Ray Peat on the Immune System

January 29, 2026

Physical experiences shape vitality and physiology

"Our bodies are constantly experiencing and generalizing these experiences in the way they respond; such generalized responses can limit or expand our vitality. These generalizations show up in our anatomy, physiology, and ecosystems – with changes in immunity, metabolism, gene expression, and behavior."

September 2017 - Ray Peat's Newsletter

Role and effects of parathyroid hormone in aging

“Phosphate, which predominates in grains, beans, nuts, meat, and fish, increases our production of parathyroid hormone, while calcium and magnesium inhibit its production. This hormone, which rises with age, suppresses immune defense, and in excess causes insomnia, seizures, dementia, psychosis, cancer, heart disease, shortness of breath and pulmonary hypertension, osteoporosis, sarcopenia, histamine release, inflammation, and calcification of soft tissues, as well as many other problems.”

September 2017 - Ray Peat's Newsletter

Effect of cortisone on protein conversion and immunity

"Cortisone stimulates the conversion of protein into sugar, and since there are no stored proteins (except for small amounts circulating in the blood), this means cortisone begins converting the organism into fuel for the problem area. In acute emergencies, lymphatic tissues shrink first; this is acceptable because they can be restored after the animal recovers, and their function – immunity – partly depends on a longer time horizon, from days to weeks. However, if these tissues are chronically depleted by stress or malnutrition, an infection is more likely to be fatal, as in old age or poor populations."

Nutrition For Women

Immune system failure as a key feature of cancer

"Cancer patients are typically not even able to produce a normal inflammation response, as if they were heavily dosed with anti-stress hormones of the cortisone type. The failure of the immune system, which normally can eliminate cancer cells during their formation, seems to be a key feature of cancer."

Nutrition For Women

Normalization of the immune system by testosterone and progesterone

"Some of the changes of aging are probably related to autoimmune reactions, where the body attacks itself; both testosterone and progesterone normalize the immune system and dampen autoimmune problems."

Nutrition For Women

Interaction of stress, immune function, and fat metabolism in phagocytosis

"Stress, the immune system, and fat metabolism are involved in complex interactions. For example, it is known that a fat, triolein, stimulates phagocytosis – as does magnesium."

Nutrition For Women

Normalization of the immune system by steroids and thyroid hormones

"Polyunsaturated oils inhibit the immune system and thus probably suppress symptoms. Steroids (e.g., progesterone) and thyroid hormones normalize the immune system when present in normal amounts."

Nutrition For Women

Harmful Effects of Iron on Antibodies and Immune Response

"In in vitro tests, iron damages the ability of antibodies to destroy germs. In the body, iron seems to be hidden during infections because of this effect on the immune system."

Nutrition For Women

Shrinking of the thymus gland during fasting and its effects on immunity

"The thymus gland, essential for immunity, shrinks during fasting. Chronic infections like tuberculosis are more common in malnourished people. However, fasting has been successfully used to treat certain diseases. It can be useful in diagnosing food allergies, as well as some forms of schizophrenia."

Nutrition For Women

Role of caffeine in immunity and potential anti-cancer properties

"Caffeine can – both through nerves and directly – boost immunity. Injected into the brain of an animal, it was found to slow cancer growth. Recently, it was accidentally discovered that a very small amount of caffeine, mixed with the tars from cigarette smoke, prevented this material from causing cancer."

Nutrition For Women

Cultural acceptance of suffering as a strengthening practice

"When looking at the broader culture of Western civilization, the mortification of the flesh for the sake of the soul might be a relevant context for these persistent attitudes in medicine and biology. Athletes are told: No pain, no gain, and many people adopt the idea that suffering generally toughens you up – fasting, cold showers, jogging are said to improve immunity and delay aging."

November 2017 - Ray Peat's Newsletter

Historical perspectives on the treatment of autoimmune diseases

"The idea of autoimmune disease can be traced back to Paul Ehrlich's theory of immunity, and his concept of a therapeutic 'magic bullet' has dominated the medical approach to treating autoimmune diseases."

November 2016 - Ray Peat's Newsletter

Metchnikoff and beyond: The immune system in harmony with the microbiome

"The embryologist Elie Metchnikoff regarded immunity as an aspect of the organism's ability to maintain its own integrity."

November 2016 - Ray Peat's Newsletter

The development of immunological theories: A holistic perspective

"Although the concept of a guiding organismic field, which most embryologists supported, disappeared in the 1950s, a similar holistic view reemerged in the 1990s in Matzinger's danger theory and Cunliffe's morphostasis and damage theory of immunity. In this view, the destruction of pathogens is not the purpose of the immune system but a side effect of maintaining organismic integrity."

