Caffeine basics: an overview from a nutritionist

cup of coffee next to a laptop

If your morning doesn’t *truly* start until after your morning cup of coffee, you’re not alone. But as important as it might be to start your day, you might wonder: how does caffeine work and am I drinking too much? Here, we break down the basics of caffeine. (Psst, don’t worry, you can loosen your grip on your coffee mug – we would never take that away.)

How is caffeine absorbed?

In short: caffeine is a stimulant that revs up your nervous system’s activity, which includes your brain.

When you’re sipping on your morning brew or ice-cold soda, the caffeine is absorbed in your gut and goes into your bloodstream, and then travels throughout your body to your brain. And depending on the rate of your metabolism, it can take anywhere from 15 minutes to 2 hours for blood levels to peak and the effects of caffeine to kick in.

Are there benefits to caffeine?

·       Caffeine increases alertness

This isn’t surprising, but caffeine can help you feel more awake. Caffeine works by blocking certain receptors, including adenosine, a receptor in your brain that influences sleep and fatigue. These blocked receptors then release brain chemicals like serotonin and noradrenaline1 to temporarily lift tiredness and exhaustion – giving you a surge in energy.

·       Caffeine can improve mood

Why are we less grumpy after coffee? The boost in energy *definitely* helps. But also, when adenosine is blocked, another brain chemical released is dopamine, which helps improve your mood and feeling of happiness.1

·       Caffeine can improve athletic performance

Not only does caffeine help with mental clarity and energy, but it can also help with exercise according to some research. Drinking a cup of coffee or caffeinated beverage can be a great pre-workout drink. Getting 150-200mg of caffeine an hour before exercise helps with endurance and muscular strength, while reducing fatigue and exhaustion according to a study.2

How much caffeine is safe?

Depending on your body weight, lifestyle, metabolism and some other factors, your caffeine tolerance may vary. But on average, about 4 cups of coffee (400mg of caffeine) is considered generally safe according to the FDA.

But since everyone metabolizes caffeine differently, it’s important to recognize that caffeine isn’t for everyone. And the effects of caffeine can differ – while some may feel a boost in energy, others can feel increased feelings of jitteriness, nervousness, headaches, irritability or digestive issues.

The bottom line

Caffeine can help with energy, alertness and even mood, but the benefits and effects aren’t the same for everyone. Caffeine should be ingested in the morning or early afternoon to ensure it doesn’t impact your sleep. It’s also important to understand your tolerance – if you’re noticing any negative symptoms after drinking caffeinated drinks, it’s best to reduce or stop your intake.

Looking for something else to support your energy levels, check out 5 alternatives to coffee!

About Agnes 

Agnes is an accredited nutritionist by SNDA (Singapore Nutrition & Dietetics Association). Before Persona, she worked in community settings, providing training and managing events. She loves working with people and is passionate about changing people’s lives through nutrition.

Do you have questions about supplements? Reach out to one of our experts, or take Persona’s free nutrition assessment, and learn exactly what you need to take your wellness to the next level.    

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.     

This information is not intended as a substitute for the advice provided by your physician or other healthcare professional, or any information contained on or in any product label or packaging. Do not use the information from this article for diagnosing or treating a health problem or disease, or prescribing medication or other treatment. Always speak with your physician or other healthcare professional before taking any medication or nutritional, herbal, or homeopathic supplement, or using any treatment for a health problem. If you have or suspect that you have a medical problem, contact your health care provider promptly. Do not disregard professional medical advice or delay in seeking professional advice because of something you have read in this article.       


  1. McLellan TM, Caldwell JA, Lieberman HR. A review of caffeine’s effects on cognitive, physical and occupational performance. Neurosci Biobehav Rev. 2016;71:294-312. doi:10.1016/j.neubiorev.2016.09.001
  2. Tabrizi R, Saneei P, Lankarani KB, et al. The effects of caffeine intake on weight loss: a systematic review and dos-response meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr. 2019;59(16):2688-2696. doi:10.1080/10408398.2018.1507996

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