Quick answer: what do mitochondria actually do?
Mitochondria are tiny structures inside most of your cells that help convert energy from food and oxygen into forms your cells can use. They also help regulate heat production, cellular signaling, stress responses, metabolism, and the removal of damaged cellular components. They are part of the basic machinery that lets your muscles contract, your brain function, your immune system respond, and your cells repair themselves.
Think less about “more energy” and more about energy flow
Mitochondrial researcher Dr. Martin Picard describes the body as working within a limited energy budget. Exercise, infection, chronic psychological stress, digestion, and tissue repair all create demand. When those demands pile up, you feel tired, recovery slows, and exercise feels harder. Simply adding more fuel does not necessarily fix it — if the system is already overloaded, more food can create more work rather than more usable energy.
Stress has an energy cost
A stress response costs energy. Heart rate rises, muscles tense, attention narrows, blood glucose can increase. That makes sense when you need to run from danger; it is less helpful when the danger is a work email replayed for six hours. Picard's group is also studying GDF15, a cellular stress signal that appears to rise when tissues are under metabolic strain — still developing science, but psychological stress clearly creates measurable biological responses.
Exercise stresses mitochondria on purpose
Exercise creates a temporary energy demand that signals muscle to adapt and increase mitochondrial capacity, which is why training can make you feel more energetic over time. There is an important exception: people with ME/CFS or some forms of long COVID can experience post-exertional malaise. A 2024 Nature Communications study found abnormalities in skeletal muscle metabolism and mitochondrial function in people with long COVID after exercise. For those patients, activity may need to be carefully paced with medical guidance.
Food is fuel, but more fuel is not always better
If energy intake repeatedly exceeds what the body uses, metabolic problems can develop: insulin resistance, excess visceral fat, fatty liver, and abnormal blood sugar. Picard uses the term "energy resistance" as a conceptual model for a mismatch between energy pressure and the body's capacity to process it. Stored calories and usable cellular energy are not the same thing.
Red light therapy and mitochondria: real, but early
Red and near-infrared light are studied for effects on cellular metabolism, a field called photobiomodulation. One proposed target is cytochrome c oxidase in the mitochondrial electron transport chain. A small 2024 human study used 670-nanometer red light for 15 minutes before a glucose tolerance test and reported a lower rise in blood glucose. Promising, but not proof that red light treats diabetes. CoolCRYO offers red light therapy as one tool, not a substitute for sleep, movement, nutrition, or medical care.
NAD+, urolithin A and the supplement boom
NAD is essential to energy metabolism, but most people do not have a diagnosed NAD deficiency, and evidence that more NAD+ improves healthy mitochondria is limited. Urolithin A has more human data: a randomized trial in JAMA Network Open of 66 adults ages 65 to 90 found improvements in some muscle endurance measures and metabolic biomarkers, but it did not significantly improve its primary measures of six-minute walking distance or maximal ATP production versus placebo. Promising, not proven magic.
What actually helps
Move regularly with progressive exercise you can recover from. Strength train if you are able. Avoid constant overeating, especially highly processed food. Sleep enough to recover. Take chronic stress seriously. Spend time outside. And if your energy changed significantly — unexplained fatigue, exercise intolerance, shortness of breath, dizziness, post-exertional crashes — get evaluated. Sometimes low energy is anemia, thyroid dysfunction, insulin resistance, nutrient deficiency, sleep apnea, medication effects, or heart or lung disease. Picard and colleagues also published a study in eLife showing gray hairs can sometimes regain pigment, with changes tracking periods of psychological stress.
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