A recent study on vitamin D and breast cancer risk was published that once again points the way to vitamin D as a safe and important strategy in lowering breast cancer risk. The study included about 6,500 women between the ages of 25 and 74. Approximately half the women were diagnosed with breast cancer and half were not. According to the study results, a vitamin D supplement intake greater than 400 IU/day compared with no vitamin D supplement intake, reduces the risk of breast cancer by about 25%. This Canadian population-based, case-control study also observed that there was no influence of calcium supplement intake and breast cancer risk.
Commentary: This is just one study in a growing list of research publications demonstrating that vitamin D deficiency is associated with an increased risk of breast cancer, and other studies demonstrating that raising one’s serum level of vitamin D can lower the risk of breast cancer and breast cancer recurrence. Included below, is an article I published in the Townsend Letter for Doctors. While perhaps a bit technical for the non medical reader, I think the message is clear enough: Vitamin D is associated with a lower risk of breast cancer with the optimal guide of a maintenance dose that would achieve a serum 25 hydroxyvitamin D level of > 52 ng/mL in order to have a 50% reduction in breast cancer incidence.
Here is the article in total:
The Vitamin D and breast cancer link: Understanding associations, prevention, intervention; Townsend Letter for Doctors and Patients; August/Sept 2010, Issue #325/326
Tori Hudson, N.D.
Vitamin D deficiency has been associated with the increased risk of several cancers, including breast cancer. Given that breast cancer is the most common cancer in women in the United States, efforts towards identifying modifiable risk factors, targets for prevention with any lifestyle modification or nutritional influence is especially appealing.
One of the initial observations suggesting the potential for vitamin D to reduce breast cancer risk and mortality was from ecologic studies where higher latitude and therefore lower UV light, was associated with increased breast cancer incidence and
Epidemiological evidence is limited but in the first National Health and Nutrition Examination survey Follow-Up Study, higher sun exposure or high dietary or supplemental vitamin D intake, while not statistically significant, was consistently observed as an association with a decreased risk for breast cancer.[vii] In the Nurses’ Health Study, a higher dietary intake or total intake of vitamin D including supplementation was significantly associated with a lower risk of premenopausal breast cancer.[viii] An updated study was done with a cohort in a case-control study nested within the Nurses’ Health Study. The relationship between plasma levels of 25 (OH)D and 1,25 (OH)2 D and breast cancer was prospectively examined.[ix] Women in the highest quintile of 25(OH)D had a nonsignificant lower risk of breast cancer compared with those in the lowest quintile, when both metabolites were analyzed. The association was stronger in women ages 60 years and older, but still, results were not statistically significant. The authors concluded that high levels of 25(OH)D, and perhaps 1,25 (OH)2 D may be modestly associated with a reduced risk of breast cancer. This association with low levels of serum D and higher risk of breast cancer was very significant in a previous study, where women in the lowest quartile of serum 1,25(OH)2D had a risk of breast cancer 5 times higher than those in the highest quartile.[x]
This suggestive evidence led to a population-based case-control study in Ontario, Canada.[xi] Women with invasive breast cancer diagnoses and women without breast cancer were identified and telephone interviews were completed for 972 cases and 1,135 controls. A reduced risk of breast cancer was associated with increasing sun exposure for girls aged 10-19 in those with the highest quartile of outdoor activities versus the lowest. A breast cancer reduced risk was also associated with cod liver oil use and > 10 glasses of milk per week vs none. The associations were weaker for women ages 20 to 29 and there was no evidence of an association for ages 45 to 54. In this study, it appears that vitamin D could be associated with a lowered risk of breast cancer, but particularly in ages when the breasts are developing.
Two calcium and vitamin D studies have not shown any relationship. The relationship between vitamin D and breast cancer was prospectively assessed among 10,000 premenopausal and 20,000 postmenopausal women who were enrolled in the Women’s Health Study.[xii] Intake of calcium and vitamin D was determined from self-reported questionnaires about diet and vitamin use.
During an average follow-up of 10 years, the overall incidence of invasive breast cancer was 2.6% among premenopausal women and 3.6% among postmenopausal women. Among premenopausal women, the hazard ratio for developing breast cancer was 0.61 for women in the highest versus lowest quintiles of calcium use and 0.65 for vitamin D intake. No benefit was seen for these nutrient intakes and breast cancer risk in postmenopausal women.
