Yerba Mate: a real friend for endurance athletes?

New research on the herb ‘Yerba Mate’ suggests a double whammy of benefits for endurance athletes

Many sports supplements come and many sports supplements go, but few stand the test of time and rigorous scientific scrutiny. Among the long list of wannabes, supplements such as carbohydrate, whey protein, creatine, caffeine and beetroot juice (nitrate) stand out precisely because a large number of studies have provided irrefutable evidence that they work consistently for a wide range of athletes in a wide range of circumstances. But that doesn’t mean of course that athletes should turn their backs on lesser known supplements. Provided there is good data in the scientific literature showing their efficacy, they may well be worth considering. Remember, there was a time not so long ago when caffeine and creatine were relatively unknown and unresearched!

The promise of Yerba Mate

One supplement that is relatively unknown in the West, but for which evidence on exercise performance benefits is steadily accumulating, is the herb known as ‘Yerba Mate’ (botanical name ‘Ilex paraguariensis’). Yerba Mate is a highly antioxidant-rich plant found widely in South America, and which is used to make a popular, bitter-tasting beverage of Yerba Mate tea. Around a decade ago, researchers became interested in Yerba Mate for its purported general health benefits⁽¹⁾. As research has progressed, a lot of evidence has accumulated that the consumption of Yerba Mate can produce a number of specific benefits, many of which are particularly relevant to those with sedentary Western lifestyles. These include:

1. Powerful antioxidant and anti-inflammatory effects^(2-4).
2. A lowering of blood lipids (fats)⁽⁵⁾.
3. A lowering of excess blood glucose (thus reducing the risk of pre diabetes)⁽⁶⁾.
4. A weight (fat) loss effect⁽⁷⁾.

However, during the past five years, Yerba Mate has also been investigated in the context of exercise performance. A 2018 study on trained cyclists found that five grams of Yerba Mate ingested for five days resulted in improved performance⁽⁸⁾. In a 30-minute time trial, times were around 2.2% faster and averaged 2.3% more power when they took Yerba Mate compared to a placebo. Other studies on Yerba Mate and exercise performance have shown that at low-to-moderate intensities, Yerba can increase the proportion of energy derived from fat (so-called ‘fatmax’ – see figure 1 and this article) and also increase the amount of energy expended overall⁽⁹⁾.

---

Figure 1: Fatmax and exercise intensity

Exercise intensity (expressed as %HRmax and %VO2max) and fat oxidation. Fat oxidation increases from low to moderate exercise intensities, peaks at Fatmax and decreases as the exercise intensity increases further. The grey area represents the Fatzone: a range of exercise intensities where fat oxidation is high.

---

Fat burning, fasting and Yerba Mate

Much of the research into Yerba Mate and fat burning during exercise has been on subjects who exercised in the fasted state. Why is this? Well, a large body of research shows that consuming carbohydrate prior to exercise inhibits the process of fat burning in muscle cells and reduces the proportion of energy derived from fat^(10,11). Therefore, studies have looked at subjects exercising in the fasted state (to ensure optimal fat burning) and compared the results with other subjects exercising in the fasted state but who also took Yerba Mate pre exercise^(6,12).

From a practical point of view, regular readers of SPB will know that exercising first thing in the morning (ie after an overnight fast) is an effective way of reducing carbohydrate availability to the muscles, thus helping to train fat burning ability. The same is true during periods of dietary carbohydrate restriction, when muscles are forced to derive more energy from fat. These so-called ‘train low’ strategies can help athletes in two ways:

• By utilizing a greater proportion of fat for energy, they can help in weight management.
• By improving fat burning during endurance competition, they offer a theoretical potential advantage via a carbohydrate sparing effect.

The downside of these strategies however is that they also appear to blunt performance on the day by down-regulating the energy pathways used to burn carbohydrate^(13,14). Given the performance enhancing effects observed with Yerba Mate when taken in the fasted state, it’s possible therefore that athletes might benefit from its use when undertaking train-low strategies – by increase fat oxidation and helping sustain performance.

Yerba Mate and carbohydrate

Most athletes don’t train low all the time; train-low strategies are generally undertaken alongside deliberate training sessions or periods of time with high carbohydrate availability – so-called ‘train high’. This is particularly important in the run up to a race. The idea is to train the muscles to burn more fat (train low) but to also undertake the very high-intensity sessions needed for maximum race performance (which requires sufficient/ample carbohydrate – ie train high). Then on race day, the athlete can both be efficient at burning fat while working at a very intense level thanks to good levels of muscle carbohydrate (glycogen).

