d-βHB was measured immediately on whole blood using a handheld monitor and enzyme-based reagent strips (Precision Xtra, Abbott Diabetes Care, UK). Samples were stored on ice, centrifuged and duplicate plasma aliquots stored at −80°C. All urine passed during the visit was collected, the total volume recorded, and 1 ml aliquots taken, frozen and retained for analysis.

In a keto-adapted individual where ketone metabolism is brisk with up to 100 grams or more being oxidized (i.e., ‘burned for energy’) daily, the small amount lost in breath and urine as acetone is minor. But because this breakdown occurs spontaneously without needing the help of enzymes, it also happens to AcAc in a stored beverage or food (even in an air-tight container), making the shelf-life of AcAc-containing products problematic. Thus all current ketone supplements consist of BOHB in some form rather than the naturally occurring mix of BOHB and AcAc produced by the liver.


Exogenous ketones have become a popular nutritional supplement since their introduction in 2014. Unfortunately there is a lot of inaccurate information and marketing you have to read through to find the truth about them. This article does the hard work for you. It gets right to the true benefits and drawbacks of exogenous ketones supported by research studies.
I simply use this to attempt to reduce the symptoms of the "keto-flu" when I'm entering ketosis after blowing my carbs out. The holidays are particularly bad for falling off the keto band-wagon. I've used this three times now to transition back into ketosis and I can report that it does seem to reduce the effects of the keto flu (headache, weakness) that I'd normally experience transitioning back into a low-carbohydrate diet. I typically take it for 3 days and then stop because by that time I'm in ketosis again, but I'd imagine you could take it longer.
Compared to our other cellular gasoline (carbs), we can store an unlimited supply of energy from ketones in our body within our fat. When you’re reliant on carbohydrates, you’re forced to keep your tank partly full as we can only store just over 2,000 calories of glycogen from carbs. An empty carb tank results in carb-withdrawal symptoms from not being able to switch into a ketone or fat burning metabolism.

There’s debate raging about which dietary tactic is the god particle for making you leaner, faster and healthier. How the ketogenic diet option squares off against the low carb route is vital for understanding the ways in which exogenous ketone supplements work. To get into ketosis the natural way, you need to keep your carb intake low enough for long enough for your body to begin using use fat as fuel. Your liver then converts a portion of that fat into energy molecules called ketones. These work together with glucose as a fuel source, but can actually kick in faster, allowing your body to operate more economically during lengthy, high-energy exercise efforts.
If you have already mastered the Very Low Carbohydrate (VLC) or ketogenic way of eating, and/or are eating at a caloric deficit, exercising or fasting you are naturally creating the optimal conditions for your body to produce ketones and put your body into nutritional ketosis. By strict adherence to a well-formulated ketogenic diet (complete with higher levels of mineral salts) you should be able to produce all the ketones you need naturally (endogenously). If you are new or inexperienced in ketogenic eating however; or if you or a family member struggles to adhere to a ketogenic diet, then supplementation with exogenous ketones may be very beneficial. Not only will ketone supplements help to mitigate hunger and carb cravings, but they will also help you stave off carb flu symptoms (see below), giving you the best possible chance of long-term success.
*These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure or prevent any disease. Information on this site is provided for informational purposes only, it is not meant to substitute medical advice provided by your physician or any other medical professional. You should not use the information contained on this site for diagnosing or treating a health problem, disease, or prescribing any medication. Please read product label before use. Best results are only achieved when combined with diet and exercise program. Results not typical for any or all claims.
I’m not sure whether I am leto-adapted but have been following the keto program for about 6 weeks. The scale and the eye confirm I have been burning fat. I’ve been using ketostix to keep track of ketones as I don’t prefer to prick my fingers to get blood measurements. I have reached my weight loss goal and planning to transition to maintenance in the next couple of weeks. I’m curious if exogenous ketones will be aid in maintaining my weight.
d-βHB was measured immediately on whole blood using a handheld monitor and enzyme-based reagent strips (Precision Xtra, Abbott Diabetes Care, UK). Samples were stored on ice, centrifuged and duplicate plasma aliquots stored at −80°C. All urine passed during the visit was collected, the total volume recorded, and 1 ml aliquots taken, frozen and retained for analysis.
Price: The supplements are expensive – very expensive. At the top end, if you follow Prüvit’s guidelines on “getting in the n8tive zone” (which is such a gimmicky marketing slogan it almost makes me cringe), you will require 2 servings of their Keto-OS product per day. This means around 60 servings per month, which will set you back a whopping $390 per month if you buy direct from their website! In the case of Prüvit, this is in part due to the multi-level marketing structure they operate under.

