Q: I’ve heard that taking cod liver oil can add both vitamin D and omega-3 fats to my diet. Is there any risk to taking it?
A: Cod liver oil does provide both vitamin D and the omega-3 fats known as EPA and DHA, which may help promote several aspects of health. However, cod liver oil contains ten times more vitamin A than vitamin D. Both of these vitamins are fat soluble, and our body stores them in our tissues. Vitamin A is important for health, including vision and our immune system, yet excessive amounts are linked with decreased immune function, liver damage and increased tendency for weakened bones (including risk of spontaneous bone fractures, occurring even without a fall). Older adults seem especially vulnerable to excess vitamin A, apparently because it takes more time to clear the vitamin from the body. Vegetables, fruits and other plant foods that supply beta-carotene and other carotenoids that the body can use to form vitamin A do not pose this risk. The current recommendations for total intake from food and supplements are equivalent to about 2000 to 3000 IU vitamin A. Official standards identify total vitamin A (that’s not counting beta-carotene and other carotenoids) intake from food and supplements as safe up to 10,000 IU per day. One teaspoon of cod liver oil might supply 4500 IU of vitamin A that, with other dietary sources, could put someone well beyond recommended levels. Unless your doctor specifically recommends such high levels of vitamin A for you, if you want to supplement vitamin D and omega-3 fat, other sources may pose less risk of excess vitamin A.