Assessing the Validity of Bulletproof Coffee’s Claims

Abstract

'Bulletproof Coffee’, a popular beverage composed of coffee, grass-fed butter, and medium-chain triglyceride oil, has gained significant attention for its purported benefits including cognitive enhancement, increased alertness and energy, appetite suppression, and improved metabolic outcomes. However, the scientific evidence supporting these claims remains limited. This review aims to evaluate the evidence and determine the validity of claims regarding Bulletproof Coffee. Studies published between 2010–2023 were retrieved and evidence pertaining to cognition, alertness and energy, hunger and satiety, serum cholesterol, and gastrointestinal tolerance and Bulletproof Coffee were evaluated. The findings suggest that the current evidence base is small, and overall, there is weak or insufficient evidence to support the claimed benefits of Bulletproof Coffee. In particular, there were no significant improvements in cognition, alertness, or energy levels from Bulletproof Coffee compared to regular coffee. The impact on hunger, satiety, resting energy expenditure, and fat oxidation appeared equivocal, with effects offset by the additional calorie intake of Bulletproof Coffee. Further research with more rigorous study designs, larger sample sizes, diverse populations, and standardized methodologies are required in addition to an examination of potential health risks associated with regular Bulletproof Coffee consumption.

Full text

Citation: Goldman, D.M.; Lambert,
K.; Quarshie, M.; Craddock, J.C.
Assessing the Validity of Bulletproof
Coffee’s Claims. Beverages 2023,9,
101. https://doi.org/10.3390/
beverages9040101
Academic Editor: Rafael Carlos Eloy
Dias
Received: 30 October 2023
Revised: 20 November 2023
Accepted: 5 December 2023
Published: 11 December 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
beverages
Review
Assessing the Validity of Bulletproof Coffee’s Claims
David M. Goldman 1, Kelly Lambert 2, Michael Quarshie 1and Joel C. Craddock 2, *
1Metabite, Inc., 43 W. 43rd St., Suite 101, New York, NY 10036, USA; dmg2140@tc.columbia.edu (D.M.G.)
2School of Medical, Indigenous and Health Sciences, Faculty of Science Medicine and Health, University of
Wollongong, Wollongong, NSW 2522, Australia
*Correspondence: jcraddock@uow.edu.au
Abstract:
‘Bulletproof Coffee’, a popular beverage composed of coffee, grass-fed butter, and medium-
chain triglyceride oil, has gained significant attention for its purported benefits including cognitive
enhancement, increased alertness and energy, appetite suppression, and improved metabolic out-
comes. However, the scientific evidence supporting these claims remains limited. This review aims
to evaluate the evidence and determine the validity of claims regarding Bulletproof Coffee. Studies
published between 2010–2023 were retrieved and evidence pertaining to cognition, alertness and
energy, hunger and satiety, serum cholesterol, and gastrointestinal tolerance and Bulletproof Coffee
were evaluated. The findings suggest that the current evidence base is small, and overall, there is
weak or insufficient evidence to support the claimed benefits of Bulletproof Coffee. In particular,
there were no significant improvements in cognition, alertness, or energy levels from Bulletproof
Coffee compared to regular coffee. The impact on hunger, satiety, resting energy expenditure, and
fat oxidation appeared equivocal, with effects offset by the additional calorie intake of Bulletproof
Coffee. Further research with more rigorous study designs, larger sample sizes, diverse populations,
and standardized methodologies are required in addition to an examination of potential health risks
associated with regular Bulletproof Coffee consumption.
Keywords:
Bulletproof Coffee; butter coffee; MCT; medium-chain triglyceride oil; cognitive function;
alertness; energy; hunger; satiety; narrative review
1. Introduction
Cardiovascular disease (CVD) stands as the leading cause of worldwide mortality [
1
].
Research has firmly established a connection between elevated levels of total cholesterol and
LDL cholesterol, and the occurrence of CVD [
2
]. Diet, particularly the intake of saturated fat,
plays a significant role in modulating these cholesterol levels [
3
]. Consequently, minimizing
saturated fat consumption has become an internationally accepted strategy to mitigate CVD
risk [
4
]. However, the promotion of foods and beverages high in saturated fats persists [
5
,
6
],
leading to three quarters of American adults surpassing recommended intakes [7].
Butter coffee is an increasingly popular beverage, with a valuation of USD 90 billion
in 2022 that is forecast to reach USD 138 billion by 2032 [
8
]. Bulletproof Coffee is a form of
butter coffee that consists of ground coffee with added fat in the form of grass-fed butter
and medium-chain triglyceride (MCT) oil [
9
]. The beverage was intended to replace a
meal at breakfast and is often included in the diets of people who follow low-carbohydrate
(including ketogenic) diets [
10
]. One cup (237 mL) contains 230 calories, 25 g total fat,
21 g saturated fat, 0 g carbohydrates, and 0 g protein [
11
]. Numerous claims have been
attributed to Bulletproof Coffee including heightened focus and energy, reduced hunger
and cravings, fat burning, and an overall productivity boost surpassing that of conventional
coffee [
9
,
12
,
13
]. There are several mechanisms by which these benefits are proposed to
accrue [
9
]. Polyphenols in coffee are proposed to increase focus and memory. Grass-fed
butter is described as a rich source of conjugated linoleic acid and butyrate, which are
claimed to increase fat oxidation and enhance brain function, respectively. The dietary fats
Beverages 2023,9, 101. https://doi.org/10.3390/beverages9040101 https://www.mdpi.com/journal/beverages

