Caffeine 101

Caffeine, oh caffeine. The love language of many people because, let’s be honest… is there anything better (or more necessary) than that first sip of warm coffee from your favorite mug in the morning? And you’re not alone in this love affair because approximately 90% of adults worldwide consume caffeine daily in some form or another. In the Americas, most of Europe, and Australia, coffee is the prevalent source of caffeine while tea is preferred in Asia and parts of South America. In fact, tea consumption is nearly three times as much as coffee and is the second most consumed beverage worldwide (water comes in first).

So what exactly is this magic substance we rely on daily? What effect does it have on our bodies? What are its health benefits and what negative impacts does it have? Well, let’s dive right in!

What is caffeine and where does it come from?

Caffeine is a stimulant to the central nervous system and is naturally found in multiple plants including coffee and cacao plants. Other than coffee and tea, caffeine is commonly consumed in soft drinks, energy drinks, dietary supplements, chocolate and even coffee ice cream.

How does caffeine work in our bodies?

Caffeine is rapidly absorbed in the gastrointestinal tract and its levels peaks in our blood stream between 15 minutes to 2 hours. Oral caffeine is nearly 100% bioavailable, meaning just about 100% of the amount we ingest subsequently has an active effect on our body. Food can slow the rate at which caffeine is absorbed, but does not decrease its bioavailability. For example, drinking your morning coffee on an empty stomach will give you a quicker spike in energy as opposed to drinking it while eating breakfast.

Caffeine is mostly broken down in the liver with less than 5% excreted in our urine unchanged. Its half-life (the time it takes for caffeine’s active substance level in our body to reduce by half) is approximately 5 hours, however many things can alter this including defects in the enzymes used for breakdown, hormones, gender, smoking status and pregnancy. In the third trimester of pregnancy, caffeine’s half-life can actually double!

We’ve all heard that caffeine effects our sleep and here’s how. Caffeine mimics an inhibitory neurotransmitter involved in the sleep-wake cycle called adenosine. Because they look alike, caffeine can actually bind to adenosine receptors but instead of telling the neurons to slow down they keep firing. Subsequently, multiple other hormones which all play a role in sleep are either increased or decreased including dopamine, glutamine, norepinephrine (adrenaline), serotonin, melatonin, and GABA. Basically, caffeine can interact with hormones responsible for deep sleep and, in turn, cause wakefulness.

How can caffeine effect our health?

  1. Neurologic. Individuals that consume low to moderate amounts of caffeine daily have increased alertness, energy, concentration, and improved reaction time. While this can often be beneficially, caffeine can also cause increased anxiety, nervousness, and insomnia. Caffeine has also been associated with a decreased risk of Parkinson and Alzheimer disease.
  2. Cardiovascular. Despite rumors, evidence shows that caffeine consumed in moderation does not causes arrhythmias (abnormal heart rhythms) including atrial fibrillation. Acute increase in blood pressure can be seen in caffeine naïve individuals but is less likely to occur in those who regularly drink coffee. Overall, moderate caffeine consumption (400mg daily or less) is not associated with an increased risk of cardiovascular disease.
  3. Diabetes. Caffeine intake has been associated with a decreased risk of diabetes.
  4. Gastrointestinal. Caffeine can improve constipation as it stimulates smooth muscle and has been associated with a decreased risk of cirrhosis.
  5. Cancer. Acrylamide is a substance found in roasted coffee and is a known carcinogen in animals, however, most human data does not show a correlation between caffeine intake and cancer. Alternatively, the antioxidant properties of coffee and tea may actually reduce our risk of developing cancer.
  6. Pregnancy. Caffeine metabolism decreases dramatically during pregnancy, it crosses the placenta, and the underdeveloped baby metabolizes it very slowly. High levels of caffeine consumed by mom are linked to increased fetal heart rate variability, an increased baseline heart rate, and increased breathing activity. All this being said, there is not convincing evidence linking adverse pregnancy outcomes with recommended caffeine intake (see below). Alternatively, high caffeine intake throughout pregnancy has been linked to miscarriage and low birth weight.

How much caffeine is okay to consume daily?

According to the FDA, consuming 400mg of caffeine daily (or approximately 4 cups of coffee) is generally considered to be a safe amount for a healthy individual. For pregnant or breastfeeding woman, the American College of Obstetricians and Gynecologists recommends 200mg of caffeine daily. And, according to the American Academy of Pediatrics, children under 12 years old should avoid caffeine altogether, while children 12 and older should limit their intake to no more than 100mg daily.

Caffeine toxicity.

Too much caffeine consumption has been associated with non-life-threatening tremors, agitation and palpitations, however, excess can also lead to severe cardiac and neurologic complications including seizures and abnormal heart rhythms.

Caffeine intake of greater than 1.2 grams in a single dose can lead to toxicity while 10-14 grams can be fatal. Severe toxicity is not typically seen by simply consuming coffee or tea as this would be roughly equal to 100 cups of coffee, but is more commonly seen when caffeine pills are abused.

Caffeine withdrawal.

Caffeine withdrawal can occur in individuals who consume as low as 100mg daily. Withdrawal symptoms including headaches, fatigue, irritability and brain fog typically occur within 24 hours from last intake and can last for up to 9 days.

Average caffeine amount in common products.

ProductServing Size (oz)Caffeine Amount (mg)
Decaffeinated coffee85
Espresso 150-90
Tea 850-120
Coca Cola1235-45
Sprite12 0
Red Bull8.480
Monster Energy drink16160
5-hour Energy drink2215
Coffee ice cream850-80
Hershey kisses 9 pieces9
Hot chocolate85-15
Excedrin1 tab65

In summary, as with most things in life, caffeine in moderation is okay and may actually provide some health benefits. But just remember, too much of a good thing is no longer a good thing!

Love, Jessica


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