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.
8 responses so far ↓
Claire // May 13, 2008 at 10:14 pm
“…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! ”
http://community.wddty.com/blogs/fooddoctor/archive/2008/05/12/Anti_2D00_allergy-foods.aspx
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…”
*sigh*
Wulfstan // May 14, 2008 at 8:16 am
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?
Derik // May 14, 2008 at 3:16 pm
It’s the classic cautionary tale:
An experiment is done with mice; 33% survived, 1/3 died and the other one escaped!
dvnutrix // May 14, 2008 at 3:55 pm
The mouse is hiding because it would far rather be chewing linen cloths and gnawing cardboard than following the paleo diet.
Peter // June 2, 2008 at 3:45 am
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!
dvnutrix // June 2, 2008 at 9:57 am
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.
Christopher // October 19, 2008 at 6:18 pm
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.
Angie // October 31, 2008 at 1:36 pm
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!
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