The blood levels of BOHB that can be achieved with the salts or ester formulations are in the 1-3 mM range, similar to what can be achieved with a well-formulated ketogenic diet in insulin sensitive humans, but well below levels achieved after a 4-7 days of total fasting (Owen 1969). In more insulin resistant humans, the ester formulation may deliver higher blood levels than a sustainable diet (as opposed to short term fasting). For example, in the Virta IUH Study of over 200 patients with type 2 diabetes, blood ketone mean levels were 0.6 mM at 10 weeks and 0.4 mM after 1 year.
Getting into a state of ketosis normally involves eating a ketogenic diet consisting of around 80 percent fat, 15 percent protein, and 5 percent carbs. Over time, the body transitions from burning carbs for fuel to burning ketones—an alternative fuel source that the liver makes by breaking down fat, explains keto diet expert Amy Davis, RD, LDN. Since advocates say that ketosis can help you lose weight fast, think more clearly, and feel more energized, it’s tempting to try.

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.

You may wonder why we are emphasizing on using these specific oils. Well, this is because the extra virgin oil is an unprocessed form, and contains lauric acid that is antimicrobial in nature and is good for brain health. (This is the same lauric acid that is naturally found in breast milk as well.) Its antibacterial property also indirectly supports the growth of Candida that keep your gut healthy.
Administration of ketone supplementation significantly reduced blood glucose over the course of the study (Fig. 3a, b). MCT (5 g/kg) decreased blood glucose compared to control within 30 min which was sustained for 8 h at baseline and at week 1. MCT (10 g/kg) likewise decreased blood glucose within 30 min and lasted through the 12 h time point during weeks 2, 3, and 4. BMS + MCT (5 g/kg) lowered blood glucose compared to control from hours 1–8 only at week 1. BMS + MCT (10 g/kg) lowered blood glucose compared to control within 30 min and remained low through the 12 h time point at weeks 2, 3, and 4. Rats supplemented with BMS had lower blood glucose compared to control at 12 h in week 4 (10) (Fig. 3a). Administration of BD did not significantly change blood glucose levels at any time point during the 4-week study. KE (5 g/kg) significantly lowered blood glucose levels at 30 min for week 1, 2, 3, and 4 and was sustained through 1 h at weeks 2–4 and sustained to 4 h at week 3. (Fig. 3b).
A common question is why BHB is the go-to ketone body for exogenous ketone supplements. The likely reason is a combination of its efficient conversion into energy and its ease of formulation. In other words, that it is easier to formulate BHB into a nutritional supplement. And the body efficiently converts BHB to acetoacetic acid, which effectively raises blood ketone levels.
If you’re wondering how to get into ketosis in 24 hours, and whether it’s even possible with such a short turnaround time, then combining a keto diet with intermittent fasting is a must. I am a massive advocate of not only the ketogenic diet but also the practice of daily fasting – I swear by it! It’s not for everyone as it does require a lot of discipline to pull off. But if you can commit to it, the benefits in my opinion are well worth it. So you may be wondering what intermittent fasting is? Well, it’s the practice of performing a daily fast from food and (caloric) drinks for at least 16 hours of the day.
The final graph, below, shows the continuous data for only VO2 side-by-side for the 20 minute period. The upper (blue) line represents oxygen consumption under control conditions, while the lower line (red) represents oxygen consumption following the BHB ingestion. In theory, given that the same load was being overcome, and the same amount of mechanical work was being done, these lines should be identical.
But there have also been studies done showing that the Inuit Eskimo’s do not actually reach a state of ketosis. This is due to numerous factors. One being that the diet the eskimo’s eat ‘would not be expected to cause ketosis, because the calculated anti-ketogenic effect of the large protein ingestion was somewhat more than enough to offset the ketogenic effect of fat plus protein.” 
Some think so because higher ketone levels imply increased fuel for the brain and heart (that prefer ketones), and increased protection against inflammation and oxidation. But are the health benefits coming from the ketones themselves, or are they coming from the state you have to put your body in to actually produce them? And if you're kicking yourself out of ketosis by ingesting ketones would you still get the same benefits?
This research is a good reminder to discuss with your doctor before taking any supplements. Given the widespread use of calcium supplements, more research is required before any final conclusions can be drawn. Several ketone companies have tried to avoid the large sodium loads but instead relied on a bump in the calcium content from the BHB ketone salts, seemingly without consideration for the aforementioned results. Calcium BHB will likely absorb slower compared to sodium BHB due to digestion and absorption kinetics.  For those looking to optimize brain uptake of ketones, this probably isn’t the best strategy (as uptake is directly proportional to the levels in the blood).   Be cautious of supplements running from the sodium and chasing the calcium BHB instead, and make sure you factor that into your overall daily needs.
Other studies have found that fasting was as effective as chemotherapeutic agents in delaying progression of different tumors and increased the effectiveness of chemotherapeutic drugs against melanoma, glioma, and breast cancer cells. Although this research may not apply to your life, it does suggest that intermittent fasting can help support your body in times of toxic stress.
We’ve all been taught that high sodium intake is bad for us, similar to how we’ve been told for decades that fat is the driver of coronary heart disease, and consuming large amounts will kill us.  Sodium has been thought to increase blood pressure, and therefore increase the risk of heart disease, kidney disease, stroke, osteoporosis, and stomach cancer. Thus, many of us tend to avoid consuming foods or supplements with labels that have high amounts of sodium.
All data are presented as the mean ± standard deviation (SD). Data analysis was performed using GraphPad PRISM™ version 6.0a and IBM SPSS Statistics 22.0. Results were considered significant when p < 0.05. Triglyceride and lipoprotein profile data were analyzed using One-Way ANOVA. Blood ketone and blood glucose were compared to control at the applicable time points using a Two-Way ANOVA. Correlation between blood βHB and glucose levels in ketone supplemented rats was compared to controls using ANCOVA analysis. Organ and body weights were analyzed using One-Way ANOVA. Basal blood ketone and blood glucose levels were analyzed using Two-Way ANOVA. All mean comparisons were carried out using Tukey’s multiple comparisons post-hoc test.
Taking exogenous ketones not only eliminates the need to follow a strict ketogenic diet to achieve ketosis (so you can have your high carb cake and eat it too), it can also help users get there faster. “They can expedite the process of getting into ketosis and becoming fat adapted,” Davis explains. “They can also help people push past the keto flu and potentially experience more mental energy and clarity than from diet alone.”

