The Bulletproof Diet: Lose Up to a Pound a Day, Reclaim Energy and Focus, Upgrade Your Life

Overall score

Scientific accuracy

Reference accuracy

Healthfulness

How hard would it be to apply the book's advice? Very difficult

Book published in 2014

Published by Rodale

First Edition, Hardcover

Review posted January 18, 2019

Primary reviewer: Seth Yoder

Peer reviewer: Stephan Guyenet

Table of contents

1. Introduction
2. Scientific accuracy
3. Reference accuracy
4. Healthfulness
5. Most unusual claim
6. Other
7. Conclusion
8. Updates

Claim 1. This first claim is that a high saturated-fat diet is beneficial for health. This claim is worth exploring, but ultimately is not well supported by the scientific evidence. One point in favor of saturated fat is that a systematic review evaluating over 100 feeding studies indicated that replacing carbohydrates in the diet with saturated fats did not affect glucose control or insulin sensitivity. However, the review also indicated that replacing either carbohydrates or saturated fats with unsaturated fats, particularly polyunsaturated fats, is beneficial for controlling blood sugar levels.

Randomized controlled trials suggest that reducing saturated fat intake reduces the risk of cardiovascular disease. Some controversial review articles have stated that evidence does not “clearly support” diets low in saturated fat to reduce the risk of cardiovascular diseases; however, when individual saturated fats are analyzed certain fatty acids such as palmitic acid and stearic acid are associated with higher CVD and diabetes risk (although stearic acid is controversial because it does not have substantial negative effects on blood cholesterol levels). These saturated fatty acids constitute the majority of the fats found in animal products like butter and meats that are encouraged in TBD.

One of the defining characteristics of TBD is a preference for products like butter and beef from grass-fed cows instead of conventionally raised cows. The book claims that the grass-fed beef has “more conjugated linoleic acid (CLA), which is a type of naturally occurring trans fatty acid that improves brain function, causes weight loss, and reduces your risk of cancer.” (page 48) To support this, it cites a study demonstrating higher concentrations of CLA in grass-fed beef compared with grain-fed. However, the results of the study might be disappointing. The starkest difference in CLA concentrations detailed in the study were found in rump cuts where the cattle fed grain long-term had 25.2mg per 100g of meat and the grass-fed cattle had only 31.5 mg per 100g of meat. To put this in perspective, that’s a difference of 6.3 mg or 0.0063 grams of CLA in a piece of meat about the size of a burger patty. Moreover, TBD does not cite any evidence supporting the health claims regarding weight loss, brain function, or cancer or any evidence that difference of 6.3 mg is clinically significant. Nevertheless, scientific evidence does exist suggesting benefits of CLA supplementation for weight loss and potential anticancer and antidiabetic properties. It should be noted, however, that most of the human weight loss trials supplemented individuals with several grams of CLA per day and the trials lasted only a few weeks. Additionally, the anticancer research is almost exclusively from cell cultures and animal trials, and not human clinical trials. There is no evidence suggesting that the tiny differences in intake that would result from following TBD guidelines would impact weight or health in any way, and it seems unlikely.

TBD also advocates a reduction of dietary grains and fruits. With respect to this claim, there just is not much evidence to support it. Moreover, what evidence exists suggests that consumption of whole grains is linked with reduced risk of cardiovascular diseases, cancer, diabetes, and obesity. There is also evidence that gut bacteria can utilize the indigestible parts of grains such as the lignans and cellulose to produce beneficial compounds such as enterolactone and butyrate. Fruit consumption also has a well-documented association with reduction in CVD and cancer risk, in addition to containing beneficial bioactive compounds.

In many cases, TBD makes no effort to support the claims it has made. When it does cite sources, these are typically reputable peer-reviewed journals.  However, in some cases TBD relies on personal anecdotal evidence for support. Here is such an example from page 31 that strains credulity:

“I figured that if what we’ve been taught about diets is true, I’d gain a pound of fat for every extra 3,500 calories I ate, especially if I ate tons of fat. To really stack the deck against myself for the experiment, on August 6, 2009, I stopped exercising, cut my sleep to less than 5 hours a night (which is also supposed to make you fat), and started eating between 4,000 and 4,500 calories from the Bulletproof Diet each day. About 70 percent of those calories came from Bulletproof fats. According to most nutritionists, I should have gained a dozen pounds in a month of eating this way. Instead, the opposite happened. Suddenly, I was on fire. My brain worked effortlessly, I didn’t need more sleep, and I even grew a six-pack. I couldn’t believe it, and I’ll admit that I spent a lot of time in front of the mirror marveling at how flat my stomach was becoming as I literally stuffed myself with food.”

