Long-wavelength light, such as red and near-infrared, enhances mitochondrial function by improving ATP production and reducing oxidative stress, with benefits extending to vision, blood glucose regulation, brain health, and aging. This type of light penetrates deeply into tissues—even through clothing and skull—enabling systemic effects from localized exposure. In contrast, excessive short-wavelength light from LEDs impairs mitochondrial activity, potentially contributing to metabolic dysfunction, eye strain, and reduced longevity. The balance between long and short wavelengths in lighting environments is crucial, as modern artificial lighting often lacks the full-spectrum quality of sunlight. Simple interventions like using incandescent or halogen bulbs, increasing daylight exposure, and applying targeted red light therapy can significantly improve metabolic and visual health, especially in older adults or those with mitochondrial dysfunction.