of us—including 85 percent of American adults—caffeine is a daily ritual that kickstarts our mornings and powers us through our afternoons. (And, in some case, is also keeping us up at night.)

But even if you can’t imagine life without caffeine, you might still wonder… 

• Is this actually healthy?
  
  
• Am I drinking too much? Should I toss out this fourth cup?
  
  
• Is this going to make my anxiety worse today?
  
  
• Am I going to regret this when I try to sleep tonight? 

I’ve got the answers for you. 

Get ready to learn the truth about caffeine. Plus, get some simple tricks for figuring out whether getting your daily caffeine fix is working for you or against you. 

What’s Caffeine and How Does It Work? 

Caffeine is a natural stimulant found in coffee, tea, cacao, and energy drinks. It’s technically a psychoactive drug, meaning it changes how your brain works—you feel more alert, focused, and energized.

But how does that actually happen?

As you go about your day, a molecule called adenosine builds up in your brain.

It fits into special “slots” that help trigger drowsiness. The more those slots get filled, the sleepier you feel.

By the end of the day, most of them are full—and you drift off to sleep.

Caffeine works by slipping into those same slots—but without making you tired.

Think of it like filling all the seats before adenosine can sit down. With nowhere to go, adenosine can’t do its job—and you feel more awake.

That’s not the whole story, though.

Caffeine also ramps up activity in parts of your brain that control alertness, focus, and mood.

It nudges your system to release more dopamine and adrenaline, which is why you might feel more upbeat or sharper after your first cup.

So no, caffeine doesn’t give you energy in the same way food does. But it does delay tiredness and make you feel more alert—at least for a while. 

When it wears off and adenosine finally gets through, that’s when the crash can hit. Or, if you drink it too late, you might have trouble winding down—because your brain never got the message to rest.

Is Caffeine Good or Bad for You? 

Ultimately, how well you tolerate caffeine depends on your unique body.

One key factor is caffeine’s “half-life.”

Half-life is the time it takes your body to clear out half of the caffeine in your system. For most people, that’s about 4 to 6 hours (which is why sleep experts usually recommend cutting off caffeine at least six hours before bedtime).²

But this process keeps repeating. If you drink 200 milligrams (mg) of caffeine at noon, you’ll still have around 100 mg in your system by dinnertime, and about 50 mg around bedtime. If you started with a larger dose—say 400 milligrams—you’d still have much more in your system later in the day.

That lingering caffeine can block adenosine from doing its job, making it harder for your brain to wind down when it’s time to sleep. So it’s not just when you drink caffeine that matters—it’s also how much.

Simple enough in theory, but your genes play a part in how well your body metabolizes caffeine.

Some people are “fast metabolizers,” meaning their body breaks down caffeine more quickly. These are often the folks who can have an after-dinner coffee and still fall asleep easily.

Others are “slow metabolizers,” which means they’ll be more sensitive to caffeine’s stimulant effects for longer. If that’s you, your 3 p.m. pick-me-up could keep you wired far past bedtime—even if you followed the six-hour cutoff recommendation.

But as to whether it’s generally helpful or harmful? Let’s take a look at what the research says.

When It’s Helpful 

You already know that caffeine perks you up and sharpens your focus.

Even better, a growing body of evidence points to a number of ways that moderate caffeine consumption can support your health.

Here’s a quick snapshot but first, an important caveat: The benefits noted below are based on research that’s more specific to coffee, which in addition to caffeine, includes other compounds that can contribute to your health, like antioxidants. (Read: The benefits don’t apply to sodas and energy drinks loaded with sugar.)                                                                                                                                                                                        Caffeinated coffee may: 

• Help reduce the risk of depression (in moderate amounts)³
  
  
• Lower your risk for type 2 diabetes, certain cancers, and Parkinson’s disease^4–6
  
  
• Offer women in particular some protection against Alzheimer’s disease^7,8
  
  
• Amplify the effects of over-the-counter medications (such as ibuprofen or acetaminophen) to help relieve headaches and other types of pain⁹
  
  
• Act as an appetite suppressant in the short term, which could be helpful for people trying to manage cravings or reduce mindless snacking. This effect varies from person to person and tends to be mild, but it can be part of why a morning cup of unsweetened coffee helps you feel more in control of your eating early in the day.

And—whether you love running, prefer weight training, or enjoy a weekend pickup game—caffeine has been shown to boost all types of exercise performance (though it appears to work best for endurance activities).¹⁰

Plus, it doesn’t take a lot: The sweet spot is about 3–6 milligrams per kilogram of body weight about an hour before your activity. (Or about 200-400 milligrams for a 150-pound person.)

But before you run to the nearest coffee shop, let’s explore when caffeine might not be so ideal. 

When It’s Potentially Harmful… or Simply Not-So-Healthful

Most adults can safely consume 400 milligrams of caffeine per day. That’s about four 8-ounce cups of coffee.

But… this doesn’t apply to everyone all the time. 

Depending on your sensitivity to caffeine, you may get jittery or anxious, or experience heart palpitations or an irregular heartbeat. This is a sign you might be overdoing it and need to cut back—or take a holiday from caffeine altogether and see how it affects you.