When TBD does cite scientific evidence, it often does so selectively, focusing on evidence that does not represent the body of evidence as a whole, or should be interpreted cautiously. For example, on page 45 TBD states the following:

“[A]n exhaustive analysis of 76 academic studies involving more than 600,000 participants found that saturated fat consumption is in fact not associated with coronary disease risk. This is well known in the antiaging world where I cut my teeth, and it’s baked into (pun intended) the Bulletproof Diet.”

The study cited here is a rather controversial meta-analysis published in 2014 in the Annals of Internal Medicine that concludes “Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.” However, this is not equivalent to concluding the inverse: that higher saturated fat consumption protects against cardiovascular disease. The conclusions drawn by this meta-analysis do not provide evidence supporting TBD’s claim that increasing saturated fat intake is beneficial.

Another claim TBD makes that is supported by a typically reputable source that is conveying poor information in this case is the following on page 29:

“In the 1950s, a scientist named Ancel Keys rocked the world of nutrition by claiming, with some pretty convincing research, that saturated fat caused heart disease. The low-fat diet craze immediately stormed the scene and has unfortunately stuck around ever since, despite the fact that we later learned Keys threw out data that didn’t fit his model. In other words, he manipulated the research to make it look like it backed his theory that saturated fat caused heart disease, but in fact the science didn’t support his theory at all.”

And again, on page 45:

“As you read in the previous chapter, saturated fats have been vilified ever since Ancel Keys used faulty research to back his claim that they lead to heart disease […]”

This is a false narrative about Ancel Keys and his work that has nevertheless been often repeated throughout the low-carbohydrate community. TBD’s source of this information comes from The New York Times, which is generally considered to be a source of credible information. In this case, however, it was from a review of Gary Taubes’s book Good Calories, Bad Calories, where the reviewer repeats Taubes’s questionable account of Keys’s career. This account is dispelled by a more complete and accurate accounting of Keys’s work.

Claim 2. Moving on to claim #2, TBD claims that modern, conventional foods are contaminated with bacteria and toxins, particularly mycotoxins (a class of toxins produced by fungi), that can harm you and prevent optimal performance. The subject of food safety is not a common topic in diet books, and often gets overlooked. Still, food contamination is a genuine concern as food recalls occur nearly every day. However, these recalls are typically due to contamination from foreign material, a pathogen such as Listeria, or undeclared allergens, not mold contamination. Nevertheless, mycotoxins such as patulin, aflatoxin, and ochratoxin A (OA) do exist in some food products. Mycotoxin-producing fungi can occur in fields where crops are grown, and sometimes processing methods do not completely remove them. The issue here is that while TBD does cite some evidence that mycotoxins exist in food, it makes no effort to demonstrate that the levels are high enough to impact health. For example, on page 9-10 TBD states,

“Mold toxins are present in a significant amount of coffee. One study testing green coffee beans grown in Brazil showed that more than 90 percent were contaminated with mold before processing, while another revealed that almost 50 percent of brewed coffees are moldy.”

16 out of 40 brewed coffee samples in his cited study contained ≤1/µg OA/kg coffee (that’s 40 percent), but there is no further evidence suggesting that this level of OA would lead to diminished performance or health problems. In fact, this level is well within the acceptable limits established by the European Union.

There also is little discussion of the role of a food manufacturer in this context. There is a brief description of how coffee is stored and roasted, but no discussion of food safety management systems in manufacturing. For example, food manufacturers and processors are typically required to have a food safety plan that has analyzed potential food safety (and increasingly, food quality) risks and take concrete steps to mitigate those risks. Documentation must be kept for years and gets reviewed by the FDA during unannounced inspections. The FDA has the authority to mandate recalls, embargo product, and revoke its registration and ability to do business if significant hazards are present.

For example, patulin is a known mycotoxin with risks to apples and apple juice manufacturing. Therefore, manufacturers must take appropriate steps to reduce the risk of contamination, which could include requiring letters of guarantee from apple suppliers, patulin test results from the suppliers, inspection of each shipment of apples, sorting and culling of any suspect apples from inventory, and finished product testing. If there are gaps in any of this documentation it could be a significant violation of Good Manufacturing Practices as defined in 21 CFR 117.

As mentioned above, TBD cites sources that support the assertion that mycotoxins exist in food products, however, none support the book’s claim that these toxins are present at levels that lead to negative health or performance consequences. The food we eat on a daily basis contains a number of toxins that are harmful to health at high doses, but irrelevant at the doses commonly consumed. To demonstrate that mycotoxins are relevant, TBD has to demonstrate that they are present at a high enough concentration to matter.

