Ray Peat on Adaptation

September 26, 2025

The costly adjustments of serotonin production

"Different types of stress increase the production of serotonin and various pituitary hormones, leading to adaptations in the organism, but at the cost of inflammation and degeneration. Studies of several pituitary hormones have shown that they have aging-accelerating effects, leading to edema, inflammation, fibrosis, and reduced lifespan. W.D. Denckla's experiments, which demonstrated the enormous life-extending effect of removing the pituitary gland while simultaneously supplementing with thyroid and glucocorticoid hormones, suggest the possibility of finding ways to prevent the overproduction of serotonin and its associated hormones and cytokines."

– September 2019 – Ray Peats Newsletter

Criticism of the scientific approach to organismic adaptation

"By defining the organism and the environment according to its ideology of mechanistic reductionism, official science has radically misrepresented the nature of organismic adaptation."

– September 2017 – Ray Peats Newsletter

Environmental influences on physical development

"If our environment shrinks, if there isn't enough food, we can adapt, for example by replacing muscle with fat and by having babies with small brains (the brain is an energy-intensive organ, even if its efficiency increases with its cost). If our environment meets our needs, our brains and muscles grow. The lower leg (like the brain) is a good indicator of environmental support: parents who grew up in a population with atrophied-looking lower legs can have children with well-developed legs when milk becomes plentiful."

Nutrition for Women

Estrogen increase due to stress and its effects on male behavior

“Stress leads to an increase in estrogen and a loss of anti-estrogens such as thyroid hormone, progesterone, and (in males) testosterone. Male monkeys that are bullied have reduced testosterone levels, and this effect persists long after their environment has improved. The stress of submission appears to lead to an adaptation in the form of passivity. Their passivity prevents further harm, but we don't know how stressful their continued submission is.”

Nutrition for Women

Selye's discovery of the phases of the adaptive system and stress immunization

"Hans Selye discovered that the adrenal glands are a key component of our adaptive system. In the first stress phase, there is a shock response (with changes similar to those of estrogen dominance), involving damage to various tissues. In the second phase, the adrenal glands protect the animal, and this protection lasts until exhaustion sets in. By subjecting rats to preliminary stress, Selye found that he could induce adaptation to other, subsequent stressors—a kind of immunization against stress."

Nutrition for Women

Adaptive hypothyroidism caused by stress and strenuous exercise

"Cortisone also inhibits the thyroid gland. Any stress, including strenuous exercise, causes this protective slowing of the metabolism. The slow heartbeat of runners is largely a result of this adaptive hypothyroidism."

Nutrition for Women

Conversion of thyroid hormones during stress and aging

"When a baby is born, or when a person experiences other stress, such as an infection, or when a person ages, the most well-known thyroid hormone, thyroxine, is not converted into the more active form T3 (triiodothyronine) in the normal way. In these emergency situations, reduced oxygen consumption is a useful adaptation."

Nutrition for Women

Selye's stress phases and their effects on tissue

"Selye divides stress into three phases: alarm, resistance (or adaptation), and exhaustion. Three tissues usually show effects first: thymolymphatic tissue shrinks, gastrointestinal tissue becomes inflamed and bleeds, and the adrenal cortex enlarges."

Nutrition for Women

Maternal adaptation to fat and infant dependence on glucose

"During pregnancy, the mother's body adapts to increasingly relying on fat for energy, so that most of the available sugar can be used by the baby. The brain consumes most of the body's glucose, so mental fatigue can easily affect blood sugar levels. The developing baby is extremely dependent on glucose as an energy source, and its brain can be damaged by sugar deprivation."

Nutrition for Women

Pregnancy, similarities to diabetes and blood sugar trends

"Pregnancy itself is similar to diabetes, due to the adaptation to the oxidation of fat instead of sugar, so a slight predisposition to diabetes can be seen as supporting pregnancy. Older women are more likely to have some degree of diabetes or elevated blood sugar. With each pregnancy, there is a tendency for blood sugar to be higher and the baby to be larger and more precocious."

