Tuna salad and raw tuna are two of my favorite foods. Canned tuna is really cheap and I am currently on a tight budget. I want to understand what would be a non threatening way I can spend majority of my food budget on tuna.
Worried about tuna giving you mercury poisoning? Here's the exact study that caused this concern. It's recommendations are much higher than that of the FDA and online calculators: http://www.atsdr.cdc.gov/toxprofiles/tp46.pdf
Pages 24-25 of the report states:
No consumption advice is necessary for the top ten seafood species that make up about 80% of the seafood sold in the United States: canned tuna, shrimp, pollock, salmon, cod, catfish, clams, flatfish, crabs, and scallops. The methylmercury in these species is generally less than 0.2 ppm, and few people eat more than the suggested weekly limit of fish (i.e., 2.2 pounds).
They also showed that a person can chronically (for >365 days) ingest .0003mg per kg of bodyweight of mercury per day with no adverse effect (pages 509 and Appendix 10).
Thus, someone who weights 80kg (176lb) could thus safely ingest 0.024mg of mercury a day. Given that tuna is about .2ppm (parts per million) mercury, that equates to 120g tuna per day. Note that this is not the maximum safe amount but merely the highest they tested, so the maximum safe level is not known.
In terms of grams per bodyweight, it changes per person. A 150lb person can safely consume 3.75oz of tuna per day, whereas a 210lb person can consume over 5oz per day.
TL;DR You can safely eat 1.5g/kg (0.7g per lb) of bodyweight in canned tuna per day.
Note: USE MODERATION WHEN EATING ANYTHING