Ames and Wallock suspect that the non-methyl folate fraction of seminal fluid is likely to be important for sperm integrity, possibly to prevent defective repair of DNA and consequent chromosome breaks. Ames and his UC Berkeley colleagues proposed in 1997 a mechanism by which folate deficiency could cause chromosome breaks and cancer, based on the fact that when sufficient folate is not available to synthesize DNA, chromosomes can break. This leads to chromosome breaks when DNA is being repaired and subsequent mutations. The findings in the Fertility and Sterility report support this model, the authors claim. Wallock noted that childhood cancer is thought to be due to inheriting one mutant gene from one of the parents, and that most mutations in the fertilized egg come from the sperm.
Some scientists theorize that men pass on mutations to their offspring twice as often as women.
Others also have found associations between male health and the health of their children. Andrew Wyrobek of Lawrence Livermore National Laboratory, for example, has shown that male smokers have more sperm with an abnormal number of chromosomes. These data make more plausible the increasing epidemiological evidence that smoking fathers have more children with childhood cancer, Wallock said. The Ames group is currently investigating the effect of inadequate intake of other vitamins on genetic damage to sperm. Wallock, in particular, plans to look for specific genetic damage in the sperm of men with low folate levels.