High levels of homocysteine are associated with increased risks for a number of illnesses. Hyperhomocysteinemia is a risk factor far osteoporosis, Alzheimer’s disease, Parkinson’s disease, stroke, cardiovascular disease, cancer, aortic aneurysm, hypothyroidism and end renal stage disease among other illnesses. I would add schizophrenia and bipolar disorder.
I have been arguing that high homocysteine levels point to the transsulfuration pathway being dysregulated. That there are so many illnesses associated with high homocysteine combined with the ineffectiveness of folic acid in reducing risk ratios for various illnesses point to high homocysteine levels being a proxy for other dysregulated biological processes. I have been arguing than high homocysteine levels are associated with increased risks for epigenetic dysregulations.
Folic acid supplementation, which reduces homocysteine levels, does not decrease risk ratios for the various illnesses that high homocysteine levels are associated with, for example, cardiovascular illnesses. Folic acid is ineffective as homocysteine must be metabolized through the transsulfuration pathway. Increasing remethylation of homocysteine to L-methionine does not fix the transsulfuration pathway leaving folic acid ineffective in decreasing risk ratios for various illnesses. Very unfortunately increasing levels of L-cysteine through supplementation with N-acetyl-L-cysteine, cysteine, cystine or lipoic acid also does not work where such supplementation can be very dangerous.