Vitamin B12 is part of the vitamin B complex, a series of eight water-soluble vitamins necessary for the human diet. According to the Mayo Clinic, vitamin B12 helps maintain healthy nerve cells and red blood cells and is needed to make DNA. It is also integral to the metabolism, the chemical reactions that sustain life. Vitamin B12 is found most abundantly in animal products. Unless otherwise marked, a serving is worth 3 oz.
Seafood
Breaded and fried clams contain the highest amount of vitamin B12 of all seafood, containing 570 percent of the daily value. Trout contains the next highest amount, but it depends upon the source: wild trout has 90 percent of the daily value, but farmed trout only has 50 percent. Salmon follows with 80 percent of the daily value, while haddock, a marine fish from the North Atlantic, contains 20 percent, and white tuna, 15 percent.
Meat
A slice from the liver of beef contains a superior amount of vitamin B12 to other meat--it is worth 800 percent of a person's daily value. By contrast, the actual meat of beef from a top sirloin, broiled, contains 40 percent. A double patty cheeseburger is worth 30 percent. Roasted ham doesn't contain very much vitamin B12. It only has 10 percent, but half a breast of roasted chicken contains even less at 6 percent.
Dairy Products
A single cup of yogurt is the best source of vitamin B12 from dairy products, although it contains just 25 percent of the daily value. That is followed by a cup of milk at 15 percent and a large egg at 10 percent. However, egg contains a substance called avidin that blocks the absorption of vitamin B12 in the body, which makes it a less-than-adequate source.
Other Sources
You can also take vitamin B12 as a dietary supplement. Much of the daily value is present in one or two capsules and usually exists in the form of cyanocobalamin, which is converted into a more active form in the body. There does not appear to be any difference in the absorption of different forms. However, only about 10 mcg, or micrograms, of a 500 mcg supplement is actually absorbed in healthy people. In addition, many products are fortified with vitamin B12, including breakfast cereals, soy and energy bars.
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