With the increasing excitement and emerging scientific research surrounding keto, more and more people are trying out the high-fat, low-carb diet for body composition and exercise performance. Maybe you’re one of them!

While the health benefits are promising, you may have also found that maintaining a state of ketosis can be extremely difficult, especially with the Western diet’s love affair with carbohydrates.

If that’s the case, you may want to consider optimizing your keto diet. Supplements could be a great tool that can help you get into a deep state of ketosis faster than dieting and / or fasting alone.

he most widely-available keto supplements on the market are exogenous ketone salts, which are formed when ketones (energy-generating molecules derived from fatty acid breakdown) are bound to a mineral ion. Let’s assess some of the nuances around ketone salt supplements and other types of exogenous ketones to help you make the best decision for optimizing ketosis.

Ketones 101

Before launching right into ketosis, it’s important to understand the science behind ketones themselves.

Ketones are a fundamentally different fuel source than the carbohydrates, fat, and protein that our bodies typically rely on for energy. A highly efficient energy source, the body produces ketones when pushed to its limits – either during extreme carb restriction¹ or after heavy exercise.²

Achieving Ketosis

Ketosis is generally defined as elevated blood ketone levels greater than 0.5mM.¹ There are two types of blood ketones: endogenous and exogenous ketones. Both ultimately can get you into a state of ketosis, albeit through very different methods.

Endogenous ketones are produced by the liver, usually when someone is in a fasted state or on a ketogenic diet. The production of endogenous ketones can take weeks or months of strict dieting.¹ But there’s a payoff to that patience: your body ends up becoming fat-adapted; learning to use fat as fuel when carbohydrate intake is depleted. This process is sometimes referred to as nutritional ketosis.

Taking exogenous ketones can deliver a fast-acting, deep state of ketosis almost immediately.

Exogenous ketones are often consumed as a dietary supplement or through food consumption. They can put you in a state of ketosis,³ but the body isn’t “technically” ketogenic because the ketones were delivered from an external source (meaning, the body didn’t produce from fat them itself). Exogenous ketones don’t trigger natural ketone production, but they still lead to elevated blood ketone levels.

Different Types of Ketone Bodies

The three primary ketone bodies are beta hydroxybutyrate (BHB), acetone, and acetoacetate (AcAc). Most exogenous ketones products utilize BHB rather than AcAc because BHB is more stable and easier to make into a sellable product while acetone is considered to be a waste product of fatty acid breakdown.

Acetoacetate is created in the liver from the breakdown of fatty acids, and is then mostly converted into BHB for transport in the blood. Any AcAc in the blood can be either taken up into the cells or spontaneously broken down to produce acetone–which cannot be used for energy production. Acetone is removed from the body through waste product like urine, or through the breath.

BHB is the ketone body present in the blood at the highest level when produced naturally.⁴ This is because it doesn’t spontaneously degrade like AcAc .

Once taken up into the cells from the blood BHB offers the advantage of being reduced easier than AcAc. This means that when BHB is converted into AcAc inside the cell’s mitochondria, it generates NADH–a coenzyme needed for ATP production. AcAc whiffs on the energy-providing power of NADH. Plus, when an AcAc-based supplement is consumed, the body will reverse-convert some of to BHB, which actually uses up those NADH molecules.

Ketone salts typically come as a powder containing BHB bound to a mineral salt (usually either sodium, potassium, or calcium) or an amino acid (like lysine or arginine). These powdered BHB salts are commonly dissolved in liquid to be consumed in drink form.

Despite the lack of published work analyzing the effects on biomarkers or performance measures in humans, ketone salts are a growing market. It is important to note that the FDA doesn’t recognize ketone salts as GRAS (Generally Regarded as Safe) food ingredients.

Many studies have been conducted in rats^5,6,7 and have shown relatively low levels of BHB in the blood. Human studies showed similar results, with clinical trials reporting blood BHB levels of 0.6 – 1 mM after ketone salt drinks.^8,9,3

One recent study in young adults illustrated the differences between salts and esters (more on these later) acutely: ketone salts provided a peak D-BHB of 1 mM whereas the same amount of BHB in a ketone ester raised blood BHB levels to 2.8 mM.³

For performance, data has been mixed at best. Four studies investigated the effects of ketone salts in athletes (total n = 22) with none of the studies finding significant improvements in performance markers.^8,9,10,11 In one study, performance actually decreased by 7%, and GI distress (ranging from nausea to diarrhoea to vomiting) was reported in a high percentage of athletes.^10,12

While ketone salts are relatively inexpensive and may be a nice co-deliverer of other nutrients, BHB levels are only raised slightly–to 1 mM.^8,9 ,³ There are also some health concerns with consuming enough salt to raise BHB significantly.

Excessive salt consumption may have long-term health implications.

High salt intake is linked to hypertension, cardiovascular disease and even stomach cancer.¹³ The 2015 – 2020 Dietary Guidelines for Americans recommends 2,300mg of salt consumption a day; but most Americans consume 3,400mg daily. Some ketone salt products contain nearly 70% of the recommended daily allowance of sodium in a single serving.

A perceived benefit of ketone salt supplementation is a potential replacing of lost electrolytes. Electrolytes loss is a common problem in the early weeks of the keto diet. However, electrolyte imbalances usually don’t persist after keto-adaptation period of about 28 days,¹⁴ and so then excessive salt consumption may still be harmful.

Let’s review: ketone salts provide sub-optimal BHB, have no effect on performance and may cause significant GI issues. That could be why some makers of ketone salts have cited studies conducted on ketone esters.

