Most supplements rely on BHB as the source of their exogenous ketone bodies. BHB is converted to acetoacetic acid with a small quantity converted to acetone through a acetoacetate decarboxylase waste pathway. Some of the acetoacetic acid will enter the energy pathway using beta-ketothialase, which converts acetoacetic acid to two Acetyl-CoA molecules (see diagram below2).

Now onto the best ketone supplements. All of these 5 are great products with good customer experiences and reviews. The list contains 3 MCT oil powders and 2 BHB salts. Since it’s just 5 products, there’s no room for bad quality. If you see a lower rating it may be due to price/value, the taste or perhaps a lack of third-party inspection certificates.
The ketone esters are, hands-down, the worst tasting compounds I have ever put in my body. The world’s worst scotch tastes like spring water compared to these things. The first time I tried 50 mL of BHB monoester, I failed to mix it with anything (Dom warned me, but I was too eager to try them to actually read his instructions). Strategic error. It tasted as I imagine jet fuel would taste. I thought I was going to go blind. I didn’t stop gagging for 10 minutes. (I did this before an early morning bike ride, and I was gagging so loudly in the kitchen that I woke up my wife, who was still sleeping in our bedroom.) The taste of the AcAc di-ester is at least masked by the fact that Dom was able to put it into capsules. But they are still categorically horrible. The salts are definitely better, but despite experimenting with them for months, I was unable to consistently ingest them without experiencing GI side-effects; often I was fine, but enough times I was not, which left me concluding that I still needed to work out the kinks. From my discussions with others using the BHB salts, it seems I have a particularly sensitive GI system.

The USDA guidelines recommend less than 2400 mg of sodium per day for healthy adults, and 1500 mg or less for individuals over the age of 50 or at risk for hypertension[2]. For reference, 2300 mg of sodium is the equivalent of about one teaspoon of salt.  Even though these recommendations are promoted by the American Heart Associated and other health-related organizations, recent research has claimed that there is simply not enough evidence to support these guidelines[5]. Worldwide 24-hour urinary sodium excretion data suggest that the normal range is actually 2500-5000 mg per day, which is what most of us consume daily[6]. Additionally, people with high activity levels or chronically low blood pressure may require more sodium than the average person.
Another important difference between endogenous and exogenous BOHB is that most synthetic BOHB used in dietary supplements is a mixture of the two ‘D’ and ‘L’ isomers, whereas endogenously produced BOHB consists of just the D-isomer. Metabolically, the two isomers are very different, and current published information indicates that most of the energy and signaling benefits of BOHB derive from the D-form. This is potentially problematic because the L-isomers are not metabolized via the same chemical pathways as the D-forms (Lincoln 1987, Stubbs 2017), and it remains unclear whether humans can convert the L-form to the D-form.
Beta-hydroxybutyrate (BHB) is a ketone body produced in the liver naturally under conditions when glucose isn’t very available. Other types of ketones produced via the restriction of dietary carbohydrates are acetoacetate and acetone. A VLCHF or ketogenic diet provides the optimal conditions for this process. Fasting, exercise and/or basic caloric restriction are all also methods for promoting ketogenesis (literally, the making of ketones).

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.
Exogenous ketones can lower appetite during a fast. After an overnight fast, normal weight human subjects either drank a ketone ester supplement or a calorie-matched glucose drink. Compared to the glucose drinkers, the ketone drinkers had lower insulin, lower ghrelin, greater satiety, and less hunger. This can be useful for people trying to extend their fast who don’t want to or can’t yet deal with the hunger. You’re still taking in energy, but the metabolic profile remains similar to that of a fasted person.
Let’s briefly discuss some organic chemistry. Two molecules that are “the same” but mirror images of each other (like your hands) are known as enantiomers, a type of spatial isomer. Beta hydroxybutyrate comes in two forms, D-β-hydroxybutyrate (“right-handed”) and L-β-hydroxybutyrate (“left-handed”). D-β-hydroxybutyrate is the form that is naturally produced in the body and is most bioavailable when taken exogenously.