Beverages 2023,9, 101 2 of 13
in butter are also proposed to slow the absorption and sustain the release and bioavailability
of caffeine. Lastly, MCT oil is proposed to increase blood levels of ketone bodies, which
enhances brain function and fat oxidation.
Survey data from a recent study of 210 American college students demonstrate the
pervasiveness of beliefs in the legitimacy of claims surrounding Bulletproof Coffee. More
than half of survey respondents believed that the beverage promotes fat loss, enhances con-
centration, decreases stress levels, and increases energy. An additional 20 percent remained
unsure, demonstrating the pressing need for a comprehensive scientific examination of
Bulletproof Coffee to provide consumers with accurate information [
14
]. Similarly, Google
Trends data indicate that the term “Bulletproof Coffee” remains of interest since its peak in
2018 [15].
Review Scope
Given the potential health implications of habitually consuming this high-saturated
fat beverage, understanding the scientific foundation underlying the purported benefits of
Bulletproof Coffee becomes critically important. This narrative review therefore aims to
summarize the existing body of evidence regarding Bulletproof Coffee. In doing so, the
review will equip healthcare professionals with the necessary information to offer informed
recommendations and assist consumers in making educated decisions about Bulletproof
Coffee consumption based on the available scientific evidence.
2. Materials and Methods
2.1. Literature Search
This narrative review searched for research on the effects of Bulletproof Coffee on
outcomes relating to product claims. Although this is a narrative review, the source arti-
cles were identified using a systematic search strategy. The online databases MEDLINE
(PubMed) and Google Scholar were searched from 2010 to August 2023 for eligible studies.
Key search terms, including MeSH terms, were determined in accordance with the PICO
method: “human subjects” for participants; “Bulletproof Coffee”, “butter coffee”, and
“medium-chain triglycerides coffee” for interventions; and “cognition”, “alertness”, “en-
ergy”, “hunger”, “satiety”, “resting energy expenditure”, and “fat oxidation” for outcomes.
All PubMed results and the first 200 Google Scholar results for each keyword search were
reviewed.
2.2. Study Eligibility and Selection
Studies were considered eligible if they: (1) were interventional studies or case reports,
(2) were published in scientific journals, as dissertations, or as conference abstracts, (3)
included human subjects, and (4) included outcome measures pertaining directly to claims
made in Bulletproof books or the company website (i.e., cognition, alertness, energy, hunger,
satiety, energy expenditure, fat oxidation). Studies were excluded if they: (1) were narrative
reviews, (2) did not include both coffee and a source of concentrated fatty acids (i.e., ghee,
butter, medium-chain triglycerides) in the experimental group, (3) were conducted in
populations with cognitive diseases (e.g., dementia) or diseases known to affect metabolic
rate (e.g., Hashimoto’s thyroiditis), (4) only included outcome measures unrelated to claims
made in Bulletproof books or the company website (i.e., cellular inflammation), or (5) were
unavailable in the English language.
Preliminary screening was completed in duplicate by reviewing the titles and abstracts
to assess eligibility by researchers DG and MQ. Studies not meeting the inclusion criteria
were excluded. Full text articles were reviewed in duplicate by DG and MQ.
2.3. Data Extraction and Synthesis
Methodology characteristics and outcomes were extracted from eligible studies. Ex-
tracted data included subject characteristics (age range and baseline coffee consumption),
dietary provisions in the experimental and control groups (if a control group was included),

