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The Truth About Lactate (Part II)

This is part II of a series I wrote about lactate. If you want to see the other parts:

As I discussed in part 1, lactate often gets a bad rap, but there’s so much more to this molecule than meets the eye. It’s not just a byproduct of intense exercise—lactate plays a key role in energy production in the whole body. I’ll explain as well how elevated lactate levels at rest can actually be a red flag for metabolic health. Let’s break it down. 🔍

🧪 Glycolysis 101: breaking down glucose

Glycolysis is the process where glucose is broken down to produce energy (ATP). Traditionally, on the assumption that the glycolytic pathway has two different outcomes/end products, it’s been described in two forms: aerobic (with oxygen), producing pyruvate and anaerobic (without oxygen), producing lactate. However, this differentiation is completely outdated, since lactate is always the end product of glycolysis, even in the presence of oxygen. 📌

Here’s how it works:

  • Glycolysis converts glucose into pyruvate.
  • Then, a portion of pyruvate enters the mitochondria, where it undergoes the TCA (tricarboxylic acid) cycle and ETC (electron transport chain) to produce even more energy.
  • However, most of the pyruvate is quickly converted into lactate, even when oxygen is present. This lactate isn’t wasted; it serves as a continuous fuel source for the body. It can either also enter mitochondria, where it’s converted back to pyruvate and further utilized for energy production OR shuttled to different tissues, where it can be turned back into glucose or used directly for energy.

💳 The VISA of energetics

This flexibility allows lactate to be used by every consumer cell everywhere it goes, acting like the “visa” of energetics. Particularly neurons, astrocytes, cardiac and skeletal muscle rely on lactate for fuel. It moves between cells and organs, becoming the preferred fuel in high-energy demand contexts. Lactate shuttles energy, whether it’s being recycled in the liver through the Cori cycle into glucose or directly used by neurons and muscle cells for fuel. Even cancer cells tap into lactate for rapid growth. Essentially, lactate is a crucial, versatile energy carrier across the body’s metabolic networks.

⚠️ Resting Lactate and Metabolic Health: A Warning Sign

While increased lactate production is normal during exercise, elevated resting lactate levels can indicate metabolic issues. Here’s why this matters:

  • In healthy individuals, lactate levels return to normal (~1mmol) after exercise, reflecting efficient energy metabolism. But in those with metabolic dysfunction (i.e. type 2 diabetes, obesity), resting lactate levels tend to be higher (1.5-3 mmol). This suggests that their cells are struggling to efficiently convert glucose into energy, even at rest.
Mitochondrial dysfunction. Credit to Iñigo San Millán
  • Why is this bad? Elevated resting lactate often signals impaired mitochondrial function—the energy powerhouses of our cells. When mitochondria don’t work properly, cells rely more on glycolysis for energy, producing excess lactate.
  • High resting lactate levels are associated with chronic inflammation, increased risk of cardiovascular disease and cancer.

Essentially, elevated resting lactate is a sign that metabolic health is under stress, inflexible and inefficient.🚨

💡 The Takeaway: Lactate Tells a Bigger Story

Lactate isn’t just an exercise molecule. Lactate is critical to energy supply, acting as an essential fuel for many tissues like the brain, heart and skeletal muscles. Furthermore, it can be a metabolic marker that gives us insights into our overall health. While it’s a crucial fuel in both rest and intense exercise conditions, elevated resting lactate levels could be a signal that metabolic health is compromised.

Lactate as a metabolic marker

#MetabolicHealth #Lactate #Glycolysis #ExerciseAndHealth #Metabolism #Prevention #Sports #Exercise

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