Researchers studied how vitamin B12 and folate deficiencies affect male fertility in mice. They found that mice lacking these important B vitamins had lower sperm quality, damaged sperm DNA, and reduced testosterone levels. The study suggests that certain enzymes involved in processing amino acids were affected by the vitamin deficiencies. These findings highlight why getting enough B vitamins through diet is crucial for men’s reproductive health. While this research was done in mice, it provides important clues about how B vitamins support male fertility in humans.

The Quick Take

  • What they studied: How lack of vitamin B12 and folate affects sperm quality and male reproductive health
  • Who participated: Male mice were divided into two groups: one eating normal food and one eating food without B12 and folate vitamins
  • Key finding: Mice without adequate B12 and folate had significantly fewer healthy sperm, more damaged sperm DNA, lower testosterone, and weaker testicular function compared to mice eating normal food
  • What it means for you: This suggests that men should ensure they get enough B12 and folate in their diet to maintain healthy sperm and reproductive function. However, this study was in mice, so more human research is needed to confirm these findings apply to people

The Research Details

Scientists conducted an experiment where they divided male mice into two groups. One group ate regular mouse food with normal amounts of B vitamins, while the other group ate food specifically lacking vitamin B12 and folate. The researchers then measured many different aspects of the mice’s health, including sperm quality, hormone levels, and how well their reproductive organs were working. They looked at sperm under microscopes, measured chemical markers in the blood, and examined genes and proteins related to vitamin metabolism.

This experimental approach allows researchers to directly test whether vitamin deficiencies cause reproductive problems, rather than just observing that they happen together. By controlling exactly what the mice ate, scientists could be confident that any differences between groups were due to the missing vitamins, not other factors. This type of controlled experiment is important for understanding cause-and-effect relationships in nutrition.

This is a controlled laboratory study, which is strong for testing specific biological mechanisms. However, the study was conducted in mice, not humans, so results may not directly apply to people. The researchers measured multiple markers of sperm health and reproductive function, which strengthens confidence in the findings. The study appears to be well-designed with clear comparisons between groups, though the exact number of mice used wasn’t specified in the abstract.

What the Results Show

Mice that didn’t get enough B12 and folate had significantly lower sperm counts and reduced sperm movement compared to mice eating normal food. The sperm from deficient mice also showed more abnormal shapes and structures. When researchers examined the sperm DNA closely, they found increased damage and changes in how the DNA was packaged inside sperm cells. Blood tests showed these mice had much lower levels of B12 and folate, higher levels of a harmful compound called homocysteine, and lower testosterone levels—the main male hormone. When scientists looked at the mice’s testicles under a microscope, they saw that the tissue structure was damaged and the organs weren’t producing sperm as efficiently as they should.

The study found that sperm DNA methylation—a chemical process that helps control which genes are active—was significantly decreased in the vitamin-deficient mice. This suggests that B vitamin deficiencies affect not just sperm structure but also how genes are regulated in sperm. Interestingly, while the researchers expected to find increased oxidative stress (cellular damage from harmful molecules), the actual levels of reactive oxygen species in sperm cells were similar between groups, suggesting the damage may occur through different mechanisms than initially predicted.

This research builds on existing knowledge that B vitamins are essential for proper cell function and reproduction. Previous studies have shown that homocysteine—a compound that builds up when B vitamins are deficient—can harm sperm quality. This study adds detail by showing exactly which enzymes in the metabolic pathway are affected and confirming that the damage extends to sperm DNA structure and testicular tissue. The findings align with clinical observations that men with B vitamin deficiencies sometimes experience fertility problems.

This study was conducted in mice, not humans, so we cannot be certain the same effects occur in men. The abstract doesn’t specify how many mice were used in each group, making it difficult to assess statistical power. The study measured gene expression at the RNA level but found no significant changes in actual protein levels for some key enzymes, which raises questions about which measurements best reflect what’s actually happening in the cells. Additionally, the study doesn’t tell us how long the vitamin deficiency lasted or whether the effects could be reversed by restoring normal B vitamin intake.

The Bottom Line

Men should ensure adequate intake of vitamin B12 and folate through diet or supplementation. Good sources include leafy greens, legumes, eggs, dairy products, and fortified grains for folate, and meat, fish, eggs, and dairy for B12. If you have concerns about fertility or suspect vitamin deficiencies, consult a healthcare provider for testing and personalized recommendations. (Confidence: Moderate—based on animal research with strong biological plausibility, but human studies are needed)

Men concerned about fertility or reproductive health should pay attention to B vitamin intake. This is particularly important for men with dietary restrictions (vegetarians/vegans for B12), digestive disorders that affect nutrient absorption, or those taking certain medications that interfere with B vitamin metabolism. Women planning pregnancy should also ensure adequate B vitamins, as these affect overall health and may influence partner fertility. People without fertility concerns can still benefit from adequate B vitamin intake for overall health.

If someone is deficient in B vitamins, improvements in sperm quality typically take 2-3 months after correcting the deficiency, since sperm production takes about 74 days. Hormone levels may improve within weeks of adequate B vitamin intake. However, individual results vary based on the severity of deficiency and overall health.

Want to Apply This Research?

  • Track daily B vitamin intake by logging foods rich in folate and B12. Set a goal to consume at least one source of each daily (e.g., one serving of leafy greens for folate, one serving of animal protein for B12). Monitor consistency over 8-12 weeks.
  • Add one B-vitamin-rich food to each meal: breakfast (eggs or fortified cereal), lunch (spinach salad or legumes), dinner (fish or meat with vegetables). If dietary changes aren’t feasible, discuss B-complex supplementation with a healthcare provider and track supplement adherence in the app.
  • Set monthly reminders to assess energy levels, mood, and overall wellness as indirect indicators of B vitamin status. If tracking fertility-related concerns, note any changes in health markers over 3-month periods. Consider periodic blood work to confirm adequate B12 and folate levels, especially if dietary intake is limited.

This research was conducted in mice and has not been confirmed in humans. While the findings suggest B vitamins are important for male reproductive health, this study alone should not be used to diagnose or treat fertility problems. If you have concerns about fertility, sperm quality, or vitamin deficiencies, consult with a qualified healthcare provider or fertility specialist who can perform appropriate testing and provide personalized medical advice. Do not start or stop any supplements without discussing with your doctor, especially if you are taking other medications or have underlying health conditions.