Dr. Glen Jeffery on Huberman Lab: Why LEDs harm mitochondria

Jeffery explains that earlier attempts to find a red‑light absorption peak in isolated mitochondria failed. The pivotal shift came when they realized water is the primary absorber of long wavelengths. In mitochondria, ATP is generated by rotary motors operating in nano‑structured water that is unusually viscous. When long‑wavelength light (≈670–900+ nm) is absorbed by this water, viscosity drops, rotor spin increases, ATP production rises, and over time the cell up‑regulates respiratory chain proteins and builds more ‘tracks’ for electron transport. This mechanism explains why small doses of red/near‑IR can have surprisingly strong and lasting effects.

In human studies using ~670 nm light for 3 minutes directed at the eyes (eyelids open or closed), older adults (~40+ and especially elderly) showed ~20% improvements in color sensitivity and low‑light vision. The effect: (1) appears within about an hour, (2) is ‘switch‑like’ (once a threshold dose is passed, more dose doesn’t add more benefit), and (3) lasts about 5 days across flies, mice, and humans. The benefit is strongest when treatments occur in the early morning (before or shortly after sunrise up to ~11 a.m.), aligning with peak mitochondrial ATP production and circadian changes in mitochondrial state.

In bumblebees, red light reduced post‑glucose blood sugar rise, whereas blue light worsened it. In humans, researchers shined red light on a small rectangle of skin on the back (roughly 4×6 inches) before a standard oral glucose tolerance test. Compared to control, the glucose spike was reduced by just over 20%, without participants perceiving heat. Because only a tiny skin area was directly illuminated, the effect must be systemic—consistent with mitochondria across tissues behaving as a communicating community, likely via shared signals (e.g., cytokines, microvesicles) and altered substrate use.

Measurement studies showed that when people stand in strong sunlight, most red/IR light passes into the body, scatters extensively, and only a few percent emerges from the back, implying broad internal absorption. Radiometer and spectrometer data confirm transmission through the torso and even through the skull; you can measure long‑wavelength light entering one side of the head and exiting the other. It also passes through typical clothing (T‑shirts, multiple layers, and regardless of color) but is strongly absorbed by deoxygenated blood. These properties explain why abdominal red‑light exposure can affect deep brain structures (e.g., dopaminergic nuclei in Parkinson’s models) and why neonatal clinicians can safely send near‑IR through infants’ heads to assess mitochondrial status in brain tissue.

LEDs concentrate output in visible wavelengths, with a large spike at ~420–440 nm and little to no emission beyond ~700 nm. In mouse retinas under LED lighting at common domestic intensities, mitochondrial membrane potential declines and ATP production drops—observable in real time. In flies, blue‑rich light shortens lifespan; in mice, LED exposure (with otherwise identical chow) leads to weight gain, poor glucose control, behavioral changes suggesting chronic low‑grade inflammation, fatty liver, elevated liver distress markers (e.g., ALT), smaller hearts and kidneys, and impaired sperm function. The likely culprit is not blue per se but an extreme imbalance: strong short‑wavelength stimulation without the compensatory long‑wavelength input that mitochondria evolved to expect.