You have no idea how excited I am about today's post. My friend Mick has agreed to be the first one to post in this new series of posts that I decided to call Sunday Salon late one night after brainstorming with a friend and my other good friends gin & tonic. I've lined up some amazing people who either write blogs that I read myself or who do other cool things that I admire (like do really cool research, or have a hobby that I think is really impressive) to write about something they care about.
Mick (who writes a lovely blog about living in the States - Legal Nonresident Alien) is starting us off writing about the paleo diet and I am really happy he decided to write this post because it pretty much sums up my feelings about this 'diet' just more eloquently. Since I hope you will leave a comment if you have thoughts about this you want to share I'll add mine as the first comment myself.
Hello. I’d like to thank Katharina for giving me a whole new audience to rant at. My name’s Mick, and I’m a
neuroscientist by day, and a drunken Glaswegian by night. Two of my favourite
pass-times are ranting about things that annoy me, and food (cooking or eating,
both bring me immense pleasure). So I’m going to combine my passions and rant
about a food-related issue: fad diets. Well, one fad diet in particular, the
paleo diet.
The paleo diet (or paleolithic diet, to use its Sunday name) is a
fairly new food fad which recommends that we only eat foods which were
available to paleolithic man: fruits, some vegetables, meat but (allegedly) no
grains such as wheat. I’ll get into specifics later. The premise of the paleo
diet is that modern humans evolved in the paleolithic time so we should only
eat foods that were available at that time because evolution hasn’t equipped us
to deal with many of the foods in the modern diet.
The argument is usually framed in two parts: firstly, that we have
only evolved to digest and metabolise foods available 20,000 years ago.
Secondly, that modern hunter-gatherer tribes do not suffer from the “diseases
of civilisation” such as heart disease, high blood pressure or cancer, so the
modern diet is obviously the cause of all our woes.
Anyway, my arguments against paleo will vary from petulant ones
which will be mostly petty point-scoring, to more detailed ones backed by
scientific fact. Extra points for those who spot which ones are which. I’ll
begin by discussing which foods are acceptable in the paleo diet, and which are
verboten.
Foods allowed in the paleo diet are those which were available to a
hunter-gatherer: fish, meat, eggs, insects, fruit, vegetables, nuts and
mushrooms. Oh, plus herbs and spices. Foods not allowed in the paleo diet
include grains (corn, barley, wheat, oats, rice, etc), dairy products, refined
sugar, salt, processed oils, starchy vegetables (potatoes, sweet potato, cassava, etc)
and, oddly enough, legumes (all beans, peas, lentils). The grain list also
includes stuff made from grains, obviously, such as bread and pasta. Just
think: a world without cheese, beer or bread?
Paleo flaw number one: the list of allowed and forbidden foods is
based on our best guesses of what paleolithic man (and woman) ate. This list is
based on a lot of assumptions that are not, really, testable. Inferences can be
made from modern hunter-gatherer populations and also from archaeological
evidence, and this is what paleo proponents do. Unfortunately for the
archaeologists, evidence of diet is hard to come by (squishy stuff like
vegetables and people don’t preserve very well) so concluding anything other
than looking at gnawed bones and saying “we ate meat” is tricky at best.
Paleo defenders will then tell you to look at modern hunter-gather
tribes to see what they eat. They will generally cherry-pick the tribe that
most suits the particular angle that they are trying to defend. In my field, we
call cherry-picking your evidence Bad Science. Do you really think that the
diet of modern Inuits, mostly fish- and meat-based because not much grows in the Arctic, will be similar to that of tribes living in
the South American rain forests, sub-Saharan Africa or in the middle of a
desert in the Australian outback? The truth is that humans are
bloody resourceful animals and will always manage to survive with whatever is available, be that grubs, tubers or Big Macs.
Let's take a look at the foods that are forbidden in the paleo diet. How about grain? Paleolithic man didn't eat or process grains so modern man shouldn't eat them, right? Two years ago, an article published in PNAS demonstrated that processing of grains and perhaps even production of flour was being carried out 30,000 years ago, so caveman did actually eat grains. We can go even earlier: another PNAS article shows us that Neanderthals were also processing starchy grains, related to sorghum, as well as plants from that other class of foods forbidden on the paleo diet, namely legumes. Did I mention that our Neanderthal cousins were cooking these foods as well? The YOUNGEST Neanderthal remains found so far are around 32,000 years old, although DNA evidence suggests that some of their genome lives on in us. Further evidence of this can be seen in my home town of Glasgow: try Sauchiehall St around 2am on a Saturday morning and you'll see what I mean.
