Biased NHS reporting of Vitamin d/cancer research.
Posted: Sun Dec 02, 2007 7:49 am
Behind the headlines Vitamin D cancer merits questioned
Once again the NHS Knowledge Service displays bias and ignorance regarding Vitamin D.
We see bias and ignorance in the use of the word high in the following sentence.
“it did find that people with high levels of Vitamin D were 72 per cent less likely to die of bowel cancer
The study actually reported those “with levels 80 nmol/L or higher associated with a 72% risk reduction compared with lower than 50 nmol/L,
It is dangerously misleading to imply to the general public that 80nmol/l is a high vitamin d status. You should be aware from The Vitamin D requirement in health and disease Robert P. Heaney that 80nmol/l is the threshold that maximises calcium uptake.
80nmol/l should be the minimum level for the average UK adult.
100nmol/l is the level that maximises the availability of Calcitriol the active metabolite of D3.
130nmol/l is the level associated with the lowest incidence of all cancers.
Vitamin D Appears to Cut Breast and Colorectal Cancer Risk CME
NATURAL levels found in those who live and work in the sun are around 125-175nmol/l (see the Heaney paper link above) so to describe as High a level that is only barely adequate to sustain calcium uptake and is less than half that naturally sustained, displays an unacceptable level of bias and ignorance on your part.
Your bias is again displayed in the use of the word well in the sentence
“The study is a well conducted cohort study, however it has a couple of important limitations..If the purpose of the study was to hide the latitudinal - seasonal differences in Vitamin D status and their impact on cancer incidence, it may have been “well conducted but surely you can see that by measuring the Vitamin D status of those in the North when their status was at it’s summer high and comparing them with the lowest status of those in the south, this was bound to blur the differences between them. We know from the many studies on the impact on prognosis of season of diagnosis/treatment of many cancers that the low vitamin d season produces the worst outcomes. A well conducted trial would have ensured samples from North/South were collected simultaneously. An even better conducted trial would have collected several samples from each participant throughout the year so a more realistic assessment of vitamin D insufficiency status and it’s impact on cancer incidence could have emerged. You repeat the researchers’ assertion “There was no variation in risk when considering the season or latitude that the sample was collected from, but you fail to make the point that this trial was bound to come to this conclusion from the fundamentally flawed way those samples were collected.
You do not query the study authors’ findings that “ no link between 25(OH)D levels and cancer risk, although they found 28 women got breast cancer, 20 in the group with the lowest vitamin D level but only 8 in the highest. What do you think The American Cancer Society would be telling women if the numbers were reversed, if the 20 women who got breast cancer were in the high vitamin D group?
Your own bias is reflected in your inability to see the bias in others.
It occurs again when you report
“some evidence of protection against bowel cancer.Four times as many people died from bowel cancer in the vitamin d insufficient status group, that’s a 72% reduction and you report that as “some evidence of protection. I’d like to see any other substance reporting a 72% reduction in cancer incidence.
We must ask ourselves why the NHS Knowledge Service aren’t willing to see biased reporting even when it is so blatantly obvious.
Once again the NHS Knowledge Service displays bias and ignorance regarding Vitamin D.
We see bias and ignorance in the use of the word high in the following sentence.
“it did find that people with high levels of Vitamin D were 72 per cent less likely to die of bowel cancer
The study actually reported those “with levels 80 nmol/L or higher associated with a 72% risk reduction compared with lower than 50 nmol/L,
It is dangerously misleading to imply to the general public that 80nmol/l is a high vitamin d status. You should be aware from The Vitamin D requirement in health and disease Robert P. Heaney that 80nmol/l is the threshold that maximises calcium uptake.
80nmol/l should be the minimum level for the average UK adult.
100nmol/l is the level that maximises the availability of Calcitriol the active metabolite of D3.
130nmol/l is the level associated with the lowest incidence of all cancers.
Vitamin D Appears to Cut Breast and Colorectal Cancer Risk CME
NATURAL levels found in those who live and work in the sun are around 125-175nmol/l (see the Heaney paper link above) so to describe as High a level that is only barely adequate to sustain calcium uptake and is less than half that naturally sustained, displays an unacceptable level of bias and ignorance on your part.
Your bias is again displayed in the use of the word well in the sentence
“The study is a well conducted cohort study, however it has a couple of important limitations..If the purpose of the study was to hide the latitudinal - seasonal differences in Vitamin D status and their impact on cancer incidence, it may have been “well conducted but surely you can see that by measuring the Vitamin D status of those in the North when their status was at it’s summer high and comparing them with the lowest status of those in the south, this was bound to blur the differences between them. We know from the many studies on the impact on prognosis of season of diagnosis/treatment of many cancers that the low vitamin d season produces the worst outcomes. A well conducted trial would have ensured samples from North/South were collected simultaneously. An even better conducted trial would have collected several samples from each participant throughout the year so a more realistic assessment of vitamin D insufficiency status and it’s impact on cancer incidence could have emerged. You repeat the researchers’ assertion “There was no variation in risk when considering the season or latitude that the sample was collected from, but you fail to make the point that this trial was bound to come to this conclusion from the fundamentally flawed way those samples were collected.
You do not query the study authors’ findings that “ no link between 25(OH)D levels and cancer risk, although they found 28 women got breast cancer, 20 in the group with the lowest vitamin D level but only 8 in the highest. What do you think The American Cancer Society would be telling women if the numbers were reversed, if the 20 women who got breast cancer were in the high vitamin D group?
Your own bias is reflected in your inability to see the bias in others.
It occurs again when you report
“some evidence of protection against bowel cancer.Four times as many people died from bowel cancer in the vitamin d insufficient status group, that’s a 72% reduction and you report that as “some evidence of protection. I’d like to see any other substance reporting a 72% reduction in cancer incidence.
We must ask ourselves why the NHS Knowledge Service aren’t willing to see biased reporting even when it is so blatantly obvious.