The problem? Exogenous ketone supplements work by flooding your bloodstream with ketones. But unless you’re also eating a ketogenic diet (and producing a steady stream of ketones naturally), those supplemental ketones won’t stick around forever. “The benefit of exogenous ketones is limited due to their excretion through the urine,” explains Madge Barnes, MD, family medicine specialist with Texas Health Family Care. In other words? They’ll only work for a few hours until you pee them out. As a result, you need to keep on supplementing—which can get expensive. Twenty single-serving packets of Prüvit’s Keto//OS MAX Pure Therapeutic Ketones, for example, cost $130. (The company doesn’t specify how often you should take them.)
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. (
BHB supplementation can drastically enhance your insulin sensitivity, resulting in better shuttling of blood glucose into cells.[10] With type-2 diabetes and insulin resistance becoming growing concerns, BHB supplementation may provide a promising alternative for healthy blood glucose regulation in the coming years.Even for everyday gym goers and fitness enthusiasts, increasing insulin sensitivity via BHB supplementation can be a great benefit as this puts your body in a better position for partitioning nutrients/carbohydrates to energetically demanding, glycolytic tissues, such as skeletal muscle.
There are many top-rated exogenous ketone supplements, which is a great resource to help get your body to adapt faster and produce at a high-performance level, but you need to be careful how they can effect you and your energy levels and your general mood each day, so it’s important to check with your local physician and be safe about it. Remember that when you switch over to this diet, you must maintain high sodium levels during the process. It is recommended to add more 'keto salt' to your daily intake, starting off gradually and increasing it to as much as 500g a day. You need to add salt and electrolytes to your routine, because a person can lose levels through their urine, which causes your body to become more dehydrated and can leave you feeling a little sick and weak if you don't have the balance properly set up. Most exogenous ketone supplements we found have quite a bit of sodium in their ingredients, which helps you reach the level of salt intake you need each day. It is important to understand how this whole process works before even thinking about tackling it yourself. This is why you should consult with a professional to seek out advice and address any concerns that you may have before getting started.

Think about it like building muscle, good supplements can enhance your results, but if you don't eat right and exercise, supplements are just useless. You can't just sit on the couch to watch TV, eat potato chips all day and drink some supplements and expect to gain muscle. A supplement is not a miracle. It's just an addition and before you add it to your diet, you need to get the basics right first, which is dieting and exercise in the case of building muscles. The supplements are not going to lift the heavy weights for you. You do!

You may find a tiny amount here and there is ok (i.e., 2g of sugar with a meal full of fat may be ok).  But if you are starting out I would recommend cutting all sugar from your diet, and most importantly avoiding any sugar consumption on an empty stomach. For best results track your ketone levels before and after meals to see the impact the food has on your ketone levels.

Whereas ketone esters are 100% D- form, most ketone salts are a 50/50 mix of left and right-handed beta hydroxybutyrate, which is known as a racemic mixture. These beta hydroxybutyrate molecules are linked to a mineral, such sodium (Na), calcium (Ca), potassium (K), or magnesium (Mg). This kind of ketone supplement gets broken down to left and right-handed version of beta hydroxybutyrate along with the mineral.

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.
Improved cognition: Elevated plasma ketone concentrations divert the brain to utilize ketone bodies for synthesis of phospholipids, which drives growth and myelination. Normally, glucose would be the preferred substrate, which is much less efficient.14 BHB seems to act as a signal for neuronal pathways. These enhance synaptic plasticity, cognition and neuronal stress resistance. 15 In rat studies, ingestion of a ketone ester for 5 days improved their spatial learning and memory. 16.
For the ketone esters, on the other hand, repeated doses of 20-30 grams in any one day may be possible. Thus these products may be able to maintain a modest level of ketonemia without dietary carbohydrate restriction. Thus some of the cardiac and brain fueling benefits may follow, not to mention the epigenetic effects limiting oxidative stress and inflammation. But given the recent observation that administered ketone esters markedly reduce circulating free fatty acids (Myette-Cote 2018) — possibly due to an insulin-tropic effect or direct suppression of lipolysis (Taggart 2005) — their sustained use in people with underlying insulin resistance may compromise their long-term benefits by promoting weight gain unless combined with carbohydrate restriction.

