All Your Caffeine Questions Answered

Facts About Caffeine: All Your Questions Answered

Publish Date May 7, 2023 3 Minute Read
Author By Richie Santucci, RDN, LD, CDE, NCSF-CPT

Often, just thinking of our favorite coffee or tea drink can fill us with a little warm fuzzy feeling, especially on those colder days. But are there any risks to drinking caffeine? How much is too much? Are there any benefits to caffeine? Is caffeine a diuretic? Let’s explore the many different aspects of this stimulating nutrient.

How Does Caffeine Affect the Body?

Caffeine is a stimulant, meaning it stimulates blood flow in the body. It does this by encouraging vasoconstriction, or the contracting of the blood vessels, which accelerates blood flow and can even make the heart beat faster. With this capability, caffeine can stimulate blood flow to several organs in the body, including the brain, resulting in a temporary boost in mood and mental sharpness. This increased blood flow is also believed to be key to possibly preventing cognitive decline, Alzheimer’s Disease and Parkinson’s. Just think of that little burst of brainpower you get with that first cup or two of your favorite caffeinated drink in the morning.

Coffee is the most common form of caffeine consumed in the US and caffeine is often believed to be responsible for many of its beneficial effects. New research has found that 2-3 cups of coffee per day were associated with beneficial effects on metabolic syndrome, hypertension and diabetes. Coffee was also recently shown to be inversely related to the risk of coronary heart disease, heart failure, arrhythmia, stroke, CVD and all-cause mortality. It’s important to note some of these benefits may be due to nutrients in coffee other than caffeine.

How Much is Too Much?

Many of us can feel when we may have consumed too much caffeine, ranging from a few milligrams to many cups of coffee. But what should the daily intake of caffeine really be limited to? The FDA recommends consuming no more than 400 milligrams per day, but depending on the caffeine content in your preferred beverage or food, your daily intake may differ. Some people may even experience side effects when consuming fewer than 400 milligrams of caffeine. Everyone responds differently to caffeine, so listen to your body and know your personal tolerance level when enjoying your favorite caffeine-containing foods. And when it comes to kids, the American Academy of Child and Adolescent Psychiatry recommends that children 12 and under avoid caffeine altogether and that kids aged 12-18 should have no more than 100 milligrams of caffeine per day.

Here is a list of some of the most common caffeine-containing products with the average caffeine in milligrams. However, you should always remember to check the label for the actual caffeine content in the foods and drinks you are consuming.

Common Caffeinated BeveragesAmountCaffeine Content
Regular coffee


96 mg

Decaf coffee


2 mg

Regular espresso

1 oz

64 mg

Decaf espresso

1 oz

0 mg

Black tea

8 oz

47 mg

Green tea

8 oz

28 mg

Regular iced tea

8 oz or 1 serving size of mix

30-45 mg

Dark chocolate

1 oz

12-20 mg

Milk chocolate

1.55 oz

9 mg

Herbal teas

8 oz

most are caffeine-free, but check the label!


8 oz

22 mg

Energy drink

8 oz

70-250 mg

Risks of Caffeine

While no set amount of caffeine will cause someone to experience negative effects, as discussed above, the FDA recommends limiting consumption to 400 milligrams per day or less. How your body reacts to caffeine depends on your tolerance and how quickly your body metabolizes caffeine. Talk to your healthcare provider if you have any further questions. Possible side effects of excessive caffeine may include:

  • Insomnia
  • Jitters
  • Anxiousness
  • Fast heart rate
  • Upset stomach
  • Nausea
  • Headache
  • Unhappiness (dysphoria)

Is Caffeine a Diuretic?

One of the most common questions dietitians get asked about caffeine is if it’s a diuretic. The answer is: We don’t know! Multiple studies show that having 250-300 milligrams of caffeine per day doesn’t cause excessive fluid loss outside of the regular fluid consumed in the day. If you’ve experienced increased urination after consuming a drink containing caffeine, it may be due to increased blood flow to the kidneys, stimulating urine production. Many studies suggest that the increased urine output experienced after caffeine consumption may be limited to those who irregularly consume caffeine.

The National Academies of Sciences, Engineering, and Medicine recommends a daily fluid intake of 11.5 to 15.5 cups, or 91 to 125 ounces. This includes water, other drinks, and the water found in food. However, individual fluid needs can vary based on your age, weight, health status, activity and weather conditions, so always talk to a dietitian for more personalized fluid requirements.

Caffeine is a stimulant that should be enjoyed in moderation within the limits of your body’s tolerance. It may be tempting to depend on the short-term bursts of energy that it brings. However, if we get increasingly dependent on caffeine for energy and develop a tolerance to our regular caffeine intake, it can become less effective, even as we add more daily. Do your best to care for your body with love by enjoying nourishing foods, drinking adequate fluid, getting sufficient sleep and rest, and engaging in regular physical activity. Remember to enjoy your favorite caffeine-containing foods and drinks in moderation.

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Disclaimer: This information is educational only and is not meant to provide healthcare recommendations. Please see a healthcare provider.