Scientists discovered that vitamin B12 plays an important role in keeping your muscle cells healthy and energetic. When mice didn’t get enough B12, their muscles couldn’t produce energy as efficiently, and harmful substances built up in their muscle cell powerhouses called mitochondria. When older mice received B12 injections directly into their muscles, their energy production improved. This research suggests that B12 deficiency might make muscles weaker and less able to function, but more studies in humans are needed to confirm these findings.

The Quick Take

  • What they studied: How vitamin B12 affects the ability of muscle cells to produce energy, and what happens when there isn’t enough B12
  • Who participated: Male laboratory mice of different ages and genetic backgrounds. Some mice had a genetic change that reduced their B12 processing ability, while others were normal. Some ate regular food with B12, others ate B12-free food. Older mice received B12 injections into their leg muscles.
  • Key finding: Mice without enough B12 had weaker energy production in their muscles and harmful buildup of a substance called uracil in their muscle cell powerhouses. When older mice received B12 injections, their muscle energy production improved.
  • What it means for you: This research suggests that getting enough B12 may be important for keeping your muscles strong and energetic. However, this study was done in mice, not humans, so we can’t yet say for certain that the same thing happens in people. If you’re concerned about B12 levels, talk to your doctor about getting tested.

The Research Details

Researchers used two different approaches to study B12 and muscles. First, they compared normal mice to mice with a genetic change that made it harder for their bodies to use B12. They fed some mice regular food with B12 and others food with no B12 to see what happened. They measured how well the muscles could produce energy and looked for damage inside the muscle cells. Second, they took older mice and injected B12 directly into their leg muscles once a week for 8 weeks, then checked if their muscle energy production improved. The scientists examined the tiny powerhouses inside muscle cells (called mitochondria) to see if B12 affected how they worked.

This research approach is important because it helps us understand exactly how B12 affects muscle function at the cellular level. By using both genetic changes and dietary changes, the researchers could see if B12 deficiency causes problems in different ways. Testing in older mice is also valuable because older people often have lower B12 levels and weaker muscles, so the results might be more relevant to aging.

This study was published as a preprint, meaning it hasn’t been reviewed by other scientists yet, so we should be cautious about the findings. The researchers used careful measurements of muscle function and looked at the actual damage inside cells, which is good. However, the study was only done in mice, not humans, so we can’t assume the same results would happen in people. The sample sizes aren’t clearly reported, which makes it harder to judge how reliable the results are.

What the Results Show

Mice that couldn’t process B12 properly (due to a genetic change) had weaker energy production in their muscles compared to normal mice. When mice ate food without any B12, their muscles showed even bigger problems with energy production, especially in the red muscles that need lots of energy (like the soleus muscle in the calf). The researchers found that harmful uracil buildup in the muscle cell powerhouses was about 10 times higher in mice on the B12-free diet. This uracil buildup appeared to be connected to the weaker energy production. In older mice that received B12 injections directly into their leg muscles, one type of energy-producing system (called complex IV) worked better after 8 weeks of treatment.

The study found that different parts of the muscle were affected differently by B12 deficiency. Red muscles, which use lots of oxygen and energy, were more sensitive to B12 problems than white muscles. The genetic change that reduced B12 processing affected multiple energy-producing systems in the muscle cells, not just one. The direct injection of B12 into muscles appeared to be more effective than just changing diet, at least in the older mice studied.

Previous research had shown that B12 deficiency causes problems in the DNA inside cell nuclei, but this study adds important new information by showing that the DNA inside muscle cell powerhouses (mitochondrial DNA) is actually more sensitive to B12 deficiency. The findings support earlier work showing that B12 is important for making new DNA and that deficiency can cause harmful substances to build up. This research extends those findings specifically to muscle tissue and shows that these changes actually affect how well muscles can produce energy.

This study was only done in mice, so we don’t know if the same thing happens in humans. The study didn’t measure how much B12 the mice actually had in their bodies, so we can’t be sure the ‘deficient’ mice were truly deficient. The sample sizes for some of the experiments aren’t clearly reported. The study was published as a preprint, meaning other scientists haven’t reviewed it yet. The researchers only looked at male mice, so we don’t know if female mice would respond the same way. The study didn’t look at whether the muscle weakness actually affected how well the mice could move or exercise.

The Bottom Line

Based on this research, maintaining adequate B12 levels appears important for muscle health and energy production (moderate confidence level, since this is mouse research). If you have symptoms of B12 deficiency like fatigue or muscle weakness, ask your doctor to check your B12 levels. People at higher risk for B12 deficiency (older adults, vegetarians, vegans, people with digestive problems) should be especially careful to get enough B12 through food or supplements. However, taking extra B12 beyond what you need probably won’t give you extra muscle power.

This research is most relevant to older adults who may have lower B12 levels, people with B12 deficiency or absorption problems, vegetarians and vegans who don’t eat animal products (the main source of B12), and people with muscle weakness or fatigue. People with normal B12 levels don’t need to change anything based on this study. Athletes looking to improve performance shouldn’t expect B12 supplements to help unless they’re actually deficient.

In the mouse study, changes in muscle energy production were visible after 8 weeks of B12 supplementation. In humans, it might take weeks to months to see improvements in muscle strength or energy after correcting a B12 deficiency, depending on how severe the deficiency was and how long it lasted.

Want to Apply This Research?

  • Track your energy levels and muscle fatigue on a daily scale (1-10) if you’re correcting a B12 deficiency. Also note any changes in exercise ability or muscle soreness. If you’re supplementing with B12, track your intake and look for patterns in your energy over 8-12 weeks.
  • If you’re at risk for B12 deficiency, use the app to set reminders to eat B12-rich foods (meat, fish, eggs, dairy, fortified cereals) or take supplements as recommended by your doctor. Track which foods you eat and how you feel to see if there’s a connection between B12 intake and your energy levels.
  • Set up monthly check-ins to rate your overall muscle strength, exercise capacity, and energy levels. If you’re supplementing with B12, track consistency of your supplement use. After 8-12 weeks, review your energy and strength trends to see if there’s improvement. Share this data with your doctor at your next visit.

This research was conducted in mice and has not yet been peer-reviewed. The findings cannot be directly applied to humans without further research. This information is educational and should not replace professional medical advice. If you suspect you have a B12 deficiency or are experiencing muscle weakness or fatigue, consult with your healthcare provider for proper testing and treatment. Do not start B12 supplementation without discussing it with your doctor, especially if you take medications or have existing health conditions.