One of the Laws of Life, the Law of Vital Accommodation, states “The response of the vital organism to external stimuli is an instinctive one, based upon a self-preservative instinct which adapts itself to whatever influence it cannot destroy or control”. This means that when a human is exposed to a stimulant, the organism will try to defend itself from these substances, but if the defense is not possible, then the body will try to accommodate to it.

The intake of a stimulant produces the following phases in the body:

1) Refusal: Reaction against the product by developing a more or less strong acute disease
2) Tolerance and accommodation: Ceasing of the acute reaction. Stimulation and craving for that substance. Desensitization to the substance with the subsequent need to increase the amount. Protective reaction.
3) Exhaustion: Development of the chronic disease and organ failure.

Dr. Shelton explains the process the body undergoes from a strong refusal of the toxic substance to a resignation and tolerance:
“The first effort of the living organism, in response to adverse influences, is to overcome and destroy these. Failing in this it attempts to accommodate itself to such conditions and influences. For, what it cannot overcome, it must learn to endure or perish.
The man who habitually indulges in stimulation would exhaust and destroy himself with but few indulgencies if the organism had no means of curbing its reactions against the stimulation and thereby lessening the expenditure of vital power. The first effect of stimulation is exaltation of function; if it is long continued, or often repeated, exhaustion with an almost total abolition of function results. The repeated use of stimulants would soon result in death. But their repeated use soon brings about a condition in which the organism ceases to respond so readily and violently to the stimulant. If the former amount of stimulation is to be received from the stimulant a larger amount of the stimulant must be used.
All normal individuals are possessed of a natural repugnance to poisonous and injurious substances. The instinctive aversion to any kind of poison may be perverted into an unnatural craving after that poison. Instinct is plastic. If the warnings of the organic instincts are unheeded, and the offending substance is again and again forced upon the body, nature, true to the law of self-preservation, seeks to prolong life by adapting the body to poison.
The first smoke usually occasions a very powerful reaction against it on the part of the organism. The young man or woman is made very sick; there is headache, nausea, vomiting, loss of appetite, weakness, dizziness, muscular relaxation, tremor, weakness, etc. So long as the physiological powers and instincts are undepraved and unimpaired they instantly perceive the poisonous character of the tobacco and give the alarm to the whole system. A vigorous effort is made to destroy and eliminate it and the user is forced to throw away his tobacco. But if he continues to repeat the performance, the reaction against it grows less and less with each repetition until, finally, he is able to use many times the original amount without producing such results. His system learns to tolerate it and adapts itself to its use as far as possible. The system soon becomes depraved and its power impaired by the use of the tobacco, its poisonous character is no longer detected and no alarm is given; rather a craving for the substance is developed. However, the habitual use of any substance that is injurious in itself cannot in any way render it harmless or beneficial and the habitual presence of any such substance is injurious to life, even, though, no energetic effort is made to resist its action.
What is here said of tobacco is true of other poisonous substances. Ordinarily the user of drugs such as tobacco, opium, alcohol, cocaine, etc., becomes so accustomed to their use that he is able to take at one time enough of his favorite drug to kill several non-users outright, and yet, it only produces in him an apparent normal condition of comfort and strength.
If given time the body is able to adapt itself to all kinds of varying conditions. Only sudden and violent changes become immediately destructive of life. If we suddenly force upon the non-user the amount of alcohol, arsenic or opium used by the accustomed, it may cost his life.
Under natural living conditions, where enervating influences are removed and the organism is gradually strengthened, the body arouses itself to acute eliminating efforts or crises. These, too, occur, apparently, in accord with the law of periodicity and are similar to all other crises. Crises usually last until the disease producing factors have been reduced to the toleration point. this point varies with the individual and with the varying conditions of the individual. Thus the greater the amount of vitality one possesses, the less morbid matter will his system tolerate, and as the vitality of one with chronic disease is gradually raised, his toleration point also rises so that crises occur.
After toleration for any deleterious substance has been established, those acute reactions that followed its initial employment, arise only when one takes an unaccostumed amount of his accustomed poison. I will give a few examples from life to illustrate what I mean by this.
A man who suffers from constipation resorts to epsom salts to force his bowels to move. They work like a charm. He continues to use them until toleration is established and, then, finds that in order to secure the desired movement, he must increase the size of the dose. By using more slats than the body has learned to tolerate he secures bowel action. Similarly, physicians, in giving stimulants to their patients, find that they must continually increase the size of the dose, or, resort to another and unaccustomed poison, to secure the desired stimulation. The body is forced to accommodate itself to such substances, so that it no longer reacts violently against them, or else it will exhaust itself in the frequent reactions.
Arsenic may be taken with food as a seasoning; as freely as table salt, with as little immediate evidence of its poisonous character; and even prussic acid, which kills instantly like lightening, where the body is wholly unaccustomed to its action, may with proper care be gradually brought to act upon the human system, till it can be used with considerable freedom.
This wonderful capability of the living body to adapt itself by physiological depravity to the action of poisons of every kind, has not only led the human race to the excessive use of such substances as means of intoxication, but, almost as a necessary consequence, has also led them to the full belief that those substances are innocuous and salutary.
From an experience of this kind, the poisonous character of tea, coffee, tobacco, opium, alcohol, and all other narcotic substances, has been boldly and vehemently denied, by those who habitually use them as means of stimulation and intoxication.”

