‘The Paleo Diet’: Latest fad based on bad science?

If there’s one thing I can’t stand its people who manipulate the ignorant with bad science for profit. If you are going to claim something make sure those claims stand up to rigorous investigation. This isn’t news to people who know me well but it might be to you, my dear readers.

I should probably give you a bit of background to the statement I just made, and probably the title of this little blog post. I don’t want any misunderstandings after all.

Paleo Diet

Some weeks ago I was having a look at www.everythingbooksandauthors.com and their listings of free ebooks. One of the books available was called ‘Quick and Easy Paleo Recipes: 50 healthy gluten free meals’ by Tracy Daniels. I like to cook and it didn’t cost anything so I bought the Kindle book to see what the recipes were like. It was the introduction that intrigued me and sent me in search of further information about this ‘Paleo Diet’.

The claim that the Paleo diet was ‘dairy-free, but it also does not include grains or grain products[1]’ was interesting; there was no explanation as to why dairy and grains are banned in the ‘Paleo Diet’, or why it is call that, in the recipe book so obviously I went looking for more information. I found the information in a book called ‘The Paleo Revolution’ by Victoria Smith.

Hunter-gatherer lifestyle

According to this title ‘The Paleo Diet is designed to mimic the eating habit of our Paleolithic ancestors, consuming foods that our ancestors did over ten thousand years ago’[2]. So there we have our explanation. The author gives this reasoning:

 ‘We would like to avoid such things as auto-immune diseases, cancer, cardio-vascular disease, and obesity. Our ancestors were largely free from those diseases, as suggested by archaeological and anthropological evidence so it seems to be a good idea to see what they did right[3]… Agriculture was developed roughly ten thousand years ago. At that time the human diet changed tremendously[4]… our anatomy has not really adapted to handle some agricultural products[5]’

She then goes on to cite ‘anti-nutrients’ such as enzyme inhibitors and lectins as evidence for this and that ‘Diary is new food to the human diet, so most adults are unable to break down lactose[6]’.

I became somewhat sceptical at this point. As you may be aware, I’m rather overweight and I have been for about eighteen years. I’ve tried losing weight with a variety of diets, such as Weight Watchers and Slimming World, but found them expensive and unsustainable once one stops going to meetings. These days I try to eat healthily and exercise a little every day. In all these years of attempting to eat sensibly I’ve always been told that wholegrain pasta, rice etc as well as potatoes, and low fat dairy products are essential parts of human nutrition because they provide complex carbs and protein, provide long lasting, slow release energy, and roughage to clean out the intestines.

But I thought I’d do some more reading to try to find out a little more. Nowhere in my research on the websites promoting this diet did I find any citations of scientific research papers to back up the claims of ‘Paleo Diet’ supporters or promoters. Other things bothered me as well. There was a claim repeated many times that humans haven’t changed in 50,000 years and that 10,000 years is not long enough for our DNA to evolve enough to accommodate dietary changes. As far as I knew when first reading about this diet, nobody knows for certain what humans ate 50,000 years ago, nor is there any evidence that humans were perfectly adapted to their lifestyles. My mind kept thinking ‘surely people ate beans and wild grains if they knew they would provide nutrition, or how would they know to cultivate them?’ The change from hunter-gatherer to settled pastoral lifestyle was not sudden, as I understand the archaeological evidence, but a gradual change over hundreds or thousands of years.

Help arrives – and brings clarity

I stayed puzzled for a few weeks until, coincidently, I picked up a copy of New Scientist[7]. The cover story was about six common health myths that are not supported by rigorous evidence. Included in the six, along with the old ‘sugar makes children hyperactive’ and ‘being a bit overweight means you will die sooner’ myths, was number six ‘We should live and eat like cavemen’[8].  Apparently the most searched for diet on internet search engines in early 2013 was ‘Paleo diet’. According to the article the hypothesis on which this diet is based, called the ‘evolutionary discordance hypothesis’ was put forward by S. Boyd Eaton, a medic, and Melvin Konner, an anthropologist, at Emory University in Atlanta, Georgia in 1985. Their hypothesis is the origin of the claims that our genes haven’t changed in 50,000 years but our diets and lifestyles have changed dramatically in the last 10,000 years and we haven’t had time to evolve. Thus diabetes, heart disease and cancers are rife – if we ate like hunter gatherers we’d be healthier, fitter and therefore happier.

Certain aspects of the diets, such as exercising more and eating less highly processed foods are in agreement with current evidence, but others such as cutting out grains, legume and dairy aren’t, and the evidence suggests that the reasons given for taking them out of your diet are flawed. Recently Marlene Zuk, who is an evolutionary biologist at the University of Minnesota in Saint Paul, has written a book that counters these claims.  Her evidence against the claim that we have not evolved to eat grains and dairy is genetic.

Many people have extra copies of genes for digesting the starch found in grains, and lactose tolerance – the ability to digest milk as adults – has evolved separately in different populations. This essentially debunks the claim that we haven’t evolved to eat these things. 10,000 years is clearly plenty of time, unless people have been eating grains and drinking milk as adults for a damn sight longer than 10,000 years.

In an article in The Lancet[9] evidence was presented which shows that it is not clear that ancient hunter-gatherers were any healthier than modern humans. Maybe they did get cancers and diabetes but died before these diseases left the evidence for us to find on bones? Maybe people died before they had a chance to develop cardio-vascular diseases? In addition to this, we also actually don’t know for certain what people ate 50,000 – 10,000 years ago. Whatever they did eat would probably not look like anything we eat now, other than superficially; after all there has been several thousand years of selective breeding of domesticated animals and plants.

Conclusion

In light of the evidence available I think I won’t be one of those joining this dietary ‘revolution’. My initial interest has been overwhelmed by my misgivings about the scientific basis of the claims made for it. It sounds plausible, at first glance, but on deeper analysis it is clearly flawed and based on poor understanding of human evolution and genetics. The cynic in me says that it’s just another gimmick to part the ignorant from their cash and a product of the diet industry. Interestingly enough, the authors of the original hypothesis on which the ‘Paleo diet’ is based have revised the hypothesis ‘in light of the latest evidence’ and ‘now include low-fat dairy and whole grains in their recommended foods’[10]. Strange that they should add these just as evidence begins circulating that their hypothesis is flawed.

I’ve attempted to provide some sources if you’d like to read them for yourselves. As an informed source of information, I trust New Scientist and its writers. I’m sure the writers of the books mentioned feel great confidence in their ‘lifestyle’ but they have still made insupportable claims. I cannot trust them.

The food looks nice though.

Rose

[Edit: just been to the New Scientist website; here’s the relevant link:

http://www.newscientist.com/special/six-health-myths? ]

---