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Is the Paleo Diet Actually Good For Your Gut?

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Like clockwork, when a new diet appears in the public, there is a mix of praise and scrutiny. Depending on how the fundamentals fare in the scientific realm, the recommendations may be adopted by society or dismissed as a fad and slowly fade away. Yet some entries in the nutritional field tend to stick it out, despite the controversies, and stay relevant for generations.

One such meal plan is the Paleolithic Diet, which was first described in 1975 by Walter L. Voegtlin, a medical researcher who focused on resolving alcohol addiction as well as gastrointestinal function. He postulated in his book, The Stone Age Diet that despite our technological and civil advances, our biological evolution and ecological requirements had not changed significantly. In turn, our nutritional needs were most likely no different than those of our early ancestors. By choosing the same foods they ate, we might have a happier and healthier life.

Over the years, studies have unveiled even more information about the impact of nutritional ecology and how reliance on a diverse source of nutrition, as proposed by the Paleo Diet's seven fundamentals, can be beneficial. Back in 2008, a group of Swedish researchers found a short-term Paleolithic intervention could yield significant benefits to everyone. In 2009, the positive impacts of the diet on Type 2 Diabetes and cardiovascular disease were highlighted. By 2010, a trial with individuals suffering from heart disease showed how going Paleo may lead to an improved quality of life.

Despite the information gathered on the benefits of the diet on the body, there has been far less focus on the effect of the nutritional guidelines on the gut microbiota, which is a driver of human health. Part of the reason for this exclusion rests in the realization our microbiomes have changed in relation to our external advancements rather than our internal evolutions. Yet, by the same respect, they are the major drivers of digestion and have a significant impact on our health. This opens up a quandary in which the microbial nature of our gut bacteria may hamper the benefits of the ancestral food choices.

Last week, an international team of researchers provided a glimpse at the relationship of the Paleo Diet and both the ancient as well as the modern microbiome. Their unique approach involved culturing fecal samples from vegetarian humans as well as an animal model for Paleolithic eating, the gelada baboon. The bacteria from the feces were divided into separate culture flasks and 'fed' one of two specific diets -- Western, consisting of high levels of digested potato starch; and Paleo, composed primarily of digested grass.

At specific time intervals over 72 hours, a portion of the culture was extracted and analyzed to identify bacteria as well as short-chain fatty acids, which are known to be a significant regulator of our metabolism. Finally, the team explored how the extracts affected the function of mouse colon cells by measuring the levels of a hormone known to be involved in appetite suppression and weight control, peptide Y or PYY.

When the microbial composition of the two species over the 72 hour period was examined, there was only one surprise. The human sample exposed to the potato starch lost most of its good bacteria, including the probiotic lactobacilli. This all but confirmed the negative influence of a high-starch, Western diet. As for the grass, there were neither benefits nor detriments; the microbiota was as stable. As for the gelada samples, there were no changes. In this particular stage of the experiment, the Paleo Diet came out a winner.

But that was its only high point. When the levels of short chain fatty acids were measured, there was literally no difference between the Western and Paleo conditions for either geladas or humans. The situation was worse in terms of the appetite suppressant, PYY. The grass actually produced a lower level of hormone than the potato. The data suggested little to no benefit from the Paleo Diet in comparison to the Western counterpart.

There was one more surprise that offered some perspective on the results seen in the clinical trials over the last few years. Human cultures had the ability to quickly adapt to either starch or grass treatment and eventually develop a stable concentration of the short-chain fatty acids and other metabolites affecting appetite. This suggests there may be some benefit in short term changes to effectively shock the system. Yet longer term use for goals such as weight reduction and improved health may not be as effective. Thus, while the Paleo Diet would be an effective means to start a new regimen of social behaviour change, the actual benefits to health would be short-lived.

The conclusions from this one study using one sole food source (i.e. potato or grass) is limited in its scope. Even the authors suggested the need to explore the impact of protein to understand the current Paleo Diet. As such, little exists to detract from the momentum of this movement. However, the results do highlight the effect on the microbiome and the possibility for a lack of long term benefits. This may not be entirely negative. As Voegtlin suggested in his book back in 1975, by changing the ecology of our bodies, we may begin to change our overall lives. While his diet won't be the only answer, there is every reason to believe it would make for a great start.


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