The Curse of the Paleolithic Diet: When Studies Go Bad

A break from our usual Holford coverage, to discuss a recent EJCN Short Communication on “Effects of a short-term intervention with a paleolithic diet in healthy volunteers“. The study began with a small sample of 20; however, a high proportion of these dropped out, and the researchers appear to have lost some of the data on many of those remaining in the study. Moreover, a surprising proportion of those involved showed signs of illness, and the study lacked a control group. Frankly – with so much going wrong – I rather felt for the researchers: one could almost conclude that the Paleo diet is somewhat cursed. However, they were blessed in one respect: plenty of positive media coverage, meaning that the NHS felt the need to offer a critical response to the study.

Because of these problems, while the study concludes that the intervention showed some apparently positive effects, the problems with it mean that (as the authors rightly acknowledge) considerably more research is needed before conclusions can be reached. Frankly, we struggled to see much useful information to be gained from this problematic study.

The study began with 20 subjects; of these

One subject did not start, one missed the laboratory test, four broke the study, three because of illness and one could not fulfil the diet

This significantly reduces the power of the study. However, matters were worsened considerably when

Owing to a computer error, food registration data were available for eight subjects regarding normal diet (two men, six women), and seven regarding paleolithic diet (one man, six women); complete data were available for six subjects (one man, five women)

It’s mean to mock – and I know that we all occasionally have computer problems – but to lose so much important data does seem unfortunate.

Next – drop out rate. 14 subjects completed the study, 1 dropped out because they found the diet too hard to fulfil. In other words, 1/15 subjects could not stick to this diet for three weeks, even given the extra motivation provided by being included in the study.

We should also ask what type of illnesses were causing people to drop out. For 3 healthy subjects to become too ill to complete the study – compared to just 14 who did complete – seems notable: of course, the illnesses may have been absolutely nothing to do with the diet, but I would like more detail. Also, the study found that “Two subjects showed elevated CRP, probably virus infection related”. If 3/20 subjects are too ill to complete, and 2/20 seem to have picked up a virus, this does seem to flag up a potential concern.

Moving on, then, to what the study did show. It does show that — if people stick to a restricted diet, which pretty much eliminate ‘junk’ food, for a few weeks — they do tend to lose weight. Eating a diet with lots of fruit and veg, and limited saturated fat and salt intake, correlated in the study to higher vitamin C levels in subjects’ blood, and reduced blood pressure. This is all well and good, but not exactly surprising: as the NHS notes

Low calorie, low salt diets are expected to have an effect on weight and blood pressure in people who are overweight or have high blood pressure

One should also note that – presumably because of the restrictive nature of the Paleo diet – calcium levels were reduced. A final caution is that the write-up the study is not entirely clear as to what foods were allowed, and why: for example, mineral water intake was restricted; while I am all for avoiding bottled water and environmental and financial reasons, I fail to see why tap water is more Paleo than bottled. Moreover, the study write-up does not specify whether or not a number of ‘staple’ foods – eggs, for example – were allowed.

Here at HolfordWatch, we certainly don’t object to diets which are low in ‘junk’ and high in fruit, vegetables, fish etc. However, we would be reluctant to subject ourselves to a diet as restrictive as the Paleo diet without seeing much stronger evidence for its benefits. This study also failed to show whether the Paleo diet is safe for periods longer than three weeks, or whether people find it palatable in the longer term. We would, anyway, emphasise that you should speak to your doctor or dietician before trying anything so radical: a Paleo diet would certainly not be suitable for everyone.



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47 responses to “The Curse of the Paleolithic Diet: When Studies Go Bad

  1. Claire

    “…one could almost conclude that the Paleo diet is somewhat cursed.”

    Spooky…did you know the ‘Nebuchadnezzar diet’ has recently resurfaced on wddty? Guess what, it involves excluding dairy and don’t worry your silly heads about calcium –

    “And don’t worry about the calcium issue – just eat plenty of leafy greens, just like the cows, and you’ll have that covered! ”

    Those of you easily upset by wilful muddling of allergy and intolerance had probably better not read any further:

    “Allergists insist that an allergy can only be diagnosed by specific tests, and that people who say they’re “allergic to” some food or other environmental element are often not technically allergic. Basically, it doesn’t matter what you call it…”


  2. Wulfstan

    Basically, it doesn’t matter what you call it…

    Which it doesn’t, unless you are threatened by anaphylaxis, want to research immunotherapy, need to distinguish between stuff you might be able to control your exposure to and stuff you can’t and generally want some practical principles. So, not a problem unless you are a what WDDTY would term a nit-picking worrywort but there is probably a Bach Flower Remedy for that.