The only evidence TBD presents to support the idea that trace levels of mycotoxins in food impact health or performance is a study commissioned by Asprey and apparently conducted at Stanford university (page 72):

“I designed a study to determine what impact, if any, my mold-tested beans would have compared to coffee from local coffee shops. It was these results that confirmed what I’d discovered myself and verified with a few guinea pig friends. To do this test, I started by registering with an institutional review board, which issues approvals for tests conducted on humans to verify that they’re safe. I worked with a Stanford researcher to put together a statistically valid, uncomfortably rigorous set of tests. We asked 54 people, recruited from the Bulletproof Executive Facebook page, to conduct two batteries of cognitive function tests per day for 4 weeks while using different combinations of butter and coffee:

Lab-tested Upgraded Coffee (black)

Coffee made with beans from a local shop (black)

Lab-tested Upgraded Coffee with butter

Coffee made with beans from a local shop with butter”

Asprey recruited experimental subjects from his audience and had them drink his low-mycotoxin “Upgraded coffee” or Starbucks dark roast prior to taking a battery of cognitive tests. The results, presented on pages 72-73, suggest that people who drank the Upgraded coffee performed better than people who drank Starbucks coffee.

However, this study does not convincingly support TBD’s claims, for the following reasons:

1.      The study began in 2012, and six years later it still hasn’t been published in a scientific journal where it can be fully evaluated (all we have is the impressionistic sketch provided in TBD). For reasons described below, the study probably wouldn’t be accepted by a credible peer-reviewed journal, which may explain why it hasn’t been published.
2.      The study wasn’t blinded, meaning that people knew whether they were drinking Upgraded coffee or Starbucks. This is especially important because Asprey recruited experimental subjects from among his fans, who were already biased in favor of Upgraded coffee. It’s not difficult to imagine that his fans may have performed better on the Upgraded coffee, and worse on Starbucks, simply due to this fact. These types of effects can be substantial, which is why pharmaceutical trials are usually blinded and placebo-controlled.
3.      The study design is inherently unable to determine if mycotoxins impact cognitive performance. There are probably a number of subtle chemical differences between Upgraded coffee and Starbucks, of which slight differences in mycotoxin levels may have been one. Since mycotoxins weren’t isolated as a variable, we cannot logically conclude that they were responsible for the effect. Differences in cognitive performance could have been due to different levels of caffeine, or something else. To properly isolate the effect of mycotoxins per se, a valid experimental design would be to randomize people to two groups, without telling them which group they’re in: 1) Upgraded coffee, 2) Upgraded coffee plus trace levels of mycotoxin (at the concentration normally found in Starbucks). If there were a difference in cognitive performance between the two groups, you could then logically conclude that mycotoxins are responsible. This outcome seems highly unlikely given the very low levels of mycotoxin involved.

Claim 3. The third claim in TBD that is addressed here is about antinutrients: the claim that antinutrients can be found in certain foods that cause inflammation, damage the gut, and prevent the absorption of important nutrients which all lead to poor health and sub-optimal performance. In fact, TBD bases much of its nutrient guide in the latter half of the book on the concentration of antinutrients it possesses.

Indeed, there are substances found in plants that have been shown to bind to minerals such as calcium and magnesium and reduce their absorption. TBD dedicates some space to exploring these types of substances like phytate, oxalate, and lectins. It also correctly indicates that antinutrients can have beneficial effects as well, although these are not explored in as much depth as their antinutrient properties. One such potential benefit is that antinutrients like phytates and lectins can reduce both the glucose and insulin response after a meal. Interestingly, this likely works by the same mechanism that makes them antinutrients. TBD also correctly advises soaking or cooking foods in water to reduce their concentration of antinutrients.

TBD claims many of our modern-day illnesses — such as CVD, cancer, and diabetes — are linked to inflammation. Indeed, this link is supported by a large swath of evidence. However, what’s less supported is TBD’s alleged cause of all this inflammation, which is a condition colloquially known as leaky gut. The theory is that certain foods, such as wheat gluten, trigger a response in the epithelial cells lining the intestinal tract causing them to be less tightly bound to one another. This then leads to “toxins,” bacteria, and undigested food to enter the bloodstream, which causes inflammation throughout the body.