Also, as you age, your ability to metabolize caffeine will slow down, which can lead to increased caffeine sensitivity. So, pay attention to your body’s cues.

There are also cases where certain medications (such as muscle relaxants, antidepressants, or beta-blockers) or health conditions (such as IBS or severe hypertension) can make you more sensitive to caffeine or cause some undesirable side effects. This is something to discuss with your doctor directly. 

Some general caffeine precautions: 

If you’re pregnant or breastfeeding…

... it’s best to either avoid caffeine or keep it under 200 milligrams per day—about 10 to 12 ounces of brewed coffee. 

During pregnancy, your body breaks down caffeine much more slowly, especially in the third trimester, so it stays in your system longer. Studies have linked high caffeine levels to lower birth weight.¹¹

What’s more, if you’re breastfeeding, caffeine can pass into your milk. Newborns metabolize caffeine very slowly, so regular intake can lead to prolonged exposure as it lingers in their system.

If you have a mood or mental health disorder…

... you may be more susceptible to caffeine. While some evidence has linked moderate coffee consumption with a lower risk of depression and anxiety,³ other studies show that caffeine can increase the risk of anxiety (and that goes even for those without an existing mental health disorder).¹² 

Another study found that too much caffeine—the equivalent of about 5 cups of coffee—may trigger panic attacks in those with panic disorders, and may increase anxiety in adults both with and without panic disorders.¹³ 

If you struggle with poor sleep and use caffeine to compensate…

... you could end up stuck in an unhappy cycle. 

You sip on a coffee in the afternoon to get by, only to have that extra caffeine keep you from getting much-needed rest later that night. You wake up in the morning exhausted, so you load up on more coffee… the cycle continues. 

Over time, poor quality sleep can do some serious harm to your overall health.

Plus, while studies show that caffeine may initially perk you up, it won’t help with “placekeeping” skills—those tasks that require correctly following instructions and keeping track of things—which are essential for a productive day.¹⁴ 

(If you want to learn how to achieve better, deeper sleep, check out my FREE Sleep Master Class.) 

If you have a sensitive stomach…

... caffeinated beverages may worsen acid reflux symptoms.¹⁵

And, if you’ve ever had to sprint to the restroom after drinking too much, you’re likely familiar with the common coffee side effect of diarrhea.

Coffee and caffeine intake are also associated with increased odds of irritable bowel syndrome (IBS).¹⁶ (Indeed, if you have IBS and are overweight, caffeine can significantly worsen your symptoms.)¹⁶

If you have high blood pressure…

... be sure to monitor how caffeine affects you. 

Caffeine can cause a short-term spike in blood pressure—especially if you’re not a regular coffee drinker.¹⁷

And while one daily cup of coffee doesn’t seem to harm cardiovascular health, drinking two or more cups a day has been linked to a higher risk of heart-related death in people with severe hypertension (160/100 or higher).¹⁸ That said, the research is mixed in this area. Since caffeine sensitivity varies widely, it’s smart to check in with your doctor to see what’s right for you.

Personalize Your Caffeine Intake

As you can see, when it comes to caffeine, there’s no one-size-fits-all answer. 

While your partner might breeze through three cups of coffee a day with no issues, your body might respond very differently. 

The real secret? Tuning into your unique response to caffeine and making decisions that support your well-being.

Here are three ways to start personalizing your caffeine routine.

1. Track Your Symptoms

Try keeping a simple log for a week. Note what you’re drinking, when you’re drinking it, and how you feel over the next few hours and into the evening. Pay attention to signs like jitteriness, anxious thoughts, energy crashes, difficulty sleeping, or digestive upset. 

These can be subtle (or not-so-subtle!) signs that caffeine isn’t working in your favor. You might be surprised to see patterns emerge that you hadn’t noticed before.

2. Experiment with Timing and Dose

If you’re sensitive to caffeine or prone to sleep issues, try limiting your intake to mornings only and keeping your daily dose under 200 milligrams (about twelve total ounces of black coffee). Then observe how your energy, mood, and focus shift. 

Some people feel better on less; others do well with a little more. You may even find that swapping to green tea or a half-caf option provides the perfect balance.

3. Consider a 1–2 Week Break

When people do my 10-Day Detox program, I have them completely eliminate caffeine. Why? Taking a break helps your body reset its natural energy rhythms and gives your system a chance to recalibrate without artificial stimulation. 

The benefits can also surprise people. One recent participant found that giving up caffeine significantly increased his focus and made him feel more relaxed and less irritable. Yet before he started the detox, he didn’t think caffeine had any effect on him at all. He was wrong!

If you’re used to drinking caffeine daily, you might initially go through withdrawal—headaches, irritability, or fatigue are common for a couple of days—but most people feel more balanced, calm, and clearheaded by the end of the week.

Even if you’re not doing the full detox, taking a short sabatical from caffeine can be a powerful way to learn how it’s really affecting your energy, mood, sleep, and cravings. It doesn’t have to be forever—it’s just about information gathering. 