Beverages 2023,9, 101 3 of 13
outcomes (cognition, alertness, energy, hunger, satiety, resting energy expenditure, fat
oxidation), and the methods used to measure outcomes (cognitive assessments, subjective
measures, indirect calorimetry). Effects in identified themes were reviewed in a narrative
synthesis.
3. Results
Following the literature search 204 articles were identified. After excluding 198 articles
(18 duplicates, 155 that did not investigate both coffee and ghee, butter, or medium chain
triglycerides, 23 that did not present original data, and two that exclusively measured
variables impertinent to Bulletproof Coffee claims), six articles met the inclusion criteria and
were included in the final synthesis. Figure 1illustrates the selection process. A narrative
analysis of these studies presented six key themes (Table 1), and results are classified in
accordance with these themes.
Beverages 2023, 9, x FOR PEER REVIEW 3 of 14
Methodology characteristics and outcomes were extracted from eligible studies. Ex-
tracted data included subject characteristics (age range and baseline coffee consumption),
dietary provisions in the experimental and control groups (if a control group was in-
cluded), outcomes (cognition, alertness, energy, hunger, satiety, resting energy expendi-
ture, fat oxidation), and the methods used to measure outcomes (cognitive assessments,
subjective measures, indirect calorimetry). Effects in identified themes were reviewed in
a narrative synthesis.
3. Results
Following the literature search 204 articles were identified. After excluding 198 arti-
cles (18 duplicates, 155 that did not investigate both coffee and ghee, butter, or medium
chain triglycerides, 23 that did not present original data, and two that exclusively meas-
ured variables impertinent to Bulletproof Coffee claims), six articles met the inclusion cri-
teria and were included in the final synthesis. Figure 1 illustrates the selection process. A
narrative analysis of these studies presented six key themes (Table 1), and results are clas-
sified in accordance with these themes.
Figure 1. Article selection process.
Figure 1. Article selection process.
3.1. Cognition
The effects of Bulletproof Coffee on cognitive function were investigated in two
randomized interventional trials (Table 1). Crampton et al. conducted a single-blind,
randomized crossover design to explore the acute effects of Bulletproof Coffee on cognitive
performance. The study included six healthy, coffee-drinking participants. On two separate
occasions, separated by a seven-day washout period, subjects consumed either 10 ounces
(296 mL) of Bulletproof Coffee or regular black coffee equivalent to 114 mg caffeine in
both conditions. Cognitive performance was evaluated through the Digit Substitution Task
(DSST), at baseline and at 60- and 170-min post-consumption. The findings suggested no
significant differences in cognitive function, as gauged by the number of correct responses
on the DSST, between the Bulletproof Coffee and black coffee conditions [16].
Bergauer et al. led another investigation that used a double-blind, placebo-controlled,
crossover design to explore the effects of Bulletproof Coffee on cognition. The study in-
cluded 21 regular coffee-drinking healthy undergraduate students who consumed
1–4 cups
of coffee daily. On separate testing days, participants ingested either Bulletproof Cof-
fee, regular coffee, or decaffeinated coffee, estimated to contain 80
±
10 mg/100 mL,
80 ±10 mg/100 mL
, and 3
±
10 mg/100 mL of caffeine, respectively, with wash-out peri-
ods of at least 4–5 days between sessions. Cognitive performance was assessed 45 min after
coffee administration in 96-min testing sessions that included two working memory-related
tasks: the immediate and delayed spatial memory task (SMT) and the N-back task. The
results showed no superior performance in cognitive tasks for participants consuming
Bulletproof Coffee compared to those consuming regular or decaffeinated coffee [
17
]. The
authors nonetheless address that caffeine demonstrates potential to enhance performance
by exerting stimulatory effects on the central nervous system (CNS).

Beverages 2023,9, 101 4 of 13
Table 1. Studies examining the effects of Bulletproof or butter coffee on outcomes related to company claims, health, and gastrointestinal tolerance.
Author (Year) Design Participants (n);
Age (Range) Duration Baseline Coffee Intake Intervention Control Measurements Results
Crampton (2021)
[16]R, SB, C, CO 6; 17–33 2 visits with 7~-day
washout period “regular coffee consumers”
(details NR)
15 mL MCT oil, 15 mL
grass-fed ghee, 296 mL
caffeinated coffee 296 mL black coffee Cognitive performance,
hunger, and satiety
No significant difference in
cognitive performance;
Significant increase in fullness
for Bulletproof Coffee
compared with black coffee
Bergauer (2021)
[17]R, DB, C, CO 21; “Second year
bachelor students”
(details NR)
3 visits with at least
4–5-day washout
periods 237–946 mL/day
1 T grass-fed butter, 1 T
MCT oil, black coffee
providing 190 +/−10 mg
caffeine/237 mL
(1) Dark roast coffee
providing 190 +/−10 mg
caffeine/237 mL, 0.5 t
grass-fed butter; (2)
Decaffeinated coffee
providing 3 mg
caffeine/100 mL, 0.5 t
grass-fed butter
Spatial memory,
working memory,
mood including
alertness,
contentedness, and
calmness
No significant difference in
memory or mood dimensions
Significant increase in alertness
for decaffeinated coffee
condition; Significant decrease
in alertness for regular coffee
condition; Significant
interaction effect for placebo
and regular coffee conditions
Fritchen (2016)
[18]R, DB, C, CO 12; 20–25 2 visits with 7-day or
shorter washout period Equivalent to
226–426 mg/day of caffeine
4 mg caffeine/kg body
weight in the ratio 1 T
grass-fed butter:1 T MCT
oil:355 mL black coffee
4 mg caffeine/kg body
weight from black coffee
Alertness, satiety,
resting energy
expenditure and fat
oxidation,
gastrointestinal
tolerance
Significant increase in alertness
in both conditions; No
significant difference in
alertness between groups;
Significant increase in satiety in
Bulletproof Coffee condition;
Nonsignificant decrease in
satiety in black coffee condition;
Difference between groups NR;
Significant increase in REE and
RQ in Bulletproof Coffee
condition; Significant decrease
in RQ in Bulletproof Coffee
condition; No significant
difference in REE or RQ in black
coffee condition; Difference in
REE and RQ between groups
NR; Increase in gastrointestinal
intolerance scores in
Bulletproof Coffee condition;
No difference in gastrointestinal
scores in black coffee condition