There is some evidence that intestinal permeability (aka “leaky gut”) can occur in individuals with an inflammatory bowel disease (IBD) such as Crohn’s, when triggered by certain foods. What’s more controversial about TBD’s claims is that this happens to “everyone, not just those who are sensitive to gluten” and the alleged mechanism by which this occurs: an overrealease of a protein called zonulin. TBD claims that eating gluten increases zonulin levels, which opens the junctions between the epithelial cells leading bacteria, undigested food, and toxins to “flood into your blood stream” causing inflammation throughout the body. This is quite an overstatement of what the literature indicates. First of all, TBD cites no literature to support this statement, but much of the research on zonulin so far has been performed by Alessio Fasano from Harvard. His work on the subject indicates that zonulin is indeed upregulated by gliadin (a component of gluten) and some species of bacteria. However, there is currently no evidence that eating gluten actually increases intestinal permeability in healthy people, nor has it been shown to increase levels of inflammation.

To be clear, the intestinal tract is evolved to be “leaky,” in a sense, because water is typically absorbed via passive diffusion through gut, and there are various mechanisms used to transport other nutrients like electrolytes, vitamins, and macronutrients. However, absent a serious GI disease, there is currently  no evidence gluten or any other food causes it to become leaky in the way TBD describes it, allowing food molecules, toxins, and bacteria to indiscriminately enter the bloodstream.

Claim 1

Summary of claim

TBD advocates consumption of a high-fat diet (particularly saturated fat), consisting of mainly meats and grass-fed butter, while restricting consumption of grains and fruits. TBD is moderately low carbohydrate, prescribing some amount of carbohydrate consumption from specific sources. The book claims that this diet pattern has a variety of benefits, including weight loss, reduction of disease, beneficial changes in the gut microbiome, and improved mental function.

Supporting quote(s) and page number(s)

“Fat is the foundation of the Bulletproof Diet…” (page 30)

“Fat is the most important and least inflammatory macronutrient, and on the Bulletproof Diet, 50 to 70 percent of your daily calories should come from the right kinds of fats.“ (page 43)

“The Bulletproof Diet is all about fat, but the type of fat you consume is key.” (page 58)

“[F]ruit is full of performance-sapping fructose and should only be eaten in small amounts.” (page 50)

“The Bulletproof solution is to eat a modest amount of Bulletproof carbs (about 30 grams, plus vegetables), but only with your evening meal or soon after. Once or twice a week, eat 100 to 150 grams.” (page 85)

Criterion 1.1. How well is the claim supported by current evidence?

0 out of 4

This claim receives a score of 0, indicating that the claim is opposed by current evidence. The current available evidence suggests that diets high in saturated fats and red meats are not beneficial and have been associated with chronic diseases such as cancer, cardiovascular disease, metabolic syndrome, obesity, and diabetes. While grass-fed sources of foods like beef and butter may have a slightly improved lipid profile, there is no evidence that this minor change in fatty acids would offer clinically significant protective benefits from these diseases. Further, diets like the Mediterranean diet that are high in fruits, vegetables, and whole grains and low in red and processed meats have been linked to improved health.

 

Criterion 1.2. Are the references cited in the book to support the claim convincing?

3 out of 4

This item was scored a 3, indicating that the references that are provided are moderately convincing. When TBD does support a claim by citing something previously published, it generally chooses reputable sources such as peer-reviewed articles. Although on occasion, these sources are weak, such as anecdotal accounts.

Criterion 1.3. How well does the strength of the claim line up with the strength of the evidence?

1 out of 4

This item was scored a 1, indicating that the evidence suggests substantially more uncertain effects relative to the author’s claim. The evidence generally disfavors this claim, and the evidence is unclear that slight alterations in the fatty acid profile with grass-fed as opposed to conventionally-raised cattle would have a meaningful impact.

Overall (average) score for claim 1

1.3 out of 4

Claim 2

Summary of claim

TBD claims that modern, conventional foods are contaminated with bacteria and toxins, particularly mycotoxins, that can harm you and prevent optimal performance.

Supporting quote(s) and page number(s)

“Most people are exposed to chronic low doses of mold toxins in every single meal, but they are invisible and particularly hard to identify. The more mold toxins you eat, the more damage they do over time. I probably never would have recognized this if it weren’t for my familiarity with toxic mold.” (page 7)
“Besides coffee, the main sources of mold toxins in your diet are wheat, corn, and other grains, but peanuts, fruits, chocolate, and wine are often tainted with mold toxins, too. Mold toxins accumulate in the milk from cows that eat contaminated grains.” (page 11)

“When exposed to even low levels of mold toxins, many people lose their edge. At higher levels, mold toxins cause serious damage, such as cardiomyopathy, cancer, hypertension, kidney disease, and even brain damage.” (page 9)

Criterion 1.1. How well is the claim supported by current evidence?

