# Lactic acid

Category: Metabolism

Lactic acid and carbon dioxide have opposing effects. Intense exercise damages cells in ways that cumulatively impair metabolism. There is clear evidence that glycolysis, producing lactic acid from glucose, has toxic effects, suppressing respiration and killing cells. Within…

10 passages · 2 authors · 2012–2020 · Most-cited: [Ray Peat](https://bioenergeticoracle.com/md/voices/ray-peat/index.md)

Canonical page: https://bioenergeticoracle.com/concepts/lactic-acid

## Synthesis

**Lactic acid** is a metabolic byproduct of *glycolysis* that Ray Peat positioned as a fundamental disruptor of healthy physiology, standing in direct opposition to **carbon dioxide**. [Source 1, 2] Peat argued that while a well-adapted organism oxidizes glucose completely to carbon dioxide, stress of any kind—whether from intense exercise, emotional strain, or disease—shifts metabolism toward the inefficient production of lactic acid, which then acts as a toxic signaling molecule. [Source 2, 6] He noted that a very well-developed athlete resists producing lactic acid, whereas a sedentary person forced to exercise is flooded with it, demonstrating that the molecule is a marker of inadequate oxygen and fuel delivery to tissues. [Source 2] Crucially, carbon dioxide produced by healthy oxidative metabolism directly suppresses lactic acid formation, a relationship exemplified by the **lactate paradox** at high altitude, where adapted individuals with higher tissue carbon dioxide can work intensely without generating the toxin. [Source 2]

The danger of lactic acid extends far beyond the familiar muscle burn. Peat described it as a *pro-inflammatory, swelling-producing, tumor-promoting* agent that functions as a local poisoner. [Source 3, 5] It triggers the release of inflammatory mediators, stimulates the growth of new blood vessels, and promotes fibrosis. [Source 3, 4] In diabetes, the inability to oxidize sugar fully leads to chronic lactic acid production, and Peat stated that lactic acidosis was historically a common cause of death for diabetics. [Source 2, 6] He extended this mechanism to Alzheimer's disease and general aging, framing them as conditions involving accumulated mitochondrial damage from sustained glycolytic stress. [Source 1] Dinkov and Peat further connected chronically elevated blood lactate to cancer, noting that it can be a diagnostic indicator even before a tumor is found, as the lactate itself becomes carcinogenic to other tissues. [Source 7]

At the cellular level, lactic acid production creates a deceptive pH paradox. Peat explained that a healthy respiring cell is slightly acidic, around pH 6.8, due to carbon dioxide. [Source 3] When a cell is stressed and shifts to glycolysis, the conversion of pyruvic acid to lactic acid draws a proton from the NADH system, causing the *cell's interior to become alkaline* while the extruded lactic acid acidifies the surrounding environment. [Source 3, 8] This internal alkalization disrupts the cell's normal regulatory systems and, when sustained, contributes to the self-replicating nature of tumors, as the normal acidic conditions maintained by carbon dioxide are lost. [Source 8] Peat identified endotoxin as a primary trigger for this cascade, with lactic acid then becoming the agent that activates downstream symptoms like blood clotting, serotonin effects, and edema. [Source 7]

The systemic consequences of lactic acid involve a web of hormonal disruption. Roddy has detailed how lactic acid stimulates the release of **prostaglandin E2**, which increases the aromatase enzyme and produces new estrogen, establishing a vicious cycle that further suppresses oxidative metabolism. [Source 9] Peat noted that even a 50% elevation in circulating lactic acid, caused by a poor diet or low thyroid function, is sufficient to initiate the inflammatory process. [Source 10] He emphasized that stress itself, without physical exertion, can shift metabolism toward lactic acid production by activating fat burning, and he criticized ketogenic diets for framing this background lactic acid formation as a virtue rather than a menace. [Source 10] The liver must expend significant energy to detoxify lactic acid by converting it back to glucose, meaning that dietary sources from fermented foods like yogurt or sauerkraut impose a metabolic burden equivalent to physical stress. [Source 3, 5]

## People also ask

### How does lactic acid promote cancer according to Peat?

Peat and Dinkov argued that chronically elevated blood lactate is carcinogenic to tissues and can serve as a diagnostic indicator before a tumor is found, while at the cellular level the internal alkalization caused by lactic acid production disrupts normal regulation and contributes to the self-replicating nature of tumors.