    As a matter of interest, do cows go in much for leafy greens in addition to grass or is it they graze where they are tolerated? Where would one sign up for the additional bovine stomachs? Just how much leafy green veg would I need to eat in a day? Is there any resolution on the issue of whether oxalates in some green vegetables prevent the absorption of calcium – or, as asserted on some sites that fail to give references – is that now disproven?

    How much sunshine do I need to metabolise this calcium? And exercise to make use of it?

  3. Derik

    It’s the classic cautionary tale:

    An experiment is done with mice; 33% survived, 1/3 died and the other one escaped!

  4. The mouse is hiding because it would far rather be chewing linen cloths and gnawing cardboard than following the paleo diet.

  5. Peter

    Prior to the invention of farming we survived for millions of years without consuming a single dairy product, so clearly there are other sources of calcium just as good or better. What I do know is that three days after adopting the paleo diet and dropping all dairy and grains from my diet the nasty joint inflammation I had suffered for years disappeared like some sort of weird magic. So much for all of the doctors I,ve consulted about it. I didn’t get sick on the diet, I just feel 10 years younger!

  6. Yes, we survived to the ripe old age of 30 or thereabouts with a high infant mortality rate. Now, lots of contributory factors were involved but, not an impressive set of figures.

    And yes – other cultures survive without dairy. Oddly enough, some of them chew bones as well as deriving calcium from plant sources.

    It is excellent news that your joint inflammation disappeared so readily and unfortunate that no one had ever recommended such a course of action to you before. I hope that you keep well on your new way of eating and that you have had it checked by a dietitian to ensure that it is sustainable for you over a number of years, if that is what you are planning.

  7. Christopher

    The idea that hunter gatherers only lived to the age of 30 or 40 is simply not true. The mean lifespan is very misleading. This is because the infant mortality rate is very high, and this considerably drives down the mean lifespan. If you take 10 people with half of them dying at birth and the other half living to be 80 you have a mean lifespan of 40, which is obviously not at all representative of the actual lifespan

    The fact is that hunter gatherers that made it through childhood years lived about as long as modern day humans, without most of the degenerative diseases civilized cultures experience There are plenty of statistics to back this up.

    The high infant mortality rate is mostly due to infectious diseases overpowering the child’s still developing immune system, which happens with virtually every other creature in the wild. This is part of the process of natural selection.

    So it seems that our ancestors lifestyle, which included their diet, kept them alive just as long as we will live, but with superior physical health that enables them to enjoy their longevity. That is one of the reasons why some advocate a paleolithic diet.

  8. Angie

    I’ve been following this diet for over three months now and all my digestive problems, which I had suffered with for many years, disappeared within a week. It’s easy to follow and delicious if you just give it some thought and add some creativity. Cravings for sugar and junk never enter your head. I feel fantastic, have lost weight, gained muscle and boundless energy, look about ten years younger and now enjoy life so much more. This is the diet we are all genetically programmed to eat and I’ll be following it from now on. Those who critise it have clearly not tried it!

  9. Mark

    I have decided to follow this diet and have been for about 2 weeks now. I have found I am much more vivid and lively at work, and first thing in the morning. I have found that previous back and joint pains have gone, and reactions I used to get from eating certain types of fruits.

    The reasons I decided to start following it are purely because the theory is simple and scientifically logical. I would recommend it to anyone.

  10. Alex

    This is the case when experiment which went wrong is used to undermine the whole idea. Blame the experiment and researches, not the diet itself.
    I am one of those who benefited greatly from following paleo regiment and crossfit .
    I personally do not believe in short term paleo at all. I think it takes a long time for a body to adjust to any new nutritional intake physiologically, also mental distress of sudden intervention should not be underestimated either. I took me whole year of very small changes to switch to paleo and stick with it.
    You said “…However, we would be reluctant to subject ourselves to a diet as restrictive as the Paleo diet without seeing much stronger evidence for its benefits…”.
    I am not sure if you are familiar with Dr. Cordain work. If not please refer to “Published Research” on
    I also invite you to visit, and forums where you can find hundreds of people who are following paleo with one single purpose of taking their fitness to highest possible level and health. There is no dogma on these forums, people would adapt whatever works best, paleo and zone diet combination seem to be winners so far.

    • paleo

      I agree. It takes a minimum 12-18 months to adopt a full paleo diet. I took about six years to fully switch.

