When you climb into a hot tub, it pays to edge in slowly. The water can be so hot as to be unpleasant, until you get used to it. Then it will feel pleasant. When you step into a swimming pool, the water sometimes feels cold. But after a few minutes, you get used to it. The scent of pine trees or fragrant flowers is wonderful, at first. But then you get used to it, and soon you may hardly even notice it.
How is it that our internal experience can change so dramatically, even when our environment is staying the same? How is it that we so easily “get used to” things? It turns out that scientists have carefully studied this striking phenomenon, which they refer to as neuro-adaptation. This process is called “neuro-adaptation” because it involves nerves and adaptation.
Our sensory processes are dependent upon the activation of sensory nerves. It is through the activation of various sensory nerves that we are able to see, hear, smell, sense touch, and to taste. The activity of these various sensory nerves tells our brains what is going on, and to what degree of intensity. For example, when you are sitting in a dimly lit room, and you turn on more light, your visual nerves become more active. They help your brain to notice an increase in brightness. Similarly, if you increase the volume on your stereo, your auditory nerves become more active. They help your brain to notice the increase in sound intensity. This same principle works for all of the five senses.
We tend to think that our nerves provide us with a very accurate depiction of real-world stimulation, but surprisingly, this is not the case. Let’s go back to the example of sitting in a dimly lit room. If you turn on all of the lights, it will seem very bright. However, if you later go outside into full sunshine, that will seem brighter still. When you go back inside, it will seem dim, even though all of the lights are still on. Clearly, your nerves are not providing you with an “accurate” depiction of reality in these instances. They are providing a relative depiction. Your senses are highly responsive to change. They tell you when a new stimulus is brighter or dimmer, louder or softer, hotter or colder, and so forth, but not precisely how bright, or loud, or hot. Perception is largely a gauge of relative change.
The reason our nerves provide us with relative, rather than absolute, information is partly because our nerves are designed to adapt to a steady level of stimulation. When there is a sudden increase in stimulation, your nerves increase their rate of “firing” (the basic mechanism that communicates sensory information to the brain). Any change in the intensity of a stimulus results in a change in the firing rate of the appropriate sensory nerves. For example, when you brighten the lights, your visual nerves will increase their firing rate. When you later dim the lights, the firing rate will be reduced.
In this article, we shall focus on an aspect of “getting used to” things that can lead to enormous, often deadly, problems.
After we brighten the lights in a room, our visual nerves increase their firing rate, but only for a little while! After a few minutes, the firing rate will slow down, or “adapt,” to the new, higher rate of stimulation. Sometimes, the nerves may even slow down their response to the level that they were previously firing at the lower level of illumination. This is why even a brightly lit room will seem merely “normal” after your sensory nerves adjust to it.
All of our sensory nerves work in this manner. When we first enter an office, we might be distracted by a noisy air conditioner. But after a while we will likely cease to notice it. When a person first starts smoking cigarettes, he is acutely aware of the smell of the smoke. He smells it on his fingers, in his clothes, and in his car. But before long, he won’t notice it at all. He will have “gotten used to it.” He may never notice it again unless he quits smoking. Only then will his sense of smell re-calibrate to a more smoke-sensitive state. Then he will be able to smell the smoke, just like everyone else does.
Like our other sensory nerves, our taste buds also will “get used to” a given level of stimulation, and this can have horrific consequences. The taste buds of the vast majority of people in industrialized societies are currently neuro-adapted to artificially high-fat, high-sugar, and high-salt animal and processed foods. These foods are ultimately no more enjoyable than more healthful fare, but few people will ever see that this is true, because they consistently consume highly stimulating foods, and have “gotten used to” them. If they were to eat a less stimulating, health-promoting diet, they soon would enjoy such fare every bit as much. Unfortunately, very few people will ever realize this critically important fact!
A gruesome tale
If a frog is placed in a pan of water, it often just sits there. If the pan is heated, ever so slowly, the frog may never notice that the water temperature is rising. He will “get used to” the increasing heat, and may be unaware that anything is amiss. Even with no barrier to his escape, he is as likely as not to sit in the pan, and boil to death. His sensory capabilities may fail to adequately warn him that action is required for his survival, and he may only survive if the heat is turned down.
For the past several decades, the modern American diet has been increasing in animal protein, animal and vegetable fats, refined carbohydrates, and added oil, salt, and sugar. In just the past two decades, our caloric intake has slowly escalated by 650 calories per person, per day. Not surprisingly, obesity and other diseases of dietary excess are at all-time highs. But just a few decades ago, our nation’s dietary habits were remarkably different. Meat was an expensive commodity, for some, a “treat.” The same was true for refined flour products, refined sugar, and oils. But times have changed. Today, almost everyone in America can have all they desire of these rich foods, and they do, virtually every day.
From the perspective of our natural history, a daily life with such dietary choices is extraordinary. For hundreds of thousands of years, our ancient ancestors scratched and scraped, struggling against the harsh forces of nature in order to get enough food to survive. Even today, in undeveloped countries, significant food shortages are still a great concern, with millions dying each year from starvation. Yet, in a mere blink of history’s eye, in just a few decades, industrialized societies have arisen from environments of scarcity and have transformed themselves into societies of unprecedented abundance. The most striking feature of that abundance is a virtually unlimited supply of food.
An abundance of food, by itself, is not a cause of health problems. But modern technology has done more than to simply make food perpetually abundant. Food also has been made artificially tastier. Food is often more stimulating than ever before, as the particular chemicals in foods that cause pleasure reactions have been isolated, and artificially concentrated. These chemicals include fats (including oils), refined carbohydrates (such as refined sugar and flour), and salt. Meats were once consumed mostly in the form of wild game, typically about 15% fat. Today’s meat is a much different product. Chemically and hormonally engineered, it can be as high as 50% fat or more. Ice cream is an extraordinary invention for intensifying taste pleasure, an artificial concoction of pure fat and refined sugar. Once an expensive delicacy, it is now a daily ritual for many people. French fries and potato chips, laden with artificially-concentrated fats, are currently the most commonly consumed “vegetable” in our society. These artificial products, and others like them, form the core of the American diet. Our teenage population, for example, consumes 25% of their calories in the form of soda pop!
Most of our citizenry can’t imagine how it could be any other way. To remove (or dramatically reduce) such products from America’s daily diet seems intolerable, even absurd. Most people believe that if they were to do so, they would enjoy their food, and their lives, much less. Indeed, most people believe that they literally would suffer if they consumed a health-promoting diet devoid of such indulgences. But, it is here that their perception is greatly in error. The reality is that humans are well designed to fully enjoy the subtler tastes of whole natural foods, but are poorly equipped to realize this fact. And like a frog sitting in dangerously hot water, most people are being slowly destroyed by the limitations of their awareness.
A pleasure trap
Figure 1 (above left) depicts a devastating dietary trap. People consuming a whole natural foods diet will experience a normal range of pleasure from eating low-fat, high-fiber, unprocessed foods, shown as Phase I. However, if concentrated, adulterated, processed foods are consistently allowed in the diet, they quickly will become preferred.
In Phase II, we see that these products are typically experienced as better, that is, more pleasurable, than natural foods. This is the result of the heightened pleasure-inducing characteristics of artificially-produced foods. However, within a short period of time (a few weeks), the taste nerves adapt to this higher level of stimulation, and reduce their firing rate. This reduces the pleasure experience of artificially-stimulating foods back down to normal levels (Phase III).