### Why does Peat consider dietary lactic acid from fermented foods harmful?

Peat noted that the liver must expend significant energy to convert lactic acid back to glucose, so consuming fermented foods like yogurt or sauerkraut imposes a metabolic burden comparable to physical stress.

### What is the relationship between carbon dioxide and lactic acid production?

Peat described carbon dioxide as directly suppressing lactic acid formation, with healthy oxidative metabolism producing CO2 that prevents the glycolytic shift, a relationship demonstrated by the lactate paradox where altitude-adapted individuals with higher tissue CO2 resist lactic acid buildup.

## Related concepts

- [Lactic acidemia](https://bioenergeticoracle.com/md/concepts/lactic-acidemia/index.md)
- [Oxidation](https://bioenergeticoracle.com/md/concepts/oxidation/index.md)
- [Aldosterone](https://bioenergeticoracle.com/md/concepts/aldosterone/index.md)
- [Glycolysis](https://bioenergeticoracle.com/md/concepts/glycolysis/index.md)
- [Parathyroid Hormone (PTH)](https://bioenergeticoracle.com/md/concepts/parathyroid-hormone-pth/index.md)
- [PUFA (polyunsaturated fatty acids)](https://bioenergeticoracle.com/md/concepts/pufa-polyunsaturated-fatty-acids/index.md)

## Cited passages

Passage numbers match the `[Source N]` markers in the synthesis above.

### Source 1 — Glossary

Ray Peat · Glossary

> Lactic acid
>
> Lactic acid and carbon dioxide have opposing effects. Intense exercise damages cells in ways that cumulatively impair metabolism. There is clear evidence that glycolysis, producing lactic acid from glucose, has toxic effects, suppressing respiration and killing cells. Within five minutes, exercise lowers the activity of enzymes that oxidize glucose. Diabetes, Alzheimer's disease, and general aging involve increased lactic acid production and accumulated metabolic (mitochondrial) damage.

### Source 2 — Herb Doctors: Field Biology

Ray Peat · Interview · Sep 19, 2014 · http://l-i-g-h-t.com/files/herb-doctors-field -biology.mp4

> **Andrew Murray:** That kind of reminds me – and I know we’ve discussed this previously on shows of – various parts through various shows. But lactic acid, now this is something that I think most people can identify with – well, there’s two forms of it, perhaps that most people will probably quite commonly associate it with. One we think would be in yogurt, lactic acid formed during the fermentation process, but I think probably more commonly still during exercise when people exercise their muscles, when either running or aerobically exercising, the lactic acid builds up in the muscles. It is often felt as a cramp. And this is the same lactic acid that you are saying is completely a destabilizer of the cell and quite disruptive to the field.
>
> **Ray Peat:** Yeah. A very well developed athlete will not produce lactic acid too easily. A sedentary person, who is forced to exercise, will be flooded with lactic acid because they haven’t developed the system for delivering oxygen and a fuel to the tissues. So a really good athlete is resistant to producing lactic acid. And carbon dioxide produced by healthy metabolism directly participates in suppressing lactic acid and in maintaining and promoting oxidative energy production. And a place where you can see this is people who live at high altitude where the balance between oxygen and carbon dioxide leaves the bodies having a higher residual carbon dioxide level. They can work very intensely without producing lactic acid. That’s called the lactate paradox sometimes because ordinarily oxygen efficiency is what turns on lactic acid, but once you get adapted and are able to produce a lot of carbon dioxide or hold it in your tissues, then that in itself prevents this toxic formation of lactic acid.

