You would think it would be a simple matter to compare the nutrient value and caloric content of two eggs versus tuna packed in water.  The  Star Advertiser  had the  following graphic  from U.S. Agricultural Research Services of the Department of Agriculture that surprised me, but that is because there was a serious flaw: Let me start with tuna: Good source of protein, omega-3 fatty acids and B vitamins. However, can contain  mercury . Most of the mercury come from coal burning. However, volcanic eruptions can also add mercury. Tuna contains more mercury than salmon, oysters, lobster, scallops and tilapia. Mercury is not easily excreted and builds up in tissues over time. Depends on the type of tuna ( in parts per million ): Light canned tuna:  0.126 ( light means a smaller tuna species ) White Albacore tuna:  0.350 Yellowfin tuna, fresh or frozen:  0.354 Bigeye tuna, fresh or frozen:  0.689 Bluefin tuna, fresh or frozen:  0.8 Mercury exposure can lead to impaired motor skills, memory