Exogenous Ketone Supplements

Intro

Work on exogenous ketone supplements began in the early 2000's and have recently garnered a large amount of attention when their use was rumoured in the Tour de France by several professional cycling teams. Since then, there has been a lot of claims made about the benefits and use of these supplements (improved cognition/weight loss/clinical benefits) with very little published research to back them up, but this is now changing as more groups are applying for and gaining access to funding for projects. Their main purpose is to increase the levels of circulating ketones in the blood without being in a carbohydrate depleted state such as starvation or a ketogenic diet. Through the modulation of carbohydrate/fat/protein metabolism and intracellular signalling that they are theorised to improve athletic performance/recovery/adaptation.

Ketone bodies (KB) are short chain, four carbon organic acids and are now readily available in a number of commercial supplements. Beta-hydroxybutyrate (BHB) is the most abundant KB in the blood and the one used (for the most part) in these products. Supplementation of KB in their free acid form is both expensive and ineffective at producing nutritional ketosis, so they are combined with other molecules to improve absorption. 

Types of Ketone Supplements:

(i) Ketone Salts: The most common KB supplements available to the general public, which is simply a BHB molecule attached to a sodium/magnesium/pottasium/calcium salt. One typical serving of BHB salts delivers 12-13g of BHB and 1.5g sodium and has the ability to increase circulating KB to 0.5-1.0mM. They can be in either liquid or powder form and are considered equally as effective. 

Data from KetoSports KetoForce 

(ii) Ketone Esters: Primarily used in research, a BHB/AcAc molecule attached to an alcohol unit. There are two prominent ketone esters: the R,S-1,3-butanediol acetoacetate diester currently used in Dominic D'agostino's lab and the Veech (R)-3-hydroxybutyl (R)-3-hydroxybutyrate ketone monoester. Acute ingestion of either ester can result in short-term (0.5 to 6 h) nutritional ketosis indicated by BHB concentrations >1 mM. For the Veech ketone monoester, ingestion at a dose of 573 mg/kg body weight resulted in BHB concentrations of 3.0 mM after 10 min and rising to 3.0 mM 30 min after ingestion

From Cox et al. (2016) in Cell Metabolism

(iii) Added Ingredients: A lot of KB products you'll see contain extra ingredients such as MCT oils and amino acids. These ingredients are added to further enhance their ketogenic properties, with some being more efficacious than others. MCT oils may be worth adding in (make sure it's C8) for it's ability to stimulate ketogenesis in the liver as there is a linear relationship between dose of MCT ingested and blood BHB concentrations. Some amino acids (leucine, lycine) are ketogenic but their contribution to a ketogenesis is very small.

From Cunnane (2016) from Annals of the New York Academy of Sciences

Below is a list (click to visit spreadsheet) of the current exogenous ketone products available on the market 

Problems With Ketone Supplementation:

(i) Taste: There have been progress made in this area but people tend to find the supplements hard to swallow after repeat bouts.

(ii) Cost: More expensive than your average sport supplement with the ketone esters currently going in the thousands/litre.

(iii) Gastro-intestinal problems: Nausea/diarrhoea/vomiting etc. can occur when ingesting large volumes all at once. 

Key Points:

1. Research on KB supplementation and its applications is still in the early stages (both clinically and in sporting applications) so its use must be considered on a case by case basis (if at all until more research presents itself)

2. Consider the type of supplement you use as ketone esters are more efficacious at raising blood levels. Mixing ketone salts with other ingredients such as MCT oils may further enhance their ketogenic capacity. 

3. When first using products like these, titrate yourself on to them, as large doses can cause stomach problems. 

References

Abraham R. Ketones: controversial new energy drink could be next big thing in cycling. 2015. http://www.cyclingweekly.co.uk/news/latest-news/ketones-controversial-new-energy-drink-next-big-thing-cycling-151877

Clarke K, Tchabanenko K, Pawlosky R, Carter E, Todd King M, Musa-Veloso K, Ho M, Roberts A, Robertson J, Vanitallie TB & Veech RL (2012). Kinetics, safety and tolerability of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate in healthy adult subjects. Regul Toxicol Pharmacol 63, 401–408. 

