Fish and seafood

Fish is an excellent source of protein.
Fish usually has less fat and calories than meat.
Just like meat, fish also contains vitamin B12, which is extremely important if you lean towards plant based diet.
Fatty sea fish contains extremely important Omega 3 fat acids which are essential (must be consumed) and they are also good for heart health and prevention of heart disease, heart attacks, strokes, etc.
Sea fish can contain high levels of toxic mercury, so before eating, inform yourself about mercury levels. In general, the smaller the fish, the less mercury. Large sized fish often contain more mercury due to process of bioaccumulation (they eat smaller fish which also contain mercury, and gradually, most mercury is concentrated in fish on the top of the food chain)
Canned sardines are excellent source of Calcium (important if you limit the milk intake), protein, Omega 3, vitamin B12 and Vitamin D, but like any other canned food, they can have trace amounts of Bisphenol A or Phthalates. So maximum intake should be no more than 2-3 cans a week. Otherwise, they are a true nutritional powerhouse, true superfood. They are also extremely low in mercury, which makes them very safe.
Other seafood is also excellent source of protein, vitamins, and other nutrients, but always be careful about possible contaminants.
Sea vegetables are excellent source of Iodine, and the ONLY reliable source. If you don’t eat sea vegetables, you must take iodized salt.