You are probably wondering how there could possibly be a benefit to eating less frequently that goes beyond what you are already getting with a ketogenic diet. Restricting carbs and eating enough fat and protein does come with a plethora of health benefits, but when you add intermittent fasting to your lifestyle you can increase energy and reverse aging by harnessing the power of a nobel prize winning process.
Medium-chain-triglycerides are fats that are easily absorbed by the body and provide a number of really powerful health benefits. Fast energy, appetite control for better weight loss, increased ketone levels—you name it. They are also one of the most convenient and flexible, too. Add it to a shake, make a smoothie, or take a spoonful of it straight with some water for a quick, healthy keto boost that lasts all day. If you’re the kind of person that struggles to stick to a diet or eat a lot throughout the day, MCT oils are the perfect keto supplement.
Although most of the research has been done utilizing ketone esters, ketone salt supplementation has the potential to provide additional benefits through the extra electrolytes/nutrients that are required to make the ketones. While ketone esters are expensive due to the manufacturing process involved in making them, ketone salts might be a more convenient option for both inducing a state of ketosis and elevating blood ketone levels for various reasons we will discuss in another article.
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.
These studies were approved by external Research Ethics Committees (London Queen's Square: 14/LO/0288 and South West Frenchay: 15/SW/0244) and were conducted in accordance with the Declaration of Helsinki (2008). Studies took place at the University of Oxford between September 2014 and September 2016. Participants were healthy, aged 21–57, non-smokers and had no history of major illness. Female participants were using oral contraception to minimize the effects of menstrual phase on results. Participants provided written informed consent prior to inclusion, and completed a confidential medical screening questionnaire to determine eligibility. Anthropometric characteristics are shown in Table ​Table1.1. Sample sizes were chosen following an estimated power calculation based on the effect size in previous work using KE drinks (Clarke et al., 2012b; Shivva et al., 2016).
Neuroprotective benefits: A natural part of the aging process is neurodegeneration, which is largely responsible for cognitive defects like Alzheimer’s disease. Recent research suggests that exogenous ketone supplementation can drastically slow neurodegeneration and the resulting decrease in mental function.[7] However, the mechanism behind this finding remains to be elucidated; though, researchers suggest exogenous ketones act to reduce brain inflammation. Glucose, on the contrary, may actually accelerate inflammatory response in the brain.[8]
Blood, urine, plasma, and breath ketone concentrations following mole-matched ketone ester or isocaloric dextrose drinks in fed and fasted subjects (n = 16) at rest. Data from both of the two study visits in each condition (fed and fasted) completed by an individual are included in the analysis. Values are means ± SEM. (A) Blood d-βHB. (B) AUC of blood d-βHB. (C) Urine d-βHB excretion. (D) Plasma acetoacetate (AcAc). (E) Measured breath acetone (ppm = parts per million). (F,G) Mean d-βHB Cmax and difference between βHB Cmax over two visits when subjects separately consumed two ketone ester drinks in both the fed (F) and fasted (G) state. X axis = mean d-βHB Cmax of the 2 visits (mM), Y axis = difference between d-βHB Cmax in each visit. 95% confidence limits are shown as dotted lines. Significance denoted by: *p < 0.05 fed vs. fasted.
Once the body is able to generate energy with the help of exogenous ketones which are present in the bloodstream, it would start looking for other sources of ketones. This would encourage the body to tap into the vast reserve of fat which is accumulated in the body. Thus, the process of ketosis is accelerated when you consume extra exogenous ketones. This also leads to quicker weight loss and the body entering ketosis faster.
EK use can be compared to the nootropics that have been developed for optimizing focus, memory creation, and faster cognitive performance. While you may not notice this effect on a minute to minute basis if you keep a journal of “forgetful moments” you’ll find that you have fewer of them as time goes on. You’ll also find that you’re able to come up with better ideas, and your workflow is more efficient through the day (10, 11).
Exogenous Ketones have been shown in performance studies of both humans and animals to improve metabolic efficiency, which in essence means that your body is using better fuel that burns more efficiently over longer periods of time, and decreases the amount of fuel you need while performing. Where glucose fails (glycogen depletion), ketones pick up the slack!
