Your brain has a very tight barrier so not everything in the blood can get through. This is called the blood brain barrier. Because your brain uses 25% of the energy that your entire body uses throughout the day, you need to make sure it is fueled appropriately. Glucose can’t directly cross the blood brain barrier. When you eat carbs, you get swings in energy that is available to cross the blood brain barrier which leads to mental fog.
Over the years, we have seen and heard many different things about the effects and benefits of Raspberry Ketone supplements. Be it capsules or sprays, the discussion around them actually working always had opposing sides. So, we decided the best solution was to do our own research by conducting our own reviews on the most talked about products, to find out exactly how good they were as a "top-rated" ketone supplement.
The human studies aren’t quite there yet, but it seems likely that they’d help. A recent human case study found that ketone esters added to the regular diet improved Alzheimer’s symptoms. Animal studies indicate that adding exogenous ketones to a regular lab (read: not ketogenic) diet can reduce seizure activity and improve overall symptoms in epilepsy animal models, reverse early neuronal hyperactivity in Alzheimer’s animal models, and reduce anxiety in rats.
In fact this was one of the biggest surprises I had when exploring ketosis. For years I have been following a cyclical lower carb diet. For years I wouldn’t consume a carb until later in the afternoon (ala Carb Backloading style). After eating 5 days without any carbs I tested my ketone levels… they were 0.1 mmol. This reading was done first thing in the morning (10 hours fasted) after 5 days without a carb in my diet.
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.
KE was synthesized as previously described [29]. BMS is a novel agent (sodium/potassium- βHB mineral salt) supplied as a 50 % solution containing approximately 375 mg/g of pure βHB and 125 mg/g of sodium/potassium. Both KE and BMS were developed and synthesized in collaboration with Savind Inc. Pharmaceutical grade MCT oil (~65 % caprylic triglyceride; 45 % capric triglyceride) was purchased from Now Foods (Bloomingdale, IL). BMS was formulated in a 1:1 ratio with MCT at the University of South Florida (USF), yielding a final mixture of 25 % water, 25 % pure βHB mineral salt and 50 % MCT. BD was purchased from Sigma-Aldrich (Prod # B84785, Milwaukee, WI).
In a subset of participants (n = 7) the effect of 3.2−1 of βHB as KE and KS on blood pH and electrolytes after ketone drinks was investigated. Blood d-βHB kinetics were similar to those in the initial experiment (Figure ​(Figure3A).3A). After 60 min, blood pH declined from 7.41 to 7.31 following a KE drink (p < 0.001, Figure ​Figure3B).3B). Bicarbonate fell significantly from 23.6 ± 0.7 to 17.0 ± 0.8 mM following KE drinks (p < 0.001), but remained within the normal range (Figure 3C). Both ketone drinks significantly decreased blood potassium concentrations by 0.7 mM (both drinks p < 0.05, Figure 3D) and increased sodium and chloride concentrations (Sodium: both drinks p < 0.05, Chloride: KE = p < 0.05, KS = p < 0.005, Figures 3E,F).

Fortunately, you don’t need to be a dietary math savant to cash in on these rewards because the supplement eggheads took the liberty of creating exogenous ketones, which act as direct substitutes to the ones your body creates. Unlike other fat burners that give you the skits jitters, these are actually helping exercisers reach new personal bests while getting leaner, and are totally legal. Here’s what you need to know to get a slice of the action safely.

Concentrations of plasma non-esterified fatty acids, triacylglycerol, glucose, and insulin following equimolar ketone ester and ketone salt drinks, at two amounts, in subjects (n = 15) at rest. Values are means ± SEM. (A) Plasma FFA. (B) Plasma TG. (C) Plasma glucose. (D) Plasma insulin at baseline and after 30 and 60 min. EH, ketone ester high; EL, ketone ester low; SH, ketone salt high; SL, ketone salt low. *p < 0.05 difference from baseline value.

I’ve tried this, got a few bags of one ketone salts bound to mostly potassium and another one bound to calcium. As for working out, I find that consuming 15-20 grams of glucose ( dextrose ) 30 minutes before either a HIIT or a heavy lifting session gives me a much, much bigger boost than ketones. so they just sit in my cupboard. I also got spooked about the amount of potassium i’d consume in one go ( don’t particularly fancy a cardiac arrest ). I find it a bit useful when I have a big meeting or something else that requires super concentration and I’m fasting, other than that – it’s pretty useless. I’d probably use more of it if I could find a formula that’s mostly sodium/magnesium based rather than potassium and/or calcium.

