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What is the Verdict on Caffeine and Your Hydration?

Are you quenching your thirst with dehydration?

Caffeine and Your Body

Caffeine is the most widely consumed psychoactive drug in the world and can be sourced from coffee beans, cacao beans, kola nuts, tea leaves, yerba mate, the guarana berry, and as an additive to sodas and energy drinks, or consumed as powder or tablets (1).

If you read the post about the effects of ADH on your body and its hydration then you are already familiar with the antidiuretic hormone, ADH. We talked about how people often do not want to break the imaginary 'seal' that exist with alcohol intake. The myth that going to the bathroom when consuming alcohol ‘breaks the seal’ was explained, but does the same happen when it comes to caffeine?

The validation of the diuretic effects of caffeine depends on what source you look at. Many people that are avid coffee drinkers still may try to double their water intake or feel dehydrated if they do not. Keep reading and let’s find out why that is.


Caffeine is usually utilized to promote arousal, alertness, energy, and elevate mood (4). Caffeine is both fat and water-soluble, allowing it to cross the blood-brain barrier and act on all four adenosine receptor subtypes (A1, A2a, A2b, A3) that exist. Adenosine is a molecule that is involved in energy transfer signaling in the form of ATP. Specifically, targeting the A2a receptor promotes wakefulness effects that caffeine has (1).

The half-life of caffeine, or the time that it takes the body to eliminate one-half of the caffeine is approximately 5 to 6 hours in the average adult. However, although there are other factors that can influence metabolism. Half-life is reduced by up to 50% in smokers compared to nonsmokers (1).

This is why pregnant women are advised to limit or eliminate their caffeine consumption. Pregnant women, especially those in the final trimester, will have prolonged half-life upwards of 15 hours. Newborns will also have a significantly prolonged half-life, up to 8 hours for full-term and 100 hours for premature infants (1).

Caffeine Daily Recommendation

For healthy adults, the FDA has cited 400 milligrams a day—that's about four or five cups of coffee, equivalent to around three to five 8-ounce cups of coffee (5). However, there is wide variation in both how sensitive people are to the effects of caffeine and how fast they break it down.

Caffeine and the Bowels

Coffee has been shown to have profound effects on the gastrointestinal system; it reduces the pressure of the lower esophageal sphincter and stimulates secretion from the stomach and the small intestine, which explains why a good number of individuals have the urge to defecate not too long after drinking a coffee beverage (11).

Some studies state that coffee consumption, independent of caffeine content, increases gastrin secretion, a hormone secreted in response to a meal. When coffee increases this hormone, it produces more stomach acid and pushes digestion. Gastric acid then breaks down proteins in food and helps the body absorb vitamins. As of now, there is not significant studies centered around this concept, but coffee has been connected with the stimulation of colonic muscles, thus promoting peristalsis, the contraction and relaxation of intestinal muscles that causes bowel movements.

Caffeine and the Kidney

Caffeine is naturally occurring methylxanthine also found in tea, chocolate, and energy drinks, acts as a competitive adenosine receptor antagonist to reduce fractional sodium reabsorption in both the proximal tubule and distal nephron. While information varies, it seems that higher doses of caffeine will acutely increase urinary output, while lower to moderate doses of caffeine will not have a diuretic effect. (14)

Caffeine does not seem to inhibit the hormone ADH like alcohol does, but it is linked to urinary sodium levels being significantly higher in a coffee trial than a water trial that was conducted. The increased sodium excretion in this coffee trial falls in line with previous studies that have observed that both theophylline and caffeine enhance sodium excretion at the proximal and distal renal tubules of the kidney. The increase in sodium excretion is due to methyxanthine-induced natriuresis caused by inhibition of salt transport along the proximal convoluted tubule (15).

Caffeine and Hydration

The consensus of whether caffeine in fact acts as a diuretic or can lead to dehydration is still not final. Depending on the sources that are analyzed, both sides of the theories are suggested. Unlike alcohol, caffeine is thought to similar mild diuretic effect on your body, but mainly at high levels. The U.S. Food and Drug Administration purports caffeine has diuretic properties and advises its users to drink extra water to avoid dehydration during exercise in the heat (2). Fluid balance will be compromised by failure to consume sufficient fluid to meet ongoing water losses or by ingestion of diuretic agents such as caffeine. (3)

However, individuals such as Dr. Vigil, an associate clinical professor of family medicine at the David Geffen School of Medicine at the University of California Los Angeles, explains that it’s true that caffeine is a mild diuretic, which means that it causes your kidneys to flush extra sodium and water from the body through urine. He clarifies that although people may urinate frequently it does not indicate dehydration. By drinking caffeine beverages, our bodies are able to absorb as much fluid as it needs and expel the rest, he says. (8) Therefore, according to Dr. Daniel Vigil, a cup of Joe is actually a contribution to your hydration and not the opposite. It is suggested that if a person And experiences headaches or other symptoms after consuming caffeine, Vigil says dehydration likely is not the culprit, but a sensitivity to caffeine (8).

