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.)
Measurements taken included whole blood glucose and BHB (every 5 minutes); VO2 and VCO2 (every 15 seconds); HR (continuous); RQ is calculated as the ratio of VO2 and VCO2. In the video of this post I explain what VO2, VCO2, and RQ tell us about energy expenditure and substrate use—very quickly, RQ typically varies between about 0.7 and 1.0—the closer RQ is to 0.7, the more fat is being oxidized; the reverse is true as RQ approaches 1.0
Exogenous ketones provide the body with another fuel to employ. Think about it like an electric car that runs on both gas and electricity: by consuming ketones along with carbohydrates, the body will preferentially burn the ketones first, saving the carbohydrates for later. Exogenous ketones allow us to enter a metabolic state that wouldn't occur naturally: the state of having full carbohydrate stores, as well as elevated ketones in the blood. This could be advantageous to athletes looking to boost their physical performance.
Next, BHB salts are the only supplement that elevates BHB levels while muscle glycogen remains at capacity (low muscle glycogen can drastically impede long-duration athletic performance). In short, athletes who consume carb-based diets, and those on low-carb diets, stand to benefit from exogenous ketone supplements taken prior to training/exercise.
d-βHB was measured immediately on whole blood using a handheld monitor and enzyme-based reagent strips (Precision Xtra, Abbott Diabetes Care, UK). Samples were stored on ice, centrifuged and duplicate plasma aliquots stored at −80°C. All urine passed during the visit was collected, the total volume recorded, and 1 ml aliquots taken, frozen and retained for analysis.
We will go deep in the science behind this fascinating diet and then review some of the best exogenous ketone supplements out there in the market. Because without the knowledge and the right information about exogenous ketones that you can properly follow, you might never reach your goals and you may as well keep eating that mashed potato for dinner and club sandwich for lunch.
At baseline, 4 h after intragastric gavage, the elevation of blood ketones was inversely related to the reduction of blood glucose compared to controls following the administration of MCT (5 g/kg) (p = 0.008) and BMS + MCT (5 g/kg) (p = 0.039) . There was no significant correlation between blood ketone levels and blood glucose levels compared to controls for any other ketone supplemented group at baseline (Fig. 4a). At week 4, 4 h after intragastric gavage, there was a significant correlation between blood ketone levels and blood glucose levels compared to controls in MCT (10 g/kg) and BMS + MCT (10 g/kg) (p < 0.0001, p < 0.0001) (Fig. 4b).
As stated above, there appears to be a difference between supplemental and dietary calcium intake, which can be important to keep in mind. One study found aggregate calcium intakes above 1400 mg per day (from dietary and supplemental intake combined) to be associated with higher death rates, cardiovascular disease, and ischemic heart disease in women. A 2014 meta-analysis found an association between dietary calcium intake and cardiovascular mortality. The meta-analysis actually found a u-shaped relationship, where dietary calcium intakes that were both lower and greater than 800 mg/day were gradually associated with increased risk of cardiovascular mortality.
Over five visits, participants (n = 16) consumed either 4.4 mmol.kg−1 of βHB (2.2 mmol.kg−1 or 395 mg/kg of KE; 1 mole of KE delivered 2 moles of d-βHB equivalents): twice whilst fasted, and twice following a standardized meal, or an isocaloric dextrose drink without a meal. To improve palatability, drinks were diluted to 500 ml with a commercially available, citrus flavored drink containing 65 kCal (5 g of carbohydrate) (Glaceau, UK). The dextrose drink was taste-matched using a bitterness additive (Symrise, Holzminden, Germany). The standard meal consisted of porridge oats (54 g), semi-skimmed milk (360 ml) and banana (120 g), giving 600 kCal per person, with a macronutrient ratio of Carbohydrate: Protein: Fat of 2:1:1.
It was explained to me that exogenous ketones inhibit lipolysis (breaking down of fat cells), therefore triglycerides should be expected to go down. They theorize that ketones may promote transfer of triglycerides from blood into cells, which primes the pump for fat burning, but to verify would require conducting biopsies to measure blood versus tissue.
As seen in this exercise, glucose tends to fall quite precipitously following exogenous ketone ingestions. Without exception, every time I ingested these compounds (which I’ve probably done a total of 25 to 30 times), my glucose would fall, sometimes as low as 3 mM (just below 60 mg/dL). Despite this, I never felt symptomatic from hypoglycemia. Richard Veech (NIH) one of the pioneers of exogenous ketones, has suggested this phenomenon is the result of the ketones activating pyruvate dehydogenase (PDH), which enhances insulin-mediated glucose uptake. (At some point I will also write a post on Alzheimer’s disease, which almost always involves sluggish PDH activity —in animal models acute bolus of insulin transiently improves symptoms and administration of exogenous ketones does the same, even without glucose.)
