Main article: Latitude studies in cancer
A variety of studies have suggested that vitamin D protects against cancer. This seemingly intuitive proposition is supported by neither epidemiological nor molecular evidence. In fact, the very opposite is true. This article reviews why this body of research is most likely incorrect – or at the very least, much more complicated than articles in the popular media would have a person believe.
According to the Marshall Pathogenesis, alteration of vitamin D metabolism by a pathogenic microbiota prevents any benefit from vitamin D supplementation.
Main article: Latitude studies in cancer
Main article: Vitamin D and cancer
A number of studies have suggested that sunlight exposure, and the resulting cutaneous synthesis of vitamin D, might have a beneficial influence for certain major cancers, most notably breast, colorectal and prostate cancer. These studies have been based either on using ambient solar UV radiation as a proxy for latitude in those studies looking at the geographical incidence and/or mortality of cancer, or case–control studies using questionnaires in which individuals are asked to recall previous sun exposure. However, this data is not consistent. There are any number of counterexamples in which there is an “inverse latitude gradient.”
While some randomized controlled trials have suggested that consuming vitamin D reduces rates of cancer, larger and more carefully controlled studies show no such effect. Lappe et al published work, conducted over four years, that seemingly showed vitamin D might lower the incidence of colorectal cancer.1) The study had participants take 1,100 IU’s of vitamin D over the course of four years, a time that corresponds to the period when the short-term immunosuppressive effects of the steroid would be at its strongest.
Lappe opted to discard the data of subjects who developed cancer during the first year of the study. The rationale was that cancers during the first year would have been present but undiagnosed at entry. Of the 50 people who developed cancer during the four-year study, 13 were removed based on this premise, and only 37 cases of cancer were actually analyzed. But the 13 people who developed cancer during the first year were likely to be the study participants with the highest loads of the Th1 pathogens. They would have been the people to suffer the most from the negative impact of elevated 25-D on the immune system. If data from the 13 participants would have been included in the study, the results would have undoubtedly reflected much less of a “benefit” from vitamin D. Even the researchers admit that “their conclusion was strengthened by both the observational, substantial improvement in risk reduction when cancers occurring early in the trial were excluded.”
Another problem with Lappe's study is that it did not randomize participants on the basis of the stated primary outcome of the paper.2) As far as epidemiological research goes, this is a no-no, and is the equivalent of “moving the goalposts.” Nor did it report losses to follow-up for each intervention group separately
In a similar study looking at a larger cohort and over a longer period of time, Chlebowski et al. found no such effect.3)
In our study we found absolutely no indication of an effect of calcium or vitamin D [on cancer] — zero. And that’s over a seven-year period. It was a much larger study and a much longer study.
Jacques Rossouw, MD, National Institutes of Health ABC News
A second study by the Women’s Health Initiative found no reduction in risk of breast cancer among postmenopausal women supplementing with 1000 mg calcium and 440 IUs of vitamin D.4) Researchers at the American Cancer Society conducted a study on 68,567 postmenopausal women and found that “neither use of supplemental calcium nor vitamin D intake was associated with [breast cancer] risk.”5) And researchers at the Northern California Cancer Center found no association between dietary vitamin D intake during adolescence and subsequent breast cancer risk.6)
A 2011 systematic review of prospective studies assessing the association of vitamin D intake with the risk of colorectal cancer that vitamin D intake increased risk of colorectal cancer,7) thus directly contradicting Lappe's study.
Cohort studies are no more likely to show a long-term positive effect of vitamin D intake, The Iowa Women's Health study showed vitamin D intake seemed to protect against breast cancer in the first five years after it was taken. However, the effect began to reverse between years five and ten and was completely lost after year ten, trending towards an opposing effect.8)
Longitudinal studies (those lasting decades) examining the relationship between long-term intake of vitamin D and incidence of cancer are lacking. Those that have measured incidence of various other diseases, including atopy, allergic rhinitis, and brain lesions, have found that vitamin D intake increases the rate of these diseases. There is no reason to think cancer would be substantially different.
Related article: Diseases associated with low levels of 25-D
A number of vitamin D studies point to low levels of the inactive metabolite, 25-D, as playing a causative role in the incidence of cancer. Large, well-controlled studies have not been able to verify this claim.
