I really want a legitimate answer on this too. I can’t give you any recommendations, but I’ll tell you a little about my experience with tuna…
When my local grocery store has tuna steaks on sale, I try to stock up. I think tuna is a great option for a leaner, healthier meal that’s packed with protein. The cholesterol content isn’t the greatest, and I’m not very familiar with the mercury levels. I’ll eat one 4 ounce tuna steak maybe once a week on average, but more often if I’m lifting harder. This is just anecdotal, but I swear by tuna steaks when I’m breaking through plateaus! I don’t know what it is about tuna, but for me it just works great as a lean, filling, recovery meal (along with steamed veggies). Something else to consider, cholesterol can be converted into testosterone in the body. I have no idea how much is actually converted, and we need to find out how much of the cholesterol in tuna is HDL and LDL, respectively. This is obviously more of a benefit for men as their bodies produce more testosterone in general. Testosterone, as we know, is the “holy grail” of muscle building.
I like to consult LIVESTRONG for issues like this. I just pulled it up on their website, and what do ya know!… They say tuna is great. I like to view LIVESTRONG as an unbiased and reliable source for a number of different things. They also address the mercury content in this article. It’s worth the read, and it has links to tuna steak recipes.
In regards to canned tuna, or packaged tuna, or chunk light tuna in oil… I’m NOT a fan. I go for raw tuna steaks that have not been seasoned, just packaged. Even with frozen tuna steaks, the packaging companies alert the consumer to the fact that they packaged the tuna with a small amount of carbon monoxide to retain color. (kind of like a preservative) I doubt that by the time you cook it this carbon monoxide has any real consequences on health.
For more information on mercury levels and an explanation, go to wikipedia. Contrary to popular belief, Wikipedia is actually 99% reliable on most topics.
http://en.wikipedia.org/wiki/Tuna (scroll down to mercury levels).
Here is another page on tuna steaks… This is from about.com. The info you get on about is generally correct, but can be biased. This article does a good job of breaking down the nutritional information a little more in depth, though not much.
I’ve got a link, not sure of the reliability, that discusses cholesterol associated with tuna and salmon consumption
http://www.whfoods.com/genpage.php?tname=foodspice&dbid=112 (scroll down to cardiovascular health)
I hope this helps. I’m interested to hear some other opinions. You should consider consulting a registered dietitian for a definite answer.