For every 100 grams of tuna there is about 4-5 grams of creatine which is a semi-significant amount, though there are certainly other foods which contain more that you will want to explore. There are many different benefits to a creatine-rich diet, including the fact that it helps with building muscle. This is why you will likely find creatine as an active ingredient in many muscle-building supplement products that are on the market today. Because creatine is able to rebuild ATP which is the chemical that powers your muscles, it can definitely help with bulking up if that is indeed a goal of yours.
Another benefit of getting a significant amount of creatine in your diet is the fact that it helps in storing glycogen which your muscles need in order to start the anabolic process. You need a sufficient glycogen level in order to effectively build muscle over time because it helps the muscles to heal after a workout when they are being fatigued.
Creatine is also found in red meat such as steak. Those who consider themselves to be vegetarians can definitely benefit from taking creatine supplements on a regular basis. If you are trying to build more muscle and are working out regularly, it would be a good idea to either eat more creatine-rich foods or even to take supplements in pill form in order to get what your body and muscles need.