I have decided to become a pescitarian, and I'm wondering if by only eating fish I will need to supplement any nutrients that might be missing from my diet without the other types of meat.
closed as off topic by Nathan Wheeler♦ Sep 20 '12 at 19:34
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It does depend on the fish and the cut of land meat you are comparing it to. If you were to compare tilapia with beef you'll find the macro-nutrients being very compatible. Fish is lower in cholesterol, and some types of fatty fish have a good amount of Omega-3s. Grass fed beef also has a good amount of Omega-3s in comparison to the Omega-6s, as opposed to corn/grain fed beef.
That said, the place where you are going to see the most difference is in the micro-nutrients. Both types of meat have complete amino acid profiles, so that isn't a concern. The vitamins and nutrients you'll get will be a bit different, but the biggest thing you want to keep an eye on is iron. However, different fish have different profiles. Tilapia is probably one of the cheapest and lowest quality fish, and a different kind will have more iron.
That said, if you typically supplement with a multi-vitamin, you will be fine. As to pork and chicken, both of those are typically more sensitive to the way they are fed as to their nutritional profile. The problem is all the difference is in the fat, and both of those types of meat can had high fat to meat content (referring to dark meat chicken here). Typically, animals fed a more natural diet have better nutritional profile. This is a primary reason why fish is mostly better for you than land animals--unless it is farmed (like many salmon) the fish are caught after eating naturally.