Lactic Acid and Lactic Acid Bacteria: Exercise Physiology, Lactate Shuttle, and Probiotic Fermentation

Contemporary scientific re-evaluation of systemic lactate dynamics:

• Debunking Delayed Onset Muscle Soreness (DOMS): Muscle soreness results from microscopic structural micro-tears along myofibrillar Z-discs, not lactate. Circulating lactate clears within 60–90 minutes post-exercise.
• The Cell-to-Cell Lactate Shuttle: Discovered by Prof. George Brooks; lactate is actively transported via monocarboxylate transporters (MCT1/4) to fuel aerobic cardiac myocytes, neurons, and type I muscle fibers.
• Hepatic Cori Cycle: Lactate is shunted via the bloodstream to the liver, where gluconeogenesis reconstitutes new glucose molecules for continuous energy cycling.

Microbiological features and clinical benefits of lactic acid bacteria:

• Core Genera: Lactobacillus, Bifidobacterium, Lactococcus, Pediococcus, and Streptococcus thermophilus.
• Luminal Acidification: By fermenting carbohydrates into lactic acid, LAB maintain a protective acidic environment (pH 4.0–5.0) that suppresses pathogenic pathogens like Salmonella and Clostridioides.
• Bacteriocins and Mucosal Immunity: Produce natural antimicrobial peptides (bacteriocins) while prompting mucosal dendritic cells to secrete protective secretory IgA (sIgA).

Traditional fermented foods as functional nutritional staples:

• Cultured Dairy Products: Natural yogurts and kefir enhance lactose digestion via microbial beta-galactosidase and deliver highly bioavailable calcium.
• Fermented Vegetables: Traditional sauerkraut, fermented pickles, and kimchi provide concentrated vitamin C, glucosinolates, and resilient probiotic colonies.
• Metabolic Longevity Outcomes: Clinical dietary trials link regular fermented food intake to reduced systemic inflammatory markers (hs-CRP) and superior glycemic stability.