So, if it is specifically dehydration that some are worried about, and Coffee and Health states that although there is some indication of a mild, short-term diuretic effect of caffeine, it is not strong enough to counter-balance the benefits of fluid intake from coffee drinking. The advice to avoid coffee because it causes dehydration is not supported by scientific evidence (13)

One study that was provided by NPR involved researchers at the University of Birmingham in the U.K. who studied the fluid levels of 50 men who had a habit of consuming about three to six cups of coffee each day. With this kind of moderate coffee consumption, the authors conclude that "coffee provides similar hydrating qualities to water." To compare the hydrating effects of coffee directly with water, each participant completed two phases of the study. In one phase, they drank coffee as their main source of hydration. In the other phase, the participants went off coffee and drank equal amounts of water (9)

The data showed no significant differences in the hydrating properties of coffee or water across a wide range of hydration assessment indices. Thus, thus suggesting that coffee, when consumed in moderation by caffeine habituated males contributes to daily fluid requirement and does not pose a detrimental effect to fluid balance. (15)

Caffeine and Tolerance

It is often believed that individuals who drink caffeine regularly develop a tolerance to it and its effects, therefore not reflecting differences in their hydration with or without the consumption of the component.

In a rare study where people drank nothing but tea for the 12 hour duration of the trial, there was no difference in hydration levels between them and the people who drank the same quantity of boiled water. When it comes to the consumption of coffee, one study found a 41% increase in urine, along with a rise in the excretion of sodium and potassium. But these participants had abstained from caffeine before the study, so this doesn’t tell us what would happen in people who are accustomed to drinking coffee (9).

Caffeine is a diuretic, which means it can increase urine production and, in some cases, lead to fluid loss from the body. While moderate caffeine consumption is generally considered safe and does not cause significant dehydration for most people, excessive caffeine intake or individual sensitivity can potentially contribute to dehydration. Here's how caffeine can affect hydration:

  1. Increased Urination: Caffeine stimulates the kidneys to produce more urine. This can lead to more frequent trips to the bathroom, potentially causing fluid loss.

  2. Fluid Loss: If you consume caffeinated beverages like coffee, tea, or soda in large quantities and do not compensate by drinking enough water, you may experience a net loss of fluids.

  3. Decreased Fluid Intake: Some people may reduce their overall fluid intake if they consume a lot of caffeinated beverages. This can be particularly problematic if they rely on caffeinated drinks to quench their thirst instead of water or other hydrating options.

  4. Individual Variability: Individual tolerance to caffeine varies. Some people may be more sensitive to its diuretic effects and experience increased urine output and potential dehydration more readily than others.

To mitigate the potential dehydrating effects of caffeine:

  1. Stay Hydrated: Ensure that you're drinking an adequate amount of water throughout the day, especially if you consume caffeinated beverages.

  2. Moderate Caffeine Intake: Limit your caffeine consumption to moderate levels, typically defined as up to 400 milligrams (about 4 cups of brewed coffee) per day for most adults. Be mindful of caffeine content in different beverages and foods.

  3. Balance Caffeine with Water: If you consume caffeinated beverages, try to drink water alongside them to maintain proper hydration.

  4. Pay Attention to Your Body: Be aware of how caffeine affects you personally. If you notice increased thirst, frequent urination, or signs of dehydration, consider reducing your caffeine intake.

  5. Choose Hydrating Alternatives: Consider incorporating hydrating beverages like herbal tea, plain water, or electrolyte-rich drinks into your daily routine, especially in hot weather or during physical activity.

  6. Limit Caffeine Before Bed: Avoid consuming caffeine close to bedtime, as it may interfere with sleep and increase the likelihood of morning dehydration.

It's essential to strike a balance between enjoying caffeinated beverages and maintaining adequate hydration. For most people, moderate caffeine consumption as part of a balanced diet is not a significant cause of dehydration. However, if you have concerns about caffeine or experience symptoms of dehydration, consult with a healthcare professional for personalized guidance.

Final thoughts

The verdict is still out on whether caffeine causes diuretic effects.

What are your thoughts on it? How do you feel after you drink a cup of Joe?

To hydrate or to stay awake, that is the question

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