### Source 3 — Alkalinity vs Acidity 2012 KMUD the Herb Doctors

Ray Peat · Interview · 2012

> **Herb Doctor:** The popular theory is stated that cancer cells like an acidic environment. It sounds like if a cell is stressed it likes an alkaline environment and that sounds almost exactly the opposite.
>
> **Ray Peat:** Well, it shifts internally to become alkaline when it's stressed but the produced lactic acid accumulates in it's environment and that's where the acid is, in the surroundings and then it shows up in the blood.
>
> **Herb Doctor:** Right so that's when if you've stressed your muscle out too much, then you're producing lactic acid and that makes your muscles sore.
>
> **Ray Peat:** Yeah.
>
> **Herb Doctor:** So that's a stressed cell. And does lactic acid play a big part in cancer as well?
>
> **Ray Peat:** Yeah. It not only acidifies the environment, which in itself could be actually protective if it was acidified by carbon dioxide, but it happens that the lactic acid acts as a signal to do all of the things associated with cancer, such as stimulating the growth of new blood vessels so that the inflammation continues. It signals a lot of inflammatory changes like vasodilation and formation of new blood vessels and the release of carbon monoxide and nitric oxide, lots of things producing free radicals and injury. So the lactic acid is functioning as a local poisoner and inflammatory agent. The acidity that it produces is a sign that something is wrong but it isn't the acidity in the tumor that's harmful because the tumor itself is internally alkaline.

### Source 4 — Ask the Herb Doctor: Altitude (July 2013)

Ray Peat · Interview · 2013

> **Sarah Johannesen Murray and Andrew Murray:** And, lactic acid is the thing we feel when we exercise and our muscles cramp?
>
> **Ray Peat:** Yeah, and it triggers release of a whole series of mediators of inflammation and also of fibrosis.
>
> **Sarah Johannesen Murray and Andrew Murray:** OK.
>
> **Ray Peat:** And so they’re now finding that when they are doing abdominal surgery if they blow in a fairly concentrated solution of CO2 solutions or gas, they’ll suppress the formation of fibrosis and adhesions.
>
> **Sarah Johannesen Murray and Andrew Murray:** Cause it decreases inflammation?
>
> **Ray Peat:** Yeah.
>
> **Sarah Johannesen Murray and Andrew Murray:** So, the common myth that when your muscles hurt it means they are growing bigger and that’s better, I mean the common belief, it’s a myth?
>
> **Ray Peat:** Yeah, well anything that injures your muscle, the lactic acid is probably long gone, but the damage persists and the damage involves the loss of CO2 and that causes the uptake of water swelling and so on and the swelling and the injury does cause the muscle to get bigger, but not healthier.

### Source 5 — Alkalinity vs Acidity 2012 KMUD the Herb Doctors

Ray Peat · Interview · 2012

> **Herb Doctor:** So as a side point, what do you think of foods that are high in lactic acid?
>
> **Ray Peat:** Well, even when we make it ourselves, it has these pro-inflammatory, swelling producing, tumor promoting functions. And when it's made my bacteria, it's somewhat more toxic. And when the body receives it, either from a stressed muscle or a tumor or from too much yogurt or some food that has been fermented, it goes to the liver to get detoxified. So every time you eat something with lactic acid it's the same as if you had been stressed physically. Your liver has to work extra to detoxify it and it has to have a source of energy to detoxify the lactic acid, turning it back into glucose. Glucose is right back where you started, so you've lost ground every time your liver has to process lactic acid.
>
> **Herb Doctor:** So would you consider any amount of lactic acid containing food to be a stress to the liver or do you think there's some margin of benefit?
>
> **Ray Peat:** A healthy liver doesn't notice an occasional dish of yogurt or sauerkraut or something. How I got interested in it was a long time ago I discovered Kefir. It tasted good and so I drank a little more than a cup of it each day for lunch but everytime I did that I would get a migraine-like headache every afternoon. And that started me looking up what happens to your blood sugar and inflammatory mediators when you get more lactic acid than your liver likes.

### Source 6 — Herb Doctors: Field Biology

Ray Peat · Interview · Sep 19, 2014 · http://l-i-g-h-t.com/files/herb-doctors-field -biology.mp4

> **Ray Peat:** But lactic acid is one of the basic disrupting signals if it continues too long. And it turns out that one of the basic features of diabetes is that they can’t oxidize sugar all the way to carbon dioxide. Instead they produce lactic acid. And if that continues too long, lactic acidosis is very often what diabetics used to die from. But any of these stresses will interfere with the ability to oxidize glucose in the brain or blood vessels in the organ that’s under too much stress and not getting repair materials, will shift over to producing lactic acid and the lactic acid then is a stress signal and an immune signal for the rest of the organism.