      • Of course, there remain questions about whether this diet is beneficial in the short- or long-term. I’d want to see pretty solid evidence before I gave up my bread…

  11. Alex – we started the post by saying that “we struggled to see much useful information to be gained from this problematic study.” Certainly, the study does not show that a ‘Paleo diet’ is a bad idea.

    In terms of convincing evidence for the ‘Paleo diet’, I was thinking more along the lines of a decent-sized RCT – comparing it to other diets which look promising for achieving similar goals.

    • Alex

      Jonhw, I see what you are saying. I am not aware of any studies which would compare Paleo to other regiments at this point. To convince me personally it took reading “Protein Power Lifeplan” by Michael R. Eades (Author) and Mary Dan Eades, then going over whole blog and reading all articles I was able to find on the subject by Dr. Cordain. Having read all that theory behind Paleo making decision to follow it was very logical step. I can only speak of my personal results, but I was never healthier and stronger in my life. Although I have to admit that Crossfit is probably the biggest part of my progress.

  12. Alex – sure, exercise and healthy diet are very much positive things. If a paleo diet works for you, that’s great. What I find more problematic are attempts to argue that this diet is optimal for (almost) everyone – I’d want to see much stronger evidence before accepting that this is the case.

  13. SteveH

    JohnW, Alex & others.

    A friend suggested I check out this Patrick Holford fellow. I doubted I would, even before googling this Holford Watch website, for no other reason than since around 1980, I’ve reviewed more than my share of one-size-fits-all panaceas to the human condition. And I’ve taken some life-changing journeys in the process, some of which left me changed, and some of which brought me partly back to where I started from.

    One of the conclusions I’ve come to, is that new “I have the truth” claims are endless. Especially when it comes to health and nutrition. I have noticed some common themes though. In an essay I wrote in 1993, I noted that “many health improvements seem associated with a decrease in processed food consumption coupled with an increase in fresh fruit and vegetable consumption”. My essay cited 107 references across a wide range of disciplines, and another 43 in an appendix on raw food proponents. and my essay, like all of my essays, was 1/3 of the size of my pre-editing draft. Whoopie you may say. I mention this only to illustrate that the above quoted sentence – be it right or wrong – was a distilation of much research.

    So? Okay. I did come across literature on paleolithic influences (sample list below). But in another section I note that “cultural adaptations can clearly mediate gene frequencies and their phenotypic expressions”, and I cite the example of dairying cultures and the distribution of the lactase enzyme. Adults in some cultures are indeed lactose tolerant, although such cultures appear to be in the minority (see e.g. Harrison, Tanner, Pilbeam & Baker’s 1988 ‘Human Biology: An introduction to human evolution, variation, growth, and adaptability. Or Weiss & Mann’s 1985 ‘Human Biology and Behaviour: An anthropological perspective’. Or you could check out the marvelous 1994 ‘Cambridge Encyclopedia of Human Evolution’ which I don’t have at hand, but which is an excellent single resource). And the point? There is genotypic and phenotypic variation when it comes to diet and nutrition.

    Nevertheless, and this was a major point of my essay, “modern food processing appears to have minimally influenced contemporary hominid genotypes”, especially in some aspects. I was looking at taste perception, which seems to show a clear sweetness/bitterness dichotomy directly related to energy and toxicity, and the degree to which food processing facilitates the ingestion of bitter-tasting, potentially toxic foods.

    But broadly speaking, there seems to be consensus that the industrial revolution and contemporary food-processing techniques are too recent for an evolutionary effect. This is especially bearing in mind that mortality is required to weed out genotypes and phenotypes not fortuitously able to handle changed environmental circumstance (in this case diet) – and in first world countries especially, natural selection via infant mortality no longer occurs to any significant degree – indeed the opposite: research should show the frequency of deleterious genes will be shown to be increasing, if it hasn’t already. As Harrison et al say (p.212) say “it is doubtful now if we shall ever witness again natural environments (i.e. non-man-made ones) causing directional natural selection”.

    So we continue to have a “stone age physiology”. Some key references on this from my essay were: Eaton & Konner’s 1985 article in New England Journal of Medicine (312, pp.283 – 289), Eaton, Konner & Shostack’s 1988 article in The American Journal of Medicine (84, pp.739 – 749), and Eaton & Konner’s 1985 book: “The Paleolithic Prescription”. I presume Holford’s work/s cite Eaton & Konner.