If one were to follow the spirit of paelo to its logical conclusion, other foods that should be avoided are anything that comes from the New World as none of these foods were available to paleolithic woman. So no tomatoes, bell peppers, chilies, blueberries, avocados, squash, or pumpkins, to name but a few. And domesticated animals are nothing like their wild ancestors, so paleo adherents should only eat wild-caught game, although I won't insist that they only eat game caught with stone-age weapons. Of course, paleo people don't take it this seriously.
Another of the paleo assumptions is that we evolved in the paleolithic era and not enough time has passed since for evolution to shape us in a way that is suited for the modern diet. This argument is, quite simply, wrong, and is based on a very weak understanding of biology. Alcohol dehydrogenases, the family of enzymes that metabolise alcohol, have been adapted and selected for recently in our evolutionary past. Dairy is also prohibited from the paleo diet because it wasn't around in hunter-gatherer times so we haven't evolved to handle it. Right? Wrong:
Lactase persistence into adulthood is a recent evolutionary adaptation, having arisen in the last 5000 to 10,000 years, or after paleo man became neolithic man. These are just two examples from the top of my head, so I'm sure there are many others.
What annoys me most about paleo is that it tries to use science to justify some of the dafter elements of the diet, such as avoiding legumes. This argument is based on the concept of "anti nutrients", enzymes or proteins found in plants which inhibit absorption of other minerals or nutrients from food, or inhibit digestion. Examples include lectins and phytic acid, large amounts of which are found in grains, seeds, nuts and legumes.
Lectins break down via cooking, so the argument against them is just silly. Phytic acid is a bit more interesting - it forms complexes with metal ions, making them much harder to digest. While they are present in some non-paleo foods such as rice, oats and lentils, even higher levels are found in many nuts such as almonds, brazil nuts, hazel nuts and walnuts. Nuts are recommended paleo-snacks because they were available to the cave-man. I also came across this when gathering my references, which sums the argument up with more vitriol than even I can manage.
Basically, these so-called antinutrients are found in most plants because they serve various roles, such as natural insecticides. But this is also why we use that neat trick of cooking plant matter to increase the nutritional content. As I said before, even our Neanderthal cousins stumbled across that one. Pretty much every plant contains these compounds to some degree, which is why we evolved to eat a wide and varied diet.
As an aside, something that is generally over-looked in nutrition studies is the role that gut bacteria have in digesting our food and providing us with nutrients. It is well established that gut microbes are one of the main sources of vitamin K and some B vitamins in the human diet -
our gut flora mooches on our meals and, in return, they provide us with vital micronutrients.
Our symbiotic bacteria are also capable of breaking down phytates in our diet, thereby taming the evil antinutrients. What is REALLY cool is a paper from a couple of years ago showing that gut flora of Japanese people picks up genes from marine microbes which are eaten along with seaweed. This horizontal gene transfer gives the gut flora an ability to break down sugars in the seaweed which humans can't digest on their own. How amazing is that!?
So, to summarise, is the paleo diet actually bad? Not in itself - any diet which recommends avoiding processed food and eating a diet rich in fruit and vegetables is a good diet. However, paleo excludes so many foods which are both beneficial and necessary to feed the entire planet. If everyone tried to eat meat at every meal, we'd not have much of a planet left, yet this is what paleo people tell you to do. The fact that they use bad science in an attempt to justify their position really makes me angry.
I suppose a lot of food is not about nutrition, but is cultural and a way of identifying with a certain group. Paleo seems to me to be a diet which is even pickier than veganism, but for guys and girls who still want to eat lots of meat. By all means, pick a diet that makes you happy. But trying to emulate the diet that humans ate when most people died in their 20s, either of disease, during childbirth or by becoming food for something bigger, well, that seems a bit daft.
© Michael Craig
