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Base Knowledge: Ketone supplements
Sure, it's cutting edge science that the cycling pros love—but do they work?
While I know a thing or two about ketone esters and salts, I’ve never personally experimented with them. For that reason, I avoided the topic in the New Personal Best newsletter—until Kevin asked me to write about them. Now I have no choice.
To put that into context, Kevin Nix is my Big Orange Cycling teammate and main training partner. We have an unspoken understanding that if one of us asks the other to do something, the answer is, “That’s a terrible idea! What time do we start?”
Over the years, Kevin and I have talked each other into—among other things—multiple Belgian Waffle Rides, a two-day ride from San Francisco to Los Angeles, a two-day ride from Los Angeles to Las Vegas, a five-day ride from Portland to San Francisco, several one day rides involving 90+ miles and five or six burritos (“The Steve Edwards Burrito Challenge”), countless shale scrambles and cliff bombs, and more questionable menu choices than a nutrition expert should admit to.
In other words, I’m bound by the Sacred Code of Man-Child Absurdity to cover ketones.
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What are ketones?
Even though it sounds like a daunting topic, ketones are easy to understand. As you may know, your body’s preferred source of fuel is glucose (blood sugar). You get glucose mostly from eating carbs and a little from protein. Your body also creates and stores a back-up to glucose called glycogen in your liver and muscles. When you run out of glucose and glycogen—or you’re running really low—your body breaks down your adipose tissue (body fat) for energy—but it doesn’t convert it to glucose. Instead, it converts fat into something called ketones, which it uses for fuel instead.
When someone goes on a ketogenic diet, they reduce their carbohydrate and protein intakes so that their body is forced to use ketones. They are basically an emergency fuel source. They’re meant to fuel the brain and muscles when you starve.
Whether or not forced ketosis has merit is a charged topic. I’d rather discuss something less politically touchy, like whether gun control combined with transgender bathrooms in public schools will cause global warming if Trump runs against Biden in the next election. Either way, we don’t need to go there to learn about ketone sups.
One argument for endurance athletes to supplement with ketones is that, in this situation, your body uses them for energy in addition to your glucose and glycogen. This means you spare your glycogen stores, so you have more fuel in the long run. It’s also supposed to enhance recovery—by helping you build back glycogen stores faster.
They’re also thought to increase the body’s concentration of erythropoietin, which you might know as EPO. EPO is a hormone that regulates red blood cell production. Having more EPO makes your red blood cells bigger. This allows them to carry more oxygen to your muscles—and this allows you to perform better.
A few years ago, a bunch of pro cyclists including Lance Armstrong were busted for injecting EPO. This “blood doping” is banned by the World Anti Doping Agency because misuse of EPO can lead to a number of health issues, like stroke and embolisms. (If you want to discuss EPO in more detail, let me know.)
Ketones aren’t banned in sport. From what I gather, this is for a couple reasons. First, the authorities aren’t completely certain that they work. Second, the side effects are more unpleasant than deadly.
You sometimes see synthetic ketones referred to as “exogenous,” which means “outside made.” The ketones that your body makes are called “endogenous” which means “inside made.” Those are good words to remember when talking about nutrition and biology. This knowledge might also win you a Fandango gift card at trivia night someday.
There are two kinds of exogenous ketones. Ketone salts are attached to a sodium molecule. Ketone esters are connected to an oxygen molecule. Ketone salts are cheaper—which is why you see more of them around. Ketone esters cost more, but they’ve been shown to raise blood ketone levels higher. Either way, both raise those levels to some degree.
Ketone salts can cause gut issues, which is why their dosage is tiny. Esters may be better tolerated but, again, they can be pricey. A single serving might be $20-$40.
Another drawback about ketone esters is that they can raise blood acidity, which can hamper performance, but there’s a 2021 study demonstrating you can counter this problem by adding sodium bicarbonate (baking soda) into the mix.
Note that sodium bicarbonate can also cause gut issues. If you’re serious about taking this route, Maurten has a “bicarb system” that they claim to be more tolerable.
But do they work?
There’s plenty of science showing how they work—but it’s not a ton demonstrating if they work.
For performance, the research for both esters and salts is all over the map, so it’s hard to get a clear picture. According to a 2021 systematic review, “Heterogeneity across studies makes it difficult to conclude any benefit or detriment to consuming ketone supplements on physical performance.”
(If it makes you feel better, I had to look up “heterogeneity.” It means “the quality or state of being diverse in character or content.” Now you’ll win a Fandango card and maybe complete the Sunday New York Times crossword.)
A comprehensive 2022 paper in ketones stated, “Despite the mechanistic bases for potential beneficial effects of exogenous ketone supplements, the evidence at present is overwhelmingly against exogenous ketone supplements being an ergogenic aid for athletic performance.” In other words, even though it seems like they should work, they don’t.
As for recovery, results seem more promising. The authors of a 2019 study tentatively wrote that “ketone ester intake is a potent nutritional strategy to prevent the development of non‐functional overreaching and to stimulate endurance exercise performance.”
Another 2023 study concluded, “our data indicate that intermittent exogenous ketosis may evolve as a potent nutritional strategy to facilitate recovery from strenuous endurance exercise, thereby stimulating beneficial muscular adaptations.”
Both studies involved feeding subjects ketone esters post-workout. Both studies were also limited to fit male subjects, which is lame but common in sports research.
Even that 2022 beatdown I mentioned a moment ago was cautiously optimistic when it came to recovery: “Future research should investigate whether there are other athletic contexts where exogenous ketone supplements are efficacious given the positive, albeit preliminary, data from studies on overreaching.”
Should you take them?
That’s a “you” question. Cycling pros seem pretty crazy for them—and it’s always fun to feel pro. But they can be pricy and we’re not sure how well they work.
If you want to experiment with them, I’d make sure you’ve absolutely nailed down all other nutritional aspects of your training, especially protein. Then, if you have the money and you’re really focused on recovery, maybe give them a try.
For example, if I were doing a multi-day race that I really cared about, I’d be willing to gamble $20-$40 on improved recovery—or make that $40-$80 because I’d categorically try them at least one additional time in advance to make they didn’t mess up my gut.
Personally, I plan to watch the ketone space closely. It’s just a matter of time before price decreases and research results increase. In the meantime, my current protocol allows me to follow Kevin up and down the California coast just fine without the aid of ketones, so I’m good