A little-known ingredient in energy drinks was thrust into the spotlight this week after scientists theorized it may partly explain a rise in colon cancer in young people.

Taurine is an amino acid used in Red Bull to energize cells and improve mental clarity.

However, scientists in Florida hypothesize that this ingredient could ‘feed’ harmful bacteria that have been ‘over-represented’ in the guts of people with colorectal cancer.

It’s still only a theory, and based on preliminary studies in animals and labs, so experts say there is no reason to panic yet.

But Taurine is also found in Monster, Celsius, and some Starbucks coffee beverages. So is this a reason to cut out energy drinks altogether?

The findings come as one in three adults ages 18 to 29 report regularly consuming energy drinks.

The US energy drink market is valued at about $23billion, fueled largely by sales of Red Bull, Monster, and Celsius.

The potential problem with taurine mostly relates to how much of it a person consumes.

In small amounts, it is considered safe. However high levels have been shown to cause vomiting, upset stomach, dizziness, tiredness, diarrhea, and constipation.

Researchers from the University of Florida are embarking on a trial called ROSANNA, to test their hypothesis about the substance’s harms.

Introducing the trial at the American Society for Clinical Oncology (ASCO) conference in Chicago this week, the team said it believes taurine is the ‘primary energy source’ for a bacteria that is thought to fuel colon cancers.

The team is recruiting young Americans to consume either Red Bull or Celsius energy drinks every day to test this hypothesis.

The researchers expect a 20 to 30 percent increase in the bacteria – called H2S sulfide metabolizing bacteria – from participants drinking a Red Bull or Celsius every day.

However, this prediction is based on a small number of animal studies.

Research published by the NIH states that 500 to 3,000 milligrams of taurine a day is safe (0.5 to 3 grams), though the European Food Safety Authority suggests that 6,000 milligrams (6 grams) is safe.

Excess amounts could lead to vomiting, nausea, headache, and stomach pain, according to the Mayo Clinic.

In some cases, the amino acid has been shown to halt tumors from growing and spreading by as much as 44 percent.

In others, it has been shown to prevent protective T cells from fighting cancers, allowing the disease to become more aggressive.

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While the amino acid is not actually used to build proteins in the body, like other amino acids are, it has a range of roles, including regulating the amount of calcium in nerve cells and controlling inflammation, among other things.

Here are five of the most popular drinks containing taurine.

Red Bull

Red Bull is lauded as the most popular energy drink in the world, selling 12.1billion cans last year alone.

One of the two drinks studied by the ROSANNA trial researchers, one 8.4-ounce can contains 1,000 milligrams of taurine and 80 milligrams of caffeine – roughly the same as an eight-ounce cup of black coffee.

The regular variety contains 27 grams of natural sugar, though there are sugar-free varieties as well.

The brand states that one can, which costs around $2.50, also contains vitamins B6 and B12, which help red blood cells carry oxygen throughout the body and maintain nerve cells in the brain, among other functions.

One can contains one-third of the daily recommended limit of taurine.


Celsius has shot to popularity in recent years, with its revenue increasing from $75million in 2019 to $1.3billion in 2023. Research firm Circana found that it is now the third most popular energy drink in the US.

The brand’s Sparkling Peach Vibes flavor is the other drink being looked at in the ROSANNA trial.

Like Red Bull, Celsius contains 1,000 milligrams of taurine, though the can is slightly larger at 12 ounces.

Celsius contains no sugar and only 10 calories. However, one can has 200 milligrams of caffeine, the equivalent of two cups of coffee and half the FDA’s recommended daily limit of 400 milligrams.


Similar to Red Bull and Celsius, a can of Monster contains 1,000 milligrams of taurine.

However, this can is larger at 16 ounces.

Each can also contains 160 milligrams of caffeine, or roughly the same amount of one and a half cups of coffee.

In addition to having 230 calories, Monster has one of the highest amounts of added sugar at 54 grams.

This totals more than a McDonald’s Oreo McFlurry or five Krispy Kreme donuts.

The drink has been the subject of multiple lawsuits, including one involving the death of a 14-year-old girl who drank two cans of the beverage.

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Prime Energy

While taurine is on the ingredient list for PRIME Energy, the brand does not disclose how much is in each can.

PRIME was launched in 2022 by internet personalities Logan Paul and KSI, and despite quickly rocketing to success, it has been the subject of controversy.

Last year, Senate Majority Leader Chuck Schumer asked the FDA to investigate PRIME for being marketed to children despite an ‘eye-popping level of caffeine.’

Each 12-ounce can contains 200 milligrams of caffiene, though it also as just 10 calories and no sugar.

5-Hour Energy

This energy shot is the smallest of the list, but it packs a large taurine and caffeine punch.

Each 1.93-ounce shot contains roughly 480 milligrams of taurine, nearly half that of drinks more than four times its size.

It also has 230 milligrams of caffeine, more than larger sizes of Red Bull, Celsius, Monster, and PRIME.

The ingredient label also claims the shot has more than 20,000 percent the daily value of vitamin B12.

While rare, overdosing on vitamin B12 has been shown to cause headaches, dizziness, diarrhea, nausea, vomiting, and weakness.


One 16-ounce can of Rockstar energy contains 2,000 milligrams of taurine, twice that of other popular brands like Red Bull and Monster.

Each can also contains 270 calories 63 grams of added sugar, nearly that of a small Dairy Queen Blizzard.

The drink also claims to contain vitamins B2, B6, and B12.

In one 2015 study from the Mayo Clinic, volunteers who drank Rockstar on an empty stomach in five minutes or less saw their blood pressure go up by nearly seven percent.

Additionally, their heart rate increased by an average of 3.1 additional beats.

Starbucks Double Shot Energy

Starbucks Double Shot Energy coffee drink contains both coffee and 1,800 milligrams of taurine per 15-ounce can.

The drink also claims to be more energizing than the coffee, containing 225 milligrams of caffeine.

This is nearly three times the amount in a normal cup of coffee.

Each can also has 12 grams of added sugar, about the same amount as a Kripy Kreme donut.

The ingredient label also lists 20 percent of the daily recommended value of potassium, which is key for hear function, muscle contraction, and controlling blood pressuree.