2 out of 4

This item received a score of 2, indicating references offer evidence that is intrinsically convincing but only weakly supports TBD’s claim. While mycotoxins are present in some foods according to the material TBD cites, it cites no compelling evidence that the levels of mycotoxins typically observed in foods lead to negative health outcomes or a loss of “edge.” The existing evidence indicates that mycotoxin levels found in foods are typically within acceptable ranges established by public health authorities and unlikely to harm health.

Criterion 1.2. Are the references cited in the book to support the claim convincing?

1 out of 4

This item received a score of 1, indicating that the references offer evidence that is intrinsically unconvincing but is consistent with the author’s claim. The only real evidence of negative effects or loss of “edge” that was presented was a self-commissioned study, never published in a scientific journal, that doesn’t convincingly support the idea that mycotoxins impact cognitive performance.

Criterion 1.3. How well does the strength of the claim line up with the strength of the evidence?

1 out of 4

This item received a 1, indicating that the evidence suggests substantially more uncertain effects relative to the author’s claim. Again, the only evidence of negative health effects that was presented– an unpublished experiment organized by the author– fails to rise to the level of convincing or even probable.

Overall (average) score for claim 2

1.3 out of 4

Claim 3

Summary of claim

Certain antinutrients exist in some foods that cause inflammation, irritate the gut, and prevent absorption of certain minerals.

Supporting quote(s) and page number(s)

“I began studying causes of inflammation and found a huge body of research on the abundant antinutrients in most standard diets that can cause chronic inflammation. They do this by irritating the gut, which triggers the immune system, or otherwise damaging the body’s repair and detoxification systems. The body responds as if it’s been injured and becomes inflamed in an effort to heal. Then it gets even worse—your irritated intestinal lining allows undigested food particles and bacteria to enter your bloodstream and trigger a wider inflammatory response as your body attacks these foreign particles. When these antinutrients continually damage your gut, which unfortunately happens to most people on Western diets that include large amounts of inflammation-causing processed foods, your body is forced to constantly mount a response against a perceived enemy.” (page 3)

“Antinutrients play a much bigger role in how you feel every day than you might imagine. They can be a source of severe food cravings that distract you from whatever you’re trying to accomplish, or they can rob you of nutrients and interfere with your hormone function, wearing down different systems in your body and causing slow performance declines over time. Depending on the severity of antinutrient exposure and your genetics, your body may mount an autoimmune reaction. This causes even more damage as your immune system attacks important body systems. The trick is to reduce your body’s immune response by eating fewer foods with antinutrients and avoiding entirely the foods that trigger your immune system.” (pages 3-4)

Criterion 1.1. How well is the claim supported by current evidence?

2 out of 4

This item received a score of 2, indicating references offer evidence that is intrinsically convincing but only weakly supports the author’s claim. TBD correctly claims that certain compounds in foods can prevent the absorption of minerals and other substances. However, the idea that commonly consumed substances in food disrupt the intestinal lining and cause inflammation for individuals without a GI disorder is not supported by the available evidence.

Criterion 1.2. Are the references cited in the book to support the claim convincing?

2 out of 4

This item received a score of 2, indicating that the references offer evidence that is weakly convincing but is consistent with the author’s claim. Like many of the claims made in TBD, most claims are not supported with any evidence in the text. The sources that are cited within the text are generally reputable and are mildly supportive of the claims.

Criterion 1.3. How well does the strength of the claim line up with the strength of the evidence?

1 out of 4

This item was scored a 1, indicating that the evidence suggests substantially more uncertain effects relative to the author’s claim. While the chelating (mineral-binding) properties of antinutrients are largely supported, other claims such as antinutrients leading to inflammation and permeable intestine that allows bacteria and other materials to enter the bloodstream are broadly unsupported.

Overall (average) score for claim 3

1.7 out of 4

Overall (average) score for scientific accuracy

1.4 out of 4

Reference 1

Reference

Chapter 1, endnote 11. Banks WA, Coon AB, Robinson SM, Moinuddin A, Shultz JM, Nakaoke R, Morley JE. Triglycerides induce leptin resistance at the blood-brain barrier. Diabetes. 2004 May 1;53(5):1253-60.

Associated quote(s) and page number(s)

“[C]onsuming a lot of fructose also causes leptin resistance by elevating triglyceride levels. Triglycerides impair leptin transport and prevent it from entering the hypothalamus, the structure in the brain that most needs to receive the leptin signal to inhibit hunger.” (page 14)

Criterion 2.1. Does the reference support the claim?