Consuming exogenous ketones isn't the same as following a ketogenic diet–the ketones in the blood haven't been naturally produced by the breakdown of fat stores. However, scientists believe many of the health benefits of the keto diet and fasting (aside from weight loss) are triggered by ketones. Therefore, raising ketone levels through either endogenous or exogenous ketosis could help to improve health and performance by:
So long long does it take to get into ketosis? This transition could take anywhere from 48 hours to one week. The length in time will vary depending upon your activity level, lifestyle, body type and carbohydrate intake. There are several ways you can speed up this process, like intermittent fasting, drastically decreasing your carb intake and supplementation.
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.” 
In Summary, I think it’s important to do your own research and draw your own conclusion about the long term risks of ketosis. For some people, a ketogenic diet may be a necessity given their health situation. For those of us who do not suffer from such health conditions I would present the question ‘why do you want to follow a strict ketogenic diet for an extended period’, and then follow this up with ‘are the potential risks and sacrifices worth the benefits?’
It's also important to note that you probably should follow a low carb diet or ketosis diet when using this product. Your brain prefers glucose as fuel because it's easier for the body to metabolize from food, so if you are eating a standard American diet of 100g+ carbs per day, or excessive protein, this won't help you lose weight, even with exercise because you'll have more than enough glucose to power your brain. Carbohydrate restriction, moderate protein, and lots of good healthy fat is what puts your body into ketosis.
Fortunately a new way to test ketosis has been developed - and that is by measuring acetone levels in the breath. This is rather new technology but based on the reports I have seen it does look reasonably reliable. The testing process is simple, you use a device like that made by Ketonix, you breathe into it, wait a minute or so and it will give you a color indicating the state of ketosis you are in. However, there are numerous downsides:
Exogenous ketones are ketones that come in the form of a powder that you mix with water to drink them. Exogenous ketones are controversial in the keto world. The problem is the marketing of them have made some people believe that all they have to do is use this product to get into ketosis. If your blood glucose is too high your body will not use the ketones and they will go to waste.
The way you make an exogenous BHB is by attaching it to some type of other compound (sodium, potassium, calcium, or magnesium) so that your body can process the molecule by cleaving the bond between the salt and the beta hydroxybutyrate. BHB + bound to a salt = BHB salts, which is what most people in the ketosis community call exogenous ketones. There are also things called esters, which are basically unbound BHB molecules. These are really disgusting and cause massive digestive issues, so I like to ignore them until we can produce them in a more appealing way.
The best time to start a one day fast is in the evening (neither morning nor the night) – preferably, around 6 pm. It won’t make you lose your vital energy during the daytime workouts, nor does it let you sleep with undigested foodstuff in your stomach. Taking late meals and sleeping with undigested food doesn’t allow your body to rest. So the natural healing mechanism of your body fails during the sleep time as the entire resources are busy digesting your food.
The other potentially important distinction between nutritional ketosis and chemically-induced ketosis is the potential metabolic role played by liver AcAc production and redox status. Although the ratio of BOHB to AcAc in venous blood is typically 80% to 20%, classic studies by Cahill (1975) have observed important hepatic vein and peripheral arterio-venous gradients for this ratio in keto-adapted patients. What these observations imply is that the liver produces a higher proportion of AcAc than is found in the peripheral blood, and that this is due to uptake of AcAc in peripheral cells (principally muscle) with re-release as BOHB. In the process, the reduction of AcAc to BOHB produces NAD+, which is beneficial to mitochondrial redox state and mitochondrial function (Verdin 2015, Newman 2017).
The many roles of magnesium include helping us maintain normal nerve and muscle function, as well as heart rate, supporting a healthy immune system, regulating blood glucose levels, and making energy production and protein synthesis possible[23]. Magnesium is also involved in both aerobic and anaerobic energy production. ATP synthesis (the body’s energy source) depends on enzymes that are activated by magnesium.

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.

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