Ray Peat on the Heart

January 29, 2026

Effects of hypothyroidism on muscle fatigue and metabolic products

“When metabolic energy declines, as in hypothyroidism, muscles tire easily, absorb excessive water, and the barrier structure loosens. This allows macromolecules as well as ATP and other metabolites to leak out, while foreign substances enter. Typical muscle enzymes like lactate dehydrogenase and creatine kinase appear in the bloodstream in typical hypothyroid myopathy; and heart proteins – including a specific form of lactate dehydrogenase and the muscle protein troponin – appear in the blood after heart stress or fatigue combined with hypothyroidism or systemic inflammation.”

September 2019 - Ray Peat's Newsletter

The 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

Reduction of parathyroid hormone in connection with overweight and related problems

“The reduction of parathyroid hormone through increased calcium and vitamin D is closely linked to less overweight and the health problems associated with overweight – high blood pressure, insulin resistance, heart arrhythmias, depression, and various inflammatory diseases.”

September 2017 - Ray Peat's Newsletter

Benefits of coconut oil for the thyroid and health

“The easily oxidizable short- and medium-chain saturated fatty acids in coconut oil provide an energy source that protects our tissues from the toxic inhibitory effects of unsaturated fatty acids and reduces their thyroid-suppressing effects. Animal studies over the past 60 years suggest that these effects also protect against cancer, heart disease, and premature aging. Other expected effects include protection against excessive blood clotting, protection of the fetal brain, protection against various stress-related problems including epilepsy, as well as some degree of protection against sun damage to the skin.”

Nutrition For Women

Personal and observed reports on the effects of thyroid and progesterone on mood

"The first time I took enough dried thyroid so that my heart noticeably beat faster, a pleasant feeling rose from my stomach through my chest, making me want to smile and laugh. When I observed suicidal women using thyroid or progesterone, there was a transformation (within an hour with progesterone, after several hours or longer with thyroid) – from crying to smiling and laughing; they speak of unbearable pain being replaced by pleasure."

Nutrition For Women

Essential role of thyroid hormone for cellular respiration and biological functions

"Thyroid hormone is necessary for cellular respiration and enables all higher biological functions. Without the metabolic efficiency promoted by thyroid hormone, life would hardly progress beyond the single-cell stage. Without enough thyroid, we become sluggish, clumsy, cold, anemic, and susceptible to infections, heart disease, headaches, cancer, and many other illnesses, and appear prematurely aged because none of our tissues can function normally."

Nutrition For Women

Adaptive hypothyroidism triggered by stress and intense training

"Cortisone also inhibits the thyroid. Any stress, including intense physical exertion, leads to this protective slowing of metabolism. The slow heartbeat of runners is largely the result of this adaptive hypothyroidism."

Nutrition For Women

Cardiac effects of progesterone comparable to digitalis

"Digitalis and progesterone have very similar effects on the heart (Szent-Gyorgyi, Muscle Contraction). Digitalis can raise blood pressure and increase urine production, apparently by increasing the tone of the arterioles (Abram, 1910). If the effect of progesterone on muscles also includes such an effect on arterioles, then the mystery of hot flashes during menopause – and even before – is not a mystery but merely a symptom of progesterone deficiency relative to estrogen."

Nutrition For Women

Connection between high cholesterol, hypothyroidism, and heart attacks

"High cholesterol usually indicates low thyroid function. When the thyroid is low, cholesterol is not efficiently converted into progesterone. The actual cause of heart attacks seems to be hypothyroidism and its effects, including magnesium loss."

Nutrition For Women

Contribution of estrogen to heart attacks and magnesium deficiency

"Estrogen causes heart attacks instead of healing them. It causes a magnesium deficiency that promotes blood clotting."

Nutrition For Women

Magnesium deficiency and its role in impaired fat metabolism and heart disease

"Magnesium deficiency also promotes a disturbed fat metabolism and thus contributes to heart disease."