Regarding how to stop an addiction to these stimulants, Dr. Shelton says:
“Habits, gradually built and long established, cannot usually be suddenly broken. It is often the sudden breaking off of a habit, long practiced, it is often followed by one or more crises more or less severe as the organism seeks to accommodate itself to the changed conditions.
When a bad habit, like the tobacco habit or alcohol habit, is given up, the individual will lose weight and undergo crises and this will convince him that the abandonment of the bad habit was injurious. What was really happening was the tearing down and casting out of the system of the depraved tissues and substances and this is then followed by a renewal and regeneration of the body. The crises and loss of weight are beneficial measures and should be welcomed, not feared.
The headaches suffered by the coffee user when deprived of coffee, the pams suffered by the drug addict when deprived of his drug; the the unsteadiness of his nerves suffered by the tobacco user when deprived of his tobacco; the depression suffered by the stimulant user when deprived of his stimulant - these are not evidences of the beneficial influences of these substances but are evidences of their deleterious character. Outraged nerves and other tissues are simply coming out from under their influence and making their true condition known. Greater or less suffering and discomfort which are regarded by superficial and ignorant observers as indications of an adverse change, immediately result, but the sequel is a happy issue. “

In the presence of these substances, the body’s most important protective reaction is the hardening of tissues, as Dr. Shelton explains:
“The law of accommodation cushions the bottoms of the feet of bare-foot boys, girls and adults, and guards the hands of the manual laborer by a similar cushion. In the mouth, throat, stomach, intestine and bowel, a similar hardening and thickening takes place to guard the at first sensitive linings of these organs against the constant irritation to which they are ignorantly subjected by those who use tobacco, mouth washes and gargles, alcohol, coffee, tea, salt, pepper, mustard, horse-radish, spices, cathartics, mineral waters, etc. But this is an expensive business - this business of keeping the system accustomed to the action of irritants so that the sensibilities shall not be kept under torture by these. Such protection does not render them harmless.
A similar hardening and thickening must take place in the arteries and veins. Hardening of the arteries is due to irritation caused by toxins and irritants of all kinds.
Alcohol, whether ardent spirits, malt liquors, wines, cider or other alcoholic drinks, is a strong poison. It is highly irritating to every organ and tissue of the body and there is not one of them that is immune to its destructive influence. it coagulates the protoplasm of the cells of the body, just as it coagulates, or cooks, the white of an egg. This coagulation impairs and destroys the cells.
The normal cells are then replaced by a substitute of connective tissue cells forming what is called ´scan-tissue´. This may occur in the brain and spinal cord resulting in paresis, paralysis, insanity and other nervous disease; in the liver producing sclerosis; in the heart and arteries producing hardening and other troubles in these; or it may occur in the lungs, kidneys, muscles or any other organ of the body. The functioning powers of these organs are gradually destroyed and the individual’s resistance to other disease influences is lowered.
Moderate drinkers are not immune to these effects. They receive their full share of them. In fact, the habitual ´moderate´ drinker receives more injury from alcohol than the occasional drinker who gets drunk when he does drink. It is used as a stimulant to digestion, but finally wrecks digestion.”

