The coffee fixin’s bar is already a crowded place—you’ve got your half and half, full and skim, your soy milk, almond milk, rice milk, cashew hemp “mylk,” plus your sugar-substituting simple syrup, agave, stevia, xylitol and more. Now it’s time to make room for two newcomers: coconut oil and butter. Yup, butter.

Bulletproof Coffee, recently popularized by Silicon Valley entrepreneur and self-proclaimed biohacker Dave Asprey, is a blend of black coffee, butter and MCT oil (short for medium-chain triglyceride) that he and other proponents claim will keep you energized and focused for hours. The basic principle of waking up with a mug of buttery joe is that the fats in the butter and MCT oil, which is derived from coconut oil, give you lasting energy, support cognitive function and jumpstart your body’s fat-burning machinery, slowing fat accumulation and promoting weight loss.

There’s some science to this, though there’s not complete consensus among doctors and scientists. The medium-chain saturated fats in coconut oil are shorter than those found in safflower, soybean and olive oils for example, and are metabolized differently in the body. “MCTs are a unique form of fat that require less energy and enzymes to be digested,” explains Kerry Bajaj, a health coach at Eleven Eleven Wellness Center in New York City. “As a result, they are a readily available source of energy, leading to an increase in metabolism and providing quick energy replenishment. Unlike other dietary fats, MCTs don’t get stored as fat in the body, they get burned for energy.

”Asprey got the idea for Bulletproof coffee while trekking in Tibet, where it’s custom to drink yak-butter tea. He found the delightfully creamy beverage so remarkably energizing after a high-altitude hike that upon his return Stateside, he studied the biochemistry, figured out why it worked, and naturally started marketing it as his own brand. “Bulletproof” is actually his trade name, though it’s quickly going the way of Kleenex and Xerox.

Asprey’s Bulletproof coffee includes a fresh cup of coffee brewed from his proprietary “upgraded” low-toxin coffee beans, 1 or 2 tablespoons of Bulletproof MCT oil or Upgraded Brain Octane (from his site: “18x stronger than coconut oil—for maximum cognitive function!”) and between 2 and 6 tablespoons of unsalted grass-fed butter, mixed in a blender. Some people substitute clarified butter, or ghee. And there are plenty of alternatives to Bulletproof brand MCT oil, including one from Now Sports and pineapple-coconut-flavored Be Well MCT Oil from Eleven Eleven Wellness.

There’s a debate raging over the safety of saturated fats, including MCTs, and even experts who believe the fears about saturated fat are grossly inflated think there’s cause to limit your intake. So while it’s OK to start your day the Bulletproof way, you probably don’t want to make it a multi-cup habit.

Not into frothy, buttery coffee? There are other ways to incorporate MCTs into your diet, says Bajaj. She recommends cooking omelets in MCT oil, or adding a tablespoon to a protein shake or smoothie.

READ MORE: Coffee vs. Tea—Which One Is Better for You?