### Source 7 — #36: CO2 and Mineral Balance  |  Thyroid  |  Magnesium  |  Calcium in Health and Disease  |  Current Events

Ray Peat · Interview · Oct 3, 2020 · https://open.spotify.com/episode/76Aou3s0DXgxpDoA9Wr4PS

> **Ray Peat:** Yeah, I think the lactic acid is starting with endotoxin. Lactic acid produced under the influence of endotoxin becomes the agent of endotoxin. all of the problem symptoms, blood clotting, increased serotonin effects of all sorts, inflammatory, swelling, congestion, and edema of the lungs and the brain. All of those things are activated by the lactic acid.

### Source 8 — Biochemical Health, Reduction and Oxidation — Politics & Science 2015

Ray Peat · Interview · 2015

> **Ray Peat:** A lot of people have seen disease as caused by a low pH, or too much acidity. And in the case of stress and cancer, a tumor will become very acidic. So that traditional idea has a basis. In an infection or a tumor, the inflammation produces a high concentration of lactic acid, and a very low pH in that area, which does have disruptive toxic effects [on that area]. So the body is able generally to correct that and reduce the inflammation and stop the production of lactic acid. But when lactic acid is formed, the conversion from pyruvic acid to lactic acid is drawing an extra proton out of the NADH catalyst that causes the conversion, taking away this extra proton as it leaves [the cell]. In its formation, it raises the pH inside the cell. So, even though a tumor or an infection it is...locally, you see excess acid (high lactic acid inside the cell, that's doing that) it's the reverse process: you get an increase in the pH inside the cell. So the cell, if it gets stuck in producing lactic acid because it can't produce CO2, then that means it also tends to get stuck at a higher pH. And this higher pH changes the whole system. And that's where you tend to get a self-replicating tumor; because the normal acidic conditions maintained by the CO2 are lost.

### Source 9 — Casualties of The Nutritional Dark Ages, Part I: Calcium

Danny Roddy · Article · Jul 15, 2013

> Lactic acid stimulates the release of the pro-inflammatory prostaglandin E2 (Dawes and Rushton 1994), made from polyunsaturated fatty acid arachidonic acid, which increases the aromatase enzyme and produces new estrogen. Moreover, estrogen increases prostaglandin E2 establishing a vicious cycle (Bulun, et al. 2000). Aromatase appears to be sensitive to the concentration of phosphate (Bellino and Holben, 1989).
>
> While often referred to as "the female hormone," estrogen increases what's thought to be "the mothering hormone," prolactin (D'Agata, et al., 1982; Nicoletti, et al., 1984).
>
> Prolactin stimulates PTH and vice versa (Raymond J, et al. 1982; Isaac R, et al., 1978). Prolactin increases the lipolytic pituitary hormone ACTH (Ogle and Kitay 1979), acts on the thyroid gland to decrease its activity, and on other tissues to increase their glycolysis (increasing lactate production), while decreasing oxidative metabolism (Spatling et al., 1982; Strizhkov, 1991).
>
> Calcium lowers prolactin (Kruse and Kracht, 1981).
>
> Estrogen and prolactin both increase the synthesis of serotonin. Like estrogen (Vliagoftis, et al. 1992), PTH may increase serotonin (and histamine) by liberating it from mast cells (Tsakalos N, et al. 1983). Carbon dioxide stabilizes mast cells (Strider, et al. 2010). Like prolactin, estrogen, and PTH, serotonin causes bone loss and inhibits bone formation. Anti-serotonin drugs have been used to inhibit bone loss (Yadav et al. 2010, Inose et al. 2011).
>
> PTH interferes with glucose metabolism and is part of the 'metabolic syndrome' that includes diabetes, hypertension, and obesity (Ahlström, et al., 2009; Hjelmesaeth, et al., 2009; McCarty, et al. 2003). Calcium decreases the counter-regulatory hormone, adrenaline (Luft, et al., 1988), which can increase during defective glucose metabolism.

### Source 10 — One Radio Network: Top Contrarian on Health

Ray Peat · Interview · Dec 17, 2019

> ## Lactic Acid and Stress
>
> **Patrick Timpone:** In simple dietary terms, what do we do unknowingly to increase this lactic acid?
>
> **Ray Peat:** Ideally, you would get all of your energy from carbohydrates—sugars or starches—and not have to rely on burning fat. Stress turns on fat burning, and that turns on background lactic acid formation.

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