In this post I’m going to take a look at the “Paleo Diet” from a few perspectives: Is it based on solid science? Is it healthy? Is it good for the planet? In the last post I reviewed the scientific literature on the impact of low-carb diets on health and found that the evidence overwhelmingly showed that a low-carb diet reduces the human lifespan. The only exception is when the low-carb diet is plant-based. Spoiler alert: The Paleo Diet is very much an animal-based low-carb diet, so I’ll let you draw your own conclusions there. Back to health later; first, I want to look at the rationale behind the Paleo Diet.
The science behind the Paleo Diet
In the preface to the revised edition of The Paleo Diet, Dr. Cordain mentions that the book’s sales were slow after its initial release in 2002 and didn’t really take off until 2010. He attributes this to the internet: The worth of the book wasn’t appreciated until people started to share stories about the Paleo Diet. Its appeal probably has to do with a general feeling that things were always better in the past – we have mental images of svelte paleo folk running around the countryside, gathering antioxidant-rich berries as they got a great work out. Oh, those good old Paleolithic days! Evaluation of the science behind the book took a back seat to shirtless guys sharing stories on social media about how stoked they are about going Paleo.
One of the most surprising things, for me, was how little evidence is provided to back up his claim that Paleolithic people were healthier than modern people. In an introductory section (How our healthy way of life went wrong) Cordain says, “most people just don’t realize just how healthy our Paleolithic ancestors were,” and goes on to say that he has “examined thousands of early-nineteenth and twentieth-century photographs of hunter-gatherers. They invariably show indigenous people to be lean, muscular and fit.”
Hold on – photos??
Let’s take a look at Dr. Cordain’s level of scientific rigor: He examined many photos from the last hundred years and extrapolated to conclude that the people of the Paleolithic era (3.3 million to 11,650 years ago) were in tip-top shape.
What other evidence does Dr. Cordain have that Paleolithic people were fit as fiddles? Here’s a representative statement: “The few medical studies of hunter-gatherers who managed to survive into the twentieth century also confirm earlier written accounts by explorers and frontiersmen.” There is no specific citation of these medical studies – in fact none of his claims are backed up by specific citations – there is just a general reading list at the end of the book. He did emphasize one study that I was able to find online: a 1971 paper reporting a low rate of heart disease among the Inuit population in Greenland – it has been debunked. In any case, making a case for the health of people who lived more than ten thousand years ago based on comments about the physical appearance of modern hunter-gatherers by explorers and frontiersmen is weak, to say the least. Dr. Cordain has a PhD in exercise physiology – not paleontology, archaeology, or evolutionary genetics.
The Mayo Clinic raises a few issues with Dr. Cordain’s claims in these areas:
Archaeological research has demonstrated that early human diets may have included wild grains as much as 30,000 years ago — well before the introduction of farming. Genetic research has shown that notable evolutionary changes continued after the Paleolithic era, including diet-related changes, such as an increase in the number of genes related to the breakdown of dietary starches.
The idea that we have not evolved since Paleolithic times is simply wrong, as several evolutionary biologists such as Marlene Zuk (University of California) have pointed out. Besides adopting to better digest starch since the advent of farming, populations have evolved over the last 10,000 years to digest lactose and resist malaria – even blue eye color arose and spread within that time frame.
Did Paleolithic people live longer lives?
I had expected the Paleo Diet book to be full of cool evidence that cave people lived longer lives – surprisingly there’s no discussion on lifespan. Well, did they live longer lives? This paper, published in 2011 by an anthropologist in PNAS (one of the most respected journals) looked at the proportion of younger (20-40 years old) to older (> 40 years old) Paleolithic human remains and found that only a small proportion made it to 40. “All three Late Pleistocene samples have a dearth of older individuals compared with Holocene ethnographic/historical samples.” (The Pleistocene includes the Paleolithic era while the Holocene is our current era.) It would almost certainly be generous to say that the average lifespan of Paleolithic people was 40 years.
Paleo Diet pros and cons – impact on health
Of course, people who live a “hunter-gatherer” lifestyle that involves moderate food consumption and lots of exercise are probably going to be pretty lean. A sedentary lifestyle that involves over-eating of processed food is a big problem – that’s not news. The Paleo Diet is a mix of good and bad ideas – the good ideas are not unique to the Paleo Diet and I believe that the bad ideas are harmful to both your health and the planet.
Paleo Diet rules
First, here are the ground rules of the Paleo Diet:
- All the lean meats, fish, and seafood that you can eat.
- All the fruits and non-starchy vegetables that you can eat
- No cereals
- No legumes
- No dairy products
- No processed foods
Things that the Paleo Diet probably gets right
The last two points, above, are the main reasons why the Paleo Diet might be beneficial for some. Replacing dairy and processed food with fruit and veg would be a big improvement in many people’s diets. Here’s a summary of the good ideas contained in the book (these ideas are not unique to the Paleo Diet):
- Reduce dairy
- Reduce processed foods
- Reduce refined sugar
- Eat food that is alkalizing rather than acidifying (e.g., leafy greens over meat).
I guess the issue of acid-generating food is not as well-known as the others (except for diseases like gout, caused by an excess of uric acid and often associated with a diet rich in animal-protein). Since meat is acidifying, there’s a conflict with the core Paleo Diet, which Dr. Cordain tries to resolve by saying to make sure to eat plenty of greens to balance the heavy meat intake that he prescribes. He neglects to point out that plant-based protein sources like legumes are much less acidifying than animal-based protein (sometimes they are even alkalizing).
