A quick review of the basic premise, this new lens through which I examine nutrition, general health, and mental health: humans beings will have the best chance of good physical and mental health by staying true to the diet and activities that we are evolved for. Let's get back to diet for the moment and focus on some of the differences between what we eat today, and what physically healthy peoples and cultures ate. Much of the following information is taken from Food and Western Disease (never leave home without it).
We know from several hundred years of good observation and anthropology that healthy peoples ate a wide variety of different foods, with vastly differing percentages of macronutrients (primarily differences in carbohydrates and fats - protein is usually around 15-30% of calories). The types and quality of the food they ate, however, universally differed from our current diet in the following ways:
1) no wheat, and if grain-based the grains are carefully prepared to minimize antinutrients
2) minimal amounts of omega 6 fatty acids balanced with omega 3 fatty acids (or vast amounts of omega 3)
3) reliance on whole foods with no industrial processing (therefore no highly refined carbohydrates or sugar other than perhaps seasonal raw honey and wild fruits)
In my opinion, one doesn't need to understand the science or biochemistry of these differences to go forward with a paleolithic-style diet based on the time-tested diets of healthy cultures. However, I'm interested in what it is about these differences that might cause Western disease.
I'm going to focus on #2 at the moment, and introduce a fading star of the "heart-healthy diet," vegetable oils. (Or not so fading star - this recent article trumpets vegetable oil as the second coming, though, as always, Stephan at Whole Health Source has a reasoned review.)
Corn oil, safflower oil, sunflower oil, peanut oil and/or soybean oil are ingredients in pretty much all processed food. Just check the list on the back. They are in breakfast cereal, bread and other baked goods, and also in fried items, salad dressings, mayonnaise, sauces, and are used (along with canola oil) in the fryers at most restaurants. They are cheap and relatively tasteless, which makes them perfect for certain industrial and restaurant food applications. They are also universally high in omega 6 fatty acids, and therefore we eat a ton of them in the Western diet, especially since throwing out butter, lard, and beef tallow 30-40 years ago.
How could this possibly matter? Omega 6 fatty acids are a type of PUFA (polyunsaturated fatty acid), which are required by the body to make certain hormones and signaling molecules. Omega 6 PUFAs are "essential" fatty acids - we can't make these signaling molecules without them, and we need them to live. PUFAs are made into HUFAs (highly unsaturated fatty acids - which isn't all that vital to this discussion but I like to say 'HUFA'), and omega 6 PUFAs (in particular linoleic acid) are made into the HUFA arachidonic acid. Arachidonic acid (AA) is the precursor for all sorts of *inflammatory* signaling molecules, including (as an example) COX-1 and COX-2 (which are blocked by ibuprofen and other NSAIDS that decrease pain and inflammation). (Here is a very understandable review of eicosanoids.)
Too much inflammation mediated by a high dietary percentage of the omega 6 fatty acid linoleic acid (the predominant fatty acid in corn oil) can be reasonably associated with coronary vascular disease, insulin resistance, cancer, hypothyroidism and other autoimmune diseases, thrombotic stroke, headaches, asthma, arthritis,(1) melanoma, depression, and psychosis.
But why do I keep harping on "balance" and those omega 3 PUFAs? Well, turns out the omega 3s (wild fish oil is the best source, but it is also available in grass-fed animal fat, other kinds of seafood, flax, and in more balanced levels with omega 6 in walnuts and macadamia nuts) compete in the body with the omega 6s in every which way. Omega 3s are precursors for anti-inflammatory signal molecules (which, obviously, counteract the inflammatory signal molecules). We can only store so much of either, so if we eat omega 3, we displace some of the omega 6 from our systems. Supplementing with omega 3 fatty acids has been shown to be beneficial in a number of major diseases (2). Again, we need both to survive, but if we max out on the omega 6 without any omega 3, we end up with a highly inflammatory soup of chemicals stored and floating around in our bodies predisposing us to that list again - cancer, diabetes, obesity, depression, heart disease, and autoimmune diseases.
Here are some numbers from Food and Western Disease about ratios of of omega 6 to omega 3 fatty acids in different populations (from page 46):
Omega 6/ Omega 3 ratio
Coastal fishing populations: <1
Greece in the 1900s: 2
Japan today: 4
Northern Europe today: 15
USA today: 17
And here's the real kicker about the modern diet - first we load ourselves up with vegetable oils to create a large reservoir of pro-inflammatory molecules, and then add a soup of what are thought to be highly allergenic and pro-inflammatory proteins (gluten, gliadin, beta casein A1, proteins from peanuts and similar proteins from genetically modified soy, etc. etc.). Our modern diseases can almost always be linked back to inflammation of some kind. In my mind, this combination explains why my schedule is full every day.
How can you eat less omega 6 and more omega 3? One way is to eat more paleo. Get rid of the processed food. Use olive oil and vinegar instead of supermarket salad dressing. Balance out nuts (relatively high in omega 6 too) with some fish oil from wild caught fish. Poultry fat is relatively higher in omega 6, so eat grass fed beef and wild caught fish in a nice balance with your chicken and turkey.
And here's where I really part ways with the Grand Poohbahs of nutritional recommendations - you can eat more saturated fat. (Really. It won't kill you.) Instead of baking with industrial seed oils, use butter or coconut oil. They are neutral players in the omega 3 omega 6 fat war, and plenty of healthy cultures eat a reasonable or even high amount of saturated fat (the Masai, the Kitavans, the Tokelau) and they don't drop dead of heart attacks at age 50. Or 75. Pastured butter, bone marrow, and other yummy, more traditional treats are high in saturated fats are also the best sources of some vitamins we need but just don't get in our modern diet. But more on that later.
See, here's what has happened with the nutritional recommendations over the years. First we were told not to eat saturated fat and foods high in cholesterol. It was figured out almost immediately that foods high in cholesterol (such as eggs) don't cause heart disease or even elevated cholesterol in humans, but that was deemed confusing, so the message changed to don't eat saturated fat. At first everyone was moved over to the PUFAs - vegetable oils, including all that deadly trans fat margarine, but then it was discovered that PUFAs cause cancer and trans fats are horrible, so the message switched to 'eat low fat!' We're fairly restricted in the amount of protein we can eat anyway, so a low fat diet is therefore very high in carbohydrates (our particularly vicious mix of sugar and wheat). Then everyone following this advice got REALLY fat and diabetes incidence exploded. So THEN there was more backpedaling, and the message has changed to "healthy fats" (the omega 3s and olive oil), and "whole grains" (which when eaten without careful preparation as we eat them now *may* contribute to the problem) of a Mediterranean diet. (Though a true Mediterranean diet has plenty of saturated fat too. Cheese. Butter. France. Synonymous.) And consider that most of the disease states I'm looking at require two hits from the diet to make them happen - for example, wheat lectins to open the gut, and casein protein in the blood to predispose beta cells to autoimmune destruction in type one diabetes.
But one can see that all these nutritional recommendations backflip over themselves to catch up with science, and everyone is confused, sick, fat, and unhappy. But one doesn't need to stress over food, or make food the enemy. All one has to do is to go to a basic, default paleo style diet and then add in more modern foods (such as dairy) based on observations from other cultures (like the Masai) who ate them and don't have the diseases of modern civilization. All the work has already been done for us! We just have to pay attention.