Ray Peat on lactic acid

January 29, 2026

Effects of hypothyroidism on muscle fatigue and metabolites

"When metabolic energy production fails, as in hypothyroidism, muscles fatigue easily, absorb excess water, and the barrier structure becomes looser, allowing macromolecules, ATP, and other metabolites to leak out while foreign substances penetrate. Typical muscle enzymes such as lactate dehydrogenase and creatine kinase appear in the bloodstream in typical hypothyroid myopathy, and cardiac proteins—including a specific form of lactate dehydrogenase and a muscle protein, troponin—appear in the blood following cardiac exertion or fatigue, combined with hypothyroidism or systemic inflammation."

September 2019 – Ray Peat's Newsletter

Aerobic glycolysis and lactic acid in cancer metabolism

“Aerobic glycolysis – the metabolism typical of cancer, in which lactic acid is formed from glucose despite the presence of oxygen – is promoted by serotonin.”

September 2019 – Ray Peat's Newsletter

The role of lipofuscin in plaque inflammation and calcification

"The age pigment ceroid, or lipofuscin, which is largely derived from PUFAs and associated with the foamy macrophage cells in the plaque, accumulates iron (Lee et al., 1998) and, by catalyzing oxidation, creates local hypoxia, leading to the formation of lactic acid and contributing to an inflammatory process. The products of lipid peroxidation, such as azelaic acid (Riad et al., 2018), together with lactate, lead to tissue calcification."

September 2018 – Ray Peat's Newsletter

Hypoxia, edema and hypoglycemia with elevated lactic acid in the blood

"Elevated lactic acid in the blood is a sign of tissue hypoxia. However, edema, hypoglycemia, and lactic acidemia can also be caused by other respiratory defects, including hypothyroidism, in which the tissue does not use enough oxygen; the skin appears bluish (in thin areas, such as around the eyes) when hypoxia – rather than just low oxygen consumption – is involved."

Nutrition For Women

The response of tissue to stimulation and oxygen utilization

"One response to irritation is the production of more energy, with a proportional increase in oxygen and glucose consumption by the irritated tissue; this produces more carbon dioxide, which dilates the blood vessels in the area and makes more glucose and oxygen available. When the irritation becomes destructive, efficiency is lost: oxygen is either wasted, causing a bluish discoloration of the tissue (assuming circulation continues; bluish discoloration can also indicate poor circulation), or it is not consumed, causing reddening of the tissue. As more glucose is consumed to compensate, lactic acid also dilates the blood vessels."

Nutrition For Women

Systemic effects of inflammation and fatigue on blood sugar and energy efficiency

"However, severe inflammation or deep exhaustion lowers blood sugar throughout the body and delivers large amounts of lactic acid to the liver. The liver produces glucose from the lactic acid – but at the cost of about six times more energy than is gained from the inefficient metabolism – so that this tissue becomes 90 times less efficient at the organismal level than in its original state. In addition, the inactive destruction of energy molecules (ATP or creatine phosphate) increases the waste even further."

Nutrition For Women

Adrenal response to inflammation and stress

"When the body senses inflammation or other stress (possibly by detecting changes in blood sugar, lactic acid, or carbon dioxide, or all of these together), the adrenal glands release anti-stress hormones, including adrenaline and cortisol (provided these glands are not exhausted or undersupplied). Both adrenaline and cortisol can raise blood sugar to meet the increased demand."

Nutrition For Women

Vitamin B2 deficiency and its effects on lactic acid

"Sugar waste, which leads to the formation of lactic acid, can result from a vitamin B2 deficiency, and lactic acid appears to stimulate the formation of new blood vessels."

Nutrition For Women

Lactate as a trigger for the stress response

"Lactate is a sufficient stimulus to trigger the stress response."

Nutrition For Women

The effect of thyroid gland and progesterone on protein synthesis and lactate oxidation

"However, the relevant effects of the thyroid gland (especially together with progesterone to promote the tissue response to the thyroid and to block cortisone production) are the stimulation of protein synthesis and the prevention of lactate formation – or the promotion of its oxidation, either by the tumor itself or by other tissues, to prevent it from entering the Cori cycle for gluconeogenesis."

Nutrition For Women

Lactic acid as a signal for glucose production during exertion

"The formation of lactic acid (becoming out of breath) is the most important signal that new glucose needs to be produced. That's why aerobic training is the most stressful."

Nutrition For Women

The influence of higher body temperature on the reduction of inflammation

"The higher oxygen consumption rate that occurs at higher body temperature corresponds to high carbon dioxide production and inhibition of lactate formation – maintaining a more oxidized balance that reduces inflammation."

