Mackerel is often overlooked in favor of more popular fish like salmon, but it's worthwhile adding this cold-water fish to your diet. It's a protein powerhouse, offering 20 grams of high-quality protein per 3-ounce portion. You'll also get all the vitamin B-12 you need for the day, along with moderate amounts of iron, magnesium and zinc. Try seasoning mackerel with salt, pepper, and a touch of cayenne, then roast until the skin is crispy. Serve it with roasted veggies seasoned with lemon juice, and a bed of quinoa or braised kale on the side.