When you have been a proponent of Paleolithic nutrition for nearly 30 years, have read the research on its health benefits, and have knowledge of thousands of individuals that have benefited by its adoption, you receive negative research1 with a healthy dose of skepticism. That being said, one still has to examine the research and make an objective assessment to either include it in the database of relevant studies, move it into the “more research needed” column, or confidently challenge it as yet another biased attempt to discredit an important area of nutritional research.
I say this because we’ve been here before. In fact, last time we felt the research/reporting was so poor and biased, that three of us from The Paleo Diet® Team wrote articles addressing the issue. This previous research came out of Australia, as does this new research paper published by Genoni et al. claiming the Paleolithic Diet raises serum trimethylamine-N-oxide (TMAO), a potential biomarker of cardiovascular disease (CVD). In fact, the few negative studies published about the Paleo Diet all appear to come from Australia. So, it might be worth starting by taking a quick look at some of the nutritional politics down under.
The Dietitians Association of Australia (DAA) presents itself as “the peak body for dietetic and nutrition professionals, representing more than 7,000 members around Australia and overseas.” Further, the DAA states that, “we recommend looking for the Accredited Practising Dietitian (APD) credential when choosing a dietitian.” The DAA, of course, is responsible for bestowing that title on any nutritionist wanting the same. That also means anyone coming along with something successful that they don’t own, or control, would obviously be competition and in theory could result in their member number decreasing.
So, when Australian celebrity chef, Pete Evans embraced the Paleo Diet® and simply used his skills as a chef to create recipes to share with his followers, the DAA made it a cause to discredit him at every opportunity. They have chosen to frequently attack him as unqualified and create the impression that he came up with the concept of Paleolithic nutrition, rather than address in detail the enormous body of peer-reviewed literature that supports the Paleolithic nutritional template.
You can see that the DAA doesn’t have a particularly favorable opinion of Paleolithic nutrition by viewing their assessment of the diet on their website. In their opening remarks, they state, “There is debate whether the Paleo Diet is truly healthy or not. Higher-protein diets have been examined in research and a local version has been promoted by the Commonwealth Scientific and Industrial Research Organisation (CSIRO), called the Total Wellbeing Diet[i]. However, compared to the Paleo Diet, the CSIRO Total Wellbeing Diet has been extensively studied in a variety of groups.” This is a remarkable statement as it is a complete misrepresentation of the facts. As the screen shots below show, a search on the US National Library of Medicine’s website (aka PubMed.gov), for (Paleolithic[Title]) AND Diet[Title] returns 46 results, while a search for (CSIRO[Title]) AND diet[Title] returns only 2!
The DAA wants their audience to think that the Paleolithic diet is a crazy celebrity fad with little to no research. They do attempt to address a few research papers in their assessment, but the interpretation leaves much to be desired and of course they conveniently ignore the vast body of research that exists today supporting Paleolithic nutrition.
From what I’ve seen, the DAA are doing everything they can to discredit the Paleo Diet® and protect their brand irrespective of the vast majority of the research, showing a benefit of following the Paleolithic dietary template. Which is actually a great shame, as I think the DAA is missing out on a wonderful opportunity to help the Australian populace.
As will be discussed, what the current study does highlight is that there is clearly confusion as to what actually constitutes a modern Paleolithic diet. One of the major downsides of Dr. Loren Cordain’s research going viral and the subsequent creation of the Paleo diet movement, was the simultaneous creation of many self-determined experts. They have in turn, created their own versions of a Paleolithic diet that, and unlike the template created by Dr. Cordain, have not been supported by the peer-reviewed process. So, it would make sense for the DAA to include the science and practical implementation of a modern Paleolithic Diet within their APD program to help with this confusion.
What does all this have to do with the newest research paper on the Paleo Diet from Australia?
Well, first, the research was conducted at Edith Cowan University which has a dietetics education program accredited by the DAA. On its own, that shouldn’t be a red flag, however, there are a number of other issues that need to be considered. First, the research paper, to me, was not written with the impartial tone that one is used to seeing in research papers. The very opening statement in the abstract appeared unusual. It stated, “The Paleolithic diet is promoted worldwide for improved gut health.” This statement stood out because while I am certainly aware of the benefits both clinically and from the research, it is a rather specific point given the relatively limited research related to the adoption of a Paleolithic diet and its effect on gut health.
If you conduct an advanced search at PubMed.gov using Paleolithic AND Diet AND Gut AND Health, as of this writing, you will be presented with just 13 studies that match this search criteria. One of which is this current study, leaving 12 studies that match the search. One could argue that seven of these studies could be related to the adoption of a Paleolithic diet and gut health, which again, seems limited to justify such a statement.