    But there was – and will be more – a wealth of research on diet and non-industriogenic lifestyles: For example K. O’Dea, N.G. White, & A.J. Sinclair’s 1988 article on traditional Australian Aboriginal diet in Medical Journal of Australia (148, pp.177 – 180). Or L.A. Cohen’s article on diet and cancer in 1987 Scientific American (257, [5], pp.42 – 48). Or Roger Lewin’s intriguing article in Science (224, pp.861 – 862) called ‘man the scavenger’. Or K. Milton’s (1993) ‘Diet and primate evolution’ in Scientific American (269, [2], pp.70 – 77).

    The problem I found when I began my journey was where to start. Once I started, the problem was where to stop. Once I noted repeating themes regarding diet and nutrition, I moved on in my readings (I still study evolutionary theory of course, but I can’t make a living out of that).

    So there are themes. But it’s never as simple as one would like. The Groucho Marx effect probably sums it up. John Barrow, in his book ‘The World Within a World) cites Groucho Mark: “I wouldn’t want to belong to any club that would accept me as a member”. In epistemological terms, “the only solutions…that we are clever enough to find always describe idealised solutions that will not generally arise in practice”. This paradox besets every field I’m aware of. But as contemporary philosopher Daniel C Dennett would say of course, that’s no excuse to not plug away at understanding.

  14. Dusklover

    I started the paleodiet several months ago to help alleviate a flare up of inflammatory bowel disease. My condition improved dramatically within a few days and after a month I had lost 20 lbs, my skin was clearer, I no longer needed to use deoderant, I had increased energy through the entire day, my headaches and joint pains were gone, my immunity was improved, and my intestinal tract is working perfectly. A few weeks ago I ate some grains and sugar over the course of a few days and experienced fatigue, pimples, bloating, diarrhea, headache and joint pains, and irritability.
    I think I’m just going to stick with the diet for the rest of my life, because the pain of IBD is not worth any sugar or grains or dairy!
    I’ve added olive and grapeseed oils, as well as natural peanut butter to my daily diet.
    I’ve suggested the diet to many, many people who complain about their health and weight. Those who actually tried it were sold.
    It just makes good sense to me.

    • Glad you’re in better health now. There are lots of different variants on the ‘Paleo diet’, but we would always advise people to speak to their doctor or dietitian if they’re considering cutting out ‘staple’ food groups.

      One of the concerns with Paleo diets is how sustainable they are over the longer term. Whether you stick to the diet or not, though, I do hope that the health improvements last.

      The above post focussed on critiquing a particular study on one variation of the Paleo diet. Whether this way of eating ‘works’ or not, there is still a need to ensure that research on such diets is done to a good standard.

  15. J.R. Lagoni

    I have been on a paleolithic diet for over 10 years and it has been great. No more arthritis, IBS, and I lost 40 pounds. I am 56 and I consider it a better health program then anything out there – and all you do is change what you eat to a natural diet that is in accord with our genetic composition.

    Cordain and others have done great academic/scientific work.

    • Cal Edwards

      I have been on the Paleo diet for several years after being on a low carb diet for about 10 years, and with a short (10 months) stint vegan diet between the 2. The science and logic behind the Paleo diet, plus my own experience on it, has convinced me it is the most reasonable and healthy diet one can be on. I also find it quite easy to follow: all meats (grass fed beef, buffalo for red meat), most fish, most fruit, most true nuts (not peanuts, etc.), non-legume vegetables, and no grains, potatoes, dairy, salt or sugar. I’m 62, and have no health problems. My blood pressure was slightly high, and I’ve had leg cramps all of my life until being on this diet. Both have disappeared, and all of my numbers and organs are in excellant shape. I don’t understand some comments about this diet being “restrictive”, unless it’s the legumes, potatoes and dairy aspect. I pay no attention to my calorie intake, and I never leave the table hungry. I don’t “exercise” in a formal way, although I do physical work on my small ranch. I only take vitamin D because I live so far North I almost never see the sun in the winter. I take no other supplements or medication. I can’t recommend this strongly enough.

      • Cal – glad you’re feeling good now.

        I’d say the Paleo diet is restrictive in particular because (in most versions) it excludes grains, milk and legumes: substantial parts of the diet of many cultures. I’d want to see very robust evidence before I cut so many foods out of my diet; this evidence just isn’t there.

        • Markr

          I think as an adult you have the right to choose any diet you wish, however when it comes to looking at the general population these ‘staple’ foods serve a purpose, if we removed these foods from the population im pretty sure the effects wouldnt be good! Its not simply switching everyone to this diet, there are many cultural and aggricultural issues to consider.

