The Basic Premise: The Theory of Evolution by Natural Selection is being applied to more fields than ever before. The evolutionary paradigm have allowed for huge advancements in biology, psychology, and sociology, to name a few. The concept that humans have evolved to a particular niche is nothing new. Due to natural selection, animals are well adapted to their respective environments.
The termite eats wood, the duck eats fish; this makes perfect sense. Feeding wood to ducks or fish to termites would be quite silly for one very obvious reason: natural selection shapes the biological and digestive machinery of each organism so that it functions optimally given a specific environment. Ducks would suffer great loss of health if forced to eat wood. Unfortunately, this is analogous to our eating habits today.
I hope to clearly demonstrate that we are simply not eating the foods that natural selection has endowed us with the innate capacity to digest and assimilate. An evolutionary perspective on human nutrition will be our lens as we examine our present health and eating habits from a Darwinian vantage point.
So What Did We Eat?: Humans are no different from the ducks and termites-natural selection has been working for at least 2.5 million years from (the emergence of Homo Habilis) to shape our biology to a certain diet. What was that diet? Humans lived in small hunter gatherer bands of 25-40 people primarily in the African Savannah.
Early humans were primarily hunters. Their intelligence and tool-making skills allowed our ancestors to kill animals both big and small. Our diet was also supplemented by the gathering of fresh fruits and vegetables, nuts and berries, roots, shoots, and tubers. Occasionally the lucky hunter-gatherer would stumble upon a bird egg or a tasty lizard. Fair enough, that's what we ate. Notice the complete absence of all grains (breads, rice), processed sugars, or dairy products (except for good old mom).
So the diet of hunter-gatherers was relatively high in protein, moderate in animal fat (the meat eaten was quite lean) and high in low-density, fibrous carbohydrates. Based on their high protein and substantial fat consumption (their cholesterol consumption was probably three times higher than the average American today), you might say: they must have all been fat!
Actually no. All archaeological and anthropological evidence (from extant hunter-gather tribes) shows that obesity is/was virtually non existent. In addition, there was no heart disease, high blood pressure, elevated cholesterol, or diabetes. Where did we go wrong?
Agriculture and the Refined Carbohydrate--> the Real Culprit: So, imagine evolution's surprise, when, between 8,000 and 10,000 years ago, humans suddenly developed agriculture. Our diet was instantly transformed from one based primarily on fresh meat and vegetables, to one based primarily on grains.
The results were astounding: The digestive machinery that was so perfect for two million years was suddenly useless. The body could not deal with such high levels of carbohydrates: all the known diseases of civilization began to develop, people's teeth began to rot, bones were more fragile, overall health dropped significantly.
In fact, archaeologists can easily tell if newly discovered bones are from an agricultural society or hunter-gatherer one: the hunter-gatherer bones are thicker, stronger, and more robust and indicate that they were much greater in stature (probably from high protein consumption) than their agricultural followers. This alone should be evidence that grains are not the perfect food--like many nutritionists presently claim.
The "Complex" Carbohydrate: Carbohydrates are sugars. They are either simple sugars like glucose (that which the brain uses for energy), or complex like grains and starches (which are simply chains of simple sugars). No matter what type of carbohydrate you eat, it is the function of the liver to convert it to glucose, so that the brain can get its food.
Whether you ingest pure maple syrup or wild brown rice, the body converts them both to glucose. That means that according to current U.S. RDA standards, your body has to contend metabolically with almost two cups of pure sugar a day. Yes, this also means that you're stomach cannot tell the difference between 2 bags of Skittles and generous serving of pasta; both provide the same amount of sugar.
In fact, there is something called the "glycemic index" which is a measure of how quickly the carbohydrate is converted to glucose and causes blood-sugar to rise. It just so happens that, on the basis of their glycemic indices, pasta and rice can hardly be differentiated from table sugar! In other words, their glycemic indices are nearly identical.
Now here's why carbohydrates are really bad: There is a certain hormone, called insulin, whose function is primarily to regulate blood sugar. After a big meal, or whenever blood sugar levels are high, the pancreas secretes insulin, and insulin (by ushering sugar into the cells) directs the storage of all extra energy as fat-to be saved for later.
So far so good, but the problem is that all grains create a huge increase in blood sugar (and as you now know, that also includes our treasured complex carbohydrate), so that the body must constantly produce a lot of insulin to counter all of the incoming sugar.
Hyperinsulinemia After a big pasta meal, for example, your body is "shocked" (evolutionarily speaking, because their has been no precedent) by all the sugar in your system. It secretes a great amount of insulin, in fact, it produces too much insulin! This has the effect that your blood sugar is lowered (because sugar is moved into the fat cells), but excess insulin remains in the blood.
The insulin is now ordering that all incoming food-energy be stored immediately and not be accessed, thus acting as a 'lock and key' to your own energy stores... Your blood sugar is then too low. This is why people are often tired 2-3 hours after a big, grain-based lunch (What does this imply about the traditional siesta in many countries around the world?). Hyperinsulinemia, in one way or another, is connected to the diseases of civilization.
