Yerba Mate Side Effects: What to Know Before You Drink

Yerba mate has been consumed daily by millions of people across South America for over 500 years. It’s rich in antioxidants, delivers smooth energy, and carries genuine health benefits. But like any caffeinated beverage, it’s not without considerations. At Onoiru, the exclusive European distributor of organic yerba mate from Paraguay, we believe in giving you the full picture — not just the highlights.

So let’s talk about yerba mate side effects — what’s real, what’s overblown, and what you should actually pay attention to.

Caffeine Sensitivity and Sleep

Yerba mate contains approximately 85 mg of caffeine per 240 ml serving — slightly less than coffee (95 mg) but significantly more than green tea (28 mg). For most adults, this is well within the safe daily limit of 400 mg recommended by the European Food Safety Authority (EFSA).

However, if you’re sensitive to caffeine, you may experience restlessness, increased heart rate, or difficulty sleeping — the same effects you’d get from coffee. The key difference: mate’s combination of caffeine, theobromine, and theophylline typically produces a gentler energy curve with fewer jitters. Still, avoid drinking mate within 4-6 hours of bedtime if sleep quality is a concern.

Digestive Effects

Some first-time drinkers report mild stomach discomfort or nausea, especially when drinking mate on an empty stomach. This is usually temporary and resolves as your body adjusts. The tannins in yerba mate (similar to those in wine and tea) can cause slight gastric irritation in sensitive individuals.

On the positive side, a 2022 study published in Nutrients found that yerba mate consumption actually supports digestive health by promoting beneficial gut bacteria. The polyphenols in mate act as prebiotics, feeding the microorganisms that keep your gut healthy. If you experience initial discomfort, try drinking mate after a light meal rather than first thing in the morning.

Yerba mate — a plant with centuries of traditional use

The Temperature Question

You may have seen headlines linking yerba mate to increased cancer risk. This requires important context. The International Agency for Research on Cancer (IARC) reviewed the evidence in 2016 and concluded that yerba mate itself is not classifiable as carcinogenic. What they did flag is that drinking any beverage above 65°C (149°F) — whether it’s mate, coffee, or plain hot water — is associated with increased risk of oesophageal cancer.

The solution is simple: don’t use boiling water. Traditional mate preparation calls for water between 70-80°C (158-176°F), which is already below the risk threshold. At Onoiru, we recommend 75°C as the sweet spot — it extracts the best flavour while keeping the temperature safe. If you see steam but no bubbles, you’re in the right range.

Iron Absorption

Like tea and coffee, yerba mate contains polyphenols that can reduce non-heme iron absorption when consumed with meals. A study in the Journal of Food Science measured a 20-35% reduction in iron absorption when mate was consumed alongside iron-rich foods. This is relevant for people with iron-deficiency anaemia or those on plant-based diets who rely heavily on non-heme iron sources.

The practical fix: drink your mate between meals rather than during them. Waiting 30-60 minutes after eating gives your body time to absorb iron before the polyphenols interfere. This also applies to coffee and black tea, so it’s not unique to mate.

Pregnancy and Breastfeeding

The EFSA recommends pregnant and breastfeeding women limit caffeine intake to 200 mg per day. Since a single serving of yerba mate contains roughly 85 mg, one cup per day is generally considered safe under these guidelines. However, as with coffee and tea, it’s best to consult your healthcare provider for personalised advice.

Drug Interactions

Yerba mate’s caffeine content means it can interact with certain medications, including stimulants (amplifying effects), blood thinners like warfarin (caffeine may affect metabolism), MAO inhibitors (potential for elevated blood pressure), and lithium (caffeine can affect lithium clearance). If you take prescription medication, check with your doctor before adding mate to your daily routine — just as you would with coffee.

Organic vs. Conventional: Does It Matter for Safety?

Yes. Conventionally grown yerba mate may contain pesticide residues, including glyphosate, which has been detected in several commercial brands. A 2021 study in Food Chemistry tested 30 commercial yerba mate products and found measurable pesticide residues in 73% of non-organic samples. Organic mate, by contrast, had no detectable residues.

This is one of the reasons Onoiru sources exclusively organic yerba mate from family farms in Paraguay’s Itapúa region. Our mate is certified organic under European standards, shade-grown under native forest canopy, and processed without any chemical additives. Over 130 farming families cultivate it using traditional methods that have been passed down through generations.

Organic yerba mate harvested from family farms in Paraguay

The Bottom Line

Yerba mate is safe for the vast majority of adults when consumed at moderate levels (3-4 servings per day) and at proper temperatures. Its side effects are comparable to — and in some cases milder than — those of coffee. The key precautions are straightforward: use water below 80°C, drink between meals if iron absorption is a concern, mind your caffeine total if you’re sensitive, and choose organic to avoid pesticide residues.

Five hundred years of daily consumption by millions of people is a powerful safety track record. When you combine that with modern organic certification and careful preparation, yerba mate is one of the most balanced and well-tolerated energy drinks available.

Explore Onoiru’s certified organic yerba mate at onoiru.eu — premium Paraguayan mate from family farms, harvested by lunar cycle, aged over two years, and free from any chemical residues.