HoldsUp

Huberman Lab · 2025-12-01 · Andrew Huberman (host), Glen Jeffery

Dr. Glen Jeffery: Using Red Light to Improve Your Health & the Harmful Effects of LEDs

70 research-tied claims examined: 2 contradicted 5 overstated 11 context 44 supported 8 unverified

5 Overstated
0:36:18Glen Jefferyoverstatedvery low

Shining red light on the abdomen reduces Parkinson's disease symptoms and cell loss in primate models of the disease.

"he induces Parkinson's disease in primates, which you can do pretty much overnight with a drug, and then he was giving red light to different parts of the body... but he was reducing the symptoms of Parkinson's disease in these primates very significantly with lights that were being shone on the abdomen." (said at 0:36:18)

John Mitrofanis and colleagues published a study demonstrating that remote photobiomodulation (670 nm red light) applied to the abdomen or legs provided systemic neuroprotection and reduced parkinsonian deficits in an MPTP-induced Parkinson's model. However, the abdominal application in non-human primates was only a pilot experiment involving a single monkey (n=1), while the statistically powered validation was conducted in mice (n=10 per group). Earlier primate studies from the group demonstrating significant clinical improvements in larger cohorts used direct intracranial fiber-optic delivery rather than abdominal irradiation.

0:42:23Glen Jefferyoverstatedmoderate

Long-wavelength red and infrared light can penetrate through human bone and skull tissue.

"If you look at a long-wavelength light source—and again, this is published; Bob Fosbury did this—he put his hand on one. It comes straight through his hand, but the interesting thing is you can't see the bones. It's passing through the bone. So that led me to go into grabbing a few skulls, and yeah, it's it's really not affected that much by bone." (said at 0:42:23)

Near-infrared (NIR) and long-wavelength red light do measurably penetrate human bone and skull tissue, but the speaker's claim that transmission is 'really not affected that much by bone' significantly overstates the efficiency of transmission. Experimental studies on human calvaria and cadaver models show that human skull and scalp severely attenuate light, transmitting only approximately 0.2% to 4.2% of applied NIR light (and even less for visible red light). While light does pass through, the vast majority is scattered and absorbed.

1:15:45Glen Jefferyoverstatedvery low

Mice kept under LED lighting gain excess weight and body fat due to impaired mitochondrial glucose uptake, leading to unbalanced blood glucose regulation.

"If you look at mice, you find mice put start putting on a lot of weight. They start putting on a lot of weight because their mitochondria are not taking that glucose out and it's being deposited as fat. Their control of their blood glucose, not surprisingly, becomes unbalanced" (said at 1:15:45)

Animal studies have demonstrated that artificial light exposure (particularly blue LED light) can exacerbate weight gain, increase body fat, cause insulin resistance, and impair mitochondrial oxidative phosphorylation in adipose tissue, particularly in high-fat-diet models. However, the speaker overstates and slightly mischaracterizes the mechanism: glucose is taken up by cellular glucose transporters into the cytosol rather than directly taken into mitochondria, and the observed metabolic and mitochondrial dysregulation is heavily dependent on specific lighting spectra, circadian disruption, and dietary conditions in preclinical mouse models.

1:48:45Glen Jefferyoverstatedmoderate

The lack of long-wavelength light exposure is a contributing driver in the development of myopia.

"Now, this is a very big issue in um in Asia uh and in China and we know that the absence of long-wavelength light is a driver." (said at 1:48:45)

While repeated low-level red-light (RLRL) therapy (typically delivering ~650 nm long-wavelength light) has been shown in multiple randomized controlled trials and meta-analyses—principally conducted in China—to slow axial elongation and reduce myopia progression in children, stating definitively that 'the absence of long-wavelength light is a driver' of myopia overstates the established etiology. The protective effect of outdoor light exposure is multifaceted and largely attributed to high overall illuminance, retinal dopamine release, and broad-spectrum chromatic cues. Although therapeutic red light exposure stimulates choroidal thickening and slows progression, a specific lack of long-wavelength light has not been definitively established as an independent causal driver of myopia development.

2:03:20Andrew Huberman (host)overstatedhigh

Dimming an incandescent or halogen light source in the evening will not suppress melatonin levels or disrupt circadian rhythms.

"And if you dim it down, it's not going to alter your melatonin level, circadian rhythm." (said at 2:03:20)

While dimming evening indoor lighting substantially reduces light-induced circadian disruption compared to bright lighting, claiming it will not alter melatonin levels or circadian rhythms at all overstates the protection. Controlled human trials demonstrate that the human circadian system is exquisitely sensitive to evening light across a non-linear dose-response curve: light intensities as low as 10 to 50 lux (typical of dim indoor illumination) can suppress melatonin and delay the timing of dim light melatonin onset by 22 to 109 minutes, with a median 50% effective dose (ED50) of approximately 24.6 lux.

Unverified means no publication matching the claim was located; it does not prove the claim false. Spotted an error? See the corrections policy - disputes from the people quoted are prioritized.