Lactic acid affects human bodies and the physiology of organisms large and small. From climbing stairs to breaching athletic limits lactic acid helps keep systems operational. Too much can cause health problems.
The body is made of organ systems working in harmony. The muscular system has functions like movement and blood circulation. A byproduct of muscle activity is lactic acid.
About Lactic Acid
Lactic acid, or 2-hydroxypropanoic acid, is an organic byproduct of the decomposition or breakdown of glucose or glycogen. Lactic acid fermentation occurs in the absence of oxygen.
Lactic acid has the chemical formula C3H6O3. An organic acid produced during lactic acid fermentation, it's found in food such as tofu, soy milk, cheese, yogurt, legumes, salami and sauerkraut.
Lactic acid in unpacked tofu at 10 °C increases from 67.95 to 285.07 µg/g during 15 days of storage, according to the National Institutes of Health. To extend shelf life of packaged food items like bread, desserts, olives, and jam, food manufacturers often add lactic acid.
Muscles can generate it too. When muscle activity exceeds oxygen supply, the body struggles to supply energy through oxidative phosphorylation. It uses glycolysis, a metabolic pathway to converts glucose into pyruvate.
Under low oxygen conditions, pyruvate is transformed to lactic acid, providing a rapid burst of energy. Lactic acid fermentation provides the continued production of ATP (adenosine triphosphate), the primary source of energy for cells.
Lactic acid is a buffer to maintain pH levels and prevent acidification. It tries to prevent muscle tiring or tearing. Lactic acid fermentation is associated with muscle fatigue and soreness, but also muscle recovery and growth.
As lactic acid levels rise in the muscles and bloodstream, several reactions happen.
Muscle Fatigue & Cramping: One of the most recognized consequences of lactic acid is muscle fatigue. While it is not the main cause of delayed onset muscle soreness (DOMS), its accumulation can lead to a noticeable burning sensation during and after exercise.
Recovery Post-Exercise: After exercise, lactic acid levels fall quickly as oxygen becomes more available. The body has several pathways to clear lactic acid, including converting it back to glucose in the liver (known as the Cori cycle) or using it directly for energy.
Training Adaptations: Regular training can improve the body’s ability to manage and use lactic acid more effectively. Many athletes report enhanced performance over time.
Lactic acid is also a signaling molecule influencing metabolic pathways and cell responses, contributing to body homeostasis. Lactic acid fortifies genes involved in metabolism and endurance.
Occurrence in All Animals
Lactic acid fermentation occurs in many but not all animals, and not always as a primary energy source. Humans, dogs and rabbits produce and use lactic acid.
In ruminants like cows and sheep, anaerobic fermentation breaks down cellulose. Lactic acid pulls fluid into the rumen from the tissues and blood to cause dehydration.
The blood may become more acidic, causing heart failure, kidney failure, and death. Lactic acid damages the rumen wall in rumenitis, enabling fungal or bacterial invasion of the body.
Fish and amphibians have very low levels of lactic acid. Their cold-blooded natures promote different systems.
Health Benefits: Lactic acid is important for fueling the heart and other organs during exercise. It may have therapeutic applications for conditions like ischemia and mitochondrial disorders.
Dairy Industry: In dairy, lactic acid bacteria convert lactose into lactic acid. They thickens products like yogurt and contribute to unique flavors.
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