Vitamin B12 has long been called the “energy vitamin,” but most people don’t know why. It’s not that B12 gives a direct jolt of energy like caffeine. Instead, it works at the cellular level, helping mitochondria, the tiny power plants inside cells, produce the energy muscles need to function.
New research shows just how critical this connection is. When B12 runs low, muscle cells may struggle to generate energy efficiently, and the damage can start at the level of DNA.
The vitamin mitochondria cannot work without
B12 plays a key role in helping cells build and repair DNA. When B12 is low, this process stalls, and mitochondrial DNA, the genetic instructions inside mitochondria, becomes more prone to errors. Though mitochondrial DNA is relatively small, it contains the blueprints for proteins mitochondria need to produce energy. When this DNA is damaged, cells cannot generate energy as effectively.
Low B12 starved muscles of energy
Researchers at Cornell University and the University of Alabama at Birmingham wanted to understand how B12 deficiency affects energy production in muscles. They studied two groups of mice: young-adult males that were either genetically prone to impaired B12 use or fed a B12-deficient diet for seven weeks, and older mice, roughly equivalent to older adults in human years, that received weekly B12 injections for eight weeks.
Here is what they found. Less energy production: In mice with low B12, the mitochondria in their muscles could not work at full capacity. Energy output from key parts of the mitochondria dropped by about 25% in muscle tissue rich in mitochondria. DNA errors increased: Mice on the B12-deficient diet had roughly 10 times more DNA errors in their mitochondria, a sign of instability that can further impair energy production. B12 helped aging muscles: In older mice, B12 injections doubled the activity of a key energy-producing component in their leg muscles, suggesting supplementation may help restore mitochondrial function with age.
The groups most likely to run low
B12 deficiency is more common in certain groups. Adults over 50: As people age, their bodies become less efficient at absorbing B12 from food, partly because they produce less stomach acid. Vegans and vegetarians: B12 is found almost exclusively in animal products, so those who avoid meat, fish, eggs, and dairy often need to supplement. People with digestive conditions: Conditions like Crohn’s disease, celiac disease, or a history of stomach surgery can make it harder to absorb B12.
The study notes that B12 deficiency has been linked to muscle weakness, mitochondrial problems, and increased risk of frailty in older adults.
What you can do about it
If you are concerned about your B12 levels, here are some practical steps. Eat B12-rich foods: Clams, beef liver, fish including salmon, trout, and tuna, eggs, and fortified nutritional yeast are all good sources. Consider testing: If you are over 50, follow a plant-based diet, or have digestive issues, ask your doctor about checking your B12 levels. A test for methylmalonic acid (MMA) can give a more sensitive read on your B12 status. Pair B12 with protein and strength training: Since B12 supports muscle mitochondria, combining adequate B12 with strength training and enough protein may help maintain muscle function as you age. Talk to your doctor about supplements: If you are deficient or at risk, a quality B12 supplement can help. Your doctor can recommend the right form and dose for you.
This research adds to growing evidence that B12 does far more than prevent anemia. It plays a key role in how muscles produce energy. For anyone focused on healthy aging, keeping B12 levels in check through diet, testing, and supplementation when needed is a simple way to support mitochondria and muscles for the long haul.
