Vitamin D is a hot topic among nutritionists and physicians. Once thought to be primarily useful for preventing weak bones and diseases such as rickets, vitamin D is now being considered as having a potential benefit in reducing cancer risks, lowering blood pressure and preventing diabetes, although these claims have not been conclusively proven in clinical trials. Cod liver oil, used extensively in the United States to prevent rickets in children up until the 1950s, contains large amounts of vitamin D but also contains large amounts of vitamin A, which could be harmful.
Recommended Vitamin D Doses
The Food and Nutrition Board raised the daily recommended intake of vitamin D to 600 International Units for people aged 1 through 70 and to 800 IU for those over age 70 in 2010. The tolerable upper intake limit for vitamin D is 4,000 IU for those over age 9, 3,000 IU for children ages 4 to 8 and 2,500 IU for children ages 1 to 3. The tolerable upper limit for infants is 1,500 IU for babies 7 to 12 months and 1,000 IU for those under 6 months. An 800 mg dose of vitamin D is within the tolerable upper limit, but if you're obtaining you vitamin D from cod liver oil, this dose may supply too much vitamin A. Always ask your doctor before taking the maximum dose of vitamin D, especially if you're using cod liver oil.
Tolerable Upper Intake of Vitamin A
Vitamin A can cause birth defects, liver damage, bone and joint pain and skin problems. The tolerable upper intake for vitamin A is 10,000 IU for adults over age 19; 9,333 IU in children 14 to 18; 3,000 IU for those aged 4 to 8 and 2,000 IU for those younger than 4 years old.
Cod Liver Oil Vitamin Doses
One tbsp. of cod liver oil contains 1,360 IU of vitamin D. If you're taking 800 mg of vitamin D per day, which is above the RDA but within the tolerable upper intake, you need to take 58 percent of 1 tbsp. Since 1 tbsp. equals 3 tsp, 58 percent of 1 tbsp would equal 1.74 tsp. One tsp. of cod liver oil contains 4,500 IU of vitamin A. A dose of 1.5 tsp would supply approximately 7,830 IU of vitamin A, a dose that would greatly exceed the tolerable upper limit for children under age 8. Since milk has vitamin A added and foods such as butter, eggs, fortified cereals and some vegetables also contain vitamin A, you could exceed your tolerable upper intake level if you consumed a regular multivitamin and ate foods high in vitamin A even as an adult.
Considerations
Most physicians today would not consider 800 IU of vitamin D to be too much to take. However, the amount of vitamin A in cod liver oil does concern many physicians. The amount of cod liver oil you would need to take to get 800 IU of vitamin D would supply a possibly toxic amount of vitamin A for some ages and come very close to the maximum dose even for adults. John Jacob Cannell, M.D. of the Vitamin D Council cautions against using cod liver oil as a source of vitamin D, stating that the high doses of vitamin A could be harmful and could also act against vitamin D.
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