Ray Peat on Lactic Acid

Short answer: Ray Peat treated lactic acid as the opposite of carbon dioxide. He wrote that it appears whenever respiration fails, that it then suppresses respiration further, and that it promotes inflammation and the growth signals seen in cancer.

What Ray Peat wrote about lactic acid

Lactate is formed from glucose whenever something interferes with respiratory energy production. But lactate can itself suppress cellular respiration, so the problem feeds itself. Source: Lactate vs. CO2 in wounds, sickness, and aging; the other approach to cancer

Carbon dioxide inhibits the production of lactic acid, and lactic acid lowers the concentration of carbon dioxide in several ways. Source: Altitude and Mortality

He describes the lactate paradox: people adapted to high altitude produce less lactic acid during maximal work, because they retain more carbon dioxide. Source: Altitude and Mortality, Fatigue, aging, and recuperation

Breathing too much oxygen displaces carbon dioxide and provokes a rise in lactic acid. Source: Altitude and Mortality

He wrote that lactate produces several signals that promote growth and other features of cancer, and that aspirin antagonizes them. Source: Lactate vs. CO2 in wounds, sickness, and aging; the other approach to cancer

Intense exercise raises it. Within minutes exercise lowers the activity of the enzymes that burn glucose. Source: Mitochondria and mortality

He advised avoiding foods that contain lactic acid, such as yogurt and sauerkraut, because the bacterial form is more toxic than the form the body makes under stress. Source: Mitochondria and mortality

In the cell, a rise of lactate relative to carbon dioxide changes pH and electrical charge and makes the cell take up water. Source: The transparency of life: Cataracts as a model of age-related disease

What he suggested in practice

• Vitamin B1 to increase carbon dioxide and reduce lactate.
• Sugar and thyroid function, so that glucose is burned completely.
• Activity below the point of breathlessness.
• Less fermented food.

Where he wrote about it

This topic comes up in 50 of the articles on his site. These are the most relevant ones:

• Altitude and Mortality · original on raypeat.com ↗
• Lactate vs. CO2 in wounds, sickness, and aging; the other approach to cancer · original on raypeat.com ↗
• Mitochondria and mortality · original on raypeat.com ↗
• The transparency of life: Cataracts as a model of age-related disease · original on raypeat.com ↗
• Cancer: Disorder and Energy · original on raypeat.com ↗
• Fatigue, aging, and recuperation · original on raypeat.com ↗
• Rosacea, inflammation, and aging: The inefficiency of stress · original on raypeat.com ↗
• Osteoporosis, aging, tissue renewal, and product science · original on raypeat.com ↗

My take

If you come from keto, raise carbs slowly. Your cells need time to re-learn glucose oxidation, and jumping too fast builds up lactic acid, which then blocks glucose oxidation further.

Quick answers

What did Ray Peat say about lactic acid?

That it is a product and a cause of failed respiration: it suppresses mitochondria, lowers carbon dioxide, causes cells to swell and promotes inflammation and tumor growth signals.

What did Ray Peat say about yogurt and fermented foods?

He advised avoiding foods containing lactic acid, such as yogurt and sauerkraut, because bacterial lactic acid is more toxic than the kind the body produces.