In addition to being a vitamin B12 rich food, beef is also a good source of protein, zinc, and heme-iron. The amount of vitamin B-12 in beef depends on the cut, lean fat-trimmed chuck contains the most vitamin B12 with 6.18μg (103% RDA) per 100g serving, 11.49μg (103% RDA) in a chuck steak, and 5.25μg (88% RDA) in a 3 ounce serving. Chuck is followed by sirloin (62% RDA), rib-eye (60% RDA), and ribs (58% RDA).