See also: Further Questions on Vitamin A
Many people have asked me or the Weston A. Price Foundation to respond to a recent newsletter put out by Dr. John Cannell, MD, of The Vitamin D Council claiming that cod liver oil and vitamin A supplements are “poison” and that our country’s “problem is widespread subclinical vitamin A toxicity.” The Mother Nature Obeyed blog is the perfect place to respond.
I would like to start out by saying that I respect Dr. Cannell’s efforts to raise awareness about the need for greater exposure to sunshine and vitamin D supplementation when adequate sunshine is unavailable, and that this post is not in any way a personal attack against Dr. Cannell or his work. Disagreement in science is the stone on which the knife of truth is sharpened, so in that sense Dr. Cannell and I are partners in cutting through the obscurity, uncertainty, and falsehood that lies in the way of achieving robust and radiant health.
Researchers are increasingly examining the interactions between vitamins A and D. The most recent study to do this was a January, 2010 study published in the British Medical Journal looking at the relationship between blood levels of vitamin D and the risk of colorectal cancer. The study was nested within the massive EPIC study, containing over a half a million subjects, but the vitamin D study itself contained just under 2,500 subjects. They found 1248 people within the original, large study who developed colorectal cancer after enrollment and matched them to an equal number of people from the same study who did not develop colorectal cancer during the same period of time. Then they compared dietary information and blood levels of vitamin D between the two groups, taken back when the subjects were first enrolled.
Don’t Forget the Scientific Method!
Before we consider the results of the study, let’s review a few basic principles of the scientific method. When we approach science, we first observe the world around us. When we come across an interesting observation in need of an explanation, we formulate a testable hypothesis as a potential explanation. We then perform an experiment to test the hypothesis. The results of the experiment allow us to confirm, discard, or revise the hypothesis.
Studies published in nutrition and medical journals generally fall into one of two categories: observational and experimental studies. Observational studies in these cases are usually looking at existing statistical relationships between different variables. In our particular case, we are looking at the statistical relationship between blood levels of vitamin D and the risk of colon cancer, so this is an observational study. Experimental studies also use statistics in most cases, but their key feature is that the investigators involved perform some intervention in humans, animals, isolated cells, or purified biological molecules. They will randomly distribute the study subjects or study materials into two or more groups, at least one of which is not treated with the intervention and therefore serves as the control.
According to the scientific method, the first category of studies is useful for generating hypotheses, but not for determining whether those hypotheses are true. The second group of studies, by contrast, allows us to confirm, discard, or revise the hypotheses generated by the first group.
Most modern studies test the effect of an intervention on a statistical endpoint. The researchers aim to use the treatment to increase or decrease the likelihood of a particular result. According to the laws of statistics, we can only infer whether one thing causes another if we randomly distribute study subjects into treatment and control groups. If we performed an experiment with vitamin D supplementation and then allowed people to pick whether they wanted to be in the vitamin D group or the control group, a statistician would tell us we would have to treat the study as an observation instead of a true experiment. If we found that the vitamin D group had a lower risk of cancer, the statistician would tell us that we had no basis for claiming that the vitamin D caused the lower risk of cancer. After all, in this hypothetical example, what caused some people to want to take vitamin D and others not to want to take it? We have no idea, but whatever those factors were could have also caused the reduction in cancer.
When we perform observational studies like the one published in the British Medical Journal, we try to make statistical adjustments for all of those unknown factors – we call them “confounding variables” – but the truth is that there will always be much more we don’t know about the world than we do know, so we never treat these studies as controlled experiments. After all, is there any way to statistically adjust for whatever psychological trait put someone in the mood to go out in the sun more often and go for walks, fly kites, go hiking, do cartwheels out in the park, go swimming, or do whatever else these people were doing outside in order to obtain higher vitamin D levels? Of course not.