But given that Yerba Mate can lower blood sugar spikes, a question that has hitherto been unanswered is whether the benefits of Yerba (ie increased fat burning) can be maintained when it is consumed alongside pre-exercise carbohydrate? In other words, while carbohydrate is known to suppress fat burning, can this suppression itself be ameliorated when that carbohydrate is consumed with Yerba Mate? And if it can, could athletes get the best of both worlds – ie high quality workouts and increased fat burning – by taking Yerba alongside carbohydrate. Until recently, no research has even been conducted on this topic. But now a brand new study by Brazilian scientists has just been published in the journal ‘Sports Medicine Open’, which makes for fascinating reading⁽¹⁵⁾.

New research

In this study, the researchers investigated the effects of a Yerba Mate drink consumed in the fasted state or after a carbohydrate meal on measurements of metabolism, exercise performance, and markers of oxidative stress during cycling. Eight local cyclists and triathletes were recruited, each having at least two years of experience of training and competition in cycling endurance events. The study comprised four stages: a baseline assessment and then three trial periods with a 7-day ‘washout’ between each testing period. The experimental design is shown in figure 2 but the three trial periods basically consisted of the following:

1. YMD-CHO = Yerba Mate ingestion combined with a pre-trial carbohydrate meal.
2. YMD-F = Yerba Mate ingestion in the fasted state (ie no pre-exercise carbohydrate).
3. Control-CHO = carbohydrate ‘control’ condition (ie = a pre-trial carbohydrate meal but with no Yerba Mate ingestion.

---

Figure 2: Experimental design

The dietary trials were randomized in a crossover design. T = time in minutes in relation to the exercise protocol; YMD = Yerba Mate drink; CHO = carbohydrate; YMD-F = Yerba Mate drink and fasting state; YMD-CHO = Yerba Mate drink and carbohydrate meal; Control-CHO = water and carbohydrate meal; CLT = constant load test; TT = time trial.

---

Participants were instructed to drink 250mls per day of either Yerba (an infusion of 5 grams of ultra-refined leaves in 250mls of water) or water (for the carbohydrate-only control condition) for straight seven days (always in the morning), and before the exercise protocol of each of the test periods. Exactly 60 minutes before exercise, Yerba-carbohydrate and control-carbohydrate trials, subjects consumed a carb meal (1 gram per kg of body mass) composed of white bread and corn syrup, whereas during the Yerba-fasted trial, the subjects remained in a fasted state. At 40 minutes before exercise, subjects drank 250mls of either Yerba or water according to their trial condition.

After this, all subjects performed a 65-minute cycling exercise protocol, comprised of a constant load test (CLT); a 20-min time trial (TT); and a repeated sprint test consisting of 4 x 10-second all out sprints. The experimental protocol was always carried out in the same period of the day to minimize circadian variation (time of day) effects. Blood samples were obtained at the baseline, before, during, and immediately after the exercise protocol to test for blood lipid levels and antioxidant status. Respiratory gas analysis was also carried out to determine the proportion of energy derived from fat burning, cycling efficiency and total energy expended.

The findings

The main findings were as follows:

Performance findings

• Unsurprisingly perhaps, the average power output during time trial tended to be slightly higher in the Yerba-carbohydrate condition than the Yerba-fasted condition.
• The average power output during the time trial was significantly higher in the Yerba-carbohydrate trial (259 watts) than in the carbohydrate-control trial (252 watts).
• Oxygen uptake levels were higher in the Yerba-carbohydrate time trial compared to the Yerba-fasting and carbohydrate-control trials, even though perceived exertion was no different.

Fat burning findings

• The rate of fat burning during steady-state cycling was NOT highest in the Yerba-fasted state. Incredibly, when the cyclists had consumed the Yerba-carbohydrate combination, not only did they perform better in the time trial, they also burned 13% more fat than in the Yerba-fasted state (completely contrary to what was expected). And compared to the carbohydrate-only control trial, the cyclists burned a massive 27% more fat when they consumed Yerba with the carbohydrate!
• Fat burning in the time trial (high intensity) was also hugely elevated; compared to the carbohydrate-control condition, the Yerba-carbohydrate condition resulted in an incredible 151% increase in fat burning (see figure 3). Even more astonishingly, the Yerba-carbohydrate condition resulted in a 157% increase in time trial fat burning compared to Yerba-fasted!

Blood findings

• Consuming Yerba Mate – either with carbohydrate or in the fastest state – resulted in higher circulating levels of polyphenolic antioxidants in the blood and lower levels of oxidative stress markers.

---

Figure 3: Fat burning during the time trials

Circles = Yerba-carbohydrate; squares = carbohydrate-control; triangles = Yerba fasted. Fat oxidation was massively elevated when Yerba was taken with carbohydrate – completely contrary to the norm (where carbohydrate intake suppresses fat burning.

