Mark,

Thanks for your suggestions and comments.

I take 2000 IU of vitamin D3 per day. I also take a multivitamin with (among other vitamins) the following daily dose of B's:

B1 25 mg
B2 50 mg
B3 25 mg
B5 25 mg
B6 25 mg
B12 1000 mcg
Folic acid 800 mcg
Biotin (is this a B?) 25 mcg

I've also been taking a fairly high dose of a high-quality fish oil daily (about 4 - 5 g). I've been eating reasonably well overall I think.