For the longest time, people have been arguing about what constitutes the optimal human diet. Some state that a plant-based diet, containing little or no animal source food, is the perfect diet for members of our species; others make the case that it doesn’t really matter what we eat as long as we primarily stick to whole foods; and yet others say that we should design our diet in such a way that its nutritional characteristics are similar to that of the diets our ancient ancestors ate.
As you probably know, I favor the latter idea. I don’t think eating a strict Paleo diet is the way to go for everyone; however, I think we all would benefit from eating a diet that is built on an evolutionary foundation. A rapidly expanding body of research is supporting this idea. Even those who have always been opposed to the notion that “we should eat like cavemen”, may now have to realise that there is something to this whole Paleo thing.
Popular opinion doesn’t matter. All that matters is what the data show.
Here on Darwinian-Medicine.com, as well as on many of the other websites and magazines I write for, I’ve repeatedly made the case that it’s virtually impossible to make sense of all the conflicting information on nutrition that’s out there if we haven’t got an evolutionary model to guide us. Making sense of nutrition without having knowledge about evolution and ancestral human diets is like finding a needle in a large, completely dark room. You may find the needle, if you are lucky, but it’s going to take a lot of time. In order to turn the light on, and hence, locate the needle quicky and effectively, we need to incorporate theories and principles of evolutionary biology into our nutritrional mindset.
In today’s post, I’m not going to take an in-depth look at the reasons why it’s important to consider what our ancestors ate when we plan our modern diet. This is something I’ve done many times in the past (If you want to dig into the science on ancestral nutrition, then check out my previous articles on diet or do a search for review papers on Paleolithic nutrition on PubMed). Rather, I wanted to briefly take a look at some of the recent “Paleo studies” that have been published.
I would argue that “the Diet Wars” should be fought in the world of science, not on social media, in the mainstream press, on message boards, or similar places where people throw out opinions that lack scientific support. It doesn’t matter which diet that is most popular at the moment or what some charismatic guy told you to eat. All that matters is what the data show. We are all somewhat clouded by our personal biases, but it’s important to remember that the goal is to find out the truth, not to adamantly stick to our beliefs.
There are still some people out there who seem to think that the Paleo diet doesn’t have a scientific foundation to stand upon. These individuals couldn’t be more wrong. Over the past couple of decades, several high-quality research articles and studies covering topics related to ancestral nutrition have been published, many of which I’ve talked about here on the blog. The intriguing thing about these papers is that virtually all of them come to similar conclusions. This is unheard of in nutritional science. Most of the time, you can find studies on “both sides”; some that seem to support the consumption of a diet, supplement, or food product, and some that don’t.
The days when proponents of the Paleo diet only had a couple of studies to bring forward in support of their stance are long gone. Over the past couple of years, studies devoted to this ancient nutritional regimen have started to stack up. We’re not going to go through all of them here, as I think that would bore the crap out of you – and me, as I’ve already spent more than enough time going through the research in this area. Instead, I thought I’d just focus on some of the most recent studies.
The evidence is stacking up
Last year, the first meta-analysis on the Paleo diet was published (1), and this year, several new studies have made their way onto PubMed (2, 3, 4, 5), three of which we’ll briefly look at now…
1. First is a study entitled Cardiovascular, Metabolic Effects and Dietary Composition of Ad-Libitum Paleolithic vs. Australian Guide to Healthy Eating Diets: A 4-Week Randomised Trial, published in the journal Nutrients (2). As the title suggests, this study compared the Paleolithic diet (PD) with a diet based on the Australian Guide to Healthy Eating. The participants of both study groups were allowed to eat as much as they desired, as long as they stuck with the types of foods they had been assigned to eat.
After four weeks, the participants in the PD group had lost significantly more weight than the participants who had been eating an Australian Guide to Healthy Eating Diet. The ancestral eaters lost on average about 2 kg, which is not a lot, but it’s not little either, given that the intervention only lasted 4 week. As for metabolic and cardiovascular parameters, there was no difference between the two groups.
