In November of 2008, Dr. Cannell of the Vitamin D Council published a commentary in the journal Annals of Otology, Rhinology & Laryngology attacking cod liver oil because of its high vitamin A content, claiming that vitamin A intakes above the most minimal levels would increase mortality rates, increase vulnerability to infections, cause osteoporosis, and antagonize the beneficial effects of vitamin D. Sixteen scientists signed on to the paper as co-authors. In response, Wise Traditions published my article “The Cod Liver Oil Debate,” in the Spring of 2009, which defended cod liver oil as an important and balanced source of the fat-soluble vitamins and essential fatty acids. The following November, I expanded on this article in my lecture, “Cod Liver Oil: Our Number One Superfood” at the Foundation’s annual conference.
We were not the only ones who responded.
In January 2010, Michael F. Hollick, MD PhD, a vitamin D researcher whose work I have cited in previous articles, Linda Linday, a medical doctor whose cod liver oil study formed the starting point for Cannell’s 2008 commentary, and several other colleagues, even including one researcher from the NIH, made a direct response to Dr. Cannell and his colleaugues in the pages of the same journal. What’s more, they even credited the Weston A. Price Foundation for raising concern about the balance between vitamins A and D!
“Cod liver oil,” they wrote, “available without a prescription for hundreds of years, is a valuable source of vitamins A and D, as well as long-chain omega-3 fatty acids, all of which may be important in the prevention of respiratory tract illnesses in children. In many populations around the world, cod liver oil continues to be a valuable source of these important nutrients. The across-the-board dismissal of cod liver oil as a supplement advocated by [Cannell and colleagues] ignores this reality.”
The authors pointed out that in Dr. Linday’s randomized, controlled trials, cod liver oil supplementation cut doctor’s visits for upper respiratory infections between one-third and one-half. Cannell’s paper called this “less than robust,” but most of us would consider such a reduction meaningful, especially if it could mean we could get sick half as often by taking cod liver oil! The authors, moreover, argued that retinol from animal foods is a more reliable source of vitamin A than carotenes from plant foods since there is such wide variation in people’s ability to convert carotenes to vitamin A – an argument that has crossed the pages of Wise Traditions many times in the past.
But now to the exciting part.
The authors devoted a section of their paper to the ideal ratio of vitamin A to D. “In the responses to [Cannell and colleagues] from the on-line supplement and nutrition newsletter communities,” they wrote, “the issue of the proper ratio of vitamin A to vitamin D emerged as a major concern.” They gave three references, including one to the Weston A. Price Foundation’s “Cod Liver Oil Update” from December, 2008.
In fact, the importance of balance between vitamins A and D was raised in the pages of Wise Traditions even earlier than 2008. In the spring of 2006, I raised the issue in my article “Vitamin A on Trial: Does Vitamin A Cause Osteoporosis?” when I argued that vitamin A only contributes to osteoporosis when vitamin D levels are deficient or when the ratio of vitamin A to D is massively out of balance. The following fall, I raised the issue again in my article “From Seafood to Sunshine: A New Understanding of Vitamin D Toxicity” where I presented research showing that vitamin A protects against vitamin D toxicity and introduced the possibility that vitamins A, D, and K may be cooperative factors that should all be consumed in proper balance. I more fully developed this concept in my spring 2007 article on vitamin K2, “On the Trail of the Elusive X-Factor: A Sixty-Two-Year-Old Mystery Finally Solved.”
As a result of this research, in December of 2007 I published a hypothesis on the molecular mechanism of vitamin D toxicity in the journal Medical Hypotheses entitled “Vitamin D toxicity redefined: vitamin K and the molecular mechanism,” that emphasized interactions between vitamins A, D, and K. The following year, researchers from Tufts University published a paper in the Journal of Nutrition supporting this hypothesis, showing that vitamin A protects against vitamin D toxicity in part by helping to properly regulate the production of vitamin K-dependent proteins.
One question I have never been able to answer in any of these articles is the one everyone wants an answer to: what, precisely, is the proper ratio of vitamins A and D?
Dr. Linday and her colleagues offer a suggestion: poultry studies suggest optimal A-to-D ratios between four and eight. Similarly, in her own studies showing cod liver oil protects against upper respiratory tract infections, Linday supplied her patients with A-to-D ratios between five and eight.
They also point out that rat studies showing that vitamin A is toxic and antagonizes the effects of vitamin D used much higher ratios, ranging from 5,000 to 55,000!
It is refreshing to see a powerful defense of cod liver oil in the scientific literature, and especially refreshing to see the work of the Weston A. Price Foundation cited therein.
We owe a big thank you to Dr. Linda Linday (MD) of St. Luke’s-Roosevelt Hospital Center in NY, NY, Dr. John C. Umhau (MD, MPH) of the NIH in Bethesda, MD, Richard D. Shindledecker of New York Downtown Hospital in NY, NY, Dr. Jay N. Dolitsky (MD) of the New York Eye and Ear Infirmary in NY, NY and Michael F. Holick (PhD, MD) of Boston University Medical Center in Boston, MA.
Read more about the author, Chris Masterjohn, PhD, here.