Stirring butter into your coffee sounds delicious, but the supposed health benefits are questionable. Here's what the science says about this trendy keto beverage.

Christine Byrne
April 13, 2020
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Bulletproof coffee started trending years ago among paleo devotees and hardcore CrossFitters, and it has since crept into the mainstream. But what is bulletproof coffee, exactly? Originally popularized by Dave Asprey, the creator of the Bulletproof diet (who has no medical credentials or health-related degrees), the original recipe calls for 1 cup brewed coffee, 1 teaspoon to 2 tablespoons MCT oil, and 1 to 2 tablespoons grass-fed butter, all mixed in a blender until foamy. On that original recipe page, Asprey claims that starting the day with bulletproof coffee can help those who follow intermittent fasting or the keto diet "feel satiated, alert and focused," and that both grass-fed butter and MCT have unique benefits. People following a ketogenic or low-carb, high-fat diet have also been in on the trend. But is any of that really true? Here's what an expert has to say, based on the evidence.

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Why does the bulletproof coffee recipe call specifically for MCT oil?

Some people think of bulletproof coffee as just coffee with butter mixed in, but it's actually more granular than that. Specifically, you're meant to use a mix of grass-fed butter and MCT oil. "MCT oil is a supplement that contains medium-chain triglycerides (MCTs)," says Kelli McGrane, R.D., of Lose It!. "The oil is most commonly extracted from coconut oil, but it can also be made by processing palm kernel oil." One tablespoon of the MCT oil that Bulletproof sells contains 130 calories and 14 grams of saturated fat.

So, what's special about this particular type of fat? "MCTs are saturated fats that are made up of 6 to 12 carbon atoms, compared to long-chain triglycerides, which have 13 to 21 carbon atoms," McGrane says. No need to get too science-y here, but because of this shorter chain length, she says, "MCTs are broken down more efficiently in the body and may be more likely to be used for immediate energy rather than stored as body fat." Some people claim that MCT oil can boost brain function, energy and blood sugar control, but there's not enough evidence to say that this is actually the case (learn more about MCT oil and the science behind the health benefits).

What about grass-fed butter?

Compared to conventional grain-fed butter, grass-fed butter (made of milk from grass-fed cows) is typically higher in vitamins A and K, McGrane says. And, one study found that grass-fed butter contains more omega-3 fatty acids than conventional butter.

Despite its slight nutrient edge, grass-fed butter is still high in saturated fat: 1 tablespoon delivers 100 calories and 8 grams of saturated fat. The amount of omega-3s also doesn't come close to that in, say, salmon (consider trying these top plant-based omega-3s to add more to your diet).

Is it OK to be eating that much saturated fat in coffee?

Suppose you make bulletproof coffee with 1 tablespoon each of MCT oil and grass-fed butter (the lower end of what Asprey's recipe recommends). That cup of coffee would contain 22 grams of saturated fat; 14 grams from MCT oil, 8 grams from grass-fed butter. The American Heart Association recommends that someone eating 2,000 calories per day eat no more than 13 grams of saturated fat per day, and the Dietary Guidelines for Americans recommend no more than 22 grams per day. Either way, a single cup of bulletproof coffee puts you at or well above the limit.

Is that a good idea? "The short answer is no," McGrane says. "While the relationship between saturated fats, especially MCTs, and heart health isn't as straightforward as we once thought, research still shows a relationship between saturated fat intake and increased levels of LDL (bad cholesterol)."

Plus, that's not accounting for any other saturated fat you may get in your day by eating meat or having some cheese.

But wait, what about those claims that bulletproof coffee can improve your metabolism, your mood or your health?

Saturated fat aside, bulletproof coffee's purported benefits include improved metabolism, mood, brain function and overall health. But are any of these evidence-based? Not really. "Currently, there aren't any studies that have studied the health benefits of bulletproof coffee specifically," McGrane says. "Most of the claims surrounding bulletproof coffee are due to the MCTs in it. And while there's some research to suggest that MCTs may have benefits for health, such as weight loss and mood, more research is needed to prove its effectiveness in most healthy adults."

It seems silly to even ask at this point, but is bulletproof coffee a nutritious breakfast choice?

Because it's so high-calorie, bulletproof coffee is meant to be a breakfast substitute, not something you eat alongside a traditional breakfast. Part of the reason it's so popular among keto dieters is that all of its calories come from fat, with no carbohydrates or protein. That alone should raise alarm bells for anyone who understands basic nutrition. "While bulletproof coffee provides fat and possibly vitamins A and K (if using grass-fed butter), [it lacks] essential nutrients like protein, fiber, and most vitamins and minerals," McGrane says. "Plus, bulletproof coffee is very high in calories and saturated fat, which can be problematic."

While fat is important for satiety and fullness, protein and fiber play a role in this as well. It's possible that the high-calorie breakfast drink wouldn't fill you up the way a more balanced breakfast might (check out our healthy breakfast recipes for inspiration).

Bottom line: Bulletproof coffee isn't a healthy breakfast choice.

Because of its high calorie and saturated fat content, and its low protein and fiber content, bulletproof coffee just isn't a healthy breakfast choice. If you're curious about trying bulletproof coffee, or if you've already tried it and love the taste, it's probably fine to drink a cup every once in a while, McGrane says. But as with other high-calorie, nutrient-poor foods, it's best to drink bulletproof coffee in moderation, and not as a substitute for nutrient-dense foods like fruits, vegetables, whole grains, legumes, nuts, seeds and lean proteins.