Vitamin D May Reduce the Risk of Colorectal Cancer
So, back to the results of the study. Among those study subjects who developed colorectal cancer, there were more subjects with low vitamin D levels at the beginning of the study and fewer subjects with high vitamin D levels at the beginning of the study than there were among those who did not develop colorectal cancer. The authors used statistical calculations to estimate that subjects with 25(OH)D levels above 40 ng/mL were 23% less likely to develop colorectal cancer and those with levels between 20 and 30 ng/mL, and that those with levels below 10 ng/mL (extremely deficient) were 32 percent more likely to develop colorectal cancer.
Does Vitamin A Antagonize Vitamin D?
So where does vitamin A come in? Vitamin D status seemed to be related to the risk of colorectal cancer only in people consuming very low amounts of vitamin A.
The researchers split people into three groups according to vitamin A intake: those who consumed less than 1500 IU/day, those who consumed more than 3000 IU/day, and those who consumed some amount in between those two values. To put this in perspective, the RDA for vitamin A is 3000 IU/day for men and 2300 IU/day for women. In those consuming less than 3000 IU of vitamin A per day, low vitamin D status was associated with an increased risk of cancer and high vitamin D status was associated with a decreased risk of cancer. In those consuming more than 3000 IU of vitamin A per day, however, the magnitude of these relationships became so small that they lost statistical significance, which means the effect of vitamin D status was so small that it could not be distinguished from the effect of chance.
Naturally, opponents of vitamin A supplementation like Dr. Cannell have seized on the fact that high vitamin D status was not associated with the benefit of a decreased risk of colorectal cancer in those consuming the RDA for vitamin A. They have, however, ignored the fact that low vitamin D status was not associated with the harm of an increased risk in the same population. And thus they claim without any true justification that vitamin A intakes at or above the RDA render vitamin D useless and that vitamin A-rich cod liver oil constitutes “poison.”
Of course, it is a far leap from “vitamin A” to “cod liver oil” in this case because there is no indication where the vitamin A came from in this study. Perhaps some subjects took cod liver oil and others took multivitamins or drank fortified milk and ate fortified breakfast cereals. The vitamin A in natural foods, including cod liver oil, could act differently than the vitamin A added to fortified foods and to supplements.
It is most important, however, that we recognize the proper place of this and similar studies within the scientific method. As observational studies, they offer us the chance to formulate a hypothesis, but they do not “prove,” “show,” or “demonstrate” that the hypothesis is true.
The authors of the of BMJ study themselves recognized these limitations. “The strong inverse associations of the present [observational] study,” they wrote, “suggest that further research efforts should concentrate less on observational findings and more on clinically relevant studies to determine whether vitamin D has a causal role in colorectal cancer prevention or whether it is a marker of other events.” Similarly, noting that the relationship between vitamin D status and colorectal cancer was more statistically robust for 25(OH)D levels under 75 nmol/l (30 ng/mL), the authors wrote, “This finding suggests that raising very low levels of 25(OH)D to the mid-range may protect against colorectal cancer, and that levels of 75 nmol/l might not significantly reduce the cancer risks any further, but this needs to be proven in a clinical trial.”
Some people, Dr. Cannell for example, have looked at observational studies like this and offered the hypothesis that vitamin A antagonizes vitamin D and that most people in modern society consume too much of it. I have offered an alternative hypothesis. In my articles “From Seafood to Sunshine: A New Understanding of vitamin D Safety,” and “The Cod Liver Oil Debate,” I have argued that vitamins A and D act as molecular partners and that it is important to consume a diet rich in both vitamins in order to make each safe and effective. I also incorporated this view into my peer-reviewed hypothesis paper, “Vitamin D Toxicity Redefined: Vitamin K and the Molecular Mechanism,” a hypothesis that was partly confirmed in an animal study conducted by researchers at Tufts University, which I wrote about over at The Daily Lipid.
