Vitamin B12 plays an important role in the creation and maintenance of all the cells in the human body, including sperm cells and the replication of DNA. As such, it has long been argued that a Vitamin B12 shot can help to increase sperm counts and thus increase men’s fertility rate. Unlike some of the claims made about the possible benefits of Vitamin B12, this one has been tested extensively and there is some clinical evidence supporting the proposition. Much of this evidence weak and inconclusive, therefore many medical professionals do not consider Vitamin B12 a viable treatment for low sperm counts. Nevertheless, since there is little risk of problems stemming from taking supplemental Vitamin B12, many fertility experts to recommend men with low sperm counts take large doses of supplementary Vitamin B12.
There have been a number of studies exploring the relationship between Vitamin B12 shots and sperm counts since the 1970s. It has been conclusively shown that men suffering from a Vitamin B12 deficiency have lowered sperm counts and that taking supplementary Vitamin B12 in large doses corrects this problem. However the results are more mixed when it comes to men that are not deficient but still have low sperm counts. A Japanese study, conducted in 1982 but published in 1984, is representative of the common results. Men with low sperm counts were given very large daily doses of Vitamin B12 (1,500 micrograms) to see what the effect was. The result was that about 42 percent of the subjects showed improvement, 42 percent were unchanged, and the remainder actually got worse. Most other studies have also come up with these very debatable results, so the nutrient’s effectiveness is questionable.
Nevertheless, the fertility experts and nutritionists also have a valid point: in most cases, there is very little risk of negative side effects of taking large doses of supplementary Vitamin B12. Further, since around half of the men in most fertility studies did benefit from taking large doses of the vitamin, there seems a good likelihood that it will help many men, with very little likelihood of problems. So the “there is nothing to lose by trying” perspective is perfectly valid in this instance.