Beverages 2023,9, 101 5 of 13
Table 1. Cont.
Author (Year) Design Participants (n);
Age (Range) Duration Baseline Coffee Intake Intervention Control Measurements Results
Baumeister
(2021) [19]DB, C, CO 7; 22–29 10 visits with 24-h
washout periods NR
(1) 10 mL tricaprylin,
150 mg caffeine, 250 mL
decaffeinated coffee; (2)
10 mL tricaprylin, 250 mL
decaffeinated coffee; (3)
10 mL tricaprin, 150 mg
caffeine, 250 mL
decaffeinated coffee; (4)
10 mL tricaprin, 250 mL
decaffeinated coffee; (5)
5 mL tricaprylin, 5 mL
tricaprin, 150 mg caffeine,
250 mL decaffeinated coffee;
(6) 5 mL tricaprylin, 5 mL
tricaprin, 250 mL
decaffeinated coffee; (7)
10 mL coconut oil, 150 mg
caffeine, 250 mL
decaffeinated coffee; (8)
10 mL coconut oil, 250 mL
decaffeinated coffee
(1) 150 mg caffeine, 250 mL
decaffeinated coffee; (2)
250 mL decaffeinated
coffee
Sensory; Hunger,
satiety, side effects
Increase in hunger and decrease
in satiety in all conditions; Most
common side effects were
difficulty concentrating,
abdominal pain, nausea,
headache; Abdominal
symptoms were most common
in oil-based conditions
McAllister
(2020) [20]R, DB, C, CO 10; “College-aged”
(details NR) 3 visits; Washout
period NR 237–473 mL/day
(1) 21 g MCT oil, 7 g coconut
oil, stevia-based sweetener
(quantity NR), 473 mL
caffeinated coffee; (2) 31.5 g
MCT oil, 10.5 g coconut oil,
stevia-based sweetener
(quantity NR), 473 mL
caffeinated coffee
Stevia-based sweetener
(quantity NR), 473 mL
black coffee TC, HDL-c, TG
Significant increase in TC,
HDL-c in all conditions, no
difference between groups;
Significant decrease in TG in all
conditions, no difference
between groups
Toklu (2015) [21] CR 1; 59 y “Several months”;
further details NR NR
1–2 cups per day of
Bulletproof Coffee (2 T
unsalted grass-fed butter,
1 T MCT oil, 1–2 cups coffee)
None TC, LDL-c, HDL-c, TG,
non-HDL-c
Increase in TC, LDL-c,
Non-HDL-c; Decrease in TG
following Bulletproof Coffee
C—Controlled; CO—Crossover; CR—Case report; DB—Double blind; Gastrointestinal—GI; HDL-c—High-density lipoprotein-cholesterol; kg—Kilograms; LDL-c—Low-density
lipoprotein-cholesterol; MCT—Medium-chain triglycerides; mg—Milligrams; NR—Not reported; R—Randomized; RQ—Respiratory quotient; REE—Resting energy expenditure;
SB—Single blind; T—Tablespoon; t—teaspoon; TC—Total cholesterol; TG—Triglycerides.

Beverages 2023,9, 101 6 of 13
3.2. Alertness and Energy
Several trials have explored the potential impact of Bulletproof Coffee on subjective
perceptions of alertness and energy. Bergauer et al. utilized the Bond & Lader questionnaire
to measure several dimensions of mood including alertness, contentedness, and calmness,
both before and after coffee consumption. There were no significant effects from either Bul-
letproof Coffee, regular coffee, or decaffeinated coffee on any mood dimension. However,
a significant increase in alertness was observed post-consumption of the placebo drink,
and a significant decrease in alertness was noted after the ingestion of regular coffee. A
significant interaction effect was detected between coffee condition and time point (pre-
and post-test) for the placebo and regular coffee condition, but not for the Bulletproof
Coffee condition [17].
In a separate study, Fritchen investigated the influence of Bulletproof Coffee on alert-
ness using a randomized, double-blind, crossover design. Twelve healthy undergraduate
students who habitually consumed coffee were instructed to eat a standardized meal 12 h
before testing, followed by a 12-h fasting period. Baseline alertness was assessed using a
five-point Likert scale questionnaire. During the testing session, participants had 20 min to
consume either Bulletproof Coffee or regular black coffee, each providing 4 mg caffeine/kg
of body weight, and the procedure was repeated with the other coffee condition within
a seven-day period. Subsequent to metabolic assessments (discussed later), participants
completed the questionnaire again 60 min post-consumption. The data revealed significant
increases in alertness scores from pre- to post-consumption for both Bulletproof Coffee and
black coffee. No significant differences in score changes were identified between the two
testing conditions [
18
]. The results suggest that heightened alertness is primarily linked to
the caffeine content in coffee, which the authors describe is a common byproduct of the
role caffeine plays as a CNS stimulant.
Bulletproof Coffee typically consists of a blend of coffee, grass-fed butter, and MCTs,
but is frequently consumed merely as coffee with MCTs or coconut oil [
19
]. In a controlled,
double-blind trial by Baumeister et al., seven young, healthy participants underwent a 12-h
fasting period prior to the testing session. During the intervention, participants consumed
10 mL of three MCT mixtures or coconut oil, either with or without 150 mg of caffeine,
in 250 mL of decaffeinated coffee. This was conducted over ten sessions, each separated
by 24-h washout periods. Subjective perceptions of energy levels were assessed through
questionnaires given during coffee ingestion and again 240 min post-testing. The ingestion
of the test solutions did not result in increased energy or activity [19].
3.3. Hunger and Satiety
Bulletproof Coffee has been claimed to reduce hunger and assist with satiety [
12
]. One
randomized, double-blind, crossover trial conducted by Fritchen assessed satiety levels
through questionnaires administered at baseline and 60-min post-ingestion. Participants
indicated significantly enhanced levels of satiety on a five-point Likert scale questionnaire
following consumption of Bulletproof Coffee (0.875
±
0.31; p< 0.05). In contrast, feelings of
satiety declined in the black coffee condition, but this change was not statistically significant
(0.417
±
0.30; p> 0.05). Differences between Bulletproof Coffee and regular coffee were not
determined [18].
Crampton et al. measured satiety in a randomized, single-blind, crossover design trial.
Hunger and fullness were assessed by questionnaire at baseline in a fasted state and 60- and
170-min post-consumption of Bulletproof Coffee and black coffee. A significant condition
by time interaction was observed, resulting in increased measurements of fullness (p= 0.04)
and reductions in perceived prospective food consumption (p= 0.02) in the Bulletproof
Coffee condition compared to black coffee [16].
Satiety was also measured in another double-blind randomized controlled interven-
tion. The questionnaire was administered before and 240 min after Bulletproof Coffee
consumption. The questionnaire consisted of six items on hunger and satiety that were

