A recent one talks about how "pre-formed Vitamin A" (retinol as opposed to beta-carotene) neutralizes much of the benefit of Vitamin D; he refers to cod liver oil as "poison" due to its high(?) amount of vitamin A.
Here's a part of a much longer email (ask if anyone wants me to forward the whole thing off-list):
Let"s look at Dr. Pamela Goodwin"s study from the University of Toronto that studied breast cancer survival. This a very different study as it looked at vitamin D levels obtained after the diagnosis of breast cancer and subsequent survival in 535 Toronto women between 1989 and 1996. Vitamin D levels ranged from 3 ng/ml to 70 ng/ml. The women with the lowest levels were about twice as likely to die and to suffer distant cancer recurrence compared those with the highest levels. Ten year survival was 85% for those in the upper one-third of vitamin D levels compared to 74% in the lower one-third. However, the data suggested a U shaped curve for the women with levels above 40 ng/ml, that is, a higher risk of dying, but it was not statistically significant.an>
Goodwin PJ et al. Prognostic effects of 25-hydroxyvitamin D levels in early breast cancer. J Clin Oncol. 2009 Aug 10;27(23):3757-63.
Again, let"s ask where women would get levels above 40 ng/ml in Toronto between 1989 and 1996? Sunshine? We know the answer is no as the authors found no season
al variation in 25(OH)D levels in the 535 women, even in the women with the highest levels. So where did blood levels of 40-70 ng/ml come from in the early 1990s? Vitamin D supplements were not widely available in the early 1990s, and only contained meaningless doses when available. As sunshine was ruled out, they could only have gotten it from cod liver oil. I have emailed Dr. Pamela Goodwin, lead author, asking how hard it would be to see if cod liver oil use was asked about in the dietary questionnaire and if she could control for cod liver oil intake. She did find retinol intake was associated with higher vitamin D levels but I am particularly interested in cod liver oil intake in women with vitamin D levels above 40 ng/ml.
It's not just in breast cancer that vitamin D levels appear to have a treatment effect; it's in lung, prostate and colon cancer as well. Again, these are studies of people diagnosed with cancer to see if high vitamin D levels at the time of diagnosis are associated with improved survival.; that is, do high vitamin D levels have a treatment effect? On average, those with the highest vitamin D levels at time of diagnosis lived 2 or 3 times longer. One has to ask how high vitamin D levels are associated with greatly improved survival once you get cancer but a higher risk of getting cancer in the first place. That requires some gymnastic thinking and acrobatic basic scie
Zhou W et al. Circulating 25-hydroxyvitamin D levels predict survival in early-stage non-small-cell lung cancer patients. J Clin Oncol. 2007 Feb 10;25(5):479-85.
Ng K et al. Clin Oncol. 2008 Jun 20;26(18):2984-91. Circulating 25-hydroxyvitamin D levels and survival in patients with colorectal cancer. J Clin Oncol. 2008 Jun 20;26(18):2984-91.
Tretli S et al. Association between serum 25(OH)D and death from prostate cancer. Br J Cancer. 2009 Feb 10;100(3):450-4.
Remember, studies of vitamin D levels and subsequent risk of cancer are only one type of epidemiological study. Studies of latitude and cancer are quite clear, the less sunshine the higher the cancer risk. Studies of dietary vitamin D intake and cancer are also mostly supportive but such studies are limited by the tiny doses people get in their diets.
So it is not just autistic children that are being harmed by vitamin A. Avoid cod liver oil like the poison it is and check your multivitamins. Life Extension Foundation just reformulated their multivitamin to contain only 500
IU of preformed retinol. And, I am happy to report that Purity Products, which markets my vitamin D, has no preformed retinol at all in any of their multivitamins, only beta carotene. Purity has also stopped selling cod liver oil. Now, if only Carlson, Solgar, Nature's Way, and other companies would stop selling cod liver oil and stop selling their concentrated vitamin A supplements to a country whose problem is widespread sub-clinical vitamin A toxicity, I'd be a happier agitator.
I'm really puzzled by this, as my understanding from decades back had been that some people (myself included, I was told, and also many people from certain genetic backgrounds, e.g. coastal) do not utilize beta-carotene very well, and require adequate amounts of retinol, e.g. from fish oil, for various things including proper functioning of the thyroid gland. For me, occasional doses of fish oil vitamin A (e.g. cod liver oil) were *hugely* helpful, so I find it very difficult to think of it as "poison." So aside from the good ol' "individualization" thing, can anyone shed light on this for me?