Evolutionary nutrionists such as myself have long argued, on the basis of Darwinian reasoning, anecdotal reports, and varied dietary research, that the Paleolithic nutrition formula, when correctly applied, bolsters immunity and cognition. The assertion has strong scientific support; however, relatively little of this support is of a clinical nature. Not because the original human diet has proven powerless in this area, but rather that not that much clinical research on the matter has been carried out. Most of the trials that have been conducted to date have been focused around cardiometabolic endpoints, as opposed to outcomes associated with the brain and immune system. It’s all connected, hence, one might argue that the evidence is already there; however, it’d certainly be great to get some more specifics.
In this respect, a new study published a few months back in the open access medical journal Cureus is a welcomed addition to the science of Paleolithic nutrition.
An outline of the study
The study, which the authors decided to narrate in not one, but two papers (1, 2), looked into the effects of a carbohydrate-restricted Paleolithic-based diet with and without high-intensity exercise in the treatment of the metabolic syndrome. It’s not a revolutionary study (several other investigators have targeted the metabolic syndrome with Paleolithic nutritional means); however, it does have a couple of special attributes; the most prominent being its crossover design, the high-intensity training protocol, and the carbohydrate-restricted nature of the dietary intervention. Additionally, as mentioned above, it has some interesting endpoints.
Here’s a breakdown of the study as outlined in one of the papers:
One approach to slow the pandemic of obesity and chronic disease is to look to our evolutionary past for clues of the changing behaviors contributing to the emergence of ‘diseases of civilization’. Modern humans have deviated from the lifestyle behaviors of our ancestors that have introduced pressures (i.e. diet and activity changes) quicker than our genetic ability to respond. This caused a ‘mismatch’ between our biological systems and environment, leading to ‘man-made’ chronic diseases.
The purpose of the study was to investigate the effects of a short-term evolutionarily informed dietary and lifestyle intervention on inflammatory and cardio-metabolic profiles in individuals characterized as having metabolic syndrome (MetS).
Twelve subjects with MetS followed a crossover design with two, four-week interventions, including a carbohydrate (CHO)-restricted Paleolithic-based diet (CRPD; <50g CHO) with sedentary activity (CRPD-Sed) and CRPD with high-intensity interval training (CRPD-Ex), separated by a four-week washout period. The HIIT exercise consisted of 10 X 60 seconds (s) cycling intervals interspersed with 60s of active recovery three d/wk for four weeks. The effects of a diet with sedentary activity as compared to a diet with exercise on body composition, as well as the cardiovascular, inflammatory, and metabolic profiles, were assessed. A two-way analysis of variance (ANOVA) with repeated measures was performed with a post-hoc analysis using a simple effects analysis with a Bonferroni adjustment. The level of statistical significance was established a priori as p < 0.05.
Compared to baselines, CRPD-Sed and CRPD-Ex improved cardio-metabolic markers, including reductions in waist adiposity (-15%, -18%), body mass (-3%, -5%), body fat % (BF%; -7%, -12%), fasting plasma glucose (GLU; -20%, -27%), triglycerides (TG; -47%, -52%), fasting insulin (-34%, -39%), insulin resistance (-35%, -46%), and increased HDL-C (+22%, +36%) and VO2max (+22% and +29%), respectively. CRPD-Sed and CRPD-Ex also reduced inflammatory markers, including hsCRP (-32% and-36%), TNF-alpha (-35% and -41%), IL-6 (-29% and -40%), and ICAM-1 (-19%, -23%), respectively, when compared to baseline.
Adopting behaviors from our evolutionary past, including diet and exercise, shows favorable cardio-metabolic and inflammatory profiles in those individuals characterized with MetS.
Some interesting findings
As you can see from the summary above, the researchers found that there are marked cardiometabolic benefits to evolutionary eating in relation to the treatment of the metabolic syndrome. In this respect, the study is no different from others of its kind. What really stood out to me about it though, and is a primary reason why I decided to bring it up here on the site, is its focus on inflammation. Furthermore, I like that the authors looked into the cognitive effects of the protocol. They aren’t the first to include assessments pertaining to cognition and inflammation in their research on Paleolithic nutrition; however, their methodology has a broad and original flair to it.
As you can see from the summary above, there was a profound alleviation of inflammation. Levels of the inflammatory compounds high-sensitivity C-reactive protein, tumor necrosis factor alpha, and interleukin 6 all decreased by a whopping 30 to 40%, and there was also a marked reduction of intercellular adhesion molecule 1 – a mediator of inflammatory responses. This is of critical importance, because as we know, inflammation is at a foundational feature of a whole bunch of diseases and health problems – ranging from inflammatory bowel disease to type-1 diabetes to erectile dysfunction to cancer.
Of note, this effect was achieved in just 4 weeks and in both groups. The change undoubtedly relates to the loss of fat mass that was induced by the intervention (excessive adipose tissue is inflammatory); however, other factors related to the physiological impact of the applied diet no doubt played a role as well. This view is supported by the absence of a statistically significant difference between the two groups with respects to inflammatory markers although there were greater improvements in body composition in the exercise group.
As for the cognitive effects, there were marked improvements in both groups, both in terms of the measured niveau of brain-derived neurotrophic factor, a protein that’s involved in memory and learning, among other things, as well as cognitive tests, including a test that assesses cognitive speed and flexibility. The results reflect what many a healthy eater and fitness enthusiasts has experienced, namely that diet and exercise ‘light up the brain’.
Besides the effects pertaining to inflammation and cognition, something that stood out to me about the study is that the participants’ energy intake decreased fairly dramatically during the intervention, dropping by almost 900 kcal in both groups, although no instructions to limit calorie intake were issued. This is consistent with the results of certain other studies and reflect what many of us have experienced, namely that a shift from unhealthy to healthy eating tends to go hand in hand with a spontaneous reduction of caloric intake, probably resulting from a normalization of gut microbiota composition and leptin sensitivity, among other things.
As I was looking over the study, a couple of things stood out to me as being particularly important to mention in relation to its findings. First of all, it’s important to recognize that the study has a small sample size and that the duration of the intervention was fairly short. This certainly doesn’t invalidate its findings, particularly seeing as it has a crossover design, however, it’s obviously something that’s important to keep in mind.
Secondly, all of the participants ate the same diet. In other words, the study doesn’t allow for a comparison of the Paleolithic diet to some other diet. Thirdly, it’s important to recognize that the exercise regime that the participants in the diet+exercise group adhered to isn’t a very strenuous one. They ‘only’ did 10 cycling intervals of 60 seconds each three times per week, which doesn’t really compare to the routines of fitness devotees, athletes, crossfitters, and the like.
Increasing clinical evidence shows that Paleolithic eating isn’t just conducive when it comes to attaining a slimmer waistline, but that it has widespread physiological effects extending into areas such as cognition and immunity, thereby substantiating the claims and experiences of evolutionary nutritionists and dieters. A new study out of the U.S. is particularly relevant in this respect, as it found that the Paleolithic diet, both alone and in combination with high-intensity exercise training, is very effective against the inflammatory state that is characteristic of the cluster of disorders known as the metabolic syndrome, reducing the levels of several inflammatory markers by up to 40% in just 4 weeks. Additionally, it brought about marked cognitive improvements. This is noteworthy, as inflammation and cognitive impairment are at the root of much disease, suffering, and waste of potential.