The fascinating practical piece of information for you and I, is how scientists just discovered that critical nutrients are needed for healthy telomeres. In cell studies, researchers found dysfunctional short and long telomeres more frequently in cells with insufficient folate and thus, reduced methylation. In this particular study, the lack of folate damaged the telomere cap; they were frayed and 'beat up' leaving an open door to the chromosomal material. Now remember, without healthy telomeres, your DNA gets damaged. Before leaving folate, and moving on to B12, I want to make one more comment. Folate is the natural form of the B vitamin you think of when you hear "folic acid." But folate and "folic acid" are not exactly the same. The folate form is critical for methylation.
Human studies have confirmed that vitamin B12 is also required for healthy telomeres. A recent study published in the European Journal of Nutrition studied telomeres from 60 elderly people. They compared supplement intake with vitamin B6, B12, folate, calcium, and vitamin D versus just vitamin D and calcium. Then they measured homocysteine levels. After a year, they found that individuals who had elevated homocysteine and reduced B vitamin intake, had reduced methylation and shorter telomeres. This group was literally aging faster.
And it is interesting that rapidly dividing cells to require a lot of folate.