Deuterium is one of the most important concepts in mitochondrial health and most people have never heard of it. Here's what you need to know. Deuterium is a heavy isotope of hydrogen. It has an extra neutron, making it about twice the weight of regular hydrogen. And when it builds up in excess, it acts like a brake on your mitochondria. I think of it as an energy efficiency problem not just a water or food problem. Healthy mitochondria are designed to: ✅ Separate hydrogen efficiently through the electron transport chain ✅ Produce metabolic water that's naturally low in deuterium ✅ Maintain ATP production through the mitochondrial ATP synthase nanomotor When deuterium accumulates, that whole system slows down. ATP production drops. Oxidative stress rises. Mitochondrial function degrades over time. But here's what most people miss: this isn't primarily a food issue. It's a light and circadian issue. Who would have ever thunk. Morning sunlight improves mitochondrial signaling. UV and infrared light help structure water inside your cells. When your circadian rhythms are working properly, your mitochondria become more efficient and better at separating and clearing deuterium naturally. The chain looks like this: Light → Circadian signaling → Better mitochondrial function → Better deuterium handling This is why I keep coming back to light before food, and environment before protocols. On the food side, we focus on things that generate metabolic water and support mitochondrial function such as seafood, wild fish, shellfish, animal fats, eggs. I'm more cautious with year-round fruit, sugar, processed carbs, and tropical foods eaten out of season. Not because carbohydrates are inherently bad, but because they carry more deuterium and are best matched to the season and latitude you're actually living in. Remember too much deuterium will degrade mitochondria and slow down energy production. Historically, humans ate more fat and protein in winter and more carbohydrates in summer when UV exposure was highest and the body was better equipped to handle the deuterium load that comes with it.