2. The next study we’ll have a quick look at was also published this years and is titled Benefits of a Paleolithic diet with and without supervised exercise on fat mass, insulin sensitivity, and glycemic control: a randomized controlled trial in individuals with type 2 diabetes (3). This study, published in Diabetes/Metabolism Research and Reviews, investigated what happens when patients with type-2 diabetes are put on a PD, with or without supervised exercise, for 12 weeks.
Not surprisingly, the participants responded favorably to the intervention. At the end of the intervention period, those in the PD group had lost 5.7 kg, whereas those in the PD+exercise group had lost 6.7 kg. The participants’ leptin levels also decreased dramatically and their insulin sensitivity improved, among other things.
Perhaps surprisingly to some, the participants who both exercised and ate a hunter-gatherer style diet didn’t experience greater metabolic health improvements than those who only followed the diet. Actually, leptin levels decreased more in the PD group than in the PD+exercise group. This doesn’t mean that exercise isn’t important in the management of type-2 diabetes (it definitely is); however, it does indicate that it’s more important for patients with this condition to eat healthy, than it is to exercise – which is what many of us nutritionists have been saying for a long time.
3. The last study we’ll take a quick look at hasn’t yet been published, but some of the results have been made public (6). Since the study population of this interventional trial is small, the study lacks a control group, and the paper hasn’t yet been published, the results should be taken with a grain of salt. However, the study is interesting nonetheless. The thing that separates this study from most other studies that seek to answer a similar research question is that its participants are lean and fairly healthy, not overweight and/or metabolically deranged.
The most interesting finding from this study is that the participants reported eating 22 percent fewer calories while on the Paleo diet than on their habitual diet. Moreover, their blood levels of interleukin-10, a immune-related compound, increased, which indicates that consumption of the PD decreased inflammation.
More and more scientists acknowledge the power of ancestral diets
The result of these new studies are consistent with that of older ones. Several studies, some of which are RCTs, have shown that hunter-gatherer, Paleo style diets are useful in the treatment of a long range of health disorders and are superior to several other “healthy” diets, including the Mediterranean diet (7, 8, 9, 10, 11, 12, 13, 14, 15).
To those of us who’ve delved into the science on Paleolithic nutrition, the findings of these RCTs are not surprising. However, to those who haven’t, they may be. The key thing to remember is that we humans, like other organisms on this planet, are biological systems that were sculpted over millions of years of evolution. Our dietary requirements were not determined in modern times, but rather, in ancient times.
The preagricultural nutritional environment conditioned the genetic make-up that we all carry inside our cells, hence, it shouldn’t come as a surprise that studies consistently show that Paleo-style diets are well-matched with human genetics. Not everyone who adopts a hunter-gatherer style diet responds with significant weight loss and experiences better health, but many do.
We can argue about the strengths and weaknesses of the studies on Paleolithic nutrition until we get green in the face. All studies have limitations and weaknesses, which are important to consider when the results are interpreted. What I’d argue, though, is that in the grand scheme of things, it doesn’t really matter whether one or a couple of the many Paleo studies that are out there have been conducted in a suboptimal way, or if some of the researchers have been slightly careless when it comes to controlling for covariates, eliminating bias, etc. The reason I hold this belief is that all the studies point in the same direction. Even if one or a couple of them may be slightly flawed, it doesn’t invalidate the results of all the others. It’s the complete body of evidence that matters, not the results from one or a couple of studies.
There’s no doubt that a diet with nutritional characteristics similar to that of the preagricultural diets that supported the evolution of the complex human brain and body is a very healthy diet. That said, I don’t think a strict Paleo diet is a good choice for everyone. The diet of each individual has to be adjusted according to that person’s needs, health condition, and activity levels. Some people, in particular hard-training athletes, may find that they need to include smaller quantities of starchy and/or fibrous grains (e.g., oats) or legumes (e.g., lentils) in their diet to feel at their best. (It could be argued that this practise is “Paleo”, as some of our Paleolithic ancestors probably did eat small amounts of certain types of grains and/or legumes.)
Now I want to hear from you: Which diet do you favor? Do you disagree with the statements I make in this article? If so, then feel free to share your thoughts, as long as you back up your arguments with scientific data.