Don’t forget that a person can have alcohol in their body even if he/she doesn’t drink alcohol at all, if he/she presents some yeasts in his/her gut flora that produce alcohol from the ingested carbohydrates. This results in the same damage as drinking alcohol.

"Tea, coffee, coca-cola cocoa and chocolate shall all be considered together because they all contain very much the same active principles and have very much the same effects. Neither of them have the slightest excuse for existences as beverages. Tea and coffee contain no food value, while the unaltered flavors of all of them are obnoxious to every unperverted taste.
They act primarily as stimulants and secondarily as depressants, or sedatives. Like tobacco, opium, and alcohol they are habit forming, and they are habit forming to exactly the degree in which they are stimulating. And they are stimulating in the degree to which they are poisonous and unfitted for the real needs of the body. The bitter, nauseous tastes of all these substances require the addition of sugar or other substances before they can be used by the undepraved taste.”

Finally, the toxicity of these products leads to exhaustion and chronic diseases:
“Give a stimulant to a man of full-resistance and he reacts to it with increased activity and an increased feeling of well-being. When the period of increased activity ends there sets in, due to the excessive expenditure of energy and substance, a period of depression.
All stimulants enable one to work beyond one’s normal strength. That is, they enable to keep on working long after nature has called for rest. They do this, not by adding to the powers of the body, but by calling out the powers held in reserve. They act in the same way a spur does on a tired horse. Slowly but surely, the reserve powers of the body are consumed under the influence of stimulants and physical bankruptcy follows.
Coffee, tea, coca-cola, cocoa and chocolate, because of their almost universal use, are great offenders in this respect. They produce enervation and sleeplessness in proportion to their use. Those who use them become coffee and tea or cocoa inebriates. They are addicts as truly as the opium user. the habitual user of tea or coffee is tired, irritable and suffers with headache and other discomforts when deprived of his habitual cup. Nervous diseases result from the employment of such nervines.
The body accommodates itself to the habitual use of tobacco, alcohol, opium, etc., to the extent of its ability to do so, but this does not prevent these substances from slowly and gradually undermining the constitution and finally resulting in disease and death.
Likewise, the unnatural and morbid conditions which have been imposed upon the system, which it has not been able to overcome but has been compelled to accommodate itself to, also, gradually and insidiously undermine the system, resulting in disease. If the body is able by the means of a crisis to overcome the disease influence then health is the result of disease. But if it is unable to overcome such influences and is not destroyed by them, it is forced to settle back into its accustomed quiet and make the condition as bearable as possible, This gives us chronic disease.”

Even if sugar, gluten and dairy products are not exactly stimulants, they have addictive properties and it has been suggested in several studies that they may be considered as “drugs”, at least for some persons, i.e. those who have difficulty digesting these products.
The following are some important studies that reveal the addictive character of sugar, which is even stronger than cocaine:
"Evidence for sugar addiction: Behavioral and neurochemical effects of intermittent, excessive sugar intake"
"Intense Sweetness Surpasses Cocaine Reward"
And here you can read more about the opioid effect of gluten and dairy products.
Tolerance to sugar, gluten and dairy products is developed in the organism the same way that tolerance to stimulants or any kind of drugs.
In infancy, from 4 months old, babies are gradually introduced to different grains or cereals, animal dairy products and other food. The organism of most of the babies refuse these foods showing up in different ways: vomiting, regurgitations, diarrhoea, eczema, mucus, etc. But we, parents, believe blindly in our doctors, who never link these diseases with food, and then we persevere giving these foods in increasing amounts and unhealthier forms, until child’s body finally gives up and stops the refusal, an inaction that we interpret as a “tolerance”. But in the same way as stimulants, what really happens in the long term is an exhaustion of the system, damages in body organs, development of chronic diseases, etc.
Later on, as teenagers, the process starts again with other more harmful substances: alcohol, tobacco, and sometimes also drugs. First there’s a rejection, second a tolerance, and finally exhaustion.
And in adulthood, if not before, we need the use of even stronger neurolytic substances, because the softer ones don’t have an effect on us anymore - we tolerate them - , and the real causes of our problems (physical, psychological or spiritual) and diseases have never been addressed.