---

Implications for athletes

On the face of it, these findings are extraordinary. Not only does Yerba Mate appear to enhance performance during intense exercise in trained athletes, it also turns our understanding of pre-exercise carbohydrate intake reducing fat oxidation during subsequent exercise completely upside down. In a sense, this double whammy of improved high-intensity performance combined with increased fat burning with the Yerba-carbohydrate combination is something of a holy grail for endurance athletes.

If confirmed in further studies, these findings could revolutionize the way athletes conduct fat-burning training and enhance fat burning during races. Instead of pursuing (often difficult) train-low regimes with all that they involve, athletes could simply consume Yerba Mate for period of time while keeping fueled with carbohydrate normally. Is there any explanation for the increased fat burning when carbohydrate is consumed? One theory has proposed that the ergogenic effects of Yerba Mate could in part be explained by synergism between caffeine and other compounds known as ‘chlorogenic acids’, which stimulates the central nervous system, through an increase in dopamine levels⁽⁸⁾. The truth however is that we don’t really know at this point.

Caution

That said, some caution is required; firstly, while 18 athletes were recruited, this study only produced data from eight athletes (the others were sidelined during the study because of the imposition of local lockdowns). Even with the very decisive findings, especially in regard to fat burning, it’s harder to generate very high levels of certainty from a study when subject numbers are low.

Another limitation is that this study didn’t include a ‘placebo’ Yerba Mate beverage - so while the fat burning results wouldn’t have been affected (your frame of mind and expectations wouldn’t be able to change body chemistry!), performance could have been. Why was there no placebo Yerba drink? The reason is simple: Yerba Mate has an extremely distinct and bitter taste. Trying to mimic it in a placebo beverage would have been virtually impossible. However, the lack of placebo is probably not a significant issue of concern anyway. After all, if the athletes’ better time-trial performances in the Yerba-carbohydrate trial were biased by a placebo effect, why were their performances not also superior in the Yerba-fasted state (which they weren’t)?

Despite the study limitations however, make no mistake – these results are very exciting indeed and signal a potential pathway for endurance athletes to maintain an ample carbohydrate intake while enhancing performance fat burning! The periodic use of Yerba Mate could also negate the need for other strategies such as train low, race high, keto periodization and time-restricted eating.

---

Using Yerba Mate

If you’re tempted to experiment with Yerba Mate tea, you don’t have much to lose as it’s not that expensive and is packed with healthy antioxidants! The biggest challenge may be getting used to the taste, although many people report that while ‘unusual’ at first, they soon get to love it. Here are some tips for beginners:

• The flavor and performance of the Yerba will depend on where the Yerba is grown, the drying process used, the time of year, and the proportion of stems versus leaves. Each brand of Yerba has a different taste, so you will need some trial and error to find your favorite.
• Yerba without stems - If you want a strong and bitter flavor, this should be your choice. When brewed, it retains the flavor longer and is the most popular type of Yerba in Uruguay and South of Brazil.
• Yerba with stems - If you are a beginner and would prefer a milder flavor, Yerba with stems is the way to go.
• Flavored Yerba - This type of Yerba is variable in composition but usually has a higher content of stems. The flavor comes usually from essences such as citrus peel or zest. You can also add your own flavors.
• Yerba blends - usually labeled in Spanish as ‘Yerba compuesta’, this refers to a mate blend that is formed by at least 60% of Yerba and a maximum of 40% of other herbs such as, mint, thyme, sage, pennyroyal, and rosemary.
• Yerba tea bags – These can have a variable percentage of stems and are a practical way of preparing Yerba tea, being brewed much like other teas (although temperature of the added water is nearer to 60-70 centigrade rather than boiling).
• Preparation – Special cups for Yerba (gourds) and filter containing straws (bombillas) are available, but Yerba tea can equally be brewed in a glass cafetiere.

---

References

1. 2011;136:378–384
2. J Funct Foods. 2017;38:308–320
3. J Funct Foods. 2013;5:1057–1064
4. Int J Food Sci Nutr. 2019;70:212–221
5. Am Coll Nutr. 2011;30:320–332
6. 2017;9:1–15
7. BMC Compl Altern Med. 2015;15:1–8
8. Med Sci Sports Exerc. 2018 Apr;50(4):817-826
9. Nutr Metab. 2014;11:1–7
10. Am J Physiol - Endocrinol Metab. 1997;273:768–775
11. J Sports Sci. 2003;21:1017–1025
12. Nutrients 2014;11:1–7. doi: 10.1186/1743-7075-11-42
13. J Physiol. 2017;595:2785–2807
14. Eur J Sport Sci. 2015;15:3–12
15. Sports Med Open. 2022 Dec; 8: 93. Published online 2022 Jul 16