An alternative to the ketogenic diet is consumption of drinks containing exogenous dietary ketones, such as ketone esters (KE) and ketone salts (KS). The metabolic effects of KS ingestion have been reported in rats (Ari et al., 2016; Kesl et al., 2016; Caminhotto et al., 2017), in three extremely ill pediatric patients (Plecko et al., 2002; Van Hove et al., 2003; Valayannopoulos et al., 2011) and in cyclists (O'Malley et al., 2017; Rodger et al., 2017). However, the concentrations of blood βHB reached were low (<1 mM) and a high amount of salt, consumed as sodium, potassium and/or calcium βHB, was required to achieve ketosis. Furthermore, dietary KS are often racemic mixtures of the two optical isoforms of βHB, d-βHB, and l-βHB, despite the metabolism of l-βHB being poorly understood (Webber and Edmond, 1977; Scofield et al., 1982; Lincoln et al., 1987; Desrochers et al., 1992). The pharmacokinetics and pharmacodynamics of KS ingestion in healthy humans at rest have not been reported.
The concentrations of blood d-βHB after KE drinks were highly repeatable whether consumed whilst fasted or fed (Figures 4F,G). The d-βHB Cmax values ranged from 1.3 to 3.5 mM when fed and 2.3 to 4.7 mM when fasted. There was no significant effect of visit order on d-βHB kinetics, with the maximal difference in d-βHB Cmax reached by one individual being 1.2 mM when fed and 1.9 mM when fasted. Approximately 61% of the variation in the data was attributable to feeding (fed vs. fasted), <1% to visit order, 16% to inter-participant variability, and the residual 24% variability due to non-specific random effects.
For the first part of my experiment, I would simply record my blood ketone and glucose levels over a period of two hours after taking the ketone esters. While I am already fairly keto-adapted and can attain nutritional ketosis fairly easily (> 0.5 mmol/L), it wasn’t until the end of my Five-day Fasting Mimicking Diet that I was even close to reaching therapeutic ketosis levels (>5.0 mmol/L).
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.

If you have been reading the science behind the ketogenic diet, you know there can be a lot of benefits associated with choosing this way of eating. There is usually a transition period from when someone chooses to go on a ketogenic diet and implements the changes to their menu to when they actually get into ketosis and are able to produce and burn ketones for fuel.

There is one viable explanation for consuming ketones. If you're in a calorie or carb-restricted state, then maybe during a workout it would make sense. But even then, that really only applies to endurance activities, since it has more to do with enhancing aerobic performance (where oxygen is required), than it does with enhancing high-intensity efforts (where it's not).
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Many of us avoid foods like processed meats and cheeses or salted nuts because of their high sodium content. However, processed carbohydrate sources can have equal or higher amounts of sodium per serving. An ounce of salted pretzels[3] has over four times as much sodium as an ounce of salted peanuts[4]. Just because we can’t taste the sodium doesn’t mean it isn’t in there. Flavors from other ingredients like sugar and spices can make it difficult to identify salt as a dominant flavor.
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Although decreases in FFA, TG and glucose occurred, there were no significant differences between the KE and KS drinks or with intake amount. Ingestion of ketone drinks significantly decreased overall mean plasma FFA from 0.7 to 0.4 mM, TG from 1.1 to 0.9 mM and glucose from 5.7 to 4.8 mM after 1 h (all p < 0.05). Concentrations were the same as at baseline by 4 h, with FFA at 0.6 mM, TG at 0.9 mM and glucose 5.1 mM (Figures 2A–C). There was a rise in insulin concentrations 30 min following all drinks, probably due to the small amount of carbohydrate in the sweetener (Figure ​(Figure2D2D).

There are several ways to approach the “intermittent” part of food restriction. One of the most common is limiting the window in which food is consumed to about eight hours a day. Another is fasting for a full 24 hours once a week, or once a month. Fasting beyond three days can be stressful on the body and should be done with medical advice and supervision.

The reason for testing after one hour was based on Prüvit’s “59-minute test”, which recommends testing ketones 45-60 minutes after taking the supplement (by the way, saying “59 minutes” instead of 60 minutes or 1 hour just sounds like another marketing gimmick to me). Kegenix Prime also promises “ketosis in 60 minutes” on its packaging. We carried out the testing at more or less the same time each day.

In conclusion, drinks containing exogenous ketones, in either ester or salt form, can raise concentrations of blood βHB in humans, although elevation of l-βHB lasts longer after racemic KS consumption. Both KE and KS drinks mildly altered acid-base balance. Exogenous ketones lowered blood glucose and lipids without inhibiting endogenous insulin secretion. The KE delivered highly repeatable blood concentrations of d-βHB, although ketosis was decreased by a meal. Uptake and elimination of d-βHB were similar when several drinks were consumed in succession. The dietary KE could maintain ketosis using drinks taken regularly around a normal meal pattern, or using a continuous infusion via a nasogastric tube. Therefore, ketone drinks are a viable and practical alternative to dietary strategies to achieve ketosis.
Increased calcium levels in the bloodstream may contribute to the hardening of arteries (atherosclerosis), which in turn can lead to a heart attack.  Calcium from supplements enters the bloodstream in one bolus, whereas we usually tend to get calcium from foods in small doses from the breakdown process. This might explain why calcium from food doesn’t create the same risk that is introduced by calcium supplements. At first glance, it seems to be the case that high calcium intake –at least from supplements–may not be ideal.