In The Face of Scientific Uncertainty, We Should Defer to Traditional Diets
To settle these opposing hypotheses, someone needs to conduct a study where humans are given vitamin D supplements or a placebo on a vitamin A-restricted diet, combined with several levels of vitamin A supplementation. As discussed earlier, the researchers would have to randomly distribute the participants to the different treatment groups.
In the mean time, there is some uncertainty over this question. We can look at other observational studies, but we should realize when we do this that we are only lumping observation on top of observation. This might help us fine-tune our hypothesis but it does nothing to help us test it. When we get to the point where we are trying to estimate vitamin A intakes in studies where they are not recorded, we are lumping speculation on top of observation and it does even less to help us test the hypothesis.
In the absence of certainty, I prefer to follow the maxim after which this blog is named: that “life in its fullness is Mother Nature obeyed.” We know that traditional diets developed over thousands of years by groups all over the world that had successfully fine-tuned nutritional strategies that allowed them to pass radiant health from generation to generation consumed diets rich in foods like liver, other organ meats, cream and butter, shellfish, or insects, that provided a rich assembly of fat-soluble nutrients that included plenty of vitamin A. We will continue to learn more about nutrition as science progresses, but we should have a better foundation than a handful of unexplained statistical correlations on which to act in the face of uncertainty. In such cases, it makes the most sense to defer to the wisdom of traditional diets.
Read more about the author, Chris Masterjohn, PhD, here.
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I have a bit of anecdotal evidence to add. I started taking about 1/2 tsp of high vitamin Blue Ice cod liver oil about four years ago and over two years noticed a reduction in colds from 3 or 4 a year (all of my adult life) to 1 or 2 a year. Then about two years ago I doubled my dose to 1 tsp per day. I went over a year with no colds, which is unprecedented for me. I finally caught a very mild cold that lasted only four days last September and that is the only respiratory illness I have had in two years now! I’m sticking with the Blue Ice fermented cod liver oil that I’m taking now 🙂
In the past, I have had issues with the palms of my hands beimncog orange. I was told by a medical professional that this has to do with hypothyroidism, and my inability to convert beta carotene into vitamin A. My palms have been a normal color for some time now, that is, until about two months ago when I incorporated High Vitamin A Cod Liver and Butter Oil, organ meats, raw egg yolks, fish eggs, and raw goat butter into my diet. I checked my supplements and found no listings for vitamin a or beta carotene, but do find that 7 of the mineral capsules I take daily have about 17,000 iu’s of Mixed Carotenoids, if that means anything. My hands were normal while taking the supplement at this dose previous to the dietary changes I mentioned.I’m wondering what your wisdom is on this and if I should cut back on the amount of vitamin A that I am ingesting through foods. Any insight is much appreciated!
I no longer trust Cannell’s ‘research’ or his interpretation of studies. I, and many others I’ve met on forums, have adverse reactions to Vit D3, even the lower amounts of 2,000 IU/day and even though we were tested and were deficient. And we do not have the conditions that would make Vit D contraindicated.
Many of us have written to Cannell to tell him this and suggest he study this, but he blows us off and seems to be an over-zealous advocate of D who seems very biased and uninterested in any study or info that might show the downside of Vit D.
I’m waiting for the long-term effects to take place in people taking these higher amounts which are not simultaneously increasing their Vit A and K levels. In 10 years I wager we will be hearing about the negative effects that the higher doses of this ‘miracle nutrient’ have had on those taking it.
An excellent summary of the scientific method. My wish would be for every schoolchild to learn it.
This is misleading, because vitamin A toxicity is mainly caused by synthetic sources, or by eating something ridiculous like the liver of a polar bear. If one were to swallow a hundred or so vitamin A tablets then certainly toxicity may occur, but you could say that of a lot of other vitamins and minerals too. Moderation is the key.
“but a deficient vitamin D status only increased the risk of colorectal cancer half as much”, half as much compared to what? to the lower Vit A group? if so, would that be proof that Lower Vit A is worse then higher? I think elaboration here would help a lot of people.
Thanks.
