SOURCES OF VITAMIN D Few foods are naturally vitamin D-rich, so fortified dairy and cereal products are often your best bet. The Institute of Medicine suggests 400 International Units, or IUs, a day for adults, but some experts believe 800 IUs or more a day may be beneficial. Food IUs per serving % of daily value Cod liver oil (1 tablespoon) 1,360 340 Salmon (3.5 oz., cooked) 360 90 Mackerel (3.5 oz., cooked) 345 86 Sardines (1.75 oz., canned in oil, drained) 250 63 Tuna fish (3 oz., canned in oil) 200 50 Milk (1 cup vitamin D fortified) 98 25 Margarine (1 tablespoon fortified) 60 15 Egg (1 whole) 20 6 Liver, beef (3.5 oz. cooked) 15 4 Swiss cheese (1 oz.) 12 3 Source: National Institutes of Health, Office of Dietary Supplements