Vitamins A and D Work Synergistically in Cod Liver Oil
Chris Masterjohn, PhD and the Weston A. Price Foundation (WAPF) report that vitamins A and D work together synergistically and one helps offset risk of overdose of the other, and they claim that taking high doses of D3 without corresponding levels of vitamin A and K2 is a mistake.
Dr. John J. Cannell of the Vitamin D Council has expressed concerns about retinol (animal-sourced vitamin A), linking it to risk of cancer and vitamin D deficiency, to which Chris Masterjohn and Stephan Guyenet responded. So far I find Masterjohn and Guyenet's points and evidence more persuasive. If Cannell is right then eating retinol-rich liver would be unhealthy. This just doesn't make sense to me when we consider that most or all land predators, including traditional human hunters, preferentially eat liver and other organs without developing high rates of cancer or vitamin D deficiency. The evidence that Cannell cites seems to be more reductionist in comparison to the evidence that Masterjohn and Guyenet cite.
See:
The Cod Liver Oil Debate by Chris Masterjohn, 2009-Apr-30, http://www.westonaprice.org/The-Cod-Liver-Oil-Debate.html
Is Vitamin A Toxicity a Concern? by Stephan Guyenet, Monday, November 17, 2008, http://wholehealthsource.blogspot.com/2008/11/is-vitamin-toxicity-concern.html
Dr. John J. Cannell of the Vitamin D Council has expressed concerns about retinol (animal-sourced vitamin A), linking it to risk of cancer and vitamin D deficiency, to which Chris Masterjohn and Stephan Guyenet responded. So far I find Masterjohn and Guyenet's points and evidence more persuasive. If Cannell is right then eating retinol-rich liver would be unhealthy. This just doesn't make sense to me when we consider that most or all land predators, including traditional human hunters, preferentially eat liver and other organs without developing high rates of cancer or vitamin D deficiency. The evidence that Cannell cites seems to be more reductionist in comparison to the evidence that Masterjohn and Guyenet cite.
See:
The Cod Liver Oil Debate by Chris Masterjohn, 2009-Apr-30, http://www.westonaprice.org/The-Cod-Liver-Oil-Debate.html
Is Vitamin A Toxicity a Concern? by Stephan Guyenet, Monday, November 17, 2008, http://wholehealthsource.blogspot.com/2008/11/is-vitamin-toxicity-concern.html