Liver

One of the most nutrient-dense foods on the earth is liver, particularly cow's liver. It is packed with fat-soluble vitamins, such as vitamin A, which is difficult to get in other parts of the diet.

In addition to being the greatest natural source of vitamin A, liver is also a rich supply of highly absorbable iron, which helps avoid miscarriage and maternal anemia, and vitamin B12, which is necessary for the proper synthesis of DNA and red blood cells. Choline, omega-3 fatty acids, and folate are also high in liver. Although you can stick to tradition and make a simple liver and onion dish, if you're not familiar with liver, you might want to try adding it to other meat-based dishes like meatloaf, shepherd's pie, or even meatballs.