Cox PJ, Kirk T, Ashmore T, Willerton K, Evans R, Smith A, Murray AJ, Stubbs B, West J, McLure SW, King MT, Dodd MS, Holloway C, Neubauer S, Drawer S, Veech RL, Griffin JL & Clarke K (2016). Nutritional ketosis alters fuel preference and thereby endurance performance in athletes. Cell Metab 24, 256–268. 

Cunnane SC, Courchesne-Loyer A, St-Pierre V, et al. Can ketones compensate for deteriorating brain glucose uptake during aging? Implications for the risk and treatment of Alzheimer’s disease. Ann N Y Acad Sci 2016; 1367: 12–20.

Evans, M., Cogan, K. E. and Egan, B. (2016), Metabolism of ketone bodies during exercise and training: physiological basis for exogenous supplementation. J Physiol. doi:10.1113/JP273185

https://ketosource.co.uk/exogenous-ketones-how-they-work/

Kesl SL, Poff AM, Ward NP, Fiorelli TN, Ari C, Van Putten AJ, Sherwood JW, Arnold P & D’Agostino DP (2016). Effects of exogenous ketone supplementation on blood ketone, glucose, triglyceride, and lipoprotein levels in Sprague-Dawley rats. Nutr Metab (Lond) 13, 9. 

Pinckaers PJ, Churchward-Venne TA, Bailey D & van Loon LJ (2016). Ketone bodies and exercise performance: the next magic bullet or merely hype? Sports Med. (in press; DOI: 10.1007/s40279-016-0577-y). 

Training Adaptations - Ketogenesis/Ketolysis

Endurance training causes a number of of adaptations in athletes, most of the attention has been placed on the enhanced delivery and utilisation of circulating carbohydrate and fat. Less is known about the adaptations relating to ketone body metabolism (ketogenesis - production and ketolysis - breakdown). 

The enzymes involved in ketogensis in the liver (BDH/ACAT/HMGCS) are unaltered as a result of athletic training and the overall activity of the pathway may even be lower. The activity of enzymes involved in ketolysis (BDH/OXCT/ACAT) are higher in skeletal muscle after 8-12 weeks of endurance training. When physiologically relevant amounts of BHB and AcAc (0.5mM and 1.0mM) are added to perfused muscle homogenates, their oxidation is increased by 2-3 fold. 

Ketogensis/Ketolysis pathways - Activity increased by endurance training indicated by +
From Evans et al (2016) - Journal of Physiology

While much of this work has been conducted in rats, it still has applications in a human model. The difference in trained and untrained humans being the rise in post exercise ketosis. We see attenuated ketosis in trained humans while untrained individuals experience an amplified level of ketosis up to 2.0mM i.e. acitivty of ketogenic pathway is lower and ketolysis is higher in trained individuals. 

From Walton (1972) - Journal of Experimental Physiology

Changes in ketolytic enzymes can also be detected in each muscle fibre type. Activity is highest in all enzymes in oxidative type 1 muscle fibres and lowest in type IIA and IIB fibres. 12 weeks of endurance training increased BDH activity in type 1 fibres threefold. OXCT and ACAT activity was increased by 26% and 40% respectively. These changes in ketolytic enzymes are localised to skeletal muscle and do not occur in the heart, kidney or brain. The transport of ketone bodies occurs via MCT1 transporters, a protein expressed highest in type 1 muscle fibres and is increased through exercise training. 

With this data in mind, increasing circulating ketone bodies through exogenous supplementation will likely benefit those who are aerobically trained with a high percentage of type I muscle fibres. These types of athletes usually compete endurance events such as long distance cycling and running. 

Next: Ketone Body Supplementation

References: 

Askew EW, Dohm GL & Huston RL (1975). Fatty acid and ketone body metabolism in the rat: response to diet and exercise. J Nutr 105, 1422–1432. 

Beattie MA & Winder WW (1984). Mechanism of training-induced attenuation of postexercise ketosis. Am J Physiol Regul Integr Comp Physiol 247, R780–R785. 

El Midaoui A, Chiasson JL, Tancrede G & Nadeau A (2006). Physical training reverses the increased activity of the hepatic ketone body synthesis pathway in chronically diabetic rats. Am J Physiol Endocrinol Metab 290, E207–E212. 

Johnson RH & Walton JL (1972). The effect of exercise upon acetoacetate metabolism in athletes and non-athletes. Q J Exp Physiol Cogn Med Sci 57, 73–79. 