It might sound absolutely crazy to go that long without food. Especially when you consider traditional diets that recommend eating 3-5 small meals each day, starting with breakfast – the “most important” meal of the day. But if you think back to hunter gatherer times, human beings didn’t always have food accessible to us. Farming and agriculture hadn’t existed so our first meal each day would vary quite vastly. If you think about the word itself, ‘breakfast’ means to break-fast. We didn’t have a set time where we would consume our first meal – it was dependent on accessibility. So if you’re wondering how you’re going to survive without going for food for 16 hours, the answer is straight forward – you can! Let’s simplify this and break down what this may potentially look like.

I stumbled onto this trend before it even blew up, I have read just about every peer-review journal of the topic, I have trialed as well as tested different methods and keto products (exogenous ketones, MCT oils, pills, etc), and lastly, I have reported and analyzed my performance to share with you all. It hasn't been an easy task, but I have also seen the fruits of the labor, and the fruit is sweet.
To determine the reason for the differences in blood d-βHB concentration, the KE and KS drinks were analyzed for enantiomeric purity. The KE contained >99% of the d-isoform, whereas ~50% of the KS βHB was the l-isoform (Figure ​(Figure1D).1D). Plasma samples from participants who consumed the high dose KS drink (n = 5) were analyzed to reveal higher l-βHB than d-βHB, the total βHB Cmax being 3.4 ± 0.2 mM (Figure ​(Figure1E),1E), with a total βHB AUC of 549 ± 19 mmol.min. After 4 h, plasma l-βHB remained elevated at 1.9 ± 0.2 mM; differences in urinary excretion of the two isoforms could not explain this observation as both d- and l-βHB were excreted in proportion to their blood AUCs (Figure ​(Figure1F).1F). Therefore, in order to determine the time required for l-βHB elimination, a follow-up experiment was undertaken in which subjects (n = 5) consumed 3.2 mmol.kg−1 of βHB as KE and KS with hourly blood and breath sample collection up to 4 h, plus additional samples at 8 h and 24 h post-drink. l-βHB was found to be 1.1 ± 0.1 mM at 4 h, and 0.7 ± 0.2 mM after 8 h, but undetectable after 24 h (Figure 1G). Low amounts of d-βHB (0.3 ± 0.1 mM) were present at 24 h, presumably due to endogenous production. Both ketone drinks significantly increased breath acetone concentration, but at a slower rate than blood d-βHB, reaching a peak after 3 h that was twice as high following the KE (87 ± 9 ppm) than the KS (44 ± 10 ppm), suggesting that d-βHB was readily converted to acetone, but l-βHB was not (p < 0.005, Figure ​Figure1H1H).
Participants consumed 13.2 mmol.kg−1 of βHB (6.6 mmol.kg−1 or 1,161 mg/kg of KE) over 9 h, either as 3 drinks of 4.4 mmol.kg−1 of βHB at 3 h intervals (n = 12), or as an initial bolus of 4.4 mmol.kg−1 of βHB given through a nasogastric tube, followed by an infusion of 1.1 mmol.kg.h−1, beginning 60 min after the initial bolus, for 8 h (n = 4). Two participants completed both conditions (total n = 14). In both conditions, the KE was diluted to 1.5 L using the same citrus water as used in Study 2.
Two ground-breaking studies have recently been published on the effects of intermittent fasting on males. One group of researchers studied the effects that 16 hours of intermittent fasting had on males that lift weights. They found that muscle mass stayed the same, fat mass decreased significantly, and the males who fasted for 16 hours a day burned more fat for fuel compared to the control group that only fasted for 12 hours.
After a few days of fasting, or of drastically reduced carbohydrate consumption (below 50 g/day), glucose reserves become insufficient both for normal fat oxidation via the supply of oxaloacetate in the Krebs cycle (which gave origin to the phrase ‘fat burns in the flame of carbohydrate') and for the supply of glucose to the central nervous system (CNS).4
There’s some support that exogenous ketones can be helpful for people already dutifully following the keto diet — but research has been limited. One thing we know for sure: These aren’t a get-thin-quick solution. “I think people are drawn to a quick, easy fix, kind of a magic bullet supplement, and it’s not that this won’t contribute to weight loss, but it’s not that magic bullet,” Griffin says.
I’m not sure whether I am leto-adapted but have been following the keto program for about 6 weeks. The scale and the eye confirm I have been burning fat. I’ve been using ketostix to keep track of ketones as I don’t prefer to prick my fingers to get blood measurements. I have reached my weight loss goal and planning to transition to maintenance in the next couple of weeks. I’m curious if exogenous ketones will be aid in maintaining my weight.
Also, it’s important to remember that just because something may be SAFE (and to reiterate, I’m not saying a long term ketogenic diet is safe), it doesn’t mean it’s good for you or beneficial. Running Marathons could be considered safe (especially if it’s on a closed race circuit), but does this mean it’s good for you? Or should you be out running marathons every day?
Over the past couple years, I’ve tried a number of ketone supplements, generally to enhance a longer fast or to offer an edge before one of my Ultimate Frisbee evenings. This Kegenix variety is one I’d recommend. I’ve also used Quest Nutrition MCT oil powder with good results as well, but there are plenty of other solid formulations to choose from.