Nutrition for Women

Chronic dietary adaptation and loss of protein tissue

"Chronic dieters can adapt to a low calorie intake (Lancet, April 5, 1975, Miller and Parsonage). This is probably partly due to a loss of active protein tissue. Comprehensive nutrition is necessary to replace such tissue."

Nutrition for Women

Recommended slow dietary change for enzyme adjustment

"Switching to a new diet or ending a fast should be done gradually, allowing at least a few days for enzyme adjustment."

Nutrition for Women

Sports training, stress hormones and thyroid function

"It is known that exercise slows the heart rate. Cortisone, which is produced by stress, suppresses the thyroid gland. (When the thyroid is underactive, less oxygen is needed, which is a useful adaptation for increasing endurance.) These hormonal changes are now known to cause infertility in both men and women."

Nutrition for Women

Role of demand and reserve capacity in physiological adaptation

"The greater the demand, the smaller the reserve capacity for future adaptation will be. Therefore, part of our physiology is to adapt our environment so that it better meets our needs."

Nutrition for Women

Metabolic energy as a constant adaptation process

"When the organism is seen as a constant process of adaptation, and not as a machine that has to make do with the parts formed in early youth, metabolic energy is recognized as something constructive, and things that reduce our energy – such as a drop in body temperature – are seen as threats to life and successful adaptation."

– November 2020 – Ray Peats Newsletter

The adaptive role of inflammation and its long-term consequences

"Inflammation is a kind of adaptive response, but it leaves behind fibrotic changes and atrophy of functional cells, as well as an increased tendency to resort to the inflammatory response again."

– November 2020 – Ray Peats Newsletter

Environmental influences on longevity and inflammation

"If lifespan is shortened by the accumulation of changes resulting from inflammatory adaptations, then living in different environments that require different types of adaptations will cause large changes in lifespan."

– November 2020 – Ray Peats Newsletter

Lifestyle choices to slow down aging and promote longevity

"Altitude and a dairy-based diet are obviously two important thermogenic factors that slow the accumulation of harmful adaptations, but there are many other controllable factors that could extend longevity even further. Reducing inflammatory factors is important, and personal choices can make a big difference, for example, choosing easily digestible foods to reduce endotoxins, avoiding polyunsaturated fats that disrupt cellular respiration and form inflammatory prostaglandins, avoiding antioxidant supplements that create a reductive excess, and choosing foods containing anti-inflammatory thermogenic compounds, such as citrus fruits with their high flavonoid content, which supports cellular respiration."

– November 2020 – Ray Peats Newsletter

Stress-induced serum cholesterol as an adaptive response

"The increase in serum cholesterol during stress is an important protective adaptation."

– November 2018 – Ray Peats Newsletter

Urgency of returning to holism for understanding developmental processes

"The holistic view of the organism and its adaptive potential, championed by Hippocrates and Aristotle, has been rejected by the new science of recent centuries. Reclaiming and creatively utilizing this perspective has become urgent if we are to understand the processes of development, including aging and degenerative diseases."

– November 2017 – Ray Peats Newsletter

Organismic reactions depend on historical, conditioned factors.

"In reality, every adaptive situation in which there is a response to a single substance or stimulus affects the entire organism, not just a single receptor substance. The reason why an organism's response to a particular stimulus increases or decreases depends on the organism's history and state, as well as the nature and intensity of the stimulus. Different aspects of the organism are affected by different substances or forces, and by different amounts of these substances or forces."

– November 2017 – Ray Peats Newsletter

Prenatal influences on brain development and adaptability

“Experiments over the last 60 years have shown that varying levels of glucose, carbon dioxide, heat, and progesterone during embryonic and fetal development can influence brain growth and the way the brain controls future development and adaptability.”