Beverages 2023,9, 101 7 of 13
evaluated using a 10-point scale. Participants reported elevated levels of hunger at the start
of the intervention due to the overnight fast (min 3
±
3.1; max 5.29
±
2.98 mean values
not provided), and all interventions resulted in increased hunger (min 6.17
±
1.84; max
8.43
±
1.13 mean values not provided) and diminished satiety (data not provided). No
significant differences in satiety were apparent between the Bulletproof Coffee and regular
coffee groups [19].
3.4. Resting Energy Expenditure and Fat Oxidization
Fritchen et al. conducted a randomized, double-blind, crossover trial to explore the
acute metabolic effects of Bulletproof Coffee. Following a 12-h overnight fast and ingestion
of a standardized test meal, baseline metabolic measurements were recorded using indirect
calorimetry. Subsequently, participants consumed either Bulletproof or black coffee, each
supplying 4 mg caffeine/kg of body weight and metabolic measurements were repeated
immediately, as well as at 30- and 60-min intervals. The results indicated a significant
interaction between time and condition for resting energy expenditure (REE; p= 0.003), with
an increase observed in both conditions. Notably, only the Bulletproof Coffee condition
demonstrated a statistically significant elevation in REE, increasing from a baseline value
of ~1665 kcal/day by 207
±
76 kcal/day at 30 min and 224
±
77 kcal/day at 60 min
post-consumption (p< 0.05). Additionally, a significant interaction effect was observed
for fat oxidation rates in the Bulletproof Coffee condition, as indicated by a significant
decrease in respiratory quotient (RQ) at 30 and 60 min (
−
0.077
±
0.015 and
−
0.068
±
0.015,
respectively; p= 0.003). No significant changes in RQ were observed after consuming black
coffee, and between-group differences for REE and RQ were not analyzed [18].
3.5. Serum Cholesterol
McAllister et al. conducted a randomized, double-blind crossover trial that measured
the effects of coffee with varying amounts of MCT oil on total cholesterol and HDL-c.
Ten men with no known history of cardiometabolic disorders who habitually consumed
8–16 ounces/day
(237–473 mL/day) of coffee underwent an
≥
8 h fast prior to testing
sessions. On three separate days, participants ingested 16 ounces (473 mL) of freshly
brewed black coffee with stevia as the sweetener and no added lipids, 28 g lipids, and
42 g lipids. Caffeine content was estimated as 100–200 mg for all conditions. Lipids
consisted of 75% MCT oil and 25% coconut oil. Participants were allowed 15 min to finish
the beverage and blood samples were collected at pre- 120 min post- and 240 min post-
prandial. The four-hour area under the curve (AUC) for total cholesterol was
777.1 ±91.0
,
776.7
±
125, and 814.8
±
66.3 mg/dL following consumption of the 0, 28, and 42 g MCT-
containing beverages respectively. The AUC for HDL-c was 225.6
±
61.8, 253.7
±
68.5,
and
263.3 ±78.3 mg/dL
. Differences in total cholesterol reached statistical significance
between the 0 g and 28 g lipids conditions (p= 0.03) and 0 g and 42 g lipids conditions
(
p= 0.02
). Differences in HDL-c also reached statistical significance between the 0 g and
28 g lipids conditions (p< 0.003) and 0 g and 42 g lipids conditions (p< 0.001). LDL-c was
not measured [20].
A case report has also been published involving a 59-year-old male with dyslipidemia
who experienced a notable rise in serum lipids after incorporating Bulletproof Coffee
into his dietary regimen. Upon discontinuation of rosuvastatin, the patient’s lipid levels
nearly doubled (total cholesterol: 138 to 215 mg/dL; LDL-c: 84 to 156 mg/dL; HDL-
c: 43 to 44 mg/dL). Serum cholesterol measurements were then repeated, after which
he began consuming one to two cups of Bulletproof Coffee daily. Over several months,
while maintaining a consistent exercise regimen, his lipid profile deteriorated further (total
cholesterol: 215 to 285 mg/dL; LDL-c: 156 to 232 mg/dL; HDL-c: 44 to 48 mg/dL), leading
to the recommendation to cease consumption [21].