Nutrition For Women

Discussion on the effectiveness of estrogen in the treatment of osteoporosis

"The argument for using estrogen to treat or prevent osteoporosis is based on the fact that estrogen reduces calcium excretion through urine. A vitamin E deficiency (and estrogen is known to increase the need for vitamin E) causes calcium to be retained by the muscles. Any toxic exposure actually causes calcium retention in soft tissues; for example, when the heart is deprived of oxygen, it takes up calcium. Since no improvement in the skeleton can be detected by X-ray, I suspect that the improved calcium retention is merely a toxic effect of estrogen."

Nutrition For Women

Clinical study links magnesium deficiency to heart disease

"There are several reasons to suspect that magnesium deficiency is often involved in heart disease; for example, in a clinical study, injected magnesium sulfate helped with angina pectoris and coronary thrombosis and tended to lower blood lipids."

Nutrition For Women

Shutes' vitamin E research shows benefits in heart disease

"The Shutes conducted extensive research on the use of vitamin E in heart disease and found that pharmacological doses of 400 mg/day or more are beneficial. They also recommended it to prevent thrombosis in other parts of the vascular system."

Nutrition For Women

Milk improves the calcium-phosphorus ratio but provides too little magnesium

"Consuming large amounts of milk improves the calcium-to-phosphorus ratio but does not provide enough magnesium to prevent cavities, heart problems, and cramps."

Nutrition For Women

Cultural beliefs about energy consumption and lifespan

"I think there are clear cultural reasons for the lack of interest in lower body temperatures. The old saying: The brighter the candle burns, the faster it goes out, is often quoted about people who seem overly energetic and enthusiastic. A variation of this idea is still widespread and taken very seriously – the notion that every person has only a certain number of heartbeats and lives longer if the heart beats slowly."

November 2020 - Ray Peat's Newsletter

Controversy over temperature in the diagnosis of hypothyroidism

"The rejection of Broda Barnes' use of temperature to diagnose hypothyroidism was partly motivated by the belief that a below-average temperature was protective. This deeply rooted belief likely contributed to the official preference for the relatively inactive thyroxine – instead of the thermogenically active thyroid (USP) and T3 – as well as to the lack of interest in the connection between hypothermia and chronic infections, cardiovascular problems, kidney diseases, chronic inflammatory diseases, and other issues that increase with age."

November 2020 - Ray Peat's Newsletter

Standard treatment of atrial fibrillation compared to thermogenic agents

“The standard treatment for atrial fibrillation is the destruction of part of the heart’s conduction system, called ablation. It costs more than $25,000 in the USA and leads to a very high rate of heart failure. Correcting the problematic prolonged QT interval with thermogenic agents like progesterone, thyroid, and aspirin (Korkmaz-Icéz et al., 2016) is not of interest to the profession.”

November 2020 - Ray Peat's Newsletter

Sensory role of the primary cilium in cells

“There is renewed interest in the primary cilium, a small projection that nearly all our cells have. It forms from the centriole after cell division is complete and the cell integrates into its differentiated functions. This cilium is a sensory organ and keeps the cell informed about its orientation and location in the body. For example, the primary cilia of cells lining blood vessels all point toward the heart—regardless of whether they are in veins or arteries; they are aligned with respect to the overall picture.”

November 2018 - Ray Peat's Newsletter

Role of cholesterol in stem cell maintenance

“Cholesterol is involved in maintaining stem cells and controlling their maturation into functional cells. A cholesterol chelator, cyclodextrin, which disrupts cellular cholesterol, causes cardiac stem cells to mature into functional heart muscle cells: B-CD fulfilled its role by increasing free intracellular cholesterol.”

November 2018 - Ray Peat's Newsletter

Brain activity and the staircase effect: interplay of structure and function

“The brain’s background activity might show what is called the staircase effect in the heart: a structural readiness seems to be lost when the tissue is not active often enough—function builds structure, and structure generates function.”

Mind And Tissue Russian Research Perspectives on the Human Brain

Diastolic heart failure: A common age-related condition

“The diastolic, relaxed phase of the heart contraction cycle often fails under stress or with age—even in fruit flies. The heart becomes stiffer and does not fill completely, so it pumps less with each beat.”

March 2018 - Ray Peat's Newsletter

Indirect cardiac effect of nitric oxide via the parasympathetic nervous system

“Nitric oxide affects the heart not only through the blood vessels. When the parasympathetic nerves act on the heart and slow down and weaken its contractions, they release nitric oxide, which reduces both the heart’s oxygen consumption and its energy production.”