– November 2017 – Ray Peats Newsletter

Survival mechanisms of the brain in stressful environmental interactions

"In mediating adaptation, the brain orients the organism towards aspects of the environment that are most likely to satisfy its needs, and this includes assessing possible future situations. In the absence of favorable prospects, the brain engages in defensive changes, increases stress hormones, triggers the fight-or-flight mechanisms, and begins converting some of its own tissues into energy and materials needed for the survival of its vital organs – brain, lungs, and heart."

– November 2017 – Ray Peats Newsletter

Inflammatory conditions and activation of the DNA exosome system

"The conditions that cause inflammation activate the adaptive exosome system, a retrotransposon system that comprises a massive block of our DNA and overlaps with the virus production mechanism."

– May 2020 – Ray Peats Newsletter

Humans as epigenetic, adaptive beings

“We are not defined as Somas produced once by our DNA, but as adaptive, epigenetic, continuously creative beings.”

– May 2020 – Ray Peats Newsletter

Effects of respiratory adaptation at different altitudes

"The fundamental principles of respiration, the Bohr and Haldane effects, describe the physical equilibria of oxygen and CO2 in humans adapted to life at different altitudes. The Haldane effect describes the fact that increased oxygen pressure reduces the amount of carbon dioxide retained by hemoglobin, and decreased oxygen pressure increases the amount of retained CO2. A steady increase in retained CO2 with increasing altitude occurs in those who adapt. People who do not adapt experience a loss of CO2 with an increase in lactate."

– May 2020 – Ray Peats Newsletter

Retroviral lineage and protective functions of exosomes

"Now that the protective and adaptive functions of exosomes and retrotransposons have been clarified, the more obvious conclusion might be that we are the ancestors of retroviruses."

– May 2020 – Ray Peats Newsletter

When adaptive stress becomes maladaptive

"Stress is experienced when processes that are normally adaptive have maladaptive effects. This happens when the organism's resources are insufficient to meet the demands of the situation."

– May 2019 – Ray Peats Newsletter

Adaptation of the embryo to intrauterine disturbances

"Experimental embryology has made it clear that development is an intentional process. An embryo can survive extreme disturbances by adapting its structures and metabolism, but these adaptations to difficult intrauterine conditions can sometimes make adaptations during childhood problematic."

– May 2018 – Ray Peats Newsletter

Energy consumption of the brain during adaptation and simplification

"The brain has an extremely high metabolic rate and uses energy to adapt to the constant influx of sensory information from the body and its environment. When energy is lacking, it reduces and simplifies. With full energy, it builds a continuous model of itself and the things it interacts with—each of which is a process. In a state of low mental energy, things become categories rather than processes, and they do not take their place in a continuous life story."

– May 2018 – Ray Peats Newsletter

Cancer as a developmental adaptation process

"If cancer is seen as an event in the body's developmental and adaptive processes, the important question is to understand the process so that the response can be modified – reducing harmful factors and supporting adaptive and corrective factors."

– May 2016 – Ray Peats Newsletter

Personalized therapy through understanding the adaptation history

"To address the specific problem of a particular person, we need the best knowledge of how an organism's history and current situation affect its ability to adapt to new situations, as well as knowledge of the therapeutic resources that are available."

– May 2016 – Ray Peats Newsletter

McClintock's discovery of gene movement in the stress response of plants

“In the 1940s, Barbara McClintock discovered that plants under stress can shift their genes to improve adaptation by producing more variation in their offspring. Instead of acknowledging that McClintock had discovered an aspect of life’s creativity, they considered the adaptive flexibility she had discovered unbearably alien to their mechanistic understanding of life.”

– March 2021 – Ray Peat's Newsletter

McClintock's research on viral evolution and epigenetics

“A simple shift in perspective can solve some old mysteries, such as how millions of virus species arose, since viruses cannot reproduce without the organisms they infect, and why our cells would retain such an immense amount of useless or harmful DNA if our DNA had evolved by eliminating the parts that did not contribute to fitness. McClintock’s work has led to an answer to these questions, as well as a foundation for understanding the intelligence of epigenetics and the inheritance of adaptations. The ‘dark DNA’ functions during embryonic development by mediating the effects of the intrauterine environment.”