2 out of 4

This reference receives a score of 2, indicating that it offers weak support to the claim. This is evidenced by the fact that the cited source is a study on mice.

Reference 2

Reference

Chapter 2, endnote 12. Prevention’s healing with vitamins: the most effective vitamin and mineral treatments for everyday health problems and serious disease; Alice Feinstein; Prevention Health Books.; 1996 Emmaus, PA. : Rodale Press

Associated quote(s) and page number(s)

“While many doctors claim that salt intake leads to high blood pressure, studies show that only certain people who already have high blood pressure react this way to salt.” (page 40)

Criterion 2.1. Does the reference support the claim?

3 out of 4

This reference received a score of 3, indicating it is moderately convincing. The cited text does state what TBD says but is a secondary source which provides commentary on the issue.

Reference 3

Reference

Chapter 3, endnote 16. Vidrine K, Ye J, Martin RJ, McCutcheon KL, Raggio AM, Pelkman C, Durham HA, Zhou J, Senevirathne RN, Williams C, Greenway F. Resistant starch from high amylose maize (HAM‐RS2) and Dietary butyrate reduce abdominal fat by a different apparent mechanism. Obesity. 2014 Feb 1;22(2):344-8.

Associated quote(s) and page number(s)

“A 2014 study found that eating butyrate was associated with an increased amount of healthy bacteria in the gut.” (page 63)

Criterion 2.1. Does the reference support the claim?

2 out of 4

This reference receives a score of 2, indicating that it offers weak support to the claim. This is evidenced by the fact that the cited source is a study on mice. Bifidobacterium was the main bacterium associated with this change, which is not mentioned in TBD; however, other studies have associated it with normal weight. See Obesity-associated gut microbiota is enriched in Lactobacillus reuteri and depleted in Bifidobacterium animalis and Methanobrevibacter smithii.

Reference 4

Reference

Chapter 4, endnote 20. Masiero E, Agatea L, Mammucari C, Blaauw B, Loro E, Komatsu M, Metzger D, Reggiani C, Schiaffino S, Sandri M. Autophagy is required to maintain muscle mass. Cell Metabolism. 2009 Dec 2;10(6):507-15.

Associated quote(s) and page number(s)

“Autophagy is required to maintain muscle mass, and it inhibits muscle breakdown in adults.” (page 86)

Criterion 2.1. Does the reference support the claim?

2 out of 4

This reference receives a score of 2, indicating that it offers weak support to the claim. The cited source is a study on mice.

Reference 5

Reference

Chapter 5, endnote 22. Earthing: The Most Important Health Discovery Ever? by Martin Zucker

Associated quote(s) and page number(s)

“Then a few months later I read about a cable systems engineering entrepreneur turned biohacker who figured out that electrically grounding himself had all kinds of positive effects on circadian rhythm and inflammation. He funded some small studies that showed grounding increases resilience because it speeds recovery, lowers inflammation, and normalizes cortisol.” (page 108)

Criterion 2.1. Does the reference support the claim?

2 out of 4

This reference receives a score of 2, indicating that it offers weak support to the claim. It’s true insofar as there is a guy who claims this in a newsletter, but the studies are dubious.

Reference 6

Reference

Chapter 6, endnote 8. Mathur N, Pedersen BK. Exercise as a mean to control low-grade systemic inflammation. Mediators of Inflammation. 2008;2008.

Associated quote(s) and page number(s)

“[C]hoosing the stairs over the elevator or taking a lunchtime walk or leisurely bike ride isn’t really exercise either because it isn’t intense and doesn’t cause a direct physiological adaptation. This is merely moving around. You won’t get the hormonal effects of real exercise from these activities, but you’ll still benefit from them. Moving decreases your risk of metabolic syndrome, breast cancer, cardiovascular disease, and vascular dementia. It also decreases overall systemic inflammation, which saps your performance and contributes to almost all known diseases.” (page 117; the emphasis is not in the original, but is included to highlight the particular claim)

Criterion 2.1. Does the reference support the claim?

1 out of 4

The reference receives a score of 1, indicating it is irrelevant. Or it’s barely relevant. TBD here is bifurcating physical activity into exercise and “merely moving around” and stating that you’ll still receive benefits from moving around. Then he cites a review on how regular exercise is beneficial. The review does not discuss moving around, light physical activity, walking, or anything similar.

Reference 7

Reference

Chapter 7, endnote 11. Ford ES, Mokdad AH. Dietary magnesium intake in a national sample of US adults. The Journal of Nutrition. 2003 Sep 1;133(9):2879-82.