November 2020 – Ray Peat's Newsletter

Oxygen supply and activation of glycolysis in working muscles

"At low altitudes, when a tissue's oxygen consumption exceeds the blood's ability to supply oxygen—as in a hard-working muscle—the tissue activates the process of glycolysis, converting glucose into lactic acid to obtain additional energy."

May 2020 - Ray Peats Newsletter

Metabolic effects of carbon dioxide and altitude sickness

“By neglecting the role of carbon dioxide in suppressing lactic acid formation, they also overlook all its other essential metabolic effects – including its role as the factor whose absence leads to the syndromes of altitude sickness.”

May 2020 - Ray Peats Newsletter

Association between chronic metabolic hyperventilation and degenerative diseases

“By ignoring the fact that 30 years of slightly elevated lactate could lead to cancer or other degenerative diseases, those who taught physiological chemistry also showed little interest in the idea of chronic metabolic hyperventilation – that is, losing a little too much CO₂ even at sea level.”

May 2020 - Ray Peats Newsletter

Chronic stress and its effects on inflammation and energy

"In a state of chronic stress, oxidative energy production is low, and inflammatory mediators are likely to be chronically elevated; typically, there is a persistently increased production of lactate and/or a decreased oxidation thereof."

May 2020 - Ray Peats Newsletter

Effects of lactate on oxygen diffusion and hypoxia

"Lactate increases capillary permeability and fluid loss, and reduces the ability of oxygen to diffuse from the alveoli into the erythrocytes. Since carbon dioxide diffuses many times faster than oxygen, this diffusion barrier leads to low blood CO₂ levels and hypoxia. Even at sea level, an increase in lactate immediately raises the diffusion barrier in the lungs."

May 2020 - Ray Peats Newsletter

The role of lactate in regulating cellular excitability

"The presence of lactate in the cells corresponds to a certain degree of reductive excess, and the degree of reduction regulates the calcium channels and thus controls the excitatory effects of intracellular calcium."

May 2020 - Ray Peats Newsletter

Stress and lactate: Effects on inflammation and exosomes

"The reduction caused by stress and/or lactate activates the channels, tightens the smooth vascular muscle and activates a wide range of other cellular activities, including inflammation and exosome secretion."

May 2020 - Ray Peats Newsletter

Anti-excitotoxic substances and the importance of the CO₂/lactate ratio

"Anti-excitotoxic substances include progesterone, memantine, minocycline, and agmatine. A high CO₂ to lactate ratio, which lowers the intracellular pH, is important to prevent excessive excitability. Thyroid hormone—in addition to directly increasing energy and the CO₂/lactate ratio—tends to raise brain temperature and increase the progesterone to estrogen ratio."

May 2018 - Ray Peats Newsletter

Oxidative metabolism to maintain protective factors after pregnancy

"In 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 excessive superoxide and lactate production. Under these conditions, cytokines can contribute to adaptation and continued development."

March 2021 - Ray Peat's Newsletter

The lactate paradox in altitude physiology

"For several decades, altitude physiologists have been puzzled by the so-called lactate paradox: the fact that physical exertion at high altitude – with less oxygen – causes a smaller increase in lactic acid in the blood than at sea level, which allows for faster recovery. This is because it is assumed that oxidative metabolism prevents the formation of lactic acid – the lower oxygen availability at high altitude should actually lead to a higher lactate level and a slower recovery."

March 2020 - Ray Peat's Newsletter

Cellular energy production and inflammation

"Impaired energy production is fundamental to inflammation. When cellular stimulation increases faster than oxygen can be supplied, there is a shift towards glycolytic energy production, whereby glucose and amino acids are converted into lactic acid."

March 2019 - Ray Peat's Newsletter

Silicon dioxide, estrogen and the formation of lactic acid

"Small particles of silicon dioxide or other inorganic or organic material (such as plastics) can – similar to radiation, oxygen deficiency, sepsis or estrogen – increase the production of lactic acid, and this lactate promotes various features of inflammation, including edema, collagen synthesis, and the growth and movement of cells."

March 2019 - Ray Peat's Newsletter

Intensity of lipolysis and disruption of restful sleep

"The intensity of lipolysis decreases during the most restorative deep sleep, but the free fatty acids themselves tend to increase lactate by blocking the oxidation of glucose to carbon dioxide and dampen glucose metabolism. This creates an inflammatory and excitatory state that impairs deep sleep."