November 2016 - Ray Peat's Newsletter

Progesterone and Vitamin D in the Restoration of Nerve Function

“Studies on the effects of progesterone on nerve function recovery after traumatic brain injuries have found that vitamin D enhances its effectiveness. By improving calcium homeostasis and counteracting the effects of parathyroid hormone, which activates calcium channels, vitamin D (25-hydroxycholecalciferol) is increasingly regarded as a neurosteroid (Groves et al., 2014; Gezen-Ak and Dursun, 2019) – as well as an essential factor for immunity.”

May 2020 - Ray Peat's Newsletter

Overemphasis on Antibodies in Defining Immunity

“The focus on defining immunity through antibody formation triggered by vaccines has led to a dangerous disregard of fundamental health facts.”

May 2020 - Ray Peat's Newsletter

Role of Inflammation in Immunity and Disease Treatment

“The doctrine that inflammation is a necessary part of immunity and leads to the destruction of the pathogen influences how diseases are treated.”

March 2021 - Ray Peat's Newsletter

Immune system: restoration or inflammation

“Our so-called immune system recognizes unfavorable changes in the structural-energetic system and responds quietly to restore the system: it removes abnormal structures and facilitates the restoration of function. If the organism’s condition is poor, instead of invisible restoration, inflammation occurs – a process in which rough, provisional repairs are made so that the damaged tissue no longer demands resources that are unavailable. A scar forms; relatively inert, fibrous tissue replaces fully functional tissue. This progresses with ongoing exposure to harmful factors and impairs the lungs, heart, blood vessels, gonads, liver, kidneys, brain....”

March 2019 - Ray Peat's Newsletter

Immunity: Innate vs. Adaptive in Organisms

“In the 1960s, when antibodies were intensively studied, Metchnikoff’s approach was called innate immunity – something more primitive and less differentiated than the evolutionarily advanced adaptive immunity of B and T cells, the bone marrow and thymus cells. However, by that time it had already been shown that plants have an example of something like adaptive immunity: a learned response to a toxin.”

January 2020 - Ray Peat's Newsletter

Role of Inflammation in Universal Pathology

"Until the beginning of this century, inflammation was mostly seen as a purely constructive part of the local healing process, but it began to be recognized that it plays a universal role in pathology. Tissue damage was no longer viewed as merely a local event. Research was driven to a reassessment of Metchnikoff's holistic, developmental view of immunity. Bystander effects – the release of substances by any injured cell that trigger similar damage 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 that produces antibodies."

January 2020 - Ray Peat's Newsletter

Neuroprotective and Mitochondria-Supporting Effects of Progesterone

"Besides its anti-estrogenic effect, progesterone is a neurosteroid, an anti-excitotoxin, and an inhibitory modulator. However, these effects in the nervous system have parallels in the immune system, where it modulates the functions of many cells, protects the thymus, slows mast cell degranulation, and inhibits the shock response. It is an antitoxin that stabilizes cell structure and function. In the mitochondria, it preserves or restores respiratory efficiency."

March 2000

Koch's Theory: Electrons and Free Radicals in Biological Processes

"At the beginning of the century, Koch postulated that electrons and free radicals are involved in the most important biological processes – respiration, movement, immunity, regeneration, etc. He was probably the first to apply the subtleties of organic chemistry (such as the activation of chemical groups by neighboring groups) to biology."

December 1999 - Ray Peat's Newsletter

Integration of the Immune System and Misleading Evolutionary Theories

"The group of processes we call the immune system is so deeply integrated with everything else in the organism that it is just as misleading to talk about the 'reason' for its evolution as it is to talk about the 'reason' for the evolution of certain pigmentations – black feathers, for example, are mechanically stronger than white ones; breeding foxes for domestication changes their fur pigmentation and their voice; selection for egg production somehow leads to suppression of feather pigmentation, and so on. Nevertheless, people like to talk about protective coloration because it is easy to link it to genetic selection."

Ray Peat's Newsletter

Psychosomatic Physiology and Mobilization of Biological Energy

"For about 50 years, the concept of 'psychosomatic' was trivialized and understood to mean: It’s just imagined. But meanwhile, studies on the physiology of helplessness show that a seemingly small difference in experience and attitude can cause a very large difference in the ability to mobilize biological energy and influence various aspects of immunity, such as natural killer cell activity. Today, there is broad agreement on the distinction between the demobilized state of helplessness and the state of active adaptation."

November 1994 - Ray Peat's Newsletter

Factors That Lower Vitality and the Influence of Immunity on Steroid Production

"In general, things that lower vitality and immunity impair our ability to produce protective steroids."