Associated quote(s) and page number(s)

“Amazingly, based on the RDA, almost all Americans are deficient in magnesium, although even that amount is thought to be too low.” (page 129)

Criterion 2.1. Does the reference support the claim?

4 out of 4

This reverence receives a score of 4, indicating the reference offers strong support for the claim.

Reference 8

Reference

Chapter 8, endnote 16. Böger RH. The pharmacodynamics of L-arginine. The Journal of nutrition. 2007 Jun 1;137(6):1650S-5S.

Associated quote(s) and page number(s)

“Too much L-arginine can be damaging for some people […]” (page 145)

Criterion 2.1. Does the reference support the claim?

4 out of 4

This reverence receives a score of 4, indicating the reference offers strong support for the claim.

Reference 9

Reference

Chapter 9, endnote 1. Zhang Y, Callaway EC. High cellular accumulation of sulphoraphane, a dietary anticarcinogen, is followed by rapid transporter-mediated export as a glutathione conjugate. Biochemical Journal. 2002 May 15;364(Pt 1):301.

Associated quote(s) and page number(s)

“Kale also contains a potent anticarcinogen called sulforaphane, which works with glutathione to remove toxins from human cells.” (page 154)

Criterion 2.1. Does the reference support the claim?

4 out of 4

This reverence receives a score of 4, indicating the reference offers strong support for the claim.

Reference 10

Reference

Chapter 10, endnote 2. Freire FC, Kozakiewicz Z, Russell R, Paterson M. Mycoflora and mycotoxins of Brazilian cashew kernels. Mycopathologia. 1999 Feb 1;145(2):95-103.

Associated quote(s) and page number(s)

“A study found 37 fungal species on Brazilian cashews, and the dominant species of mold was one that did form toxins.” (page 184)

Criterion 2.1. Does the reference support the claim?

4 out of 4

This reverence receives a score of 4, indicating the reference offers strong support for the claim.

Overall (average) score for reference accuracy

2.8 out of 4

TBD would seem to take a great deal of time and effort to adhere to rigorously. Most restaurants do not serve foods compliant with TBD. It is currently not easy to find foods in a typical restaurant that serves organic vegetables; grass-fed beef; without grains, sugars, additives; Asprey’s allegedly mycotoxin-free coffee, etc. This means that foods need to be purchased from grocery stores and boutique shops. Even still, it is not always easy to find things like organic, grass-fed beef and pastured duck.

It would also require a fair amount of time and effort to prepare all these meals at home. Traveling while maintaining compliance with the diet would be challenging. Meals would have to be either made at home and taken on the road, or, in the case of traveling via plane and staying in a hotel, foods would have to be purchased at the nearest grocery store and prepared in a room with a kitchen suite. Although it’s clear that improving diet quality will always require some effort, TBD requires quite a bit of it.

Moreover, TBD could also be substantially costlier than other diets, as organic, grass-fed foods are much more expensive. For example, as of this writing generic butter is $0.22 per ounce, while Kerrygold grass-fed butter is $2.12 per ounce— 863% of the standard price. Conventional kale is $0.25/oz and organic kale is $0.35/oz.  Conventional ground beef patties are $5.99/lb, while organic and grass-fed patties are $8.99/lb. Generic organic coffee from Safeway is $0.60/oz, and Bulletproof coffee from Asprey’s website is currently $1.25/oz (plus shipping unless you order $50 of merchandise). TBD also recommends supplements, which can be expensive.  Followers of TBD have to be willing to accept significantly higher food costs than what most diets require.

Summary of the health-related intervention promoted in the book

TBD consists of high-fat and moderate-to-high-protein foods with liberal amounts of organic cruciferous (cabbage family) vegetables. TBD discourages consumption of genetically-modified foods, grains, dairy, polyunsaturated fats, and processed foods with ingredients like monosodium glutamate or aspartame. TBD also recommends adequate sleep, physical activity, intermittent fasting, and a myriad of supplements.

Condition targeted by the book, if applicable

To lose weight and achieve optimal mental and physical performance.

Apparent target audience of the book

The book appears to target a general audience.

Criterion 3.1. Is the intervention likely to improve the target condition?

1 out of 4

In this category, TBD receives a score of one, indicating the diet is likely neutral for weight loss and increased performance, or the effects are unknown. Regarding weight loss, it is possible to lose weight on a myriad of diets, if calorie expenditure exceeds consumption. Although TBD is not ketogenic, with a fat intake of up to 70% it could reasonably be considered to be a low-carbohydrate diet, and low carbohydrates can lead to weight loss or a reduction in fat. However, the high proportion of saturated fatty acids and unrestricted intake may lead to excess calorie consumption and weight gain. Without studies being conducted using TBD, it’s difficult to predict the long term results of the diet.