OBESITY: All of the insulin in your blood signals your body to store energy for later; as fat. It doesn't matter if the food is protein, fat, or carbohydrate, the body will convert it to fat for later use. Just in time for the next ready meal. Because of how strongly carbohydrates stimulate insulin, even if a paltry number of calories are eaten, the body will store a number of them as fat.
Hmmm. In addition, after a meal- when your energy levels should theoretically be very high-because there is so much insulin you can't even use the calories you just ingested. The result: You are hungry and the body tells you to eat some "quick" energy to help correct the problem...you crave carbohydrates! Hyperinsulinemia can thus lead you to overeat, even though you may be eating more than enough calories.
DIABETES TYPE II (adult onset): After years of excessive insulin, the cells of the body are overwhelmed and lose their sensitivity to this crucial hormone, that is, they become resistant. The body responds by producing more and more insulin to counteract the fact that it takes more and more for the cells to react in the same way.
Eventually, however, the pancreas can no longer produce enough insulin to reach the now insulin-resistant cells, and diabetes (where blood-sugar levels cannot be properly monitored) is the obvious result. This also explains why recently "civilized" hunter-gatherers like Native Americans or the Australian Aboriginals are so likely to develop diabetes after leaving behind their previous nomadic lifestyle.
While the picture is undoubtedly more complicated than this (fat has also been implicated in diabetes), even common sense would lead us to conclude that the diabetic should not be eating foods that create steep cliffs and valleys in blood sugar. This can only exacerbate the problem and forces us to question the high complex-carbohydrate diet that is currently recommended to diabetics.
ELEVATED CHOLESTEROL AND HEART DISEASE: This one's a little more complicated. Here's a little background. Despite what you may have heard, cholesterol is absolutely essential for life. It is used by the cells of the body to produce various hormones and is also used to help the cells repair themselves and grow.
In addition, cholesterol does not come directly from the diet. In fact, approximately 80% of the cholesterol the body uses is actually produced by the cells themselves (anywhere from 500-1500 mg a day! Compare that with an egg which contains about 150g of cholesterol). When the cells are producing a lot of cholesterol by themselves, they do not need to draw cholesterol from the bloodstream (which comes from diet via steak and eggs...) because they already have enough.
However, if the cells significantly slow their production of cholesterol, they need to draw cholesterol directly from the blood, thus preventing excessive cholesterol build-up where it can contribute to heart damage. Well, there is an enzyme called HMG-CoA reductase, whose job it is to tell the cells to churn out their own cholesterol. And guess which master hormone stimulates this enzyme? Exactly, insulin.
So, without excess insulin, you're body will use all of the cholesterol that you eat and elevated cholesterol should disappear quickly. This is why, while eating a diet primarily of cholesterol-rich meats meant our hunter- gatherer brethren didn't have elevated cholesterol.
However, you can see why steak and potatoes (the potato stimulates insulin, the steak has cholesterol) truly raises serum cholesterol, because the cells are producing a lot of their own cholesterol and there is also a lot in the bloodstream from the steak. There are some other ways that insulin contributes to the forming of fatty deposits in the arteries. I would recommend a book called Protein Power by Eades for more information about insulin-related disorders.
CANCER - This is undoubtedly the most difficult of them all. There have been thousands upon thousands of 'correlation' studies, attempting to pinpoint consumption of certain foods and associate them with varying risks of cancer. There has been nothing absolutely conclusive, but certain patterns have been relatively consistent.
First of all, incidences of cancer in modern hunter-gatherer tribes is very low; that shouldn't surprise us. In addition, there have been numerous studies correlating vegetable (and sometimes fruit) intake with lower risk for cancer. Fish, and sometimes chicken, is consistently associated with a low risk of cancer. High intake of saturated fat (mainly from red meat) has been associated with an increased rate of cancer.
However, whether this is due to the fat itself or chemicals and carcinogens in the fat is another issue. Suffice it to say, we are best off eating lots of fruits, vegetables, chicken, and fish. If you want to indulge in red meat, it is better off to buy free range (lower in overall fat and also hormone and steroid free) and be on the safe side.
In Summary: So there it is, in a nutshell. By eating the foods that the human body has evolved to digest efficiently we can avoid the deadly diseases of civilization and significantly improve health. Everyone will need to find the balance and level of moderation that works best for them, but here are some helpful guidelines:
1) Base your meals on some sort of a lean protein (fish, chicken, lean meat). Even eggs are okay sometimes.
2) Supplement with lots of vegetables, and as much variety as possible.
3) Fruits, nuts, and berries make for excellent snacks.
4) Drink lots and lots and lots of water. We don't need sodas and "fruit" juices.
5) Breads and other grains in moderation. If given the choice, whole grain foods have many more vitamins and fibre, as well as lower glycemic indices.
6) Dairy products in moderation; choose primarily those (like cheese) that are lower in carbohydrates.
7) For the sweet-tooth: honey makes for a great natural sweetener. The true hunter-gatherer worked very hard for access to a bee hive.
The benefits of this diet will quickly become apparent. If you have weight to lose it will start coming off rather quickly. Elevated cholesterol will be quickly normalized because the underlying hormonal problem has been removed. Your blood sugar levels will be very stable and this will lead to increased energy and even higher endurance. In addition, with the increased protein intake, you are likely to gain a couple pounds in muscle mass. Hey, it's worth a shot!
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