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.
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.
The chart below shows my ketone and glucose response to consuming 40g of KetoneAid’s ketone esters, which had been calculated to be my optimal serving size based on my weight (170lbs) and type of activity (I am moderately active/athletic, but cognitive experiments are a “low” physical activity). Normally, for increased physical performance ketone esters are consumed along with some glucose, but since I was only focusing on cognitive performance I did not consume any glucose.
The CNS cannot use fat as an energy source; hence, it normally utilizes glucose. After 3–4 days without carbohydrate consumption the CNS is ‘forced' to find alternative energy sources, and as demonstrated by the classic experiments of Cahill and colleagues4 this alternative energy source is derived from the overproduction of acetyl coenzyme A (CoA). This condition seen in prolonged fasting, type 1 diabetes and high-fat/low-carbohydrate diets leads to the production of higher-than-normal levels of so-called ketone bodies (KBs), that is, acetoacetate, β-hydroxybutyric acid and acetone—a process called ketogenesis and which occurs principally in the mitochondrial matrix in the liver.6
Appetite suppression: Appetite was measured in 10 males and 5 females after consuming a ketone ester (KE) or a dextrose (DEXT) drink . Desire to eat and perception of hunger dropped after both drinks, but the KE was 50% more effective for 1.5-4hrs. Insulin levels rose for both drinks but were 3x less with the KE drink after 30mins (Fig 2). The hunger hormone, ghrelin, was significantly lower between 2 to 4 hours after drinking the KE (Fig 2). In conclusion Ketone esters delay the onset of hunger and lower the desire to eat. 8

Another source of the D-BOHB isomer is an evolutionarily ancient energy source for micro-organisms. Poly-BOHB is a long chain of D-BOHB molecules strung end-to-end. It functions in many single-cell organisms as a concentrated energy source similar to glycogen in mammals, but whereas glycogen breakdown releases individual glucose molecules, poly-BOHB hydrolysis releases single D-BOHB molecules.
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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