Essentials: Using Light to Optimize Health

Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science based tools for mental health, physical health, and performance. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we are going to discuss light and the many powerful uses of light to optimize our health. One of the reasons why light has such powerful effects on so many different aspects of our biology is that it can be translated into electrical signals in our brain and body, into hormone signals in our brain and body, and indeed into what we call cascades of biological pathways, meaning light can actually change the genes that the cells of your bodies express, and that is true throughout the lifespan. Light is electromagnetic energy. It can cause reactions in cells of your body. It can cause reactions in fruit, for instance. Right? You see a piece of fruit and it's not ripe, but it gets a lot of sunlight and it ripens. That's because the electromagnetic energy of sunlight had an impact on that plant or that tree or even on the fruit directly. Now, the second thing that you need to understand about the physics of light is that light has many different wavelengths. And the simplest way to conceptualize this is to imagine that cover of that Pink Floyd album where there's a prism, you have a white beam of light going into that prism, and then the prism splits that beam of light into what looks like a rainbow. So you got your reds, your orange, your greens, your blues, your purples, etcetera. Now the third bullet point to understand about the physics of light is that different wavelengths of light, because of the way that their wave travels, can penetrate tissues to different depths. Every biological function of light has to do with the absorbance or the reflectance of light or light passing through that particular thing, meaning that particular cell or compartment within a cell. I'd like to make it clear how this works by using the three primary examples of how you take light in your environment and convert it into biological events. We have photoreceptors in the back of our eyes. These photoreceptors come in two major types, the so called rods and the cones. The rods are very elongated. They look like rods. And the cones look like little triangles. The other place, of course, where light can impact our body is on our surface, on our skin. In the top layer of skin, which is called the epidermis, we have keratinocytes and we have melanocytes. With light exposure, those melanocytes will turn on genetic programs and other biological programs that lead to enhanced pigmentation on the skin, which we call tanning. And the third example I'd like to provide is that of every cell of your body. And what I mean by that is that every cell of your body, …