Beverages 2023,9, 101 8 of 13
3.6. Gastrointestinal Tolerance
Gastrointestinal intolerance has been reported with consumption of Bulletproof Coffee.
Fritchen et al. evaluated gastrointestinal tolerance using a Likert scale after participants
consumed Bulletproof or black coffee. Results suggested a significant increase in gastroin-
testinal intolerance scores (
−
1.33
±
0.21; p< 0.05) following ingestion of Bulletproof Coffee,
which included 22–61 g of total fat, an effect not observed with black coffee, which included
0 g of total fat. Notably, several participants (n= 5) reported difficulty relaxing during
the test due to gastrointestinal intolerance. Similarly, Baumeister et al. evaluated gastroin-
testinal tolerance by administering questionnaires to participants 240 min after consuming
either Bulletproof or black coffee [
19
]. The questionnaires indicated that side effects such
as abdominal pain (n= 7) and nausea (n= 7) were most common with Bulletproof Coffee
consumption, which is estimated to contain 9 g of total fat. It is noteworthy that participants
generally rated the perceived acidity of the beverages higher when consuming Bulletproof
Coffee [18].
4. Discussion
This narrative review evaluated the existing scientific evidence pertaining to Bullet-
proof Coffee, a high-saturated fat, caffeinated beverage. Popular claims about this product
suggest it is associated with cognitive enhancement, heightened energy levels, and satiety
benefits. However, the scientific evidence does not support these claims. From a very small
evidence base, we found there were no significant improvements in cognition, alertness, or
energy levels from Bulletproof Coffee consumption compared with regular coffee. The ef-
fects of Bulletproof Coffee on hunger, satiety, resting energy expenditure, and fat oxidation
were equivocal and likely due to the increased caloric load accompanying its consumption.
There is also evidence of possible elevations in serum cholesterol and gastrointestinal
intolerance following consumption of Bulletproof Coffee.
In the cognitive domain, studies by Crampton et al. [
16
] and Bergauer et al. [
17
] do not
support the purported benefits of Bulletproof Coffee compared to regular or decaffeinated
coffee. These findings correspond with previous research that has not consistently demon-
strated the efficacy of caffeine in enhancing memory [
22
], a critical domain of cognition.
Nevertheless, the limited sample sizes and narrow array of cognitive measures employed
in these studies may restrict the generalizability of results. Future research employing
more rigorous study designs, larger sample sizes, diverse demographic groups, and a
broader array of cognitive measures is warranted to fully elucidate the potential impact of
Bulletproof Coffee on cognition.
The impact of Bulletproof Coffee on subjective alertness and energy was divergent
between studies. Bergauer et al. [
17
] found no significant impact of Bulletproof Coffee
on mood dimensions such as alertness. Moreover, results indicated an unexpected rise in
alertness following placebo consumption, suggesting the possible interplay of expectancy
effects or other psychological factors. Results could have been influenced by the timing
of the mood assessment, given that the effects of caffeine typically peak ~45 min after
ingestion [
19
], while the Bond & Ladder questionnaire post-measurement was taken 95 min
post-consumption. Furthermore, the cognitive tasks executed during the testing proce-
dure may have affected mood ratings. Conversely, results from Fritchen [
18
] indicated
significant elevations in alertness approximately 60 min subsequent to the ingestion of
both Bulletproof Coffee and regular black coffee. Perceived increases in alertness may
have arisen from the caffeine content, which was consumed with greater temporal prox-
imity to assessments. Research from Baumeister et al. [
19
] did not produce subjective
increases in energy levels regardless of the presence or absence of caffeine or dietary fat
in coffee beverages. Post-ingestion measurements were collected 240 min post-ingestion
which, similar to the study by Bergauer et al. [
17
], is outside the window of peak effect for
caffeine [
23
]. Collectively, these studies indicate the need for a more rigorous and standard-
ized methodological approach, incorporating precise timing of cognitive assessments and