I agree the font size is exceedingly small for us old farts that like to read at WAPF. Maybe even some young farts might be havnig trouble! To be honest, I highly dislike the new web site in total. The colors are awful, the print too small and it’s difficult to find anything. I wish there were some way to be notified when new items appear on any given subject. You know, like a reminder sent to my email telling me that a new article, or blog, has been posted. Is that possible? I have tried using the subscribe dealie below, but that never seems to happen.Also, when I take my Vit D3 caps I take them with a small spoon of homemade, raw butter. I can’t take the CLO anymore. Just can’t get it down no matter how good it is for me. I also tried the CLO caps, but I burped them day and night. That was just beyond tolerable. I take Full Spectrum K (Nutricology) and am still looking for ways to improve my intake of Vitamin A. Spinach, butter, egg yolks (no liver, please) anything else I could be doing?Thanks.D.
I had bookmarked [url]http://trusted.md/blog/vreni_gurd/2009/01/18/the_cod_liver_oil_controversy[/url] by Vreni Gurd on this subject a while back since it made sense to me at the time.
There’s a lot there complimentary to WAPF’s view, but I thought this was the key nugget:
[quote]The problem is that in the modern cleaning and processing of cod liver oil, the vitamins are frequently removed, and then synthetic vitamins are added back in, and not in the same ratios that were naturally in the oil to begin with. Cod liver oil is frequently being turned into a supplement rather than the food it originally was. So often one sees ratios of vitamin A to D of 100:1, which is crazy high in vitamin A with respect to D. [/quote]
Just a thought for folks when shopping for cod liver oil. Vreni has some suggestions in her post.
I revised the paragraph under the heading, “Does Vitamin A Antagonize Vitamin D?” to make it clearer and more reader-friendly. The revision now takes up three paragraphs.
Yes, we should be all too familiar with the problems associated with interpreting results stemming from observational/epidemiological studies as being of a causative/correlative nature (refering to our good friend T. Colin Campbell here or course!!!). As Gary Taubes and many have pointed out before, it is imperative that the scientific method be applied properly before drawing any conclusions; thanks for this review Chris! There seems to be no doubt anymore as to the importance of vitamin D and sunshine. But more research is quite evidently needed to understand the role of and relation between vitamin A and D and, quite possibly, other fat-soluble vitamins.
Have to go with Panda here. The answer here is pbaorbly not, but is a reason why a history of cancer generally removes you from transplant list, except maybe for corneas. The body would likely recognize the other person’s cancer cells appropriately and kill them- those cells would not have the under the radar benefit from the immune system that cancer cells which started in your own body would have. Still, I believe no one would want to prove this theory wrong .Blessings
A little confused. In those with low vitamin A intake, high vitamin D was associated with lowered risk, while those with higher intake of vitamin A, the risk difference wasn’t significant between low and high vitamin D levels. Is that right? But what was the risk in those with high levels of vitamin D and a low intake of vitamin A compared to high vitamin D and high vitamin A?
I guess what I am asking is that, keeping vitamin D levels high, how was lower and higher vitamin A intake correlated with risk?
The data seem to be consistent with Cannell’s theory that although retinoic acid and calcitriol activate the same nuclear receptors to promote differentiation, calcitriol’s activation is somehow more robust.
In particular, at low levels of vitamin D, higher intakes of retinol seem protective. However, at moderate levels of vitamin D, the effect doesn’t exist and at high levels of vitamin D, higher intakes of retinol seem to thwart the protective effect.
I hear you on the small sample size and overall nature of the study.
I believe vit D levels are low because people are full of metals and chemcicals, which stress the liver and reduce digestion/metabolism of these nutrients, in addition to low fat diets. This would make an interesting study. Check levels of vit D and A before and after detox.
