Yerba mate is hydrating. Despite containing caffeine, the water in each serving contributes to your daily fluid intake, and the moderate caffeine content is not enough to cancel out that hydration. A study on trained runners found no difference in hydration markers between regular yerba mate and decaffeinated yerba mate, suggesting the water content is what matters most.
Why Caffeine Doesn’t Cancel Out the Water
Caffeine is technically a mild diuretic, meaning it can increase urine output. But “mild” is the key word. A 2015 meta-analysis of caffeine intake in healthy adults, with doses ranging from 114 to 741 milligrams, found that caffeine produced only a slight diuretic effect. That effect was even smaller after exercise. A standard cup of yerba mate contains roughly 70 to 85 milligrams of caffeine, which falls below even the lowest dose studied in that analysis.
The practical takeaway: you’re taking in far more fluid than any caffeine-driven loss could account for. Your body retains the vast majority of the water in each cup. This is the same reason coffee and tea also count toward daily hydration, something nutrition researchers have confirmed repeatedly over the past decade.
What the Runner Study Found
Researchers tested this directly using tereré, the cold-brewed version of yerba mate popular in Paraguay and southern Brazil. Well-trained street runners drank either regular tereré or a decaffeinated version, with the same total water volume in both groups. The result: no statistically significant difference in any hydration parameter between the two groups.
The researchers concluded that the amount of water consumed, not the substances in yerba mate (especially caffeine), was the main factor determining hydration. In other words, the caffeine in yerba mate did not meaningfully interfere with fluid retention, even during the physical demands of running.
Minerals That Support Hydration
Yerba mate brings more to the table than just water. The dried leaves are rich in electrolyte minerals, and some of these transfer into the liquid when you brew it. Potassium is the most abundant, at roughly 1,350 milligrams per 100 grams of dried leaf. Calcium, magnesium, and phosphorus are also present in significant amounts. Uruguayan yerba mate samples, for instance, contained 814 mg of calcium and 603 mg of magnesium per 100 grams of dried product.
These minerals matter because electrolytes help your body hold onto water and distribute it into cells. Potassium and magnesium in particular play roles in fluid balance. You won’t get massive doses from a single cup, since only a fraction of the minerals in the dried leaf end up in your infusion. But over the course of a typical mate session, where you’re refilling the same leaves multiple times, the cumulative mineral intake adds up. This gives yerba mate a slight edge over plain water for hydration, similar to how a dilute sports drink works.
Hot Mate vs. Cold Tereré
Traditional hot mate (chimarrão) and cold tereré are prepared differently, but both are hydrating. Hot mate is sipped through a metal straw from a gourd, with water added in small pours of around 50 to 100 milliliters at a time, repeated six to ten times per session. Tereré follows the same gradual pattern but uses cold water, sometimes with added herbs or citrus juice.
The gradual sipping style actually works in your favor. Drinking small amounts of water over a longer period gives your body more time to absorb the fluid, rather than processing a large volume at once and losing more to urine. A full mate session can easily deliver 500 to 1,000 milliliters of water, which is a meaningful chunk of your daily needs.
Cold tereré has a reputation as especially hydrating, partly because it’s traditionally consumed in hot climates where fluid replacement is urgent. There’s no strong evidence that cold water hydrates better than hot water, but the cultural habit of drinking tereré in larger quantities during heat likely contributes to its hydrating reputation.
How Yerba Mate Compares to Other Drinks
- Water: Pure water is the baseline for hydration. Yerba mate is comparable, with the added benefit of electrolyte minerals.
- Coffee: Coffee has roughly twice the caffeine of yerba mate per cup. Even so, coffee is still a net hydrator. Yerba mate’s lower caffeine makes it even less of a concern.
- Tea: Green and black tea are similar to yerba mate in caffeine content and hydration effect. All three count toward daily fluid intake.
- Sports drinks: These are designed for hydration with added electrolytes and sugar. Yerba mate provides some electrolytes naturally but no sugar, making it a lower-calorie option for everyday hydration (though not a replacement during intense exercise).
If you’re drinking yerba mate regularly and wondering whether you need to drink extra water to compensate, you don’t. Every cup counts toward your fluid intake, and the caffeine content is too low to meaningfully offset the water you’re consuming.