A typical serving of racemic ketone salts contains around 12g of beta hydroxybutyrate, of which only half is the D- form (6g). Compared to the 40g ketone esters I consumed (which are 100% D- form), I would need to consume somewhere around seven to nine packets of ketone salts to get the same amount of D-β-hydroxybutyrate (some D- form is wasted burning of the L- form), along with the huge amount of salts contained and more than a gallon of water (since the powders must be mixed). Even if one could consume that amount of ketone salts, they will probably suffer from what people often refer as “disaster pants” (aka diarrhea) due to the amount of salt consumed.


While ketone salts are widely available, unfortunately in the near-term ketone esters are in short supply and the only people who will be able to afford taking them several times per day will be elite athletes, the military, corporate CEO-types, and professional poker players. Even with economies of scale and ramping up production, the cost of raw materials to produce pure ketone esters will keep their price tag prohibitively high for most people, but could realistically get down to a few dollars per gram.
I also chatted to some Prüvit reps, who told me that it might be necessary to keep taking the supplements for a couple of months to start to see more elevated ketones. Well, the proof is in the pudding (or in this case, in the fluorescent-coloured, artificial-tasting pink drink). But I would hesitate before spending money on a two-month supply just to find out if that’s true. Real Ketones’ Kegenix Prime was associated with a decrease blood ketones. Not a good start, and we’ll get back to this point later.
MCT oil has recently been used to induce nutritional ketosis although it produces dose-dependent gastrointestinal (GI) side effects in humans that limit the potential for its use to significantly elevate ketones (>0.5 mM). Despite these limitations, Azzam and colleagues published a case report in which a 43-year-old-man had a significant decrease in seizure frequency after supplementing his diet with 4 tablespoons of MCT oil twice daily [96]. An attempt to increase his dosage to 5 tablespoons twice daily was halted by severe GI intolerance. Henderson et al. observed that 20 % of patients reported GI side effects with a 20 g dose of ketogenic agent AC-1202 in a double blind trial in mild to moderate Alzheimer’s patients [24]. We visually observed similar gastrointestinal side effects (loose stools) in the rats treated with MCT oil in our study. Rats were closely monitored to avoid dehydration, and gastric motility returned to normal between 12–24 h. Interestingly, the BMS + MCT supplement elevated βHB similarly to MCT oil alone, without causing the adverse gastrointestinal effects seen in MCT-supplemented rats. However, this could be due to the fact in a 10 g/kg dose of BMS + MCT, only 5 g/kg is MCT alone, which is less than the 10 g/kg dose that elicits the GI side effects. This suggests that this novel combination may provide a more useful therapeutic option than MCT oil alone, which is limited in its ability to elevate ketones in humans.
So if your high-fat diet includes a high amount of roasted seeds or roasted nuts, nut butters, heated oils such as heated coconut oil or heated extra virgin olive oil, barbecued meats or meats cooked at very high temperatures, then your triglyceride count is going to go up. You should have triglycerides that are less than 150mg/dL, and a triglyceride to HDL ratio that is no more than 4:1, and in most of the healthiest people I’ve worked with, triglycerides are under 100 and the triglyceride to HDL ratio is less than 2:1. If your ratio is whacked, your ketogenic diet isn’t doing you any favors.’