A recent study by the National Cancer Institute - the first study to look at the relationship between measured vitamin D in the blood and subsequent total cancer deaths - failed to show an association between baseline vitamin D status and overall cancer risk in men, women, non-Hispanic whites, non-Hispanic blacks, Mexican Americans, and in persons younger than 70 or 70 years or older.9) The study analyzed data from 16,818 subjects.
When asked by a correspondent from CBS News if vitamin D can reduce the risk of cancer, said the following:
I don’t believe vitamin D is the answer. I wish it was as simple as saying ‘If you take vitamin D, cancer will be cured. I don’t think it’s that simple.
David Fishman, M.D, Head of the National Ovarian Cancer Early Detection Program at New York University
An underreported body of research shows that levels of 25-D sufficiently high enough to suggest heavy supplementation are consistent with higher rates of cancer. Stolzenberg-Solomon et al tracked a cohort of men over the course of 16 years for pancreatic cancer.10) They found that over this time period, high 25-D levels greater than 26 ng/ml were associated with a three-fold increased risk for the cancer. It is noteworthy that according to molecular modeling research, 26 ng/ml is near the range when 25-D significantly shuts off the Vitamin D Receptor, particularly when it is already partially blocked by bacterial proteins.
Contrary to expectations, subjects with higher prediagnostic vitamin D status had an increased pancreatic cancer risk compared with those with lower status…. Our results are intriguing and may provide clues that further the understanding of the etiology of this highly fatal cancer.
Rachael Stolzenberg-Solomon, et al. 11)
Researchers at the Chinese Academy of Medical Sciences in China found a similar association between excessive vitamin D intake and esophageal and gastric cancers in men. Male subjects with levels of 25-D in the range of 48.7 ng/ml (which once again suggests heavy supplementation) were much more likely to develop one of the two forms of cancer.12) A 2011 case control study found that those in the highest 25% of vitamin D intake compared to those in the lowest 25% were significantly more likely to develop oesophageal adenocarcinoma.13)
The following research by Freedman DM, Looker AC, Abnet CC, Linet MS, Graubard BI remains unpublished
Abstract Vitamin D has been hypothesized to protect against cancer. We followed 16,819 participants in NHANES III from 1988 through 2006, expanding upon an earlier NHANES III study (1988-2000). Using Cox proportional hazard regression models, we examined risk related to baseline serum 25-hydroxyvitamin D (25(OH)D) for total cancer mortality, in both sexes, and by racial/ethnic groups, as well as for site-specific cancers. Because serum was collected in the south in cooler months and the north in warmer months, we examined associations by collection season (“summer/higher latitude” and “winter/lower latitude”). We identified 884 cancer deaths during 225,212 person-years. Overall cancer mortality risks were unrelated to baseline 25(OH)D status in both season/latitude groups, and in non-Hispanic whites, non-Hispanic blacks, and Mexican-Americans. In men, risks were elevated at higher levels (e.g., for ≥100 nmol/L, RR= 1.85 (95% CI=1.02-3.35) compared to <37.5 nmol/L).
One Norway-based study surveyed over 50,000 participants for their intake of dietary vitamin D and then compared those results to their later risk of cutaneous malignant melanoma. The researchers found that female subjects who consumed cod liver oil, which is high in vitamin D, were significantly more likely to later be diagnosed with melanoma.14)
A 2010 study showed that multivitamin use may be correlated with increased risk of breast cancer.15) In 1997, 35,329 Swedish cancer-free women completed a self-administered questionnaire that solicited information on multivitamin use as well as other breast cancer risk factors. During a mean follow-up of 9.5 years, 974 women were diagnosed with incident breast cancer.
I have avoided the sun since severe sunburn at age 10. Cancer was found in my left breast some time before MP was available. It was controlled by surgery followed by radiotherapy and Tamoxifen.
I first had lumpectomy, followed by complete breast removal and removal of some lymph nodes, because the cancer was beginning to spread into the lymph system.
While on MP, a “pre-cancerous” patch on my left arm changed and I was referred to a dermatologist for surgery, but he preferred to watch and wait as the possible cancer was on an arm with lymphoedema.
I am glad he took pictures, as the possible cancer continued to change and then disappeared entirely.
Good old MP, when followed as precisely as I was doing at that time.Sallie Q
Clinical Utility of Measurement of Vitamin D-Binding Protein and Calculation of Bioavailable Vitamin D in Assessment of Vitamin D Status 16)