Energy drinks are very popular, especially among young people.
These beverages contain stimulants, such as caffeine, which are supposed to provide a physical and mental boost.
Today’s study takes a look at how energy drinks affect heart health.
Researchers from the Mayo Clinic in Minnesota conducted a small study on how energy drinks affect blood pressure, heart rate, blood sugar and norepinephrine levels.
Basic Study Design
This was a randomized, controlled crossover study that examined how energy drinks affect heart function. It included 25 healthy men and women, aged 26 to 31 years.
There were two study groups:
- Energy drink: The participants drank 480 mL (16 fl oz) of Rockstar, a type of energy drink. It contained several stimulants: caffeine (240 mg), taurine (2000 mg), and extracts of ginseng root, milk thistle and guarana seed.
- Placebo: Another day, the participants got the same amount of a placebo drink. It was similar to the energy drink, but didn’t contain any of the stimulants.
On both occasions, the participants were fasting. They also hadn’t had any energy drinks, coffee or alcohol for at least 24 hours prior to each study day. Additionally, all study drinks were finished within 5 minutes.
Since this was a crossover trial, the participants got both drinks in random order on separate days, with less than 2 weeks apart.
Before and after drinking the energy drink and the placebo, the researchers measured circulating levels of caffeine, blood sugar, norepinephrine, blood pressure and heart rate.
Blood pressure and heart rate were also measured while the participants were under 2 minutes of stress. Responses to three types of stress were measured: physical stress, mental stress and cold stress.
Bottom Line: This small, randomized, controlled crossover study examined the effects of an energy drink on blood pressure, heart rate, blood sugar and norepinephrine.
Finding 1: Energy Drinks May Increase Blood Pressure
Blood pressure increased after the energy drink, whereas the placebo drink did not cause any statistically significant changes in blood pressure.
The chart below shows the changes in mean blood pressure in both groups:
After the energy drink, systolic blood pressure increased by 6.2% and diastolic blood pressure increased by 6.8%.
Although the study did not examine how long the effects on blood pressure lasted, they were probably only temporary.
Blood pressure also rose during physical, mental and cold stress, but the energy drink didn’t add to this increase.
Additionally, the energy drink did not affect heart rate, which remained normal after both drinks.
Bottom Line: Blood pressure increased significantly after the energy drink. Conversely, the placebo drink did not lead to any significant changes.
Finding 2: Norepinephrine Increased More After the Energy Drink
Also called noradrenaline, norepinephrine is a stress hormone that helps prepare the body for action.
For this reason, its levels are lowest during sleep, and highest during periods of stress and/or fear. It is one of the body’s “fight or flight” hormones.
In the present study, levels of norepinephrine increased after both drinks.
However, the rise was significantly higher after the energy drink, compared to the placebo.
The chart below shows the differences between groups:
As with the rise in blood pressure, the rise in norepinephrine was probably just temporary. Therefore, its health relevance is unclear.
Bottom Line: Norepinephrine levels increased after both the energy drink and the placebo. However, the increase was higher after the energy drink.
Finding 3: Blood Sugar Increased Similarly in Both Groups
Both the energy drink and the placebo drink contained equal amounts of sugar. For this reason, the blood sugar levels rose similarly after both drinks, as expected.
However, this does not seem to be the case here.
Many of the participants might have been regular coffee drinkers, or the statistical power of the study was simply not great enough to detect the between-groups difference as significant.
Bottom Line: The energy drink and the placebo contained the same amount of sugar, and blood sugar levels increased similarly after both drinks.
The main limitation of this study is the small number of participants. The study may not have had enough statistical power to detect smaller between-group differences.
Another limitation is that the energy drink contained several stimulants: caffeine, taurine, guarana, milk thistle and ginseng root. This makes it impossible to isolate the effects of the individual ingredients.
This study also only examined one energy drink, which contained a mixture of commonly used stimulants like caffeine. Other brands and products may have different ingredients.
Otherwise, this study appears to have been designed and executed well.
Bottom Line: The study’s main limitation is its small size and limited statistical power.
Summary and Real-Life Application
This small study shows that energy drinks may cause a sudden rise in blood pressure and norepinephrine.
However, the extent of this risk is unclear, and needs to be studied further before any solid conclusions can be reached.
At the end of the day, energy drinks should be used sparingly, if at all. In addition to possibly harmful stimulants, they also contain sugar and other unhealthy ingredients.
Plain coffee is a much healthier alternative.