        • Mark

          I’m not sure what you expect for ‘very robust evidence’. Before humans domesticated animals for dairy, cultivated cereal crops for grain foods and cooked legumes in pottery to make them digestible (about 20 – 10,000 years ago), ALL humans on the planet did not eat those foods. That’s about 2.5 million years without grains, dairy and legumes. Not good enough evidence? I doubt your genetic makeup is so radically different from most human beings that you would seriously compromise your health by eliminating these foods. In fact, I would say that there is very little evidence that eliminating these foods would seriously harm you.

        • There are distinct cultural factors in diet, too – cutting out what one has become used to as a staple can make it harder to eat a balanced diet. Also, there are lots of things I enjoy that I could perfectly safely stop eating or doing – but if there’s not good evidence they’re harming me, why should I?

        • Antonio

          Hi there, nope The paleo diet does not
          restrict you from milk if you take all this a bit further.
          See all the bad things about milk are from
          pasteurized and homogenized milk.
          For you to derive from it’s benefits it’s
          got to be raw milk. What’s that I hear, Salmonella? Take a look at the cases of salmonella poisining cases and you will find they were from pasteurized milk.
          Pasteurization was used when hygiene problems gave us no options when we had plagues etc. But what it does is alter the molecular structure of milk so your body doesn’t know what to do with it anymore
          it looses the enzymes that break down lactose as well as good bacteria und thus
          ze diarea from the rear.
          The raw milk contains Lauric acid as does
          raw butter and it fights cancer amongst other things. But don’t listen to silly old
          me do yourself a favour and get yourself
          as I did Mike Geary’s Fat Burning Kitchen
          ebook or that of Isabel De Los Rios.
          I am not marketing their books I bought
          these books and it changed my weight,
          fitness and outlook on food and nutrition.
          It will give you a brand new outlook and change your life as it did for me.
          Just my view thought I would share some of it with the people out there.

  16. PaleoPhil

    Like many other people have posted here, I’m doing great on a Paleo diet, and I’ve been following some form of Paleo diet for over 5 years.

    Like I said on my blog that I created mainly for friends and relatives who were interested in the secret of my health improvements, I don’t tell people what to eat. I think folks should work out for themselves what foods they do best on. However, if you don’t even try a Paleo diet, how will you know whether it works for you or not?

  17. How can we know with any certainty what pre-historic human had to eat? Did they record it in their cave paintings or perhaps write down in mysterious runes that could only be interpreted by later new age nutritional gurus?

    Some well-preserved bodies have been examined to see what they were eating before they died. However, I suspect that early

    Before the arrival of farming people probably ate what they could get their hands on which would have included some meat and fish.

    Finally, we seem to have forgotten that food can be fun. Why do we want to make our diets as dull as possible?

    • Yes – and presumably it varied depending on the environment, too. If you’re living 100s of miles from the coast, there are some foods that won’t be available to you…

    • You’re on the right track with meat and fish (Paleolithic eating is pretty simple and intuitive/instinctual), but you’ll never fully understand what the Paleolithic diet included and how scientists determine it unless you investigate and learn about it. It’s a lot more effective than trying to guess at everything.

      If you find it too dull and are not interested in the health benefits that some readers have reported above, then don’t eat it. It’s your choice. Simple.

  18. I hope followers of the paleo diet are getting the food the same way as our prehistoric ancestors.

    No visiting Tesco. Now that would be cheating?

  19. Thanks for the concern, but don’t worry about us. We’re doing fine, as you can see from the reader comments.

    As for you, do what you wish. “To each their own” and everyone wins.

  20. Don

    Like many others here, I have had great success on the Paleo Diet. I can’t even express how much more energy I have and all those weird symptoms that I tried to tell the doctor about, are gone! It is not restrictive at all. In fact, eliminating grains makes me look to other forms of carbohydrates such as vegetables, greens, fruits, nuts, etc. All vastly more healthy than starchy, dried grains. Grains are cheap, filler foods pushed on us by the farming industry. Don’t be fooled. We need carbohydrates, but not in the starchy, grainy form. The author of this post clearly has not done research and just posted a 1 sided, single study, very generic, vague interpretation of the Paleo Diet study. The post is almost irresponsible to me. So many allergies and immune system problems have been linked to grains and the mold that is inherent on them from the way they are stored. Again, this diet is far from restrictive. It’s delicious and filling leaving you full and full of energy and most importantly, healthy.

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