Ketogenic Diets and Physical Performance – Impaired physical performance is a common but not obligate result of a low carbohydrate diet. Lessons from traditional Inuit culture indicate that time for adaptation, optimized sodium and potassium nutriture, and constraint of protein to 15–25 % of daily energy expenditure allow unimpaired endurance performance despite nutritional ketosis. (

Full disclosure: after carrying out the background research, I was already, as you might imagine, feeling a little less neutral about these products. You may have noticed a hint of that in part 1 of the 2-part video series we made about the project (watch part 2 at the top of this page!). However, and although this was by no means a controlled scientific study under laboratory conditions, we designed the experiment in a very objective way. The aim was to give the supplements the best possible chance of showing the benefits they are claimed to have.

Hypoglycemia: why not to be concerned – Taking exogenous ketones can drive blood glucose levels quite low, but you are not likely to feel the typical symptoms of hypoglycemia. This is because when ketone levels are high enough, they dominate as fuel in the brain; hence, you will feel just fine despite having low blood glucose. A highly-cited study by George Cahill, found elevated ketone levels could protect fasted participants when they were administered insulin to induce hypoglycemia.
Effects of beta-hydroxybutyrate on cognition in memory-impaired adults. – Glucose is the brain’s principal energy substrate. In Alzheimer’s disease (AD), there appears to be a pathological decrease in the brain’s ability to use glucose. Neurobiological evidence suggests that ketone bodies are an effective alternative energy substrate for the brain. Elevation of plasma ketone body levels through an oral dose of medium chain triglycerides (MCTs) may improve cognitive functioning in older adults with memory disorders. On separate days, 20 subjects with AD or mild cognitive impairment consumed a drink containing emulsified MCTs or placebo. Significant increases in levels of the ketone body beta-hydroxybutyrate (beta-OHB) were observed 90 min after treatment (P=0.007) when cognitive tests were administered. beta-OHB elevations were moderated by apolipoprotein E (APOE) genotype (P=0.036). For 4+ subjects, beta-OHB levels continued to rise between the 90 and 120 min blood draws in the treatment condition, while the beta-OHB levels of 4- subjects held constant (P<0.009). On cognitive testing, MCT treatment facilitated performance on the Alzheimer’s Disease Assessment Scale-Cognitive Subscale (ADAS-cog) for 4- subjects, but not for 4+ subjects (P=0.04). Higher ketone values were associated with greater improvement in paragraph recall with MCT treatment relative to placebo across all subjects (P=0.02). Additional research is warranted to determine the therapeutic benefits of MCTs for patients with AD and how APOE-4 status may mediate beta-OHB efficacy. (

Do I still follow a ketogenic diet? Not anymore. I was strict keto for 12 weeks – enough time to experiment and learn about it. I did enjoy parts (lots of fat!) but I don’t see it as a sustainable way of eating, nor did I benefit from it health or sports performance wise (more on this in an upcoming article). But, I was following a strict keto diet – sans carbs. I think if I were to follow a ketogenic diet AND incorporate a regular carb refeed then the results may be different.
At day 29 of the study, animals were euthanized and brain, lungs, liver, kidneys, spleen and heart were harvested and weighed. Organ weights were normalized to body weight. Ketone supplementation did not significantly change brain, lung, kidney, or heart weights compared to controls (Fig. 5a, b, d, f). MCT supplemented animals had significantly larger livers compared to their body weight (p < 0.05) (Fig. 5c). Ketone supplements BMS + MCT, MCT and BD caused a significant reduction in spleen size (BMS + MCT p < 0.05, MCT p < 0.001, BD p < 0.05) (Fig. 5e). Rats administered KE gained significantly less weight over the entire study compared to controls. BMS + MCT, BMS, and BD supplemented rats gained significantly less weight than controls during weeks 2 – 4, and MCT animals gained less weight than controls at weeks 3 – 4 (Fig. 6). Increased gastric motility (increased bowel evacuation and changes to fecal consistency) was visually observed in rats supplemented with 10 g/kg MCT, most notably at the 8 and 12-h time points. All animals remained in healthy weight range for their age even though the rate of weight gain changed with ketone supplementation [53–54]. Food intake was not measured in this study. However, there was not a significant change in basal blood glucose or basal blood ketone levels over the 4 week study in any of the rats supplemented with ketones (Fig. 7).
When the results for the supplement and the placebo were within 0.2 (either % or mmol/L) of each other, we classed the supplement as neither “better” nor “worse” than the placebo. We gave a “winning brand” sticker to the brand that scored highest against the placebo for each marker, but not for physical performance, since none of the supplements performed better than the placebo for that marker.
Caveat emptor: the following post doesn’t come close to answering most of these questions. I only document my experience with BHB salts (and a non-commercial version at that), but say little to nothing about my experience with BHB esters or AcAc esters. But it will provide you will some context and understanding about what exogenous ketones are, and what they might do for athletic performance. We’ll likely podcast about the questions and topics above and cover other aspects of exogenous ketones in more detail.

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