– March 2021 – Ray Peat's Newsletter

Bacterial adaptation and similar human genetic mechanisms

“James Shapiro’s work with bacteria shows that they – supposedly one of the simplest life forms – have a ‘read-write’ genome and, by understanding their situation, can modify their genes to adapt to problematic situations. It is becoming increasingly clear that we have similar abilities to bacteria, with dark DNA being part of this adaptive system.”

– March 2021 – Ray Peat's Newsletter

Adjustment problems of premature infants in new environments

"The premature infant suddenly leaving its oxygen-depleted, CO₂-rich, sugar-rich environment and being exposed to the extremely new environment of a hospital incubator is an extreme example of how our normal adaptive responses can become destructive when misdirected by an unfavorable environment."

– March 2021 – Ray Peat's Newsletter

Tissue changes throughout life due to environmental factors

"The average person who lives for many years in an environment with limited amounts of the most supportive factors and fluctuating amounts of many harmful factors experiences a gradual accumulation of tissue changes caused by misguided adaptive factors."

– March 2021 – Ray Peat's Newsletter

Oxidative metabolism maintains protective factors after pregnancy

"During childhood and adulthood, a robust oxidative metabolism can maintain some of the essential protective factors of pregnancy, including adequate levels of glucose and carbon dioxide, good temperature regulation, and the avoidance of overproduction of superoxide and lactate. Under these conditions, cytokines can contribute to adaptation and continued development."

– March 2021 – Ray Peat's Newsletter

Life, adaptation, and epigenetic heritage

"Life is adaptation, every adaptation involves epigenetic modifications of the differentiation state, and every epigenetic change has transgenerational effects."

– March 2019 – Ray Peat's Newsletter

Pro-inflammatory environments and epigenetic limitations

"Our organisms undergo continuous processes of adaptive change in response to our pro-inflammatory environments, which include epigenetic changes that limit our potential and carry the risk of having cumulative effects in subsequent generations."

– March 2019 – Ray Peat's Newsletter

Prenatal influences and the development of autistic traits

"Today's knowledge about the prenatal influence on the development of autistic traits, in humans and in laboratory animals, agrees with Pavlov's observation that some animals were overwhelmed by stimulation to which other animals could easily adapt."

– March 2018 – Ray Peat's Newsletter

Metabolism: Adaptive Interactions in Organisms

"The idea of metabolism – substance change, adaptive interaction – implicitly includes the interactions of cells with the organism in its environment."

– March 2017 – Ray Peat's Newsletter

Overlooked effects of stress on the gut

"While the effects of stress on the gut have been known since Hans Selye described the general adaptation syndrome (with intestinal bleeding as an early sign of stress), they have not been considered in any of the major studies on brain trauma or stroke."

– March 2016 – Ray Peat's Newsletter

Serotonin: More than just a neurotransmitter

"Serotonin is often described as a neurotransmitter and is considered a substance that acts on receptors to transmit information, possibly processed in much the same way that computers process digital information. I think it's more useful to think of it in terms of fields and formative processes that determine how the organism uses energy to adapt to stress and opportunities. It is involved in the energetic and structural changes that occur during stress and adaptation."

– July 2019 – Ray Peats Newsletter

Exploring futures through adaptive physiology

"Adaptive physiology (rejecting the doctrine of timeless properties) deals with where we are going, what we are becoming, and what possibilities we have. The subject it investigates requires attention to context and temporal processes."

– July 2017 – Ray Peats Newsletter

The Symphony of Life: Embracing its Complexity

"The metabolism of the organism is a single, integrated process in which each part must adapt to the conditions of the other parts. Our nerves contain chemical receptors that detect changes in the metabolic chemicals in the blood, allowing the organism to make adaptive changes."

– July 2017 – Ray Peats Newsletter

Drastic reduction in demand under unfavorable environmental conditions

"When environmental conditions are too poor for active adaptation, many organisms can drastically reduce their needs."