I recently read a comment by Dr. Cannell in which he arrogantly dismissed his readers concerns about the known link between vaccinations and autism. To hear him tell it, Vitamin D alone is the answer to nearly all maladies, just keep your blinders on and look neither left nor right. It is disappointing to see this myopic attitude because, like WAPF, I value scientific truth, and I believe Dr. Cannell, early on, began his search unfettered by what now appears to be a blinding ego.
Not quite.Cancer is our own DNA and so theoretically if soomene elses cancer cells were placed in soomene elses body via an organ or bone transplant . . the body would reject those cancer cells as being foreign’ objects. This already happens with many types of donor patients . . the risk of graft vs host disease or total transplant rejection is high unless the patient and donor are a biological match’. Thus . . it is possible if you have a very closely related donor match that cancer could be passed much the same way a transplanted organ is accepted into the body. But this is so, so rare . . that only a handful have ever been identified as happening.So . . the risk is slim to none.
My work in fertility has lead to information regarding retinol, vitamin D, and K2 and their unique role in some areas. My findings led me to WAPF when I found this unique organization that promoted unrefined foods high in the fat soluble nutrients- the same thing I was recommending to my couples. For instance, in thin PCOS, we see a unique genetic expression in WNT paths, like beta-catenin, and HAPLN1(Kenigsberg, 2009). Beta-catenin is tied to the androgen complex and we see these women have hyperandrogenism, without the insulin resistance we see in overweight PCOS women. Instead these heavy PCOS women are positive for the FTO gene,( Kenigsberg, 2009), and vitamin D also helps these women with insulin/glucose metabolism.
The thin PCOS genetic expression of beta-catenin and HAPLN1 is similar to those susceptible to colon and prostate cancers and male pattern baldness. Vitamin D and retinol cross regulate these beta-catenin glitches, and it appears K2 cross regulates HAPLN1. It is theorized this is the reason we see a decrease in colon cancer in those that have higher vitamin D levels.
I, too, wonder about the discrepancy with retinol, as it appears in some studies to prevent spread of colon cancer and to assist in cross regulating those with certain genetic expressions. Yes, we need more studies on cod liver oil and retinols!
Darcy
Wonderful information, I just wish I could read the fine print on the new and improved website without eye strain and headache
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Dear Dr. John Cannell,Our family oposteath Dr. Beals-Becker has been treating my son with autism since he was about 2 & he is now 9. He has shown GREAT strides .He keeps up with grade level & for the most part does great. But, he still does have HUGE melt downs once he gets home (very occasional) a few melt downs have landed us in the ER due to him screaming himself into having chest pains. He takes 10,000 IU of vitamin D per day every morning He started at 1,000, then moved to 2,000 & then 5,000 & then just upped to 10,000.(over the 7 years of treatment) So, the question is Dr. Beals-Becker wanted me to contact you & ask you Dr. Cannell if this amount is enough or if we should up it again .Or should we split it into 2 5,000 doses. He does have some difficulty sleeping so we weren’t sure about a later dose of vitamin D.THANK YOU for your time.Stacy Forsyth
Mercola had a little blip that beta carotene wasn’t the antagonist, but retinol. I don’t know if what you have written here is just a fancier version of saying that….but I didn’t see it.
Taking a prenatal vitamin and hearing that there are things that might be warring with each other in there makes me think that some of the vitamins should be separated for the body’s morning/evening use.
D is recommended for my toddler – I like sunshine just fine but we live too far north in the winter for that (not to mention too close to the lake for actual sunshine to get through!)
Maybe carrots and yard work are healthier for you than supplements? 😉
This a test comment on the Vitamin A article.
Hi,
This site might not be appropriate for my question but here goes.
Does anybody have a recipe to make fermented Cod Liver Oil?
Thanks,
Ron M.
Responses to all comments follow.
Ron, I do not have such a recipe, but if anyone else does they are welcome to post it here.