Things that the Paleo Diet probably gets wrong
- Eat a lot of animal protein, even relative to the typical American diet
- Avoid starchy vegetables
- Avoid cereals
- Avoid legumes
To reiterate: an animal-based low-carb diet will likely shorten your lifespan, even though it may help you lose weight. When you think about the role of the internet in the rise to popularity of the Paleo Diet you get an idea of the root of the problem: photos and testimonials of people losing weight. As described in the last post, long-term studies on the impact of diet on health require huge effort to be done well. Anecdotal stories of weight loss (or pictures of lean people showing their abs) tell you one thing: some people lose weight on the diet. But are they healthier – how about their risk of cancer and cardiovascular disease? You need long-term scientific studies to tell you this: and they have unequivocally told us that there is a significantly higher risk of death from a low-carb diet that’s rich in animal products.
Is the Paleo Diet impartial or agenda-driven?
Is there an agenda behind the Paleo Diet? Impartiality is of course crucial to science, so I think it’s relevant to look at funding that Dr. Cordain has received in the run up to his publication of The Paleo Diet.
- Back in 1994, Cordain accepted funding from the National Rifle Association (NRA) to study “The Influence of Game Meat Consumption Upon Blood Lipid Profiles.”
- He received two grants from The Pope and Young National Archery Club (which houses an online collection of trophy animal records): “Fatty acid composition of brain, marrow, muscle and adipose tissue in elk,” and “Fatty acid composition of brain, marrow, muscle, tongue and adipose tissue in deer, antelope and elk.”
- The Wine Institute in San Francisco supported two studies: “Moderate daily wine consumption does not result in body weight gain,” and “Beneficial role of moderate daily wine consumption upon insulin sensitivity.” Dr. Cordain received over $150,000 in funding from the Wine Institute from 1995 to 1997, representing almost half of his total funding between 1982 and 1998.
What’s interesting about his funding from the Wine Institute is that Dr. Cordain has a surprising stance on wine. In The Paleo Diet, Cordain states that “alcoholic beverages were clearly not a component of true Paleolithic diets” but that “if you enjoy an occasional glass of wine or beer, that’s fine – it’s allowed here.” In two other passages he talks about the health benefits of wine. I’m not disputing that wine may be healthy in moderation, but it is concerning that Dr. Cordain has bent his otherwise strict Paleo Diet rules, in the light of his prior acceptance of substantial sums of money from the wine industry.
Prior to going Paleo, Cordain accepted funding from Gatorade (Quaker Oats) in 1991 to study the impact of drinking glucose-polymer drinks (e.g., Gatorade) post-exercise. The publication neglected to disclose funding from Quaker Oats.
He participates in events sponsored by the meat industry, such as this Mid-Atlantic Grass-Fed Beef Conference.
Reporting of his funding record stops in 1998, a few years before The Paleo Diet came out. The majority of Dr. Cordain’s publications report no funding source and no conflict of interest.
Why is the Paleo Diet so against plant-based food?
You would think that there could be a plant-based version Paleo Diet, but Dr. Cordain categorically says no to this and has been outspokenly against vegetarian and vegan diets:
Nevertheless, as a scientist, I hope that we all try to make dietary decisions based not just upon philosophical and ethical issues, but also upon foods that are good for our bodies and long term health.
Here’s an interview with Dr. Cordain on the topic of vegetarianism and veganism:
Was that a reasoned debate from someone who’s concerned about your diet? Why are legumes, an important component of most plant-based diets, prohibited in the Paleo Diet? I’m going to examine that in the next post.
Is the Paleo Diet good for the planet?
The two aspects of the Paleo Diet that align with most health studies – avoiding dairy and processed foods – also happen to be beneficial for the planet. This is a recurring theme in recent posts on seaweed and carbs – the healthiest options are often also the most sustainable. This is in contrast to the quote above from Dr. Cordain that suggests that you may have to choose between ethics and health.
In a post on cooking as the most basic form of activism, I mentioned that the amount of energy that goes into processing some kinds of convenience food is actually greater than the energy embodied in the food itself – sometimes the energy that goes into the packaging alone exceeds the energy in the food! And as you likely know by now, dairy has a high impact on the planet.
Then, the aspects of Paleo that are most at odds with health studies are also out of tune with the planet:
- Eating plenty of meat and seafood
- Avoiding starchy foods, cereals and legumes
Even Dr. Cordain admits that the Paleo diet is not sustainable:
Can our planet support 7 billion people following the Paleo Diet? We cannot dispute that there are negative environmental factors, such as excessive water and fossil energy use and large emissions of greenhouse gases, resulting from the standard process of agriculture and livestock farming. These methodologies make it seem unrealistic that even our current food production system can sustain our planet, let alone support the Paleo diet alone.
He does offer two suggestions for being more sustainable: eat organic, pasture-raised meat, or try insects. But overall, The Paleo Diet is an expensive option, both for the individual and the planet.
The foods that are prohibited by the Paleo Diet include most of the staple foods that have any chance of supporting our population without overburdening the planet. These include wheat, corn, rice, potatoes and legumes (soybeans, peas, beans, peanuts, etc.). His recommendation is to replace these carb and protein staples with two of the most unethical choices, meat and fish.
Perhaps having an excuse to indulge in these foods is one of the reasons for the rise to popularity of the Paleo Diet – even if the science behind the diet is largely wrong. But on this point there’s little doubt: we would have almost zero chance of getting through climate change intact if we all adopted the Paleo Diet. Isn’t that the most important thing, right now?