A new company is selling Ketone drinks with a promise of boosting your exercises. However, the research is mixed and the little bottles aren’t cheap.

A San Francisco start-up is now bottling and selling what they call human “superfuel.”

Human-performance company HVMN (pronounced “human”) says their new drink can help you improve athletic performance, boost energy, and even enhance focus and concentration.

What’s in this clear, odorless liquid that comes in a petite, shot-sized bottle?

It has 120 calories, no fat, no protein, and no carbohydrates.

But it does contain what the company’s top executive believes is the “fourth macronutrient” — pure ketone ester.

“Ketones are used as highly-efficient fuel for the brain and body,” Geoff Woo, co-founder and chief executive officer of HVMN, told Healthline.

Woo says his company’s new drink, called Ketone, harnesses the power of ketones in a ready-to-consume fuel for humans.

Unlike today’s energy drinks and sports supplements, Woo says Ketone relies on the body’s own reserves for natural fuel and sustained energy.

Ketones deliver a performance boost that is “unlike anything we’ve ever seen before,” said Kieran Clarke, a professor of physiological biochemistry at Oxford University in the United Kingdom, in an interview with Business Insider.

Clarke and her colleagues study ketones. They’ve been working with Woo and HVMN to translate their findings into a consumable product.

The product isn’t cheap.

One of the 2.2-ounce bottles costs more than $30.

Ketones are compounds produced by your liver when your body is unable to use its preferred source of energy, carbohydrates.

Almost all foods contain carbohydrates. When you eat them, your body turns those carbohydrates into sugar, or glucose.

The glucose is an immediate and often readily available source of energy for your body.

However, if you rob your body of carbohydrates, your body will turn to stored fat for fuel and energy. As your body burns through its fat stores, a state called ketosis, it releases molecules called ketones.

Typically, you need to either eat a high-fat, low-carb diet (such as the ketogenic diet) or go without food for long periods of time (fasting or starvation) to reach ketosis naturally.

Woo and HVMN believe if you ingest ketones directly, you can reach the benefits of a keto diet without the extreme measures.

The primary fuel in HVMN’s Ketone drinks is 25 grams of beta-hydroxybutyrate (BHB).

BHB is produced naturally by the body during a fast or period of starvation.

“A common question is why BHB is the go-to ketone body for exogenous (originates from a source outside the body) ketone supplements,” Vanessa Rissetto, a registered dietitian/nutritionist who specializes in weight loss and weight management, told Healthline. “The likely reason is a combination of its efficient conversion into energy and its ease of formulation. In other words, it is easier to formulate BHB into a nutritional supplement, and the body efficiently converts BHB into acetoacetic acid, which effectively raises blood ketone levels.”

In a July 2016 study in the journal Cell Metabolism, Clarke gave an early version of HVMN’s Ketone to a group of elite cyclists.

She also gave separate carb-rich and fat-rich drinks to two other groups for a three-group comparison.

In the study, Clarke and colleagues tested the athletes with a 30-minute cycling exercise. The results showed that the cyclists who were given the ketone drink cycled an average of 400 meters (roughly a quarter of a mile) farther than the other two groups.

“It’s not like caffeine or anything. It’s not a stimulant,” Clarke told Business Insider. “If you’re not watching what you’re doing, you think, ‘Oh I’m doing alright, everything feels normal,’ but then you look down and all of a sudden you see, ‘Oh, wow, I’ve gone a lot further than usual.’ You’ll find on a rowing machine, for example, you’re going a lot faster and you don’t even realize it.”

However, a study published this year in Frontiers in Physiology, found that participants performed worse after drinking a ketone supplement. However, this study did not use the HVMN prototype.

The study participants — again, a group of pro cyclists — were given a ketone supplement drink before their performance exercise. The cyclists did reach ketosis, but their times were two percent slower than people who did not drink the ketone supplement.

Plus, all 10 of the participants felt some gastrointestinal discomfort (“nausea, reflux, and mild discomfort”) after consuming the drink. An eleventh cyclist was unable to perform the exercise due to vomiting and dizziness.

In a 2012 study, Clarke found that side effects of ketone esters include abdominal pain, diarrhea, nausea, and vomiting.

These side effects were more pronounced in people who had the highest doses of ketone supplements.

Still, most research suggests ketone supplements are well tolerated.

Plus, many energy drinks on the market today contain high doses of caffeine or stimulants that can produce negative health consequences.

While there are no long-term studies that examine the impact of the use of ketone esters, several studies have shown that intermittent fasting can be beneficial.

Fasting can induce a state of ketosis, which is comparable to using a ketone drink to release fat stores for energy.

In early studies, fasting has been shown to increase lifespan and reduce cancer risk. It may also increase weight loss.

Likewise, the majority of studies for ketone supplement drinks have been performed on elite athletes.

Trials and research with people of more average ability have not yet been performed.

Woo suggests these drinks are for people of all abilities.

“Our primary use case is for high-performance athletes, and the existing published data very robustly supports that use case,” Woo told Healthline. “But we think long term, this will be more considered a fourth macronutrient, so everyone in the world can benefit from adding ketones in their diet.”

If you’re curious about HVMN’s Ketone drinks, you can preorder a three-pack of bottles (2.2 ounces each) for $99 on their site.

The products are scheduled to ship early next year.

While ketone drinks and ketosis may be promoted as a way to get more energy, lose weight, or boost athletic performance, Rissetto says ketosis isn’t the gold standard.

“Everyone wants a gimmick when it comes to weight loss, and time and time again, I sing the song of a varied, balanced diet,” she says. “Just hard work will, in the end, get you the result you’re looking for.”