March 2018 - Ray Peat's Newsletter

Nitric oxide causes a metabolic shift towards glycolysis.

"Even in the presence of oxygen, nitric oxide causes a metabolic shift towards glycolysis, wastefully producing lactate from glucose."

March 2017 - Ray Peat's Newsletter

Stress-induced metabolic shift and formation of reactive toxins

"When stress shifts the metabolism towards reduction and lactic acid is produced, iron atoms react cyclically with oxygen and the reducing agents, generating hydroxyl radicals and other highly reactive toxins."

March 2017 - Ray Peat's Newsletter

Stress buffers: Substances that help keep metabolism on track

“Several of these substances inhibit the release of free fatty acids and the formation of prostaglandins, and reduce nitric oxide, lactate production, inflammation, excitation, and cholinergic tone. What they all have in common is the support of a shift away from a highly reduced state towards an oxidized, energized equilibrium.”

March 2016 - Ray Peat's Newsletter

Ideology distorts the understanding of stress physiology

"The ideology surrounding stress physiology, which distorts the importance of serotonin, estrogen, unsaturated fats, sugar, lactate, carbon dioxide and various other biological molecules, has hidden the simple remedies against most inflammatory and degenerative diseases."

July 2019 - Ray Peats Newsletter

Link between hypothyroidism, chronic stress and metabolic problems

"In hypothyroidism, oxidative metabolism is reduced; as a result, the organism is constantly close to stress and hyperventilation, with chronic production of lactate and ammonia. The inefficient metabolism in diabetes has similar effects."

July 2017 - Ray Peats Newsletter

Various substances increase respiration and lower the important CO₂ level.

"Besides ammonia and lactate, other stress-related substances can also increase respiratory drive and thereby reduce essential CO₂ – for example, endotoxin, acetylcholine, serotonin, hydrogen sulfide, nitric oxide, carbon monoxide, angiotensin and estrogen."

July 2017 - Ray Peats Newsletter

Hypothyroidism, stress and associated physiological complications

“People with hypothyroidism, who produce little CO₂, are very susceptible to stress-induced hyperventilation and are often in a state of physiological hyperventilation. They are prone to overproduction of ammonia (De Nardo, et al., 1999; Marti, et al., 1988) and lactate (Zarzeczny, et al., 1996), as well as to psychoses, especially depression and mania.”

July 2017 - Ray Peats Newsletter

Effects of glucose deficiency on cell metabolism

"Glucose deficiency leads to glutamine being used as fuel, which produces more ammonia. Ammonia, in turn (through an excitatory effect on cells and the direct activation of enzymes), promotes the glycolytic use of glucose, so that even in the presence of oxygen, lactic acid is produced and the glucose deficiency is further maintained."

July 2017 - Ray Peats Newsletter

Stress-related changes in breathing and their consequences

"Stress alters our breathing and causes a vicious cycle: The lactate and ammonia produced when stimulation exceeds our oxidative capacity promote increased breathing. This leads to more carbon dioxide loss, oxidative efficiency decreases, and the formation of ammonia and lactate increases further."

July 2017 - Ray Peats Newsletter

Importance of monitoring ammonia and lactate levels

"Because of their role in the development and maintenance of pseudohypoxia and the promotion of hyperventilation, more attention should be paid to the measurement of ammonia and lactate in blood, breath and urine."

July 2017 - Ray Peats Newsletter

The bridging function of lactate between metabolism and stress response

"The reduced state leads to increased lactate production, which generates enough energy to keep the cell alive. At the same time, the lactate contributes to the stress-induced redox shift in the cell that produces it, as well as in the surrounding cells."

July 2016 - Ray Peats Newsletter

The metabolic response to a cellular crisis: a question of survival

"When cells are dangerously overstimulated, oxygen and glucose are depleted. In the case of oxygen deficiency or when the ability to use oxygen is blocked, glucose is converted into lactate; and when the glucose is exhausted, glutamine is converted into lactate."

July 2016 - Ray Peats Newsletter

The influence of lactate in a reduced cell state and the inhibition of glucose oxidation

"When oxygen is limited but lactate is unlimited, the cell's metabolic reactions shift to a reduced, electron-rich state. This state inhibits glucose oxidation by blocking the enzyme pyruvate dehydrogenase, thus promoting lactate production. These are internal processes of stressed cells that can be interrupted if the organism provides corrective factors to restore oxidation."

July 2016 - Ray Peats Newsletter

Lactate in cancer: disruptive factor or energy source?