– January 2021 – Ray Peats Newsletter

Harsh environments: Early reproduction and energy adaptation

"The stresses of a harsh environment, which make early reproduction advantageous or require accelerated tissue renewal, also favor epigenetic adaptations that reduce energy requirements."

– January 2016 – Ray Peats Newsletter

Adaptive role of estrogen during hibernation

"The increase in nitric oxide and/or hydrogen sulfide due to estrogens is adaptive for a hibernating animal, as it reduces its body temperature and metabolic rate."

– January 2016 – Ray Peats Newsletter

Epigenetic changes through stress adaptation

"In all these conditions of stress adaptation, epigenetic modifications of DNA are involved, with nitric oxide, along with estrogen and other hormones, participating in DNA methylation and histone modification, as well as a variety of other longer-lasting biochemical modifications."

– January 2016 – Ray Peats Newsletter

The double-edged role of nitric oxide

"Although a primitive adaptive system like nitric oxide may be beneficial for a species, it can be harmful to individuals."

– January 2016 – Ray Peats Newsletter

Harmful effects of long-term cortisone use during stress

“Meerson’s work has shown in detail how the normally useful adaptation hormone, cortisone, can cause so many other harmful effects when its action lasts too long or is too intense.”

– Generative Energy – Restoring The Wholeness Of Life

Limitations of cortisone without treating the underlying causes

"Although cortisone supplementation can help with a variety of stress-related illnesses, no cure will occur until the underlying cause is found. Besides the thyroid, the other class of adaptive hormones that are often imbalanced in stress-related illnesses is the group of hormones primarily produced by the gonads: the sex hormones."

– Generative Energy – Restoring The Wholeness Of Life

Thyroid gland as the main regulator of respiratory adaptation

"The thyroid gland is the most important regulatory and adaptive substance for respiration."

– Email reply from Ray Peat

Immunity: Innate vs. Adaptive in Organisms

"In the 1960s, when antibodies were being intensively studied, Metchnikoff's approach was described as innate immunity, something more primitive and undifferentiated than the evolutionarily more developed adaptive immunity of B and T cells, bone and thymus cells. At that time, however, an example of something similar to adaptive immunity, a learned response to a toxin, had already been demonstrated in plants."

– January 2020 – Ray Peats Newsletter

The role of inflammation in universal pathology

"Until the beginning of this century, inflammation was generally viewed as a simply constructive part of the local healing process, but the understanding began to take hold that it plays a universal role in pathology. Tissue damage was no longer considered a merely local event. Research was forced to reconsider Metchnikoff's holistic, developmental view of immunity. Bystander effects—the release of substances by any injured cell that induce similar injury in other cells, even in distant parts of the body (Koturbash, 2007; Kovalchuk, 2016)—and the associated persistent epigenetic changes are part of innate immunity. This system is activated by adjuvants, as is the adaptive immune system, which produces antibodies."

– January 2020 – Ray Peats Newsletter

Adaptive capacity of the organism in rich vs. poor environments

"In every situation, an adaptive metabolism takes place in the organism, and if the environment is unfavorable, the organism can defend itself by restricting its needs and its range. However, if the environment is rich and needs are easily satisfied, the organism will tend to expand its range and capabilities."

– January 2018 – Ray Peats Newsletter

Follow-up of long-term effects of early childhood hypoglycemia

"If hypoglycemia occurs during pregnancy or infancy, when metabolic intensity is at its highest, the adaptations can lead to lifelong problems."

– January 2017 – Ray Peats Newsletter

Extreme stress and biological adaptation: The balancing act of survival

“During adaptation, the functional load shifts to the system facing the new challenge, and a variety of stimuli, from nerves and hormones, activate the cells of this responding system. Resources such as amino acids can be drawn from less active systems to support the new level of function. The organism must precisely focus its stimulating factors, and resources, including glucose stored in tissues as glycogen, must be sufficient. If the stimulation is too intense or too widespread, and if too much fat is mobilized relative to glucose, self-destructive processes can occur.”