So, I was interested in seeing why this study used that statement about the Paleolithic Diet being promoted worldwide for gut health. It was cited, so I quickly turned the pages to see the source of this front and center statement, and was shocked to see that the hypothesis of this research paper was citing a 2016 book, entitled “The complete gut health cookbook” written by Pete Evans.2 Yes, that’s correct, the same celebrity chef that I referred to above that the DAA has made a common target.
Now, with no disrespect to Pete Evans, finding a book with that title does not justify a scientific research group stating that the Paleolithic diet is being promoted worldwide for improved gut health. But again, on its own, it also doesn’t mean that the research isn’t a valid topic to be investigated, I think looking at how Paleolithic nutrition can influence gut health is a great idea, and there is a significant body of research that shows that the microbiome of hunter gatherers is far more diverse than industrialized populations and correlates to the health of the host.3-33
However, it did make me think we need to dig a little deeper here as to any potential conflicts of interest. In doing so I found it very interesting to learn that Edith Cowan University banned high fat proponent and Bring Back the Fat author, Christine Cronau from speaking at the University, saying it did not align with the institute’s “evidence-based approach”.
Following the reference to Pete Evan’s “The complete gut health cookbook” was the statement, referring to the Paleolithic diet, “However, it excludes grains and dairy, food groups that form part of the evidence-based national Australian and international dietary guidelines.” “Evidence-based”, suggesting that excluding grains and dairy is not evidence-based.
Well let’s examine this statement a little further. As I have previously stated in other articles, Dr. Cordain’s book “The Paleo Answer” references over 900 sources, with only a handful not coming from peer-reviewed journal articles34. There’s also Dr. Cordain’s large body of published peer-review research, each with hundreds of references. So I would say that’s pretty much evidence-based! But how about the Australian and international dietary guidelines, are they really evidence-based? Well that’s another story, but thankfully there is an eye-opening paper published in 2015 in the British Medical Journal by Nina Teicholz, that tackles that very question.35 I highly recommend you take the time to read it.
Further, while it is correct that the Paleolithic diet excludes grains and dairy, it also excludes legumes and all processed foods. It is interesting to see how many people represent these exclusions as a negative, but when one appreciates the benefit to detriment ration of consuming these foods, one quickly understands the net benefit of elimination.
So before getting into the details of this particular study, let’s take a quick look at the database of published research on the effects of adopting a Paleolithic diet. We’ve been keeping track of this since, somewhat ironically, the landmark aboriginal study by O’Dea that demonstrated a marked improvement in carbohydrate and lipid metabolism after a temporary reversion to a traditional lifestyle36. The list of published studies can be seen at our website here.
Earlier Research By the Same Authors Actually Finds Benefits to the Paleo Diet
Of the now nearly 50 published papers looking at Paleolithic nutrition, only a few, report any negative consequences (one study’s title indicated a negative result, but the data actually revealed a positive outcome!). Dr. Angela Genoni is responsible for three publications reporting negative findings. However, her first published study37 demonstrated beneficial outcomes of adopting a Paleolithic diet but subsequent results have been negative, or perhaps better stated, they have been presented as negative findings. Consequently, I think it prudent to examine these publications ahead of her most recent paper. To clarify, in her earlier research only one study was actually conducted, and the data was presented in three separate publications.37,38,39
The opening line in the abstract of the first published paper, while certainly open for interpretation, seems grossly inaccurate, at least to me. The paper states that “limited literature surrounds the dietary pattern” and referenced three published papers despite there being over 30 studies at the time of publication (see, again, our chronological publication list). This just supports my concern that the research was not being conducted with impartiality as it is very easy to use PubMed.org and obtain these studies. And this of course does not even include the many studies that support the negative consequences of consuming grains, legumes, dairy and processed food, foods not included in the Paleo Diet®, listed in Dr. Cordain’s book, The Paleo Answer.34
In Dr. Genoni’s first study, the dietary intervention is described as follows: “Those in the Paleolithic group were provided with meal ideas obtained from “The Paleo Diet” book [Cordain, L. The Paleo Diet; JohnWiley & Sons, Inc.: Hoboken, NJ, USA, 2011.] and advised to consume lean meats, fish, eggs, nuts, fruits and vegetables, and small amounts of olive or coconut oils. Grains, cereals and dairy products were not permitted. Dairy products were replaced with unsweetened almond milk. Sugarless black coffee and tea were allowed. All vegetables were permitted on the diet, except for corn, white potatoes and legumes. To ensure adequate carbohydrate, additional fruit was recommended. Dried fruit was limited to one tablespoon per day.” I’d say this is a good recommendation to implement a modern Paleo Diet®, although one should point out that corn, potatoes and legumes are not vegetables, and there should be no need to recommend additional fruit.
