Its usually smart to avoid foods that have long, complicated words on their ingredient labels that make you scratch your head. If the ingredients sound like someone made them up, chances are they didin a chemistry lab. So its not surprising that health professionals have warned against energy drink consumption pretty much since they became popular. Reading the words on a can, you start to wonder: Does anyone really know whats in this?

The answer is yes, and also not really. We know caffeine and sugar, both of which are plentiful in energy drinks. The other ingredients, though, arent quite as ubiquitous in our daily dietsunless you frequent GNC. When it comes to safety, health experts are weary about both the amount of caffeine packed into a single can, and how all the substances may interact.

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Energy drinks caffeine content varies a lot, Sheri Zidenberg-Cherr, Ph.D., a nutrition specialist in the UC Davis department of nutrition, told SELF.

Theyre considered supplements and not a food product, so labeling requirements are quite lax, and the ones that do label caffeine content may not make it very legible. When it comes to the other, more unknown ingredients, Zidenberg-Cherr explained that even if one substance is proven safe on its own, that may change when its combined with other things.

The problem with these drinks is there are a lot of ingredients being added to them, some that have been used before in this way and others that have not, and its the mixture thats the concern, Zidenberg-Cherr said.

So whats even in that mixture? Here are some of the most common energy drink ingredients, and where they rate on usefulness and safety.

1. Ginseng

Used most commonly in Chinese medicine, ginseng is an herb that been used traditionally to treat numerous ailments. Its generally thought to boost immunity and improve overall healthyouve probably seen it added to green tea and other herbal remedies. Research doesnt conclusively back up these claims, but short-term use is thought to be safe. The concern, though, is that it may compound caffeines impact and increase side effects like increased heart rate, Zidenberg-Cherr said.

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2. Taurine

This is an amino acid that we find in protein, meat, fish, breast milk, Zidenberg-Cherr explains. It helps us maintain neurological function and regulate fluid levels. There are some claims that taking a taurine supplement can improve athletic performance, but not a lot of data exists on its efficacy or its safety as either a supplement or energy drink ingredient.

The concern has been that when its mixed with high amounts of caffeine, there could be effects on the heart, Zidenberg-Cherr said.

One 2014 review found that taurine seems to counteract some of caffeines cardiovascular effects rather than compound them.

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3. Guarana

Guarana is an herb thats often used as a stimulant in teas, either added or naturally occuring. Its major component is caffeine.

It has been associated with increased energy and enhancement of physical performance, Zidenberg-Cherr said.

Its generally recognized as safe (GRAS), but Zidenberg-Cherr notes that no one really knows if its still just as safe when compounded with other high-caffeine ingredients.

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4. Ginko biloba

This is another herb, added to supposedly increase alertness.

Theres been a lot of studies looking at it in terms of mental function and mental alertness, Zidenberg-Cherr said. But there is not very consistent information on it.

Its been used medicinally for thousands of years, according to the Mayo Clinic, and research supports its use for some medical conditions including dementia, anxiety, and schizophrenia. For other uses, evidence is lacking or mixed.

It might also depend on what other medications someone is taking, Zidenberg-Cherr added.

Oftentimes, we view herbal ingredients as safe because theyre natural, but if youre taking other medications, they could interact with some of these herbs.

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5. Carnitine

Our bodies naturally produce carnitine, a substance thats used to turn fat into energy. You can also buy it as a supplement, and it claims to boost exercise performance.

Theres not much data to encourage its use, Zidenberg-Cherr said. Theres no evidence that taking it is going to alter anything, and theres not a lot of information on its safety as a supplement.

Some studies suggest carnitine may be promising in treating various health problems, like certain heart conditions, kidney disease, and hyperthyroidism, but in all cases, more research needs to be done and supplements should not be taken without a doctors supervision.

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6. Green coffee extract

You may have heard of green coffee bean pills from that lawsuit the FTC won against a company selling them as a magical weight loss drug, with completely falsified research to back up their claims. Dr. Oz got some pretty hefty backlash, too, after promoting the bogus pills as a secret weight-loss weapon. Zidenberg-Cherr said green coffee extract, which is often listed in energy drinks and especially those claiming to be all-natural, is just another form of caffeine.

People look at it thinking its natural so its better, Zidenberg-Cherr said, but all caffeine works the same way in your body. And no, its not the magic weight-loss wonder our society has been searching for.