#326 – AMA #65: Red light therapy: promising applications, mixed evidence, and impact on health and aging

We discuss:

• Overview of topics and the motivation behind exploring red light therapy [1:45];
• The basic science of red light therapy [3:15];
• The unique penetration properties of red light [6:00];
• What happens when tissue is exposed to red light [9:30];
• Exploring red light therapy’s potential to combat aging [11:00];
• Red light therapy for treating acne [13:00];
• Red light therapy for aiding in wound healing [18:45];
• Red light therapy for hair loss: promising benefits and practical advice [24:15];
• Analyzing the evidence of a positive or negative effect of red light therapy on the eyes [28:00];
• Red light therapy’s impact on performance and recovery [30:30];
• Red light therapy’s impact on metabolic health: analyzing the limited evidence for improved glucose metabolism [32:45];
• Red light therapy for weight loss and targeted fat reduction [36:45];
• Red light therapy for inflammation, chronic pain, and injury rehabilitation [41:00];
• Red light therapy as a treatment for menstrual cramps [43:45];
• Summary: promising applications of red light therapy, unsupported claims, and costs to consider [46:45]; and
• More.

Overview of topics and the motivation behind exploring red light therapy [1:45]

In today’s AMA, we are going to focus on a single topic: red light therapy

• The plan is to cover:
  • what red light therapy is
  • how it can work
  • dive into some various claims out there around red light therapy such as:
    • potential effect on skin health
    • wound healing
    • hair loss
    • Eyesight
    • Exercise
    • performance and recovery
    • metabolic health
    • fat loss
    • Inflammation
    • chronic pain
    • and a lot more.

The basic science of red light therapy [3:15]

Introduction to Light and Wavelengths

• Light as waves:
  • Light exists as waves, which are generally very short compared to other waves, like sound.
  • Sound waves are relatively long, while light waves are much shorter.
• Shorter wavelengths mean higher energy:
  • As wavelength decreases, the energy of the wave increases.
  • For example:
    • UV light has shorter wavelengths and thus more energy than visible light.
    • X-rays and gamma rays are even shorter and carry even more energy.

Figure 1. Source: Apni Physics

Visible Light Spectrum

• Range of visible light:
  • Visible light spans wavelengths from approximately 380 to 780 nanometers.
  • Different colors correspond to different wavelengths within this range:
    • 380 nm: Violet (shortest wavelength in the visible spectrum)
    • 780 nm: Red (longest wavelength in the visible spectrum)
• Red light in context:
  • Red light is found at the longer end of the visible light spectrum, around 620-780 nanometers.
  • Red light therapy utilizes this specific narrow range of red light.

Red Light Therapy and Phototherapy

• Definition of Red Light Therapy:
  • Red light therapy specifically refers to light in the 620-780 nm range.
  • This red wavelength is more narrowly focused than white light, which includes a mixture of all visible wavelengths.
• Phototherapy:
  • Phototherapy broadly includes treatments across the full range of visible light.
  • It may also use near-infrared (NIR) light, which falls just outside the visible spectrum.

Near-Infrared (NIR) Light

• Characteristics of NIR:
  • Near-infrared light has wavelengths between approximately 790 and 1400 nanometers.
  • Unlike red light, NIR is invisible to the human eye.
• Role in red light therapy:
  • Near-infrared light is often used in conjunction with red light for therapeutic purposes.
  • NIR wavelengths are slightly longer than red light, providing different penetration and effects.

Safety Considerations and Visibility

• Visibility and potential risks:
  • The fact that NIR light is invisible can present safety challenges.
  • Invisible light might carry risks that are less obvious, as users cannot see its intensity or presence.

The unique penetration properties of red light [6:00]

Penetration Depth and Wavelength

• Comparison to UV Light:
  • Like with UVA and UVB in ultraviolet light, red light therapy’s effectiveness depends on its penetration depth.
    • See AMA #61 for more
  • Longer wavelengths, like red light, can penetrate more deeply than shorter wavelengths, though with less energy.

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