Winder WW, Baldwin KM & Holloszy JO (1973). Exercise-induced adaptive increase in rate of oxidation of β-hydroxybutyrate by skeletal muscle. Proc Soc Exp Biol Med 143, 753–755. 

Winder WW, Baldwin KM & Holloszy JO (1974). Enzymes involved in ketone utilization in different types of muscle: adaptation to exercise. Eur J Biochem 47, 461–467.

Winder WW, Baldwin KM & Holloszy JO (1975). Exercise-induced increase in the capacity of rat skeletal muscle to oxidize ketones. Can J Physiol Pharmacol 53, 86–91 

Ketone Bodies and Exercise

Much of what we know about the relationship between ketone bodies and exercise comes from pioneering work that occurred in the 60's, 70's and 80's. These works involved infusion of labelled ketone bodies (BHB/AcAc) or fasting in humans to elevate plasma levels of ketone bodies. Mentioned work is relevant to when exercise begins during hyperketonemia. 

Ketone body disposal into skeletal muscle is elevated up to five-fold during exercise, this is seen as a sharp decrease in plasma concentrations of beta-hydroxybutyrate and an increase in the metabolic clearance rate of ketone bodies. This shows exercise increases the body's ability to extract and use ketones as a fuel for muscular work alongside intramuscular carbohydrate and fat liberated from adipose tissue. 

Under prolonged fasting as the degree of ketonemia increases, so does the reduction in plasma levels at the onset of exercise (Fig), reflecting a higher reliance as a fuel source. However, we also see a reduction in the rate of appearance (Ra), rate of disappearance (Rd) and metabolic clearance rate (MCR), suggesting that ketone body production, extraction and clearance is self limiting in skeletal muscle to preserve their use as a fuel source for the brain during times of energy crisis. This threshold is likely around 2.5mM. 

Although the inhibition of oxidation is also present under exogenous ketosis, the initial rise in MCR causes a decrease in ketone body levels, which again stimulates the MCR etc. creating a loop, which is not evident during fasting ketosis, a key difference between the two conditions. As a result of exogenous ketosis in the form of infusions, levels reached approx. 6.0mM and the contribution of ketone bodies to overall fuel provision in these studies has been estimated at 2% over a 2 hour exercise bout at 52% VO2max), an intensity where you would expect a high(er) reliance on fat based metabolism. 

Post Exercise Ketosis (PEK)

At the onset of exercise in the post prandial state, ketone body levels are very low. Under these conditions, the pattern is for levels to slowly rise during the exercise period and continue to do so during the post exercise period, where they can reach 2.0mM and be maintained several hours into recovery. This can be explained by an increase in the Ra and a decrease in MCR at cessation of exercise. However, this effect can be abolished through nutritional manipulation such as glucose or alanine feedings. 

The general findings are that untrained individuals experience a higher degree of PEK than endurance trained individuals. The reason for this may lie in adaptations that take involving the ketogenic and ketolytic pathways during athletic training. However, there are divergent findings due to research methodology.

The role of PEK is likely to favour the replenishment of muscle glycogen, which goes along with the classical role of ketone bodies to preserve carbohydrate stores during times of energy crisis. This may be advantageous to athletes who place a high importance on repletion of muscle glycogen during the recovery period. Ketone bodies also spare protein, reducing alanine release during starvation and leucine oxidation. This suggests hyperketonemia during the post exercise recovery period may play a role in promoting a 'holistic' recovery model by promoting a positive protein balance and prioritising glycogen re-synthesis. 

Next: Training Adaptations and Ketone Pathways

References:

Beattie MA & Winder WW (1984). Mechanism of training-induced attenuation of postexercise ketosis. Am J Physiol Regul Integr Comp Physiol 247, R780–R785.

Balasse EO & Fery F (1989). Ketone body production and disposal: effects of fasting, diabetes, and exercise. Diabetes Metab Rev 5, 247–270.

Fery F & Balasse EO (1983). Ketone body turnover during and after exercise in overnight-fasted and starved humans. Am J Physiol Endocrinol Metab 245, E318–E325.

Fery F & Balasse EO (1986). Response of ketone body metabolism to exercise during transition from postabsorptive to fasted state. Am J Physiol Endocrinol Metab 250, E495–E501. 

Johnson RH & Walton JL (1972). The effect of exercise upon acetoacetate metabolism in athletes and non-athletes. Q J Exp Physiol Cogn Med Sci 57, 73–79. 