For all studies, the area under the curve (AUC) of blood [βHB] was calculated using the trapezium rule. In Study 3, for each of the three drinks, the initial rate of d-βHB appearance was estimated using d-βHB concentrations at baseline and 30 min post-drink, and d-βHB elimination was estimated using the AUC between the post-drink peak (60 min) and trough (180 min) d-βHB concentrations, with a baseline correction to the value at 180 min.
Our bodies are produce three types of ketone bodies for fuel: beta-hydroxybutyrate (BHB), acetoacetate (AcAc), and acetone. Each is used by the body differently. Acetone is the least abundant, produced in much smaller amounts, and is usually exhaled through the lungs rather than being used as fuel.3 Acetoacetate is part of the metabolic pathway whereby humans make and use ketones, but it tends to be found in the blood at lower levels than BHB.
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).
This was a big surprise. We were at the very least expecting that drinking a ketone supplement would cause blood ketones to rise, but an average increase of 0.33 mmol/L is very small. The supplement associated with the highest average increase in blood ketones was Prüvit’s Keto-OS Max, but it was only an increase of 0.6 mmol/L. Brianna Stubbs, the ketone researcher I consulted with, agrees that an increase of below 2.0-3.0 mmol/L is unlikely to be of much use.
Even though endurance athletes can train in a carb depleted state, they will generally consume carbohydrates in the lead up to a race (the athlete is seeking to increase the ability to run off fats by training in a carb depleted state, then benefiting from both fats AND carbs come race day). Likewise, with the brain, even though the brain can function off ketones, does it mean it’s the best state for brain function?
Exogenous ketones are also for those just looking to try it out. It lets anyone be able to access ketones simply by consuming these exogenous forms of ketones. Technically, MCTs are not an exogenous ketone such as BHB salts. They’re not ketones. But they readily convert into ketones. So MCT oils and powders are a great source of endogenous ketones. The end result is similar, and thus this top 5 list includes MCT oil powders as well as BHB salts.
Increased levels of BHB in the body were found to be associated with greater cognitive performance through better performance in memory recall tests12 on a study of 20 subjects with Alzheimer’s disease or demonstration of a mild cognitive deficit. Similarly, BHB ketone esters helped to reverse symptoms of Alzheimer's Disease in one clinical case study.13 More research in humans is needed, but the various hypotheses are backed up by strong animal data.

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