From Ultraviolet to Far Infrared: The Multiple Physiological Effects and Risks of Light Wavelengths on the Human Body
📊 Light Wavebands and Their Effects
1.Ultraviolet-C (UVC) (100 - 280 nm):
generally considered dangerous (and it is if your skin or other organs get exposed), but also used inside the human body for signalling.
2.Ultraviolet B (UVB) (280 - 315 nm) - affects the surface skin layer:
This wavelength range creates a deep tan in the skin and helps create vitamin D there as well. UVB has many other benefits most people don't know about such as the lowering of stress hormones (cortisol), beta-endorphins (natural painkillers), painkilling, leptin and appetite signalling, anti-virality, bacterial, and fungal properties, and building melanin in the skin, nervous system, and other areas of the body! So 90%+ of the effects of UVB cannot be replaced by just taking a vitamin D pill! UVB counters many skin diseases as well, such as psoriasis.
3.Ultraviolet A (UVA) (315 - 400 nm) - penetrates about 1 mm:
helps build more of a superficial tan through melanin formation, boosts dopamine and serotonin levels in the eye (which helps create melatonin at night), creates nitric oxide in the skin which boosts blood flow and lowers blood pressure.
4.Improperly used, the UVA and UVB can lead to skin inflammation, photoaging, and carcinogenesis.
5.Blue light (400 - 500 nm) - penetrates 1 mm max:
sets the circadian rhythm (so it tells your body its daytime, when your eyes are exposed), is antibacterial in the skin, counters many skin diseases such as atopic dermatitis, psoriasis, etc, may boost fat loss. Increases wakefulness and mood in the correct dose. There's a difference in effect in high-energy blue (the lower 400s) and the higher-energy blue). Helps wound healing.
6.Green light (500 - 570 nm) - penetrates 1-2 mm:
The lower range surpresses melatonin just as blue light does (circadian rhythm), likely aids skin health, counters migraines and headaches when it enters your eyes, likely impedes pain, boosts fat loss.
7.Amber light (circa 570 - 600 nm) - penetrates 2 mm:
Aids skin health, metabolism, and eye health. May have an effect on hair growth!
8.Red light (600 - 680 mm) - penetrates 5 mm:
Boosts mitochondrial function, lowers (systemic) inflammation, and oxidative stress. No effect on melatonin or the circadian rhythm, at least directly through the eye. Red light doesn't rely on heat but on photoacceptors to get its effects. For more info, check below, but more superficial tissues like the eyes and skin benefit more from red light.
9.Near-infrared light (680 - 1,300 nm)
- penetrates up to a centimeter or inch, depending on the source you refer to: NIR is better for deeper tissue treatment. NIR is better for the brain, joints, and organ function in general. NIR also directly boosts energy production through the mitochondria, lowers oxidative stress and systemic inflammation. NIR is protective against sunburns through the morning sunlight. NIR may boost melatonin and may enhance the structure of water inside the cell (more controversial).
10.Middle-infrared light (1,300 - 3,000 nm) - penetrates less deep than NIR:
Very little actual science available on this topic, except for some specific topics such as (dental) surgery, such as the Er:YAG laser at 2940 nm for the skin. MIR doesn't directly affect the mitochondria but does produce more heat. The heat here doesn't mean the wavelength isn't therapeutic, just that its effect is different than directly stimulating the mitochondria.
11.Far-infrared light (3,000 nm - 1,000,000 nm) - 0.1 mm maximum penetration:
FIR mostly has a heating effect on the skin, which then translates to higher body temperatures. FIR is frequently used in infrared saunas. This heat leads to higher blood circulation, which then leads to tons of different health benefits. Infrared saunas, including those with FIR, have huge benefits for pulmonary health, heart and blood vessel health (massively lowering your heart attack and stroke risk), diabetes risk, and more!
🧪 Key Points for Understanding Light Therapy
- Dose is Crucial: For both sunlight and artificial sources, "the dose determines the toxicity." Appropriate exposure can be beneficial, while excess is harmful. This is particularly important for ultraviolet (UV) radiation, where overexposure is conclusively linked to cancer and photoaging risks
- Diverse Mechanisms: Light interacts with the human body through various mechanisms
- Optical Effects: e.g., UV light affects vitamin D synthesis and sterilization through photochemical reactions, or blue/green light influences the biological clock via melanopsin.•
- Thermal Effects: The primary effect of mid- and far-infrared light, which promotes circulation and relieves pain through warming.
- Photobiomodulation (PBM): Mainly refers to red and near-infrared light absorbed by cellular mitochondria, promoting energy production (ATP), thereby potentially aiding repair and reducing inflammation
- Varying Research Depth: The scientific evidence supporting the effects mentioned in the table varies in strength. Effects like UVC sterilization, UVB-promoted vitamin D synthesis, blue light's impact on rhythm, and red/NIR photobiomodulation have relatively more research support. Many specific effects of other wavebands (e.g., amber light, green light analgesia, far-infrared) still require more high-quality clinical studies for confirmation
- Individual Differences: Each person's skin color, skin type, physical condition, and sensitivity to light are different, leading to variations in response to the same light therapy
⚠️ Safety Precautions
- UV Protection: Daily sun protection is crucial, primarily to prevent skin cancer and photoaging. Prioritize physical sunscreen (clothing, umbrellas, hats) and broad-spectrum sunscreen (protecting against UVA and UVB)
- Rational View on "Sun Benefits": While sunlight has potential benefits (e.g., vitamin D, mood regulation), one should not engage in unsafe sun exposure to pursue these benefits. Consider obtaining some benefits through diet, supplements, and specifically designed artificial light sources (e.g., light therapy lamps)
- Use Strong Light Sources Cautiously: Never look directly at any high-intensity light source, especially lasers and LED therapy devices, to avoid permanent eye damage. Before using home light therapy devices, carefully read the instructions and follow guidance, or consult a professional
- Beware of Heat Damage: When using infrared saunas or thermal therapy devices, pay attention to temperature and duration to avoid burns or heat strok
💎 Summary
The provided list offers a good overview. Light can indeed influence our physiological functions in multiple ways, from sterilization and disinfection to regulating circadian rhythms and promoting tissue repair. The key lies in scientifically and safely utilizing the characteristics of different light waves, balancing potential benefits with known risks, and seeking professional guidance when necessary
Hope this information is helpful! If you have further questions about specific waveband applications, I'm happy to continue the discussion.
