When the thermometer freaks out, every sip counts. We know to avoid alcohol and sugary drinks, but we often forget to monitor our caffeine intake.
Essential for waking up in the morning or getting over the afternoon slump, coffee is a major part of our summer days. But be careful: consumed in excess and without compensation, it can become the best ally for heat stroke.
Is coffee really dehydrating? The true from the false
Contrary to popular belief, a simple cup of coffee will not drain you of water. The problem is not with the drink itself, but with excess and repetition.
“Coffee does not really dehydrate at usual doses: it itself contains a lot of water, and its slight diuretic effect generally remains too weak to cause people to lose more liquid than it provides. explains Dr. Gérald Kierzek, emergency physician and medical director of True Medical.
The effect therefore mainly depends on your routine. If you are a regular consumer, your body is used to it. The major risk arises when coffee simply replaces pure water during a hot day.
The hidden mechanism of caffeine on your kidneys
To understand why the trap closes, we need to look at the star molecule of our espresso: caffeine. It is this which activates the renal system, but our body has a certain capacity to adapt.
“The supposed mechanism comes mainly from caffeine, which can increase diuresis a little by stimulating the kidneys, but the body quickly gets used to it when consumption is regular. In practice, the risk of dehydration appears especially when you accumulate a lot of caffeine during the day without drinking enough water!” specifies the medical director of True Medical.
Chaining together cups to “keep up” with the crushing fatigue of the heat, without alternating with glasses of water, thus pushes the kidneys to eliminate more than necessary.
Warning signs that should make you put down your cup
In blazing heat, dehydration can set in quietly, masked by the boost effect of coffee. It’s crucial to listen to the messages your body is sending you.
Dr Gérald Kierzek invites us to be vigilant at all times.
“Signs of dehydration to watch out for are dry mouth, rarer and darker urine, unusual tiredness, headache, dizziness, feeling weak, cramps, faster heart rate, or even confusion if the situation gets worse.” he lists.
“In a person who drinks a lot of coffee and not enough water, these signs can set in gradually, especially in hot weather or during physical activity. You must be particularly vigilant if there is little thirst or if you drink coffee, tea, caffeinated sodas and energy drinks in the same day.”
Alternatives and limits not to be crossed this summer
To get through heat waves safely without sacrificing your rituals, a few adjustments are necessary. The European Food Safety Authority (EFSA) has also set specific benchmarks to keep in mind.
“To replace coffee, the best is water, still or lightly flavored, and possibly herbal teas or caffeine-free drinks. If the objective is to maintain a ritual or a small invigorating effect, you can also choose a light tea or a decaffeinated version, but they do not replace water on their own. In terms of limits, the benchmarks for healthy adults are around 400 mg of caffeine per day maximum, with particular caution around 200 mg in one dose and lower thresholds during pregnancy or breastfeeding. concludes the emergency doctor.
As a guide, 400 mg of caffeine represents approximately 4 cups of filter coffee. A threshold to be revised significantly downwards when the thermometer rises. So this summer, the motto is simple: for every cup of coffee you swallow, force yourself to drink a large glass of water. Your heart, your kidneys and your energy capital will thank you.