I think it is pretty safe to say it is the supplements. Most tests I have been getting are coming back fine as it relates to cardio health. I actually came across a study online that was done back in 2004 (I think) that reported on some negative side effects people got from using arginine alpha-ketoglutarate, the main arginine source that is used in most NO products. It is hard to find the darn thing now. I have taken NO products over the last few years, so I think maybe these things aren't the best thing for you long-term. I know some will say it is good to lower blood pressure, but I think they can mess with your heart. Believe me, I love to take supplements that work, but if they are causing palpatations and arrythmias (sp?) is it worth it?
So what is good to take for someone that wants to build as much size and strength as possible and still be safe? I guess MRPs, protein, creatine, glutamine (if it even does anything), aminos, EFAs, vitamins. Anything else?