Michele, retinol is not an antagonist of vitamin D. Depending on what function you are looking at, you may observe antagonism, additive effects, or synergy. For example one human study in the 1940s found that both were needed together to afford protection from the common cold (synergy) but each only exhibited toxicity in the absence of the other (antagonism). At the molecular level, however, they may primarily cooperate by acting as partners. The studies done with the actual receptors suggest that vitamin A is needed to activate a partner of the vitamin D receptor and allow vitamin D to carry out its function. There is still a lot of work to be done, however, to translate how things work in the test tubes to how they work in the human body, so no one can declare with total confidence exactly how they interact. Beta-carotene is poorly converted to retinol in many people, and insofar as it is not converted, it does not have any vitamin A activity. So Mercola is correct in that sense. There is no evidence to my knowledge that in humans and other “yellow fat animals” (animals that do not have 100% conversion of absorbed carotene) that absorption and conversion is dependent on “need” so the downside of beta-carotene having no “antagonistic” effects of vitamin A is that it doesn’t have any of the other biological activity of vitamin A either, without first being converted.
Susan, thanks! Yes the web site is much better in certain respects but a lot of people feel font or other issues are a little more difficult. God willing over time it will be perfect!
Darcy, great work! Sounds like the experimental evidence is positive for retinol?
Joan, there is rarely one single answer to anything.
Janice, those might play a role but people also avoid the sun and don’t eat foods rich in vitamin D. That would be an interesting study though.
Dan, calcitriol and retinoic acid do not activate the same nuclear receptors. Calcitriol activates the vitamin D receptor (VDR) and retinoic acid activates the retinoic acid receptors (RARs). I don’t think you can conclude that high vitamin A is associated with a lower risk at low vitamin D levels from that study. See my comments on my supplementary blog post: http://www.westonaprice.org/blog/CMASTERJO/further-questions-on-vitamin-a.html.html They do not report confidence intervals for individual cells using the low-A/low-D cell as a reference, and they do not report the confidence intervals adjusted for making cell-to-cell comparisons, but from looking at the table I think it’s safe to assume that none of the cell-to-cell comparisons would be statistically significant if we properly adjusted the confidence intervals. Of course, as you note, the small size and power of the study is what prevents us from making such comparisons.
Jim, see my supplementary blog post: http://www.westonaprice.org/blog/CMASTERJO/further-questions-on-vitamin-a.html.html
Eric, thanks! Good points!
Beth, I’m not sure that applies to the vitamin A being consumed by the people in this study but it is a good point.
Rabbi, I hope my revision clarified this. If anything is still unclear, please let me know.
Robert, what is misleading?
Sizzlechest, thanks!
Cynthia, yes I do think that we will start to see some adverse effects of very high vitamin D intakes without other fat-soluble vitamins in the coming years.
Bryan, thanks for your anecdote! There was a study in the 1940s that found A and D synergistically lower the risk of colds. 🙂
Thanks everyone!
Can you make the font bigger on this site? I look at hundreds of sites and it is onlg this iste that has a text size so small as be be almost half as big as all other sites! I can’t read much here because of this.
Beth, good points, thank you!
Rabbi Hirsch, please see “further questions on vitamin A” if you haven’t read it already.
Robert, are you saying my blog is misleading or the BMJ study?
Sizzlechest, thanks, my wish too!
Cynthia, I worry about these effects to. I look forward to settling at a point where Cannell, WAPF, Mercola, and others can work towards the same goal, as we share large amounts of ground despite this issue and we are all interested in the betterment of everyone’s health, even if our hypotheses might blind us sometimes.
Bryan, just like the cold-prevention CLO studies of old!
Thanks for your comments everyone!
testing is good, but not absolutely nssaceery if you can’t afford it. Just take an average of 5000 IU per day and you’ll be fine. I got my levels up from severely deficient to 60 ng/ml (ideal range) doing that in about a year. I was tested through through my health insurance, but if you can’t be tested, just take the 5k and don’t worry about it. There are zero reports of toxicity at that level, ever.