– January 2017 – Ray Peats Newsletter

Adaptation effects on lactic acid production and muscle performance

"Adaptation to hypoxia or increased carbon dioxide limits the formation of lactic acid. Muscles are 50% more efficient in this adapted state; glucose, which produces more carbon dioxide than fat during oxidation, is metabolized more efficiently than fats and requires less oxygen."

– July 2000

Adaptive reactivity of organisms and homeostasis in cellular metabolism

"It is the subtle reactivity of the living system that maintains the adaptive organization of energy and structure. Part of the organism's reactivity is the flexibly interactive metabolism, which adaptively distributes substance and energy. Ordinary metabolism, through the adjustment of the affinities of cell substance, can explain the processes described as homeostatic more rationally than the hypothetical apparatuses of pumps and channels that are proposed in biology as deus ex machina whenever necessary."

– December 1999 – Ray Peat's Newsletter

Imperfection and adaptive capacity of organisms under stress

"Shock, inflammation, aging, and death have been proposed as survival factors based on this totalitarian view of genetics. Could it not be that organisms are simply not perfect and that some things simply go systematically wrong? That is, an organism has a certain strength, resilience, or adaptive capacity, but if it finds itself in excessively difficult conditions, then processes could arise that have never contributed to survival, as several individually valid defense mechanisms begin to interfere with each other."

– 1998 – Ray Peats Newsletter – 4

Essential role of respiration in higher organisms

"Respiration is essential for the existence of higher organisms, as it enables the maintenance of complex and adaptive structures that contain appropriately differentiated cells."

– 1998 – Ray Peats Newsletter – 3

Role of oxygen in cell acidification and edema regulation

"Oxygen, which produces carbon dioxide, makes the cell acidic, and carbon dioxide affects how cells handle water. Carbonic anhydrase inhibitors are commonly used to regulate conditions involving edema, including adaptation to high altitudes."

– 1998 – Ray Peats Newsletter – 2

Cell damage, repair and adaptive responses in the organism

"When a cell is damaged (e.g., by radiation or toxins), its inefficiency creates a small, localized distortion in the fields, stimulating repair or removal and replacement processes to the extent that the organism's resources allow. When stress is so great that the entire organism is exposed to lactic acid, the organism's adaptive resources are challenged, and potentially harmful reactions are triggered. For example, a sluggish liver during stress may allow an increase in blood lactate concentration, which can lead to the secretion of endorphins and pituitary hormones (Elias et al., 1997). The endorphins can increase histamine release, and growth hormone increases free fatty acids; increased vascular permeability can allow proteins and fats to leave the bloodstream, with cumulatively harmful effects."

– 1998 – Ray Peats Newsletter – 2

Interlinked features of cell excitation and energy in stress adaptation

"The interlocking fundamental features of cell excitation/relaxation, electrical potential, lactic acid/carbon dioxide, water retention/water loss, salt regulation, pH, and energy levels allow us to coherently visualize the biological significance of stress and adaptation. Interacting with these physicochemical events, there are many levels of biochemical and physiological processes that amplify or modify them, including regulatory systems such as hormones and other biological signaling molecules, nutritional adequacy, and the type of fuel used."

– 1998 – Ray Peats Newsletter – 2

Respiratory potential and its effect on tissue changes

"A weakened ability to produce energy oxidatively can lead to the maladaptive overproduction of collagen, porphyrins, red blood cells, and other tissues and substances, which in turn can trigger many adaptive and maladaptive changes. I think skin and mucous membranes provide a good illustration of how respiratory potential influences structure: The keratinization increased by estrogen is counteracted by vitamin A, which increases the proportion of active, differentiated cells."

– 1997 – Ray Peats Newsletter

The brain as the primary organ of cost-free adaptation

"As Felix Meerson has shown, the brain is the preferred organ of adaptation because adaptation at the level of learning has no biological cost in terms of restricting our structure and function."