Another Reason Why Vitamin B12 Is Important
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by Reed Mangels, PhD, RD
Vitamin B12 is an essential nutrient that is needed in very small amounts, on the order of several micrograms a day. A microgram is one-millionth of a gram or about 0.000000035 ounces. Despite the small amounts needed, a deficiency of this important vitamin can lead to irreversible damage to the nervous system (brain and nerves) and to developmental delays in infants.
Infertility affects 10%-15% of heterosexual couples in the United States with male infertility accounting for about a third of cases (1). Many nutrients are known to play a role in male reproductive health including vitamins A, C, D, E, folate, calcium, iron, and fat (2).
Recently, there has been some evidence that vitamin B12 could influence male fertility. A study that was published in 2024 examined the effect of low vitamin B12 levels in the blood on blood levels of male hormones in men with infertility (3).
What is the study?
This study, from Canada, examined 303 men who had been diagnosed with infertility. The men’s blood was examined for vitamin B12 and reproductive hormones, including testosterone, estradiol, and prolactin. No mention was made of the study subjects’ dietary habits.
What did this study find?
The main finding of this study was that blood vitamin B12 and blood testosterone levels had a linear relationship (3). This means that men with higher blood vitamin B12 levels were likely to also have higher testosterone levels. Men with lower vitamin B12 levels were likely to have lower testosterone levels. Testosterone is the main male sex hormone. Testosterone is needed for sperm production and plays a role in maintaining sex drive. In this study, 30% of the men had low testosterone levels. The subjects’ age and their BMI (body mass index) did not appear to affect the results. The levels of other reproductive hormones were not associated with blood vitamin B12 levels.
The results of this study suggest vitamin B12 status should be assessed as a part of the work-up for male infertility.
References:
- American Society for Reproductive Medicine. Defining Infertility. https://www.reproductivefacts.org/news-and-publications/fact-sheets-and-infographics/defining-infertility/?_t_tags=siteid:db69d13f-2074-446c-b7f0-d15628807d0c,language:en&_t_hit.id=ASRM_Models_Pages_ContentPage/_97bbc96d-df2e-40bf-8fad-2a44f2152a8a_en&_t_hit.pos=2. 2023.
- Vanderhout SM, Rastegar Panah M, Garcia-Bailo B, et al. Nutrition, genetic variation and male fertility. Transl Androl Urol. 2021;10:1410-1431.
- Rastegar Panah M, Jarvi K, Lo K, et al. Vitamin B12 is associated with higher serum testosterone concentrations and improved androgenic profiles among men with infertility. J Nutr. 2024;154:2680-2687.
To read more about vitamin B12 for vegans see:
Does the Form of Vitamin B12 Matter?
Don’t Forget About Vitamin B12
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