Beverages 2023,9, 101 9 of 13
controlling for potential confounding variables such as the cognitive tasks themselves as
well as psychological expectancy effects.
Bulletproof Coffee was associated with increased levels of self-reported satiety in one
study [
18
], but this was not corroborated by subsequent research [
19
]. In the study by
Fritchen [
18
], Bulletproof Coffee provisions included 1 tablespoon (15 mL) of both MCT
oil and grass-fed butter per 12 ounces (355 mL) of coffee, providing 200–550 calories, and
subjects indicated enhanced levels of satiety following ingestion. Baumeister et al. [
19
]
also assessed satiety following consumption of Bulletproof Coffee. The product used in
this study included decaffeinated coffee, with or without 150 mg added caffeine, with
or without 10 g of MCT or coconut oil, and omitted grass-fed butter, yielding no more
than 90 calories per condition. No significant differences in satiety were detected between
groups. Differences in the energy provisions of beverages may have contributed to the
disparate findings because the decreased calorie content might have lessened the satiating
effect of the beverage. Despite robust evidence suggesting that dietary fat is the least
satiating macronutrient [
24
], it still yields a moderate satiating effect, comparable to canola
and peanut oils [25].
The only study that assessed metabolic parameters found that consumption of both
Bulletproof Coffee and black coffee increased REE, but the results only reached statistical
significance in the experimental condition [
18
]. The magnitude of this elevation is compara-
ble to that observed following consumption of other high-fat meals [
26
,
27
], which suggests
that the postprandial elevation in energy expenditure is unlikely to confer a unique advan-
tage pertaining to energy balance. The observed increase in REE from baseline following
Bulletproof Coffee consumption can likely be attributed to the additional 200–550 calo-
ries the beverage provided from dietary fat, since caffeine content relative to body mass
was matched between conditions. The additional calories consumed from dietary fat in
Bulletproof Coffee are likely to offset the observed increase in REE. Previous research has
demonstrated that high-fat meals and beverages can increase REE in healthy individuals,
with higher polyunsaturated fatty acid (PUFA) contents yielding larger increases compared
to meals rich in saturated fatty acids (SFAs) [
28
,
29
]. Similar increases in REE have been
observed with high-carbohydrate meals [
30
–
32
], suggesting that butter and MCT oil in
Bulletproof Coffee may not play a unique role in elevating postprandial metabolic rate.
The lack of a significant difference in REE with black coffee consumption is unexpected,
given prior research indicating a 3–4% increase in REE with a 100 mg caffeine dose [
33
].
Considering that participants in the study by Fritchen consumed over twice this dosage
(~220–440 mg caffeine) [
18
], further research is needed to determine factors influencing the
impact of coffee and caffeine on REE. Potential factors may include variations in individual
responses and other underlying mechanisms modulating the thermogenic effects [34].
The only trial that examined substrate utilization following coffee consumption found
that Bulletproof Coffee, but not black coffee, produced significant increases in fat oxidation
rates [
18
]. Studies comparing substrate utilization after consuming meals or beverages high
in SFAs or PUFAs do not show significant differences in fat oxidation [
28
,
29
], indicating
that alternative sources of unsaturated fats (e.g., soymilk, almond milk) could be used in
coffee preparation if increased fat oxidation and lower saturated fat intake is desired. It is
important to highlight, however, that elevated rates of fat oxidation do not necessarily lead
to a larger body fat reduction [
35
], emphasizing the complexity of weight management.
The absence of significant differences in fat metabolism with black coffee may be attributed
to insufficient caffeine dosage and the chosen measurement modality. While all participants
consumed 4 mg of caffeine per kilogram of body weight (mg/kg) [
18
], a recent meta-
analysis on caffeine consumption and fat metabolism indicated that a dosage of 5.7 mg/kg
produces a small effect size on fat metabolism when analyzed using expired gas analysis
(e.g., respiratory exchange ratio, calculated fat oxidation) (effect size = 0.26, 95% CI [0.16,
0.37]) [
36
]. Notably, caffeine seems to exert a greater impact on fat metabolism (p< 0.001)
when evaluated through blood biomarkers (e.g., free fatty acids, glycerol) (effect size = 0.55,
95% CI [0.43, 0.67]) [
36
]. Further research is warranted to explore the effects of Bulletproof

Beverages 2023,9, 101 10 of 13
Coffee on endpoints that are more consequential to weight management, including body
weight and body composition.
Serum total- and HDL-cholesterol levels were shown to increase acutely following
consumption of Bulletproof Coffee prepared with MCT oil [
20
]. These findings correspond
with previous research showing that acute coffee ingestion increases total cholesterol and
HDL-c levels to a statistically but not clinically significant extent, due the cholesterogenic
diterpene esters, cafestol and kahweol, which are naturally present in coffee bean oils [
37
,
38
].
A meta-analysis of randomized controlled trials found that MCT oil raises total cholesterol
and LDL-c relative to comparators consisting predominantly of unsaturated fats, but not
longer-chain SFAs [
39
]. Significant changes in serum lipids may therefore be attributable to
a combination of caffeine and MCT oil, particularly if the MCT oil replaced dietary sources
of unsaturated fat present in the baseline diets of participants.
Evidence regarding the effects of long-term Bulletproof Coffee consumption on serum
cholesterol levels is limited to a case report by Toklu et al. [
21
], which indicated clini-
cally significant increases in total and LDL cholesterol experienced following months of
daily Bulletproof Coffee consumption. The report found 33% and 49% increases in total
cholesterol and LDL-c, respectively, while HDL-c levels increased by 9% [
21
]. However,
the clinical significance of the HDL-c change remains unclear, as diet-induced changes in
HDL-cholesterol cannot be directly associated with changes in CVD risk [
3
]. Consequently,
the American Heart Association recommends evaluating changes in LDL-c independently
of HDL-c [3].
While one randomized controlled trial and one case report are not sufficient to deter-
mine causality between Bulletproof Coffee and exacerbated dyslipidemia, these findings
do align with evidence between dietary fat type and hypercholesterolemia. For example, a
standard cup of Bulletproof Coffee contains 1–6 teaspoons of MCT oil and 1–2 tablespoons
of grass-fed butter [
11
]. A recent meta-analysis indicated that MCTs typically do not pro-
duce significant increases in total cholesterol or LDL-c levels [
39
]. Conversely, numerous
controlled trials have demonstrated that dairy fat, including butter, elevates LDL-c com-
pared to unsaturated vegetable oils [
3
]. It is noteworthy that the effects on blood lipids are
similar whether the butter is sourced from grass-fed or conventionally-fed cows [
40
]. The
impact of LDL-c levels on CVD risk is well established [
3
], and prospective observational
studies indicate that substituting 5% of total daily calories from dairy fat with PUFAs for
dairy fat is associated with a 24% and 25% lower risk of heart disease and stroke, respec-
tively [
41
]. Given the paucity of research exploring the relationship between consumption
of Bulletproof Coffee and hyperlipidemia, further research is needed. However, regular
consumption of butter is associated with increased LDL and total cholesterol and should
be especially limited, especially in people with a history of hypercholesterolemia [42].
Finally, gastrointestinal intolerance was associated with Bulletproof Coffee consump-
tion in both studies that assessed this outcome [
18
,
19
]. Caffeine stimulates the gastric
secretion of hydrochloric acid [
43
], but a potential explanation for the greater prevalence of
gastrointestinal intolerance observed in Bulletproof Coffee conditions may be the high fat
content. Dietary fat delays gastric emptying [
44
], a common cause of chronic nausea and
vomiting [
45
]. Dietary fat can also increase intestinal permeability [
46
], which has been
associated with self-reported gastrointestinal symptoms [
47
]. Such factors may contribute
to the pathophysiology detailed in the clinical vignette of a 48-year-old man admitted to
the hospital with abdominal pain after consuming 10 tablespoons of Brain Octane Oil, the
MCT oil sold by Bulletproof Digital, Inc., providing 140 g of total fat [
48
]. The patient
developed new onset vomiting, diarrhea, and rectal bleeding, prompting the visit to the
emergency department. His symptoms resolved with hydration, and he was instructed to
discontinue use of Brain Octane Oil. It is important to highlight that this patient consumed
five times the recommended quantity of MCT oil in the Bulletproof Coffee recipe [
9
], and
such severe symptoms were not reported in the controlled experiments. Nevertheless,
gastrointestinal discomfort was experienced by multiple participants in both trials that
assessed tolerance following Bulletproof Coffee consumption [
18
,
19
]. Further research is