Another calcium plus vitamin D study was conducted, but in this study, postmenopausal women in the Women’s Health Initiative clinical trial were randomly assigned to 1000 mg of elemental calcium with 400 IU of vitamin D daily, or placebo, for an average of 7.0 years. [xiii] While this was primarily a study to determine the effects of supplements on hip fracture incidence, invasive breast cancer was a secondary outcome. The incidence of invasive breast cancer was similar in the supplement vs placebo group. The results of this study were such that calcium and 400 IU of vitamin D supplementation per day did not reduce the incidence of invasive breast cancer in postmenopausal women, and serum 25-hydroxyvitamin D levels were not associated with breast cancer risk.
The Long Island Breast Cancer Study Project was conducted to investigate environmental factors associated with breast cancer risk. [xiv] Blood samples and data were collected from this study, to examine the relationship of plasma 25-OHD levels with breast cancer risk. Plasma 25-OHD was inversely associated with breast cancer risk. Compared with women with a vitamin D deficiency, defined as a serum 25-OHD level < 20 ng/mL, levels above 40 ng/mL were associated with a decreased breast cancer risk, and was greater in postmenopausal women, and independent of tumor hormone receptor status.
Another important study of Long Island women was a population-based case-control study where blood samples were obtained from 1,026 incident breast cancer cases and 1,075 population-based controls.[xv] Compared with women with a vitamin D deficiency, that is a serum level of 25-OHD, < 20 ng/mL, levels above 40 ng/mL were associated with a decreased risk of breast cancer, and the risk reduction was greater in postmenopausal women, nor did the effect vary according to tumor hormone receptor status.
Women with a current or past history of breast cancer might also take note of the influence of vitamin D and their breast cancer recurrence rate and mortality. Low 1,25 (OH)2D levels have been associated with a faster progression of metastatic breast cancer.[xvi] The results of the prognostic effects of 25-hydroxyvitamin D levels in women with early stage breast cancers is one of the most frequent strategies I employ in breast cancer prevention and in reducing the risk of breast cancer recurrence. This prospective study of women with early breast cancers analyzed blood levels of vitamin D. [xvii] Vitamin D levels were deficient (< 50 nmol/L) in 37.5% of women, insufficient in (50 to 72 nmol/L) in 38.5% and sufficient (> 72 nmol/L) in only 24.0% of women. Women with vitamin D deficiency had an increased risk of distant recurrence and death compared with those with vitamin D sufficiency. One of the errors that many clinicians make however when reading a study like this is confusing the lab values of nmol/L with ng/mL. Most laboratories report in ng/mL. It should be noted that 75 nmol/L is equivalent to 30 ng/mL. This study then reports that sufficiency, and a better outcome, is associated with a serum Vitamin D level of 30 ng/mL. A more rigorous standard for serum levels and breast cancer risk reduction was proposed by combining data from observational studies.[xviii] The first visible increment in prevention of breast cancer was evident with serum 25 OHD levels > 32 ng/mL. In a paper analyzing combined data from several studies on colon, ovary and breast cancer, the authors determined that prevention of 30% of breast cancer incidence could be achieved if one sustained blood levels > 42 ng/mL and they projected that a 50% reduction could occur by lifelong maintenance of serum 25 OHD levels > 52 ng/mL.[xix] They estimated that the first meaningful increment of breast cancer prevention would required a minimum of 2,000 IU/day. It is this serum level of > 52 ng/mL that I have targeted as the optimal prevention dose I utilize in my practice.
Vitamin D food/supplement intake and sufficient sun exposure are the major factors that determine serum 25 OHD levels. Several factors influence the serum increases in response to vitamin D supplementation, including body mass index (BMI) with smaller responses in individuals with a high BMI compared to those with a normal BMI.[xx], [xxi] Estrogen therapy increases serum 25 OHD levels but does not alter the serum 25 OHD response to vitamin D supplementation.[xxii] Likewise, while serum D levels decline with aging, the response to a dose of supplemental Vitamin D is not affected by aging. [xxiii]
The average increment responses to 100 I.U. per day of vitamin D supplementation varies from an increase of 1.1 ng/mL serum 25 OHD at low starting serum D levels to 0.7 ng/mL at higher or near optimal starting serum 25 OHD levels. [xxiv] The average vitamin D requirement for older adults needed to reach a serum 25 OHD levels of 30 ng/mL is 800 to 1,000 I.U. per day. Higher doses may be needed in individuals who are obese, are homebound, have malabsorption, and are dark skinned individuals. Due to declining serum levels with aging, higher doses are needed for most older adults in order to maintain 30 ng/mL. Vitamin D dosing in order to reach > 52 ng/mL requires individual assessment/testing, and follow-up testing, generally at 3 month intervals until the desired serum level is reached. A maintenance dose would then be determined, based on the desired serum level, and as I have asserted, I would recommend a 25 OHD level of > 52 ng/mL in order to have a 50% reduction in breast cancer incidence.
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