So if not salts, then what other options do you have to increase ketones exogenously? Here are two, which have shown varying degrees of success.

MCT Oil

OK–you caught us. MCT oils don’t actually contain ketones. They’re medium-chain triglycerides (MCT) fat molecules made of glycerol joined to three medium-length fatty acid chains that are between 6-12 carbons in length.

So where do the ketones come from? Ketone generation results from the breakdown of MCTs by the body. They’re processed differently than long-chain fats, which are absorbed and released into the blood via the lymphatic system, bypassing the liver (where ketones are produced). Instead, MCTs are transported straight to the liver in the blood, where they’re either used directly for energy or turned into ketones.

MCTs exist naturally in some foods such as coconut oil and dairy products. But a high amount is required to increase blood BHB. Studies on MCT supplements report that blood ketone levels following MCT use were relatively low (0.5 – 1mM).¹⁵ However, the consumption of large amounts of MCTs can cause gastrointestinal side distress.^15,16 Additionally, people who are trying to loose weight should watch out for MCTs (specially if supplementing with MCT powders) as they are highly caloric.

While MCTs aren’t exactly exogenous ketones, they do provide a substrate by which one could potentially increase blood ketone levels.

Ketone Esters

Ketone esters are salt-free liquids that contain BHB without any extras. Instead of being bound to a mineral, like BHB salts, they’re bound to a ketone precursor (like butanediol or glycerol) via an ester bond. You can tell how many ester bonds there are from the name: monoester (one), diester (two), or triester (three).

They aren’t exactly a new discovery either. The first ketone ester was developed in the late 70s, and other types were developed in the mid-90s.^17,18

There are a couple types of ketone esters being developed and sold right now with each affecting the body differently.

An AcAc diester was developed at the University of South Florida. In rodents, it increased blood D-BHB to 1 – 4mM, and blood AcAC up to 5mM.¹⁹ Animal studies have also shown that it might help with seizures,¹⁹ weight loss,²⁰ and cancer.²¹ A published study in humans, however, identified a 2% decrease in a 31km cycling time trial performance. The lack of efficacy was potentially thought to be due to low levels of BHB (less than 2mM), the short high-intensity nature of the time trial, and / or the use of AcAc vs. BHB.^22,23

The D-BHB monoester raises blood ketones to exceptional well, roughly a 3 – 6 mM increase within 30 minutes of consumption.^3,24,25,26 This means you enter into a state of ketosis faster than other products currently on the market. It was developed over the course of 15+ years by DARPA, the NIH, and University of Oxford.

And it’s salt free so it won’t impact water retention or pose any of the health risks often associated with high salt levels. Side effects of the ester itself are also minimal. A single does of D-BHB mixed with a meal replacement formula reported very little gastrointestinal issues at typical doses and only caused mild symptoms when taken at 4x the recommended amount.²⁴

Ketone esters have proved beneficial for endurance performance also.^27,26 Athletes using ketone ester drinks before a workout reported no major side effects hindering performance. This is in contrast to ketone salts and the acetoacetate diester which have reported side effects (GI issues) that hampered performance.²³ There have been published clinical trials in humans demonstrating the efficacy of ketone ester drinks on improving performance, recovery and several health outcomes such as appetite control,³ blood glucose management²⁸ and even neurodegenerative disease.²⁹

And while list of benefits of BHB monoesters runs long, for now, taste is not on that list. We’ve heard it “tastes like it works,” which is a polite way of saying that the taste is distinct and strong. But for athletes, a single bitter sip is worth the performance benefits. Certain ketone esters have FDA GRAS (generally regarded as safe) status as a food, are cleared for use in athletes by the World Anti Doping Agency (WADA), and are batch tested as part of the NSF Safe for Sport program.

For performance and recovery, human studies on ketone esters have demonstrated extremely positive results.

When consumed before exercise, the D-BHB from helps muscle work 28% more efficiently than carbs alone. This means that the body does more work with the same amount of oxygen.³⁰ In a 30-minute time trial test in which cyclists consumed the D-BHB ester before exercise with carbohydrates, riders’ performance improved by 2-3% (400m).²⁶ When taken after exercise with glucose, the D-BHB ketone ester also improved the rate of resynthesis of glycogen as well as the rate of muscle protein synthesis.^27,31

There’s also some exciting research emerging around the cognitive benefits of ketone bodies (because ketones can cross the blood-brain barrier). The D-BHB ketone ester has been shown to help mice solve maze puzzles 38% faster than normal³² as well as shown to improve cognitive performance in a simulated soccer trail.¹⁰

Are Ketone Salts Right For You?

While deciding which exogenous ketone supplement is best for you depends on a number of factors, it ultimately lands on what goals you’re looking to achieve.

Ketone salts are less expensive than ketone esters, and do provide a mild boost in ketone levels. They have a milder taste that is easier to mask with artificial sweeteners, like stevia and other natural flavors. However, the science behind ketone salts is still lacking, with no clear evidence for weight loss, cognitive ability or improved performance. In fact, in some cases, performance decreased due to overwhelmingly negative side effects.

While the taste of some ketone esters leaves something to be desired, the data pointing to increased performance in human studies makes it worth while to investigate as a potential ergogenic aid.

If you’re an athlete or dieter considering an exogenous BHB supplement for physical performance or nutritional support, evidence-based results are best for helping highlight how exogenous ketones might affect you. Ultimately, you’re choice of supplement should be based on your budget and personal needs.

Have you used BHB salts? Have you tried esters? Let us know your experience in the comments.