"When cancer metabolism increases the amount of lactate in the blood, increased respiration lowers the carbon dioxide in the blood (Gargaglioni, et al., 2003), and the loss of CO₂ affects metabolism and physiology at all levels."

July 2016 - Ray Peats Newsletter

Reductive stress and its self-reinforcing biochemical cycles

"The reduced state caused by hunger or hypoglycemia, by an excess of lactate or fat, or by oxygen deficiency, activates the release of glutamate, and the resulting excitation can switch off mitochondrial oxidation and thus exacerbate the state of pseudohypoxia. The synthesis of nitric oxide, which is activated by reductive stress, is an important factor in the suppression of mitochondrial oxidation."

January 2017 - Ray Peats Newsletter

Lactic acid in the brain: more than just a waste product

"While lactic acid and a more reductive equilibrium in the cells activate the excitatory glutamatergic system, an increased concentration of carbon dioxide inhibits this system."

January 2017 - Ray Peats Newsletter

Energy as a pivot point: Metabolic reactions to lactate and beta-hydroxybutyrate

"The use of lactate or beta-hydroxybutyrate as a metabolic fuel shifts the balance in a reductive direction – similar to how ethanol metabolism does."

January 2017 - Ray Peats Newsletter

Recognizing reductive stress based on metabolic conditions

"With aging and during stress, the metabolism of animals shifts towards reduction, with a higher ratio of lactate to pyruvate, of NADH to NAD, of ascorbate to dehydroascorbate, etc. – a state of reductive stress."

January 2016 - Ray Peats Newsletter

Re-examining the Warburg effect: glycolysis and cancer metabolism

"In extreme cases, the reductive energy from aerobic glycolysis can be consumed by fat synthesis, allowing glycolysis to continue. This can lead to cancer cells that oxidize fatty acids for energy while converting glucose into fats and lactic acid."

January 2016 - Ray Peats Newsletter

Intense training impairs metabolism through the effects of lactic acid.

"Intense training damages cells in a way that increasingly impairs metabolism over time. There is clear evidence that glycolysis, the process that converts glucose into lactic acid, has toxic effects, suppresses respiration, and kills cells. Within five minutes of physical exertion, the activity of enzymes that oxidize glucose decreases. Diabetes, Alzheimer's disease, and general aging are associated with increased lactic acid production and accumulated metabolic (mitochondrial) damage."

July 2000

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

Thyroid hormone and fatty acids in the activation of respiratory enzymes

"Thyroid hormone, palmitic acid, and light activate a crucial respiratory enzyme, thereby suppressing the formation of lactic acid. Palmitic acid is found in coconut oil and is also naturally produced in animal tissues. Unsaturated oils have the opposite effect."

July 2000

Treatment of lactic acid excess by inhibiting glycolysis

"Heart failure, shock, and other problems where excess lactic acid plays a role can be successfully treated by inhibiting glycolysis with dichloroacetic acid. This reduces lactic acid production, increases glucose oxidation, and raises cellular ATP concentration. Thyroid hormone, vitamin B1, biotin, etc., have a similar effect."

July 2000

The special role of palmitic acid in glycolysis and lactate production

"While most fatty acids inhibit the oxidation of glucose without immediately inhibiting glycolysis, palmitic acid is unusual: it inhibits glycolysis and lactate production without affecting oxidation. I suspect this is mainly due to its important function in cardiolipin and cytochrome oxidase."

July 2000

Physical exertion increases circulating free fatty acids and lactate.

“Physical exertion – like aging, obesity, and diabetes – increases the levels of circulating free fatty acids and lactate. However, ordinary activity in a holistic, integrated sense activates the systems in an orderly manner and increases carbon dioxide and blood flow.”

July 2000

Carbon dioxide and lactate dynamics in cellular processes

"While the flow of carbon dioxide from the mitochondrion into the cytoplasm and beyond tends to remove calcium from the mitochondrion and the cell, the flow of lactate and other organic ions into the mitochondrion can lead to an accumulation of calcium in the mitochondrion – under conditions in which carbon dioxide synthesis and consequently urea synthesis are throttled and other synthesis processes are altered."

July 2000

Glycolysis, pyruvate and mitochondrial function in cells

"Glycolysis produces both pyruvate and lactate, and an excess of pyruvate has almost the same inhibitory effect as lactate. Since the Crabtree effect also involves nitric oxide and fatty acids in addition to calcium, I think it makes sense to look for the simplest kind of explanation, rather than experimentally investigating all possible interactions of these substances: a simple physical competition between the products of glycolysis and carbon dioxide for binding sites – for example, on lysine – which would be equivalent to a phase change in the mitochondrion."

