On Ketone Supplements

Ketone supplementation is one of the current fads of our sport, with some influential people occasionally saying some less than informed things about them. That said, let's break this down a bit. Are there potential benefits for endurance athletes? And even if there are, are they worth the hype?

The body likes to use glucose as fuel, which is broken down from carbohydrates. Some tissues, like the brain, cannot use fatty acids directly for energy. Fun fact: the recommended daily allowance (RDA) for carbohydrates, which is 130g, was developed based on the fact that the brain independently requires around 130g per day. When carbohydrate intake is low, the body can convert other molecules into glucose to fuel the brain. Lactic acid, glycerol, and some amino acids undergo gluconeogenesis, meaning they are converted into glucose for utilization.

However, the body can’t meet all its needs for glucose through gluconeogenesis when carbohydrate intake is low. Without glucose, fat becomes the primary fuel source. Fatty acids are broken down into acetoacetate and converted to beta-hydroxybutyrate and acetone. These three molecules are what’s known as ketone bodies, and they can be used by the kidneys, heart, muscle tissue, and brain for energy in place of glucose. As long as the body is starved of carbohydrates, ketogenesis (the production of ketone bodies) will continue.

So, what exactly is a keto diet? A ketogenic diet, by definition, is a high fat, moderate protein, low carbohydrate diet. Generally, when we’re talking about keto diets, we’re talking about 5-10% of total calorie intake from carbs, or less than 50g carbohydrates per day (200 calories from carbs), 10-20% of calories from protein, and 70-80% of calories from fats. It’s hard to achieve. Fifty grams of carbs equates to roughly two medium size apples. Clinically, ketogenic diets are sometimes used to treat epilepsy, and have mixed results of use in other conditions. I will say, most of the general public “doing keto” aren’t actually doing a keto diet. They’re doing a high protein, low carb diet and just calling it something novel and exciting. I won’t even get started on the marketing of “keto” products. We’ll save that one for another day.

But what about keto supplements? When ingested, Ketone supplements are hydrolyzed in the small intestine and rapidly increase ketone levels in the blood. Often these supplements are marketed to aid in weight loss or change body composition. However, merely increasing ketone levels in the blood does not increase fat metabolism. Supplements without other dietary changes won’t cause weight loss. Although, some research suggests ketones may suppress appetite while in a calorie deficit.

In exercise, these ketones supplements provide the body with an additional fuel source outside of carbohydrates and fats. In theory, this is great. More fuel for exercise and less reliance on carbs. Potentially, this would also spare glucose stores for later in the race. Since ketones can be used by the brain, this could also mean more mental energy and better cognition. However, translation from theoretical use to practical use hasn’t been clear.

Overall, findings on ketone supplements and performance have been mixed and inconclusive. One study showed a performance benefit to well-trained cyclists using ketones supplements. In the study, athletes completed a thirty-minute time trial after an hour of steady-state riding. The subject group, which ingested carbs and ketone supplements, performed significantly better, showing around a 2% increase in performance versus the carb only control group. However, other researchers have been unable to replicate these findings, while multiple other studies concluded that ketone supplements negatively impacted performance. Another caveat of ketone supplements is their potential to cause GI distress, nausea, and dizziness which could lead to poor performance outcomes.

Ketone supplements dosage seems to be important, but there’s currently no set recommendation. We also don’t know much regarding the safety and efficacy of taking keto supplements long term.

Interestingly, because ketones may act as signaling molecules, very high doses of ketones may increase short term erythropoietin levels. Erythropoietin, or EPO, is the hormone primarily responsible for red blood cell production and perhaps the most famously abused performance enhancing drug in endurance sports. Again, this research is in its early phases, and we don’t have any conclusive evidence at this point in time to show long term benefit of ketone supplements on red blood cell production. This is merely an interesting beginning of research.

So, are they worth it? It’s too soon to say definitively. But if you’re considering trying them, I would answer that question with several follow up questions: Are you doing everything else correctly? Meaning, have you maximized your body’s ability to intake carbs during exercise? Have you already nailed your pre/during/and post nutrition strategies? Are you already on top of your recovery, sleep, and stress management? As you’d very likely see a greater increase in performance focusing on these things first. Do you have money to spare? We know that these supplements aren’t cheap so we’re talking about hundreds or thousands of dollars to replicate some of these research protocols. You’ll need to determine if the material cost is worth the theoretical benefit.

For me personally, I’m going to hold off until we have more conclusive research. That and carbs are cheap and easy to eat, but I’m excited to see how things develop in the future.

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