Is Vitamin A, a Vitamin D Antagonist?
There has been fear-mongering going on the Internet for the last couple of years concerning a rumor that relatively low amounts of vitamin A in the animal retinol form effectively blocks vitamin D from preventing cancer.
By listening to all the second and third hand information, being pass around, one could easily erroneously conclude that retinol is some kind of a toxin that will give everyone colon cancer.
Nevertheless, from our research this rumor is far from being true. The problem turns out to be exactly what we had thought it was all along. Vitamin A competes with vitamin D for absorption into body when taken at the same time. While perhaps a too simplistic an explanation, as a practical rule of thumb, this is all the information that anybody really needs to know. Do NOT take your vitamin D, along with vitamin A at the same time.
This anti-vitamin A / retinol fear mongering campaign was first started by John Cannell, MD on the Vitamin D Council Web site in his post entitled Newsletter: Vitamin D, vitamin A, and cancer that was published in January 2010.
It is all a matter of interpretation, who you believe, or who presents the best argument.
Dr. Cannell claims to be quibbling over "one sentence and a small table [in one research study], which [according to him] shows that the benefits of vitamin D are almost entirely negated in those with the highest vitamin A intake."
However, Dr. Cannell concludes his post by saying: "Avoid cod liver oil like the poison it is and check your multivitamins." Have you noticed that he is bashing cod liver oil throughout his entire post, more than vitamin A? The Natural Health Perspective certainly has.
Cod liver oil as THE vitamin D confounder
Does Dr. Cannell have any reason to be picking a fight with vitamin A? He certainly has. While Dr. Cannell has produced some fantastic videos on vitamin D, he is also selling his own proprietary formulation of vitamin D, at quite a hefty price tag.
Furthermore, Dr. Cannell refuses to get extremely specific about this "one sentence and a small table" that he is quibbling about by citing copyright law, which is not true at all. The doctrine of fair use would allow him to quote verbatim small sections of a published research study. College students, for example, do this all the time in their class assignment papers. The practice of correctly citing the work of others is quite accepted in academic circles. In addition, vitamin D researchers and advocates know about vitamin D, but little else.
In fact, Cannell first started ranting about cod liver oil being a vitamin D confounder in his "Cod Liver Oil, Vitamin A Toxicity, Frequent Respiratory Infections, and the Vitamin D Deficiency Epidemic" research paper that was published in the November, 2008 issue of the Journal of Otology, Rhinology, & Laryngology. Again even though he was the lead author of this study, he refuses to disclose any of the specifics.
In the above video, Dr. John Cannell talks about the vitamin D U-shape mortality curve that has been exhibited only in Scandinavia populations, like Finland. In a U-shape mortality curve both the extremes of deficiency and excess increases your risk of death. In addition, Cannell claims that no health benefit exists for maintaining vitamin D blood levels higher than 40 ng/mL (100 nmol/L), which position differs radically from other sites like GrassrootsHealth.net which recommends blood levels in the range of 40 to 60ng/mL (100-150 nmol/L). Further, Cannell is claiming that a cod liver oil confounder is what accounts for the undesirable vitamin D U-shape mortality curve that has been exhibited only in these Scandinavia population studies. In other words, Dr. John Cannell is speculating that vitamin A is causing the problem. However, since both cod liver oil and cold water cod fish, also, contain Omega-3 EFAs, I could just as easily speculate that Omega-3s could be the true confounder.
Vitamin A is retinol. Neither beta-carotene, nor cod liver oil is vitamin A. They are entirely different things. Throwing these terms around as if they were synonymous is just being reckless. Further, while Cannell talks about a cod liver oil confounder he is really referring to the consumption of huge amounts of cod fish.
As Dr. Cannell may or not know, the notion that vitamin A should be consumed in beta-carotene form because it always is converted by the body into just the right amount of retinol is simply NOT true. Many people are non or low-responders to the conversion of beta-carotene into retinol for a variety of different reasons. Furthermore, the older that you get the more likely you are to be a low-responder.
Retinol simply does not hang around in your liver doing nothing. On the contrary, it is use in your intestines and all your other mucus physical barriers, for example. Vitamin A, or retinol, is an important part of your immune system. Retinol can be used to cure some lung conditions. As important as vitamin D is, without sufficient blood levels of retinol you could easily end up dying from a serious contagious disease. If you want to prevent death from pneumonia then maintaining minimum levels of retinol is very important. Who could forget that Brittany Murphy, an American actress, died from undiagnosed pneumonia at age 32 in 2009?
However, the Natural Health Perspective concurs with the points made by Dr. Cannell in his above post on research studies that used test subjects from Finland and his main point that cod liver oil is a marker for the real problem.
What is wrong with cod liver oil? First, one teaspoon of cod liver oil contains approximately 5,000 IU of retinol and 400 IU of vitamin D-3. This means that you will very likely over do your vitamin A needs trying to supplement with cod liver oil in order to get more "D". Secondly, these two vitamins exist together. Thus, cod liver oil countries like Finland, Dr. Cannell reasons, got way too much vitamin A from their consumption of cod fish. In fact, these Fins obviously got much more retinol than Cannell's often cited 3,000 IU a day figure. The test subjects in the Finland studies did not supplement with cod liver oil. They simply ate huge amounts of fish.
In conclusion: the Natural Health Perspective has determined that the so-called vitamin A problem does not exist outside of Scandinavia populations that eat huge amounts of fish. People in Finland simply accumulate excessive vitamin A in their bodies, much like how polar bears do, from eating too much fish. Dr. John Cannell's cod liver oil vitamin D U-shape mortality curve confounding problem, is really caused by a cod fish consumption confounder.
Furthermore, Omega-3 EFAs could be the confounder. People who supplement with excessive amounts of fish oil could quite possibly be negating the anti-cancer effects of vitamin D. Both cod liver oil and cold water cod fish contain Omega-3 EFAs, after all.
We recommend accordingly a number of different things.
- Do not supplement with cod liver oil, even if it is fermented, in order to increase your vitamin D levels. But, if you do then you should consider it as an alternative source for just vitamin A, at approximately 5,000 IU per teaspoon.
- Do not supplement with combinations of vitamin A and D.
- Do not take a multi-vitamin because they are likely to contain retinol and synthetic beta-carotene.
- Do not supplement with beta-carotene. Meet your carotene needs from your diet.
- Do not supplement with vitamin A or retinol on a daily basis. Rather, you should be taking your retinol just once a week.
- Do NOT overdo your retinol supplementation. It really does not take that much vitamin A. 8,000 to 10,000 IU of retinol twice a week is all a person needs, even if they are currently eating a horrible diet. Watch out for supplements on the market with too much retinol per dose, such as 25,000 IU.
- Keep your vitamin D blood levels high.
In light of Dr. Cannell's comments, if the Natural Health Perspective were to change any of its recommendations, it would be as follows.
- Try meeting your retinol needs on just one day of the week.
- People confident that they are meeting their beta-carotene needs from their diet could try cutting their supplementation of retinol in half to just 8,000 to 10,000 IU, once a week.
Advanced level followers of the Natural Health Perspective should try supplementing with just retinol on one day of the week, while supplementing with vitamin D on the other six days of the week.
Here again, until you take a blood test all that you are really doing is speculating. Expensive blood tests are the only way to definitively find out how well your body is producing retinol from your diet.