The study concluded that in healthy females, the Paleolithic diet induced a more favorable effect on body composition over the short-term intervention period. The full paper can be accessed here.
The second study, published just a few months after the first publication, was titled “Compliance, Palatability and Feasibility of PALEOLITHIC and Australian Guide to Healthy Eating Diets in Healthy Women: A 4-Week Dietary Intervention”.38 As already stated, this research was part of the first study examining the cardiovascular and metabolic impacts of the diets. If you are interested in reading about the findings, you can get access to the full article here.
I would only like to make one important point. In the discussion, the authors state, “While both groups viewed the diets as healthy, a greater proportion of the Paleolithic group felt that the diet did not fit with the belief of a ‘healthy’ diet. This may reflect participant belief that the while the Paleolithic diet is high in ‘healthy foods’ such as fruits, vegetables, eggs, meats and nuts, the elimination of grains and dairy products makes the dietary pattern less healthy or unhealthy.” Well is this really that surprising given that the DAA is shouting from the rooftops, that the elimination of dairy and grains is a really, bad idea!
The third publication presented data on the dietary intake of resistant starch (RS), a dietary component that has similar physiological effects as dietary fiber and potentially related to bowel health, and the serum concentrations of TMAO, a potential biomarker of CVD.39 The full paper is also available on-line and can be accessed here. The data showed a significant reduction in RS for the Paleolithic diet but did not show a significant difference in TMAO between the two diets.
The authors speculated that the inability to see a difference in TMAO, may have been due to a small sample size and the low total energy of the diet. However, it should be emphasized that this data is from the same study that did show the Paleolithic diet to significantly improve body composition. With respect to RS, increasing RS in typical western diets may well confer a benefit, because of the low fiber intake, however, when total dietary fiber intake is high, which it is on a Paleolithic diet (confirmed by the groups own research37), increasing RS likely has little benefit.
The Most Recent Study by This Group Fundamentally Changes Their Study Design
Because the initial study only examined the effect of a Paleolithic diet over a short-term, 4-week intervention, the current study was designed to see if long-term adherence to a Paleolithic diet, compared to controls, would also see a significant reduction in RS and an increase in TMAO. Recruitment for the study was done via online advertisements.
Unlike the initial research where no increase in TMAO was seen, the data from this study did show an increase, as well as a reduction in RS. However, TMAO is a complicated topic and we will be addressing this in a detailed follow-up article in the coming weeks. But suffice to say, one cannot state that increased TMAO concentrations is causative of CVD, rather there has only been shown a correlation between high TMAO levels and CVD.
While the current study has shown an increase in TMAO, this does not match the findings of many previous studies already referenced that have shown a Paleolithic Diet to decrease markers of CVD. And correlation is not causation. Further there is a difference between exogenous TMAO from foods, primarily fish and red meat, and endogenous TMAO produced by microorganisms in the gut. To highlight this point, fish is one of the greatest dietary sources of TMAO40 and yet, fish has been well established as being cardio-protective.41 So, while fish can elevate TMAO but not be the cause of CVD, CVD could certainly be responsible for increasing TMAO, two very different physiological outcomes.
But of major concern with the current study is its design. The authors categorized Strict Paleolithic (SP) as subjects that consumed <1 serving of grains and dairy per day and Pseudo-Paleolithic (PP) as subjects that consumed >1 serving of grains and dairy per day. I think a more appropriate categorization would be SP as having <1-2 servings of grains and dairy per week and PP having <1 serving of grains and dairy per day, and even that might be a stretch (no data was presented with respect to legume consumption in the present study, although the first study did, and consumption was minimal).
So, the big question to ask here\ is: did the subjects assigned to the respective Paleolithic diets even consume a Paleolithic diet? My colleague on the Paleo Diet® Team, Trevor Connor, has also written an article about this study and shared the same concern with me regarding this question. So Trevor compared the reported dietary data and shows it in a table in his article. What it confirms is that the current study did not examine a Paleolithic diet compared to the template developed by Dr. Cordain, particularly when one compares the dietary fiber. Interestingly, when one looks at the fiber content of their initial study, as a percentage of caloric intake, the fiber content matches up very closely to the Paleolithic diet presented by Dr. Cordain in his 2002 paper.42 And this initial study showed the Paleolithic diet to improve body composition while not increasing TMAO.
So, in summary, since the current research paper didn’t actually examine a Paleolithic diet, the conclusion cannot be made that the Paleolithic diet raises serum TMAO. However, earlier research conducted by Genoni et al., when an appropriate Paleolithic diet was administered, did demonstrate a Paleolithic diet to improve body composition in a 4-week intervention, without increasing TMAO. Perhaps the most important finding of this study, is that there are many people thinking they are following a Paleolithic diet when they are not doing so, which highlights the importance of from where individuals are obtaining their information!
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