I’m concerned about the mercury levels my son might be consuming. He loves seafood and eats salmon most days for lunch at school. Can you eat too much fish? M.V. It’s good that your son likes to eat seafood, because the omega-3 healthy fat content and protein are beneficial for his development. Smaller fish, such as salmon, are less likely to contain high levels of mercury than larger fish, such as swordfish; however, they can contain some mercury. Unborn babies and children up to six years of age are most vulnerable to the toxic effects of mercury. You could introduce other protein sources, such as eggs, tofu or chicken, to his diet for variety.