January 2016 - Ray Peat's Newsletter

Role of stress-related cortisone in heart attacks

"According to Meerson, heart attacks are triggered and worsened by the cortisone produced during stress. (Meerson and his colleagues have shown that the progression of a heart attack can be halted by treatment that includes natural substances such as vitamin E and magnesium.)"

Generative Energy Restoring The Wholeness Of Life

Interaction of energy flow and structural development

"Szent-Gyorgyi said during the discussion of some of his experiments with heart muscle that function builds structure, which increases the capacity for further function. The flow of energy through matter increases the order in that matter. More life and more energy can solve many of life's fundamental problems."

Generative Energy Restoring The Wholeness Of Life

Julien de la Mettrie's physiology based on organ function

"Based on several types of biological facts—including the intrinsic mobility or excitability of the gut and heart as well as the regeneration of Hydra from small fragments—Julien de la Mettrie proposed a new kind of physiology based on the idea of organization. He believed that thinking for an organ with the structure of the brain was as natural as beating for the heart. He regarded thinking as fully compatible with organized matter."

Generative Energy Restoring The Wholeness Of Life

Intuitions about cosmic energy and the origin of matter

"Soddys, Dudleys, and Kozyrev's intuitions about how new energy and matter appear in the universe attempt to connect nearly imperceptible phenomena (time, neutrinos, background radiation) with very important processes (stellar energy, nuclear energy, cosmic radiation, the origin of matter). Creation is at the center of existence, they might say, but it is too often overlooked."

Generative Energy Restoring The Wholeness Of Life

Calcium and iron deposits in mitochondria and diseases

"Calcium and iron tend to be deposited together, and mitochondria are usually the starting points for this deposition. Iron overload has been linked to heart disease, cancer, diabetes, and many other degenerative diseases, including brain disorders."

February 2001

Limiting effect of carbon dioxide on the overexcitation of nerves and muscles

"Carbon dioxide limits the electrical depolarization of nerves and muscles, a phenomenon first discovered by Gilbert Ling. This prevents overexcitation and exhaustion of brain and muscle cells, including the heart. The presence of carbon dioxide limits the formation of lactic acid. This explains the lactate paradox during exertion at high altitude."

December 1999 - Ray Peat's Newsletter

Limiting effect of carbon dioxide on the overexcitation of nerves and muscles

December 1999 - Ray Peat's Newsletter

Blood viscosity and health problems such as stroke and heart attack

"Vasospasms, increased viscosity of concentrated blood, and disturbed coagulation processes undoubtedly contribute to a wide range of health problems, including stroke, heart attack, and multiple sclerosis."

December 1999 - Ray Peat's Newsletter

An increase in blood volume improves the efficiency of heart contraction

"Even a simple increase in blood volume enhances the effectiveness of heart contraction. Szent-Gyorgyi described a related process (the staircase phenomenon) as: Function builds structure, structure generates function."

Ray Peat's Newsletter

Misconceptions about cell mechanics lead to ineffective treatments

"The inappropriate idea of a cell as pumps and motors leads to treating shock with things that cause shock, heart failure with things that cause heart failure, and aging with things that accelerate aging."

Ray Peat's Newsletter

Toxicity of plant steroid derivatives and their regulation by DHEA and progesterone

"Digitalis and ouabain are plant steroid derivatives that are toxic to animal cells – especially heart muscle cells – by acting at a site normally regulated by substances like DHEA and progesterone."

September 1995 - Ray Peat's Newsletter

Copper deficiency and iron overload in cells

"Copper-deficient cells, for example in the heart, become overloaded with iron."

June 1994 - Ray Peat's Newsletter

The Heart as an Indicator of Stress Resistance and Longevity

"The heart gives us some clues about our overall resilience to stress, aging, disease, and death. The heart and brain are the most stress-resistant organs, and while moderate stress and malnutrition can cause the skin and thymus gland to lose more than 90% of their substance, only the most prolonged and intense stress can cause the heart and brain to lose more than a quarter of their substance."