Satiety decreased in both cases, slightly less with the supplements than with the placebo: participants reported feeling less hungry after taking the supplements than after taking the placebo. However, we are doubtful whether this would be enough of a difference to impact food intake and therefore induce weight loss indirectly, compared to not taking a supplement at all. Especially since, as noted before, BHB switches off lipolysis.
Athletic performance benefits: The use of exogenous ketone supplements for bettering physical/athletic performance is promising for several reasons. Firstly, taking exogenous ketones (particularly BHB salts) induces acute nutritional ketosis for upwards of eight hours, mimicking fasting physiology (e.g. increases fat burning, insulin sensitivity, etc.).[3]
I stumbled onto this trend before it even blew up, I have read just about every peer-review journal of the topic, I have trialed as well as tested different methods and keto products (exogenous ketones, MCT oils, pills, etc), and lastly, I have reported and analyzed my performance to share with you all. It hasn't been an easy task, but I have also seen the fruits of the labor, and the fruit is sweet.
Plenty of supplements make you a fractionally better sportsman and these are no different. The synthetic exogenous ketones helped Olympic-caliber cyclists cover an average of 411 additional meters during a 30-minute time-trial, which resulted in a two percent increase in overall speed, found a paper in Cell Metabolism. That can be the difference between feeling the glorious tug of the winner’s ribbon across your chest or rolling in with the stragglers.
The body will start making ketones when either we go extended periods without food, or we restrict the one dietary component that stops ketone formation – this being carbohydrates and also minimising protein intake as this also can halt ketone. In turn, your primary source of food is fat, with very little carbohydrate and a small amount of protein.”
I (Kim) researched the topic and planned and ran the experiment under the guidance and supervision of Dr. Andreas Eenfeldt, who touched base with me every step of the way to check the experiment design and execution for scientific rigor (to the greatest degree possible) and who has edited this writeup for quality and trustworthiness reasons. I also consulted with other keto experts and researchers to gather feedback both on the experiment design and the results data. They are referenced in the text when this was the case.
Interestingly, poly-BOHB has recently been reported to have important roles in mammalian mitochondrial membranes, cell membrane calcium channels, and in exotic functions like protein folding (Dedkova 2014). It exists in a variety of chain lengths, ranging from short to very long. It is not clear if humans can digest and use poly-BOHB consumed in the diet, but in animals, poly-BOHB appears to have probiotic and bowel protective functions. This is a rapidly evolving topic that we will be watching closely.
The liver is always producing ketones to some small degree and they are always present in the bloodstream. Under normal dietary conditions, ketone concentrations are simply too low to be of any significant benefit. A ketogenic diet and exogenous ketone supplements will increase the amount of ketone in your body. The idea that  ketones are “toxic” is ridiculous. Ketones are a normal physiological substance that play many important roles in the human body.

It’s not clear that the Weir coefficients used to estimate EE are relevant for someone in ketosis, let alone someone ingesting exogenous BHB. (The Weir formula states that EE is approximated by 3.94 * VO2 + 1.11 * VCO2, where VO2 and VCO2 are measured in L/min; 3.94 and 1.11 are the Weir coefficients, and they are derived by tabulating the stoichiometry of lipid synthesis and oxidation of fat and glucose and calculating the amount of oxygen consumed and carbon dioxide generated.) While this doesn’t impact the main observation—less oxygen was consumed with higher ketones—it does impact the estimation of EE and substrate use.

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