Do you feel clearer and calmer, or more sluggish and foggy? Or, do you notice a headache the first few days? You might be having some caffeine withdrawal that your body needs to adjust to.  

If and when you reintroduce caffeine, do so slowly and mindfully. Sometimes a reset is all it takes to notice how caffeine really affects your mood, focus, and sleep.

For some people, caffeine just isn’t a great fit. 

Ultimately, you might realize that the troublesome side effects outweigh the small boost. 

In this case, you can still have a vibrant morning ritual or a cozy afternoon pick-me-up without relying on caffeine. Here are some great caffeine-free and low-caffeine alternatives to explore:

• Herbal teas like rooibos, chamomile, peppermint, or lemon balm
  
  
• Green tea, which has about half the caffeine of a regular cup of coffee (roughly 25–45 mg), but also contains L-theanine—a compound that promotes relaxation. When combined with caffeine, L-theanine can help smooth out caffeine’s stimulating effects, leading to a more balanced, focused feeling without the jitters.
  
  
• Mushroom-based coffee alternatives
  
  
• Chicory root coffee substitutes
  
  
• Golden milk—made with unsweetened almond milk, turmeric, and cinnamon—for a warm, caffeine-free ritual with anti-inflammatory benefits
  
  
• Adaptogenic blends—caffeine-free herbal mixes with ingredients like ashwagandha or rhodiola—may support focus and stress resilience without the crash.
  

You deserve to feel your best, and whether that includes caffeine—or not—is entirely up to you. Listen to your body, experiment, and find the rhythm that works for your life.

References

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2. Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med. 2013 Nov 15;9(11):1195–200.

3. Min J, Cao Z, Cui L, Li F, Lu Z, Hou Y, et al. The association between coffee consumption and risk of incident depression and anxiety: Exploring the benefits of moderate intake. Psychiatry Res. 2023 Aug;326(115307):115307.

4. Kolb H, Martin S, Kempf K. Coffee and lower risk of type 2 diabetes: Arguments for a causal relationship. Nutrients. 2021 Mar 31;13(4):1144.

5. Zhao LG, Li ZY, Feng GS, Ji XW, Tan YT, Li HL, et al. Coffee drinking and cancer risk: an umbrella review of meta-analyses of observational studies. BMC Cancer. 2020 Feb 5;20(1):101.

6. Zhao Y, Lai Y, Konijnenberg H, Huerta JM, Vinagre-Aragon A, Sabin JA, et al. Association of coffee consumption and prediagnostic caffeine metabolites with incident Parkinson disease in a population-based cohort. Neurology. 2024 Apr 23;102(8):e209201.

7. Eskelinen MH, Kivipelto M. Caffeine as a protective factor in dementia and Alzheimer’s disease. J Alzheimers Dis. 2010;20 Suppl 1(s1):S167–74.

8. Hou KC, Chen YC, Chen TF, Sun Y, Wen LL, Yip PK, et al. Coffee and tea consumption and dementia risk: The role of sex and vascular comorbidities. J Formos Med Assoc. 2025 Feb;124(2):178–85.

9. Derry CJ, Derry S, Moore RA. Caffeine as an analgesic adjuvant for acute pain in adults. Cochrane Database Syst Rev. 2014 Dec 11;2019(12):CD009281.

10. Guest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM, et al. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021 Jan 2;18(1):1.

11. Chen LW, Wu Y, Neelakantan N, Chong MFF, Pan A, van Dam RM. Maternal caffeine intake during pregnancy is associated with risk of low birth weight: a systematic review and dose-response meta-analysis. BMC Med. 2014 Sep 19;12(1):174.

12. Liu C, Wang L, Zhang C, Hu Z, Tang J, Xue J, et al. Caffeine intake and anxiety: a meta-analysis. Front Psychol. 2024 Feb 1;15:1270246.

13. Klevebrant L, Frick A. Effects of caffeine on anxiety and panic attacks in patients with panic disorder: A systematic review and meta-analysis. Gen Hosp Psychiatry. 2022 Jan;74:22–31.

14. Stepan ME, Altmann EM, Fenn KM. Caffeine selectively mitigates cognitive deficits caused by sleep deprivation. J Exp Psychol Learn Mem Cogn. 2021 Sep;47(9):1371–82.

15. Mehta RS, Song M, Staller K, Chan AT. Association between beverage intake and incidence of gastroesophageal reflux symptoms. Clin Gastroenterol Hepatol. 2020 Sep;18(10):2226–33.e4.

16. Koochakpoor G, Salari-Moghaddam A, Keshteli AH, Esmaillzadeh A, Adibi P. Association of coffee and caffeine intake with irritable bowel syndrome in adults. Front Nutr. 2021 Jun 15;8:632469.

17. Caffeine: How does it affect blood pressure? Mayo Clinic. [cited 2025 Jun 11]. Available from: 

18. Teramoto M, Yamagishi K, Muraki I, Tamakoshi A, Iso H. Coffee and green tea consumption and cardiovascular disease mortality among people with and without hypertension. J Am Heart Assoc. 2023 Jan 17;12(2):e026477.