Koeslag JH (1982). Post-exercise ketosis and the hormone response to exercise: a review. Med Sci Sports Exerc 14, 327–334.

Nair KS, Welle SL, Halliday D & Campbell RG (1988). Effect of beta-hydroxybutyrate on whole-body leucine kinetics and fractional mixed skeletal muscle protein synthesis in humans. J Clin Invest 82, 198–205. 

Sherwin RS, Hendler RG & Felig P (1975). Effect of ketone infusions on amino acid and nitrogen metabolism in man. J Clin Invest 55, 1382–1390. 

Ketone Bodies - The Basics

Ketone bodies are short chain, four-carbon organic acids, namely beta-hydroxybutyrate (BHB), acetoacetate (AcAc) and acetone. The primary physiological role of ketone bodies is to ensure survival of the brain (can't use fatty acids) during an energy crisis, as they provide 2/3's of the brains energy during prolonged starvation and 30-40% of total body energy demands after a 3-day fast. They also play a role in energy provision in skeletal muscle, as exercise increases the capacity of muscle to extract ketone bodies from the blood and athletic training enhances the capacity of an individual to use them as a fuel source. I will deal with BHB and AcAc because acetone plays a negligible role in energy provision. BHB is technically not a ketone body as the ketone moiety has been replaced with a hydroxyl (OH) group: 

From top to bottom: Acetone, AcAc, BHB

Ketone Body Formation (Ketogenesis)

Ketone bodies are produced in the mitochondria of the liver during situations characterised by low carbohydrate availability e.g. fasting, starvation and ketogenic diets (5% carbohydrate, 10-15% protein, 85% fat) or pathological conditions e.g. type 2 diabetes. Free fatty acids (FFA) liberated from adipose tissue are the primary substrate for ketone body production. Ketogenic amino acids e.g. leucine, lysine, isoleucine, tyrosine also contribute to ketogensis but play a minor role. Acetyl-CoA is formed after these FFA undergo b-oxidation and because oxaloacetate is being used in gluconeogensis, it is unable to condense and enter the citric acid cycle. Acetyl Co-A is shuttled into the ketogenic pathway as a result. After a series of reactions the first ketone body, AcAc, is formed and is reduced in a reversible reaction catalysed by 3-hydroxybutyrate dehydrogenase to form BHB, the most abundant ketone body in the blood. These ketone bodies are transported into circulation via the solute ligand carrier 16A family of monocarboxylate transporters (MCTs) that are present on mitochondrial and sarcolemmal membranes. 

Ketone Body Breakdown (Ketolysis) - Skeletal Muscle

Once the ketone bodies reach extra hepatic tissues e.g brain, skeletal muscle they will be broken down. They are again transported inside via the MCTs and BHB is reoxidised to AcAc, which undergoes further reactions to form two molecules of acetyl CoA. This can not occur in the liver because it lacks the enzyme succinyl-CoA:3-oxoacid CoA Transferase (OXCT). Once acetyl-CoA has been formed it enters the TCA cycle via citrate synthase and ends with production of ATP to fuel muscular work. 

The levels of ketone bodies in the blood is a balance between production and breakdown. Concentrations range from <0.1mM in the post prandial state to >10mM in patients with diabetic ketoacidosis. Hyperketonemia is defined as levels above >0.2mM. Levels can be increased through fasting, ketogenic diets and supplementation and can have a range of metabolic effects e.g. lowering glucose utilisation, anti-lipolytic effetcs and lowering proteolysis, all of which are involved in survival during an energy crisis by preserving precious fuel. 

Next: Ketone Bodies and Exercise

References:

https://en.wikipedia.org/wiki/Ketone_bodies

Evans, M., Cogan, K. E. and Egan, B. (2016), Metabolism of ketone bodies during exercise and training: physiological basis for exogenous supplementation. J Physiol. doi:10.1113/JP273185

Laffel L (1999). Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes. Diabetes Metab Res Rev 15, 412–426. 

Paoli A, Rubini A, Volek JS & Grimaldi KA (2013). Beyond weight loss: a review of the therapeutic uses of very- low-carbohydrate (ketogenic) diets. Eur J Clin Nutr 67, 789–796. 

Robinson AM & Williamson DH (1980). Physiological roles of ketone bodies as substrates and signals in mammalian tissues. Physiol Rev 60, 143–187.