I interviewed Dr. Brianna Stubbs, a ketone researcher with a Ph.D. in Metabolic Physiology from the University of Oxford who is now Research Lead at HVMN, specializing in developing ketone esters. She told me that in terms of science on the ketone salts and their effect on physical performance, one of the most-cited benefits of ketone salts, the scientific studies that have been done show at best no effect on physical performance and that, currently, there is no peer-reviewed scientific research on the ketone salt products on the market.
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.
The culprit is often restaurant meals or other meals where the nutrition facts are not available with the food itself. Such “ignorance is bliss” situations allow us to avoid dealing with daunting numbers. Many people don’t hesitate to stop and enjoy a meal at a restaurant, but they freak out when they actually see the numbers on a label. By now, we all know that opting for fatty meat with a side of veggies cooked in butter isn’t that bad after all. It turns out that what you thought to be the safe, “healthy,” doctor-approved choice might not always be what you think it is.
Anti-cancer potential: Recent research suggests that ketogenic diets can blunt malignant tumor growth. This is due to the fact cancer cells can’t metabolize ketones effectively to nourish their growth and replication. Astonishingly, one study found that supplementing with BHB salts increases odds of survival in mice with systemic cancer by up to 70% in comparison to mice who didn’t receive exogenous ketones.
It might sound absolutely crazy to go that long without food. Especially when you consider traditional diets that recommend eating 3-5 small meals each day, starting with breakfast – the “most important” meal of the day. But if you think back to hunter gatherer times, human beings didn’t always have food accessible to us. Farming and agriculture hadn’t existed so our first meal each day would vary quite vastly. If you think about the word itself, ‘breakfast’ means to break-fast. We didn’t have a set time where we would consume our first meal – it was dependent on accessibility. So if you’re wondering how you’re going to survive without going for food for 16 hours, the answer is straight forward – you can! Let’s simplify this and break down what this may potentially look like.
Importantly, at Diet Doctor we do not think you need to spend any extra money at all in order to revolutionize your health. You can achieve radiant health just by enjoying authentic food that is naturally low in carbohydrates, getting plenty of sleep and some exercise (going for a walk is free) and reducing stress. A lot of you who answered the survey made exactly these points in your explanations of reasons for not taking the supplements. I whole-heartedly agree.
Proper sleep is important for hormone function and repair of the body. Not getting enough sleep is tough on the adrenals and blood sugar regulation. Try to get at least seven hours of sleep per night. If you struggle with quality sleep, create an environment that is conducive for rest. This could be keeping your room cooler, turning off all electronic devices one to two hours before bedtime or using a sleep mask.
Are you ready for a very basic metabolism overview? Most modern humans break down carbohydrates into glucose and this then breaks down further and enters mitochondria to produce ATP, which is the energy system of your cells. In other words, you use carbs for energy. When you are on a ketogenic diet, you are breaking down fats into things called ketone bodies, and this is how you provide your body with energy, instead of via carbohydrates. So, you’re either using carbohydrates for fuel or fat for fuel.
In a keto-adapted individual where ketone metabolism is brisk with up to 100 grams or more being oxidized (i.e., ‘burned for energy’) daily, the small amount lost in breath and urine as acetone is minor. But because this breakdown occurs spontaneously without needing the help of enzymes, it also happens to AcAc in a stored beverage or food (even in an air-tight container), making the shelf-life of AcAc-containing products problematic. Thus all current ketone supplements consist of BOHB in some form rather than the naturally occurring mix of BOHB and AcAc produced by the liver.
There are many different variations of intermittent fasting as well. Dr. Dom D’Agostino, the well-known ketogenic diet researcher, suggests doing a longer intermittent fast for 3 days, 3 times a year. This means not eating for 3 days, and eating normally until the next fast. Daily intermittent fasts are recommended as well. He says that it is ideal to have one to two meals after fasting for most of the day to reap the benefits of intermittent fasting every day.
If you do the same calculations as I did above for estimating fat oxidation, you’ll see that EE in this case was approximately 13.92 kcal/min, while fat oxidation was only 67% of this, or 9.28 kcal/min, or 1.03 g/min. So, for this second effort (the test set) my body did about 5% less mechanical work, while oxidizing about 25% less of my own fat. The majority of this difference, I assume, is from the utilization of the exogenous BHB, and not glucose (again, I will address below what I think is happening with glucose levels).
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