Beverages 2023,9, 101 11 of 13
warranted to elucidate the underlying factors contributing to gastrointestinal intolerance
associated with Bulletproof Coffee consumption.
The existing literature on Bulletproof Coffee provides valuable insights into the
claimed potential effects on cognitive performance, mood, energy levels, satiety, and
metabolic parameters. A particular strength of these studies lies in their deployment of
double-blind, randomized controlled designs [
17
–
20
], thereby mitigating potential biases.
Another strength involves their inclusion of coffee with varied sources of SFAs such as
MCT oil with grass-fed butter [
17
,
18
,
21
], ghee [
16
], or coconut oil [
19
,
20
]. This could also
be a limitation however, since variable dietary provisions may produce discrepant results.
Additional limitations include small sample sizes, limited demographic diversity, and
constrained cognitive and metabolic assessments. Additionally, the temporal gaps between
interventions and subsequent assessments may not fully capture the peak physiological and
psychological effects of the components within the beverage. Of the six studies included,
one was a published conference abstract and two were student theses that were unlikely to
have been peer reviewed. Therefore, findings from the present studies necessitate cautious
interpretation and warrant further validation.
Future investigations would benefit from comprehensive assessment batteries that
extend beyond short-term outcomes. For example, research could investigate the long-
term effects of Bulletproof Coffee on lipid profiles and cardiovascular health, given the
preliminary findings on its influence on cholesterol levels [
20
,
21
]. More research is also
needed to isolate the individual effects of Bulletproof Coffee made with specific ingredients
like MCT oil and grass-fed butter on parameters such as satiety and metabolic rate. Finally,
given the initial evidence of gastrointestinal intolerance [
18
,
19
], further explorations into
the safety profile are crucial, especially in populations with preexisting gastrointestinal or
metabolic conditions.
5. Conclusions
In conclusion, although Bulletproof Coffee remains a popular choice for many, cur-
rent scientific evidence does not support the claimed benefits. While the evidence base is
limited to six studies with small sample sizes, we found no significant improvements in
cognition, alertness, or energy levels in studies when Bulletproof Coffee was compared
with regular coffee. The alleged effects of Bulletproof Coffee on hunger, satiety, resting
energy expenditure, and fat oxidation remain equivocal, primarily due to the additional
calorie intake associated with the beverage offsetting any potential benefits. Additionally,
the review highlights potential health concerns linked to butter, which is a major ingredient
of Bulletproof Coffee. Some evidence suggests possible elevation in serum cholesterol, and
gastrointestinal intolerance has been reported following consumption of Bulletproof Cof-
fee. Future research, featuring larger sample sizes, diverse populations, and standardized
methodologies, is necessary to support any health claims for Bulletproof Coffee, and to
ascertain any long-term health risks associated with regular Bulletproof Coffee consump-
tion. Exploring the impact of regular Bulletproof Coffee consumption on hydration status,
kidney stones, reflux, gallstones, blood pressure, sleep quality, gastrointestinal motility,
and hyperlipidemia is also required. Such research would significantly contribute to our
understanding of the impacts of this beverage, informing public health recommendations
and individual dietary choices.
Author Contributions:
Conceptualization, D.M.G.; Methodology, D.M.G.; Investigation, D.M.G.,
M.Q., J.C.C. and K.L.; Writing—Original Draft Preparation, D.M.G. and M.Q.; Writing—Review &
Editing, D.M.G., M.Q., K.L. and J.C.C. All authors have read and agreed to the published version of
the manuscript.
Funding: This research received no external funding.
Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is
not applicable to this article.

Beverages 2023,9, 101 12 of 13
Conflicts of Interest:
D.M.G. and M.Q. are employed by Metabite, Inc., a digital platform that
facilitates evidence-based dietary change. J.C.C. and K.L. declare no conflicts of interest.
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