July 2000

The involvement of lactic acid in the breakdown of mitochondria

"In the case of a relative lack of carbon dioxide or an excess of alternative solutes and adsorbents such as lactic acid, the stability of the mitochondrial phase would decrease, and the mitochondria would degrade in both their structure and function. As a counterpoint to the idea that carbon dioxide stabilizes and activates mitochondria, the assumption that lactic acid is involved in mitochondrial degradation can also be tested experimentally – and is already supported by a considerable amount of indirect evidence."

July 2000

The Crabtree effect and the reduction of cellular energy

“In contrast to the logical Pasteur effect, the Crabtree effect tends to decrease cellular energy and adaptability. When considering many situations where increased glucose intake boosts lactic acid production and suppresses respiration, leading to a maladaptive decrease in cellular energy, I began to view lactic acid as a toxin.”

July 2000

High carbon dioxide levels prevent the toxic formation of lactic acid.

"When the carbon dioxide background is high, blood flow and oxygenation tend to inhibit anaerobic glycolysis, which produces toxic lactic acid. Therefore, a certain level of activity can be harmful or beneficial – depending on how much carbon dioxide is produced at rest."

July 2000

The influence of light on glucose oxidation and respiratory efficiency

"Light promotes the oxidation of glucose and is known to activate the crucial respiratory enzyme. Winter ailments (including lethargy and weight gain) and nighttime stress must be included in the concept of a respiratory defect: a shift towards anti-respiratory production of lactic acid, which damages the mitochondria."

July 2000

Non-toxic therapies for the treatment of lactic acidosis

"Therapeutically, even potent toxins that block glycolytic enzymes can improve function in a variety of organic disorders associated with (or caused by) excessive lactic acid production. Unfortunately, the toxin that has become the standard treatment for lactic acidosis—dichloroacetic acid—is carcinogenic and ultimately leads to liver damage and acidosis. However, several non-toxic therapies can achieve the same effect: for example, palmitate (formed from sugar under the influence of thyroid hormone and found in coconut oil), vitamin B1, biotin, lipoic acid, carbon dioxide, thyroid hormone, naloxone, and acetazolamide."

July 2000

Hypothyroidism, hyperventilation and a vicious cycle of energy loss

"Hypothyroidism suppresses respiration as an energy source, resulting in low carbon dioxide production and the formation of lactic acid, even in the absence of noticeable stress. This is similar to hyperventilation, as carbon dioxide loss is the defining characteristic of hyperventilation. However, abnormally high adrenergic activity and free fatty acids promote further hyperventilation and exacerbate carbon dioxide loss. Decreasing carbon dioxide levels further impair respiration, leading to increased lactic acid production, which in turn increases adrenergic activity – and so on, in a vicious cycle."

January 2000 - Ray Peats Newsletter

The 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 physical exertion at high altitude."

December 1999 - Ray Peat's Newsletter

Alzheimer's disease: respiratory metabolism in the brain and CO₂ deficiency

"In Alzheimer's disease, the respiratory metabolism of the brain is inhibited, resulting in a carbon dioxide deficiency with an excess of lactic acid and ammonia."

December 1999 - Ray Peat's Newsletter

Lactic acid, CO₂ and its connection to degenerative brain diseases

"If excess lactic acid in brain tissue is characteristic of Alzheimer's and multiple sclerosis, then the lactate paradox suggests that a slightly higher retention of carbon dioxide in the brains of Kashmir's inhabitants would mitigate chronic excitotoxic effects by suppressing the stress metabolism that leads to the degenerative brain diseases."

December 1999 - Ray Peat's Newsletter

Contribution of hypothyroidism to the development of glaucoma

"That hypothyroidism – by partially replacing carbon dioxide with lactic acid – could contribute to the development of glaucoma by increasing the viscosity of the aqueous humor."

1998 - Ray Peats Newsletter - 3

Muscle swelling during hypoxic stress in association with lactic acid

"The swelling of the muscles during hypoxic stress probably represents the fundamental process by which lactic acid and pH levels rise while CO₂ is lost."

1998 - Ray Peats Newsletter - 3

Alkaline state of cells that produce lactic acid

"While it is true that the entry of lactic acid into the bloodstream tends to lead to metabolic acidosis, the cell that produces the lactic acid is actually more alkaline than normal cells. The simplest way to look at it is this: when acid leaves the muscle, it becomes less acidic."