Calcium + Vitamin D = placebo in preventing breast cancer (WHI)
Does calcium plus vitamin D prevent breast cancer in postmenopausal women?
Supplementation with calcium and vitamin D was no better than placebo in preventing breast cancer. Although observational studies (ie, lower-quality studies) have reported an association, vitamin D levels had no association with breast cancer risk in this study.
Chlebowski RT, Johnson KC, Kooperberg C, et al. for the Women’s Health Initiative Investigators. Calcium plus Vitamin D supplementation and the risk of breast cancer. J Natl Cancer Inst 2008;100(22):1581-1591.
More than 36,000 postmenopausal women with no prior history of breast cancer were randomly assigned to receive 1000 mg calcium plus 400 IU vitamin D or placebo. Women were allowed to take vitamin D on their own. The women were all part of the Women’s Health Initiatives, a series of randomized controlled trials designed to assess the effectiveness of hormone therapy and dietary modification. All women in the hormone therapy trials had annual mammograms; those in the dietary trials had mammograms every 2 years. Additionally, the researchers assessed vitamin D intake and vitamin D levels. Researchers had complete follow-up on 93% of the women in each group. The researchers used intention to treat to analyze the data. At the end of the study (average follow-up = 7 years), they found a total of 528 (3.1%) invasive breast cancers in the women taking supplements and 546 (3.2%) in the women taking placebo. Additionally, they found in situ breast cancer in 145 (0.9%) women using supplements and 152 (0.9%) using placebo. Finally, deaths from breast cancer was the same in each group (0.1%). Although the cancers in the women using supplements were slightly smaller (1.54 vs 1.71 cm; P = .05), the stage at diagnosis was similar in each group. The researchers did 22 subgroup analyses, but don’t report if these were prespecified. The possibility of finding a significant relationship that is actually due to chance goes way up when you do this much data dredging, and the authors don’t describe doing any statistical adjustment to take this into account. Nonetheless, only 2 subgroups had statistically significant findings. In women with the highest levels of vitamin D intake, the risk of breast cancer was higher in women taking supplements. On the other hand, in women with the lowest levels of vitamin D intake, those taking supplements had a lower risk of developing breast cancer. Finally, vitamin D levels were not associated with breast cancer risk. This latter point is important because in observational studies vitamin D levels have been reported to be associated with breast cancer risk.
DR. WEEKS’ COMMENT: THIS IS TYPICAL OF THE PLETHORA OF PRESENT DAY SCIENTIFIC DISSERVICE: A SEEMINGLY IMPRESSIVE STUDY FOUNDED ON IGNORANCE: BE ADVISED! NO ONE WHO UNDERSTANDS VITAMIN D3 METABOLISM (AND CERTAINLY NO CORRECTIVE MEDICAL DOCTORS WHO USE THIS IMPROTANT THERAPEUTIC SUBSTANCE) RECOMMEND LESS THAN 2000 IU A DAY. I PERSONALLY RECOMMEND 5000 IU A DAY AND SOME OF MY MEDICAL COLLEAGUES PRESCRIBE 10,000 IU A DAY. SO, GIVEN THAT FACT, HOW IMPRESSIVE IS THE STUDY ABOVE WHERE THEY INVESTIGATED THE EFFECT OF A MEASLEY 400 IU AS REGARDS CANCER PREVENTION.
LET ME EXPLAIN THIS TYPICAL EGREGIOUS TYPE OF STUDY
(LITTLE MORE THAN A SMEAR JOB REALLY!)
BY APPEALING TO YOUR COMMON SENSE:
QUESTION: IS LEARNING TO SWIM IS HELPFUL TO PREVENT DROWNING?
“YES” WE WOULD ALL AGREE.
QUESTION: IN ORDER TO LEARN TO SWIM, DO YOU THINK SWIMMING LESSONS WOULD BE HELPFUL?
AGAIN “YES” IS THE OBVIOUS ANSWER.
IF SO, IMAGINE A STUDY (SPENDING MILLIONS OF TAX DOLLARS) TESTING WHETHER ONLY ONE SINGLE SWIMMING LESSON LASTING 30 MINUTES PREVENTS DROWNING. (SEE WHERE I AM GOING HERE? CORRECT DOSAGE IS THE ISSUE!)
THAT STUDY OF THE EFFECT OF ‘SWIMMING LESSONS” ON DROWNING, WOULD CONCLUDE NOT ONLY THAT SWIMMING LESSONS DON’T PREVENT DROWNING, BUT THAT TAKING SWIMMING LESSONS MAY INCREASE THE RISK OF DROWNING BECAUSE PEOPLE WILL TRY TO SWIM AFTER ONE LESSON AND DROWN…
MY RECOMMENDATION: HOLD YOUR DOCTORS AND RESEARCHERS ACCOUNTABLE TO COMMON SENSE.