I agree – the font size is exceedingly small for us old farts that like to read at WAPF. Maybe even some young farts might be having trouble! To be honest, I highly dislike the new web site in total. The colors are awful, the print too small and it’s difficult to find anything. I wish there were some way to be notified when new items appear on any given subject. You know, like a reminder sent to my email telling me that a new article, or blog, has been posted. Is that possible? I have tried using the “subscribe” dealie below, but that never seems to happen.
Also, when I take my Vit D3 caps I take them with a small spoon of homemade, raw butter. I can’t take the CLO anymore. Just can’t get it down no matter how good it is for me. I also tried the CLO caps, but I burped them day and night. That was just beyond tolerable. I take Full Spectrum K (Nutricology) and am still looking for ways to improve my intake of Vitamin A. Spinach, butter, egg yolks (no liver, please)…anything else I could be doing?
Thanks.
D.
D and Jodi, I agree the font size is too small. I’ll see what I can do about that.
D, if you exclude organ meats and CLO you will have to rely more on plant foods and hope you are a good converter. Red palm oil, and basically any fruits and vegetables with red, orange, or green colors in them.
Chris
Also, D, I believe what you want to do is use the “feed” button in the upper right to subscribe. Let me know if that doesn’t work.
Chris
My work in fertility has lead to ionrfmation regarding retinol, vitamin D, and K2 and their unique role in some areas. My findings led me to WAPF when I found this unique organization that promoted unrefined foods high in the fat soluble nutrients- the same thing I was recommending to my couples. For instance, in thin PCOS, we see a unique genetic expression in WNT paths, like beta-catenin, and HAPLN1(Kenigsberg, 2009). Beta-catenin is tied to the androgen complex and we see these women have hyperandrogenism, without the insulin resistance we see in overweight PCOS women. Instead these heavy PCOS women are positive for the FTO gene,( Kenigsberg, 2009), and vitamin D also helps these women with insulin/glucose metabolism. The thin PCOS genetic expression of beta-catenin and HAPLN1 is similar to those susceptible to colon and prostate cancers and male pattern baldness. Vitamin D and retinol cross regulate these beta-catenin glitches, and it appears K2 cross regulates HAPLN1. It is theorized this is the reason we see a decrease in colon cancer in those that have higher vitamin D levels.I, too, wonder about the discrepancy with retinol, as it appears in some studies to prevent spread of colon cancer and to assist in cross regulating those with certain genetic expressions. Yes, we need more studies on cod liver oil and retinols!Darcy
I also think that moderation is the key. Moderation and variety are both important in maintaining good health.
Responses to all comments foollw.Ron, I do not have such a recipe, but if anyone else does they are welcome to post it here.Michele, retinol is not an antagonist of vitamin D. Depending on what function you are looking at, you may observe antagonism, additive effects, or synergy. For example one human study in the 1940s found that both were needed together to afford protection from the common cold (synergy) but each only exhibited toxicity in the absence of the other (antagonism). At the molecular level, however, they may primarily cooperate by acting as partners. The studies done with the actual receptors suggest that vitamin A is needed to activate a partner of the vitamin D receptor and allow vitamin D to carry out its function. There is still a lot of work to be done, however, to translate how things work in the test tubes to how they work in the human body, so no one can declare with total confidence exactly how they interact. Beta-carotene is poorly converted to retinol in many people, and insofar as it is not converted, it does not have any vitamin A activity. So Mercola is correct in that sense. There is no evidence to my knowledge that in humans and other yellow fat animals (animals that do not have 100% conversion of absorbed carotene) that absorption and conversion is dependent on need so the downside of beta-carotene having no antagonistic effects of vitamin A is that it doesn’t have any of the other biological activity of vitamin A either, without first being converted.Susan, thanks! Yes the web site is much better in certain respects but a lot of people feel font or other issues are a little more difficult. God willing over time it will be