Cod liver oil versus fish oil and/or krill oil  

I have been reading up on what is best and I take krill oil, as I feel it is better for us than cod liver oil and even fish oil. Krill oil is basically fish but higher in the good stuff (Omega 3, etc.).

I have been reading recent studies that say that cod liver oil is too high in Vitamin A. Today's cod liver oil contains far less vitamin D than it used to, due to the deodorization process used today which removes much of Vitamin D. Vitamin A is not efficient without Vitamin D and the other way around, too, but if you overdose on Vitamin A or Vitamin D, it can actually kill you, so it is careful to monitor intake of supplements and best to get it where it comes naturally (Vitamin D is from the sun and many foods. Vitamin A from foods.

From Mercola.com is says, "Manufacturers are free to add or subtract as much vitamin A or D as they see fit. In fact cod liver oil was discovered in the sewers of England several hundred years ago by starving children who drank it and scientists noticed they did not get rickets. Cod liver oil is in fact a highly processed food that was never consumed by humans prior to this.

Dr. John Cannell, head of the Vitamin D Council, along with 15 other researchers, recently released an article “Cod Liver Oil, Vitamin A Toxicity, Frequent Respiratory Infections, and the Vitamin D Deficiency Epidemic" in the November issue of Annals of Otology, Rhinology and Laryngology. In this paper Dr. Cannell raised questions about the efficacy of cod liver oil due to its highly variable and frequently excessive amount of vitamin A. Typically modern cod liver oil contains far less vitamin D than it used to, due to the deodorization process used today which removes much of this essential nutrient.

Dr. Cannell and other prominent researchers believe the vitamin A contained in most cod liver oil is excessive, and can reduce the effectiveness of vitamin D by inhibiting the binding of its active form to your DNA, effectively preventing its ability to regulate the expression of your vitamin D-responsive genes.

The Weston Price Foundation, of which I am an advisory member, holds a contradictory view. They believe vitamin D can only effectively target genes when its “partner receptor” is activated by vitamin A. If vitamin A is absent, certain molecules called co-repressors bind to the receptors and prevent vitamin D from functioning. It is their position that cod liver oil is still a highly recommended supplement.

After reviewing the evidence, I am personally convinced that there is sufficient vitamin A in the current American diet to facilitate sufficient vitamin D activation. This does not appear to be the case in third world countries, where cod liver oil, or some other preformed retinol supplement, would still be useful.