Regarding a potential improvement in mental or physical performance, again there is no good data indicating that it may lead to an improvement in these areas. However, we may draw conclusions based on individual aspects of TBD. For example, you could look at relative fat content of the diet and see what information is available. Evidence for endurance exercise indicates that high fat diets do not improve performance; rather, these diets seem to impair energy flux. A joint position statement from American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine echoes this conclusion, stating “High-fat diets are not recommended for athletes.”

Although not discussed in this review, vitamin supplementation is also recommended in TBD. A research paper by the US Army indicates that supplementation with additional vitamins and minerals had no beneficial effect on performance. The exception was creatine, which did boost performance, but creatine is not a recommended supplement in TBD.

With regard to mental performance, there might be some suggestive evidence that TBD can be beneficial. Fatty fish and fish oils, which are generally high in omega-3 fatty acids, are both recommended on TBD. A 2012 Cochrane Review indicated that omega-3 fatty acids did not demonstrate any cognitive benefits with older adults; however, a more recent 2017 systematic review suggests that omega-3s protect against cognitive decline. Additionally, there is a very small amount of evidence that a low glycemic breakfast could improve academic performance in young people. Bulletproof Coffee, which is recommended for breakfast on TBD, would be consistent with a low-glycemic meal.

Criterion 3.2. Is the intervention likely to improve general health in the target audience?

1 out of 4

TBD receives a score of 1, indicating that it has positive and negative qualities but its overall effects might be negative. At the point of this writing there are no short or long-term studies investigating the effects of TBD. Although comparisons can be drawn between TBD and a Paleolithic-style diet due to the restrictions on processed foods, sugars, and dairy with an emphasis on meats and vegetables, TBD is sufficiently different from Paleo and more mainstream diets to be unable to draw conclusions from publications examining those diets.

There is simply not enough evidence on a diet of this type in the public domain, apart from anecdotes in TBD itself, to come to reasonable conclusions. However, what little has been published in the scientific record on TBD is one case study in the Journal of Clinical Lipidology reporting one patient doubled his serum cholesterol after incorporating 1-2 cups of Bulletproof Coffee (which includes 2 tablespoons of grass-fed butter) per day into his routine.

If one were to try to gain insight into this diet from limited data, one could read studies that examined components of TBD such as a high butter intake or a high saturated fat intake or organic vegetables to try and gain insight. For example, a 2016 meta-analysis of nine publications concluded that butter intake was associated with a marginally higher risk of all-cause mortality, but no association with cardiovascular disease or diabetes. Alternatively, a Cochrane meta-analysis concluded that replacement of saturated fat with polyunsaturated fat reduces risk of cardiovascular disease .

Two 2015 meta-analyses concluded that replacing long-chain dietary fats with medium-chain triglycerides, which are encouraged in TBD, led to a reduction in weight of about 0.5 kg (or ~1 lb), but the authors pointed out that the evidence available was low quality.

Other publications examining saturated fats indicated it was associated with dementia. A review of rodent studies concludes that any high fat diet, even for a short period of time, is associated with cognitive impairment, although it’s unclear to what degree this applies to humans.

Regarding the potential benefits of such a diet, the consumption of nearly all organic foods will likely lead to a substantial decrease in the exposure to pesticides, but it’s unclear whether this will significantly impact health. As described previously, the inclusion of cruciferous vegetables may have a protective effect against some cancers.

Criterion 3.3. Does the diet portion of the intervention promote an adequate nutrient intake for general health in the target audience?

3 out of 4

This item receives a score of 3, indicating that the diet will likely provide adequate levels of all relevant nutrients in the target audience, and a level of nonessential health-promoting nutrients that is somewhat superior to typical diets over the medium-to-long-term.

The meats will provide adequate levels of protein, essential fats, minerals (such as iron, zinc, selenium, and copper) and vitamins A, B1, B6 and B12, riboflavin, folate, niacin, and pantothenic acid. Additionally, organic meats have a more favorable fatty acid profile with lower levels of saturated fatty acids and higher levels of polyunsaturated fatty acids, even though TBD advocates the opposite of this.

The consumption of vegetables and the small amount of fruit will provide phytochemicals such as anthocyanins, carotenoids, glucosinolates, and other bioactive compounds which have been linked to positive health outcomes.

Overall (average) score for healthfulness

1.7 out of 4