perfect!Darcy, great work! Sounds like the experimental evidence is positive for retinol?Joan, there is rarely one single answer to anything.Janice, those might play a role but people also avoid the sun and don’t eat foods rich in vitamin D. That would be an interesting study though.Dan, calcitriol and retinoic acid do not activate the same nuclear receptors. Calcitriol activates the vitamin D receptor (VDR) and retinoic acid activates the retinoic acid receptors (RARs). I don’t think you can conclude that high vitamin A is associated with a lower risk at low vitamin D levels from that study. See my comments on my supplementary blog post: They do not report confidence intervals for individual cells using the low-A/low-D cell as a reference, and they do not report the confidence intervals adjusted for making cell-to-cell comparisons, but from looking at the table I think it’s safe to assume that none of the cell-to-cell comparisons would be statistically significant if we properly adjusted the confidence intervals. Of course, as you note, the small size and power of the study is what prevents us from making such comparisons.Jim, see my supplementary blog post: Eric, thanks! Good points!Beth, I’m not sure that applies to the vitamin A being consumed by the people in this study but it is a good point.Rabbi, I hope my revision clarified this. If anything is still unclear, please let me know.Robert, what is misleading?Sizzlechest, thanks!Cynthia, yes I do think that we will start to see some adverse effects of very high vitamin D intakes without other fat-soluble vitamins in the coming years.Bryan, thanks for your anecdote! There was a study in the 1940s that found A and D synergistically lower the risk of colds. Thanks everyone!
In the past, I have had issues with the palms of my hands becoming orange. I was told by a medical professional that this has to do with hypothyroidism, and my inability to convert beta carotene into vitamin A. My palms have been a normal color for some time now, that is, until about two months ago when I incorporated High Vitamin A Cod Liver and Butter Oil, organ meats, raw egg yolks, fish eggs, and raw goat butter into my diet. I checked my supplements and found no listings for vitamin a or beta carotene, but do find that 7 of the mineral capsules I take daily have about 17,000 iu’s of Mixed Carotenoids, if that means anything. My hands were normal while taking the supplement at this dose previous to the dietary changes I mentioned.
I’m wondering what your wisdom is on this and if I should cut back on the amount of vitamin A that I am ingesting through foods. Any insight is much appreciated!
I agree, many thanks to the author. Thanks for taking the time to share this,Great blog post. Thanks..
Hi
these links don’t seem to work
“From Seafood to Sunshine: A New Understanding of vitamin D Safety,” and “The Cod Liver Oil Debate,”
thanks
Vitamin D also occurs in foods. Taking an oirangc source is not toxic. Make sure you know where you get it and it is safe and needed. There are blood tests to monitor your levels. Taking as little as 5000 or as much as 50,000 over weeks or months will increase your levels. Depending on the research you read, more than 30 or 50 is the desired blood level.
This comment is in response to:
“Adverse reaction to Vit D” by Cynthia, 10 Mar 2010
Hi Cynthia.
Increasing the amount of vitamin D in the body increases the body’s need for magnesium (it is needed to metabolize the D). Upon increasing bodily levels of D, if one is in a magnesium deficient state, symptoms of that deficiency can manifest. The problem here [b]is not[/b] vitamin D but the underlying mag deficiency.
I believe Cannell’s Vitamin D Council site does make mention of this on their homepage.
In an already magnesium-starved population (mag deficiency is epidemic), this can be quite common. Interesting thing is, there has been incidence of this even when the D was received as a result of sunlight exposure only. The individual was severely magnesium deficient.
All one needs to do is stop the D, increase total body (cellular) magnesium levels, then resume the D.
Magnesium is so vital to life, this should be done anyway.
Very interesting to read all of this. It makes sense that vit A toxicity only comes from synthetic sources. It worries me though that Dr Mercola is really pushing the vit A toxicity, even with quality cod liver oil.
There is now a trend to avoid all vitamin A rich foods saying that there is a toxicity from vitamin A added to foods. I am skeptical because it is either isolated A that is added or synthetic.