One thing to remember here is that even if your calculated daily ‘keto approved’ protein allowance is (let’s say) 150g, that doesn’t mean you can eat 150g in one meal and still be in ketosis. You may find that you can’t eat more than 40g of protein at a time, otherwise you will drop out of ketosis. OR, you may find you can eat 50g of protein but you need a LOT of fat. Whereas a small serve of 15g of protein without fat might knock you out of ketosis. 
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?
Besides cutting carbs, it's important to increase your fat intake, and be moderate with protein. The fat you eat will keep you feeling energized and support ketone production. Protein is also important but if you go overboard with it, your body could enter into a process called gluconeogenesis. In gluconeogenesis, your body makes glucose from protein, and you want to avoid that.
We demonstrated that therapeutic ketosis could be induced without dietary (calorie or carbohydrate) restriction and that this acute elevation in blood ketones was significantly correlated with a reduction in blood glucose (Figs. 2, ​,33 and ​and4).4). The BMS ketone supplement did not significantly induce blood hyperketonemia or reduced glucose in the rats. The KE supplemented rats trended towards reduced glucose levels; however, the lower dose of this agent did not lower glucose significantly, as reported previously in acute response of mice [59]. MCTs have previously been shown to elicit a slight hypoglycemic effect by enhancing glucose utilization in both diabetic and non-diabetic patients [86–88]. Kashiwaya et al. demonstrated that both blood glucose and blood insulin decreased by approximately 50 % in rats fed a diet where 30 % of calories from starch were replaced with ketone esters for 14 days, suggesting that ketone supplementation increases insulin sensitivity or reduced hepatic glucose output [89]. This ketone-induced hypoglycemic effect has been previously reported in humans with IV infusions of ketone bodies [90, 91]. Recently, Mikkelsen et al. showed that a small increase in βHB concentration decreases glucose production by 14 % in post-absorptive health males [92]. However, this has not been previously reported with any of the oral exogenous ketone supplements we studied. Ketones are an efficient and sufficient energy substrate for the brain, and will therefore prevent side effects of hypoglycemia when blood levels are elevated and the patient is keto-adapted. This was most famously demonstrated by Owen et al. in 1967 wherein keto-adapted patients (starvation induced therapeutic ketosis) were given 20 IU of insulin. The blood glucose of fasted patients dropped to 1–2 mM, but they exhibited no hypoglycemic symptoms due to brain utilization of ketones for energy [93]. Therefore, ketones maintain brain metabolism and are neuroprotective during severe hypoglycemia. The rats in the MCT group had a correlation of blood ketone and glucose levels at week 4, whereas the combination of BMS + MCT produced a significant hypoglycemic correlation both at baseline and at week 4. No hypoglycemic symptoms were observed in the rats during this study. Insulin levels were not measured in this study; however, future ketone supplementation studies should measure the effects of exogenous ketones on insulin sensitivity with a glucose tolerance test. An increase in insulin sensitivity in combination with our observed hypoglycemic effect has potential therapy implications for glycemic control in T2D [40]. Furthermore, it should be noted that the KE metabolizes to both AcAc and βHB in 1:1 ratio [29]. The ketone monitor used in this study only measures βHB as levels of AcAc are more difficult to measure due to spontaneous decarboxylation to acetone; therefore, the total ketone levels (βHB + AcAc) measured were likely higher, specifically for the KE [14]. Interestingly, the 10 g/kg dose produced a delayed blood βHB peak for ketone supplements MCT and BMS + MCT. The higher dose of the ketogenic supplements elevated blood levels more substantially, and thus reached their maximum blood concentration later due to prolonged metabolic clearance. It must be noted that the dosage used in this study does not translate to human patients, since the metabolic physiology of rats is considerably higher. Future studies will be needed to determine optimal dosing for human patients.
The effects of ketone drinks on endogenous insulin secretion are unclear. Whilst the small increase in plasma insulin after KE and KS drinks may have been due to the small quantity of dextrose in the diluent, it has been proposed that ketones could potentiate or even stimulate insulin secretion. Isolated pancreatic islets secreted insulin when stimulated by ketones at glucose concentrations of >5 mM (Biden and Taylor, 1983), and small amounts of insulin are secreted in vivo following exposure to exogenous ketones in animals (Madison et al., 1964; Miles et al., 1981). In response to an intra-venous 10 mM glucose clamp, ketone ester drinks increased glucose uptake and plasma insulin (Holdsworth et al., 2017). The increases in insulin with ketone drinks taken whilst fasted were small compared to the increases seen when the ketone ester drink was consumed with a meal and with consumption of a dextrose drink. Furthermore, the lack of difference in peak plasma insulin between the two latter conditions indicates that nutritional ketosis did not inhibit or increase normal carbohydrate induced insulin production.
While we know that both MCT Oil Powders and BHB salts are proven supplements to increases ketosis, the winner of a top 5 exogenous ketones list I think should be a true direct form of exogenous ketones – one of the BHB salts. Perfect Keto’s BASE takes the win here. The edge ranking factor is its flavor. With stevia-based flavors such as chocolate sea salt, and the fact that it uses zero additives and actually tastes good, this BHB salt is going to have to take the W. They’re the only 100% coconut MCTs that don’t utilize the goMCT™ form.. this is neither a pro or con. And while it doesn’t have the best bang for your buck compared to the other BHB salts on this list, it’s the most proven as far as happy customer track record and consistent high-quality keto supplements.
A small side effect for some people is “ketosis breath”. Many people on a ketogenic diet have experienced this temporary phenomenon, and those taking exogenous ketones can experience it as well. The smell of your breath when you are early in the ketogenic diet can have a hint of acetone to it, and it might be mildly unpleasant, but it’s also harmless. Most gum is pretty low in carbohydrates and is a great option while your keto breath fades.
I feel like I should also mention that the GI discomfort is real, people. I would recommend starting this product on a weekend or a day where you’re able to just take it easy. After my first dose, which was only 1/2 scoop, I literally just felt like lying in bed all day due to feelings of nauseousness; however, by the next day I was fine and even bumped my dose to a full scoop.
I’m getting an increasing number of questions about exogenous ketones. Are they good? Do they work for performance? Is there a dose-response curve? If I’m fasting, can I consume them without “breaking” the fast? Am I in ketosis if my liver isn’t producing ketones, but my BOHB is 1.5 mmol/L after ingesting ketones? Can they “ramp-up” ketogenesis? Are they a “smart drug?” What happens if someone has high levels of both glucose and ketones? Are some products better than others? Salts vs esters? BHB vs AcAc? Can taking exogenous ketones reduce endogenous production on a ketogenic diet? What’s the difference between racemic mixtures, D-form, and L-form? What’s your experience with MCTs and C8?

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