The authors of a review published in the April/May/June 2012 issue of the journal Dermato-Endocrinology suggest that decreased production of vitamin D by African Americans may be a reason for their higher rates of cancer mortality in comparison with Caucasians.
William B. Grant of the Sunlight, Nutrition and Health Research Center in San Francisco and Alan N. Peiris of Mountain Home Veterans Administration Medical Center and East Tennessee State University write that various factors have been suggested to explain African Americans' increased likeliness of dying from a variety of cancers, including cancer stage at time of diagnosis, socioeconomic status and differences in treatment. The incidence of many of these cancers or the risk of dying from them has been associated in numerous studies with reduced sun exposure and/or lower serum 25-hydroxyvitamin D [25(OH)D] levels.
Because African Americans have a 40 percent lower serum 25-hydroxyvitamin D concentration than Caucasians due to darker skin pigmentation that impairs production of the vitamin from sunlight, Drs. Grant and Peiris suggest a causative role for insufficient vitamin D levels in the decreased survival observed in this group. The current review evaluates scientific literature concerning cancer disparities between African Americans and Caucasians, as well as studies examining vitamin D status and cancer in order to evaluate the evidence supporting this hypothesis.
Seventeen studies concerning the association between vitamin D adequacy or deficiency and cancer recurrence and survival were included in the review.
Significant associations between higher vitamin D levels and cancer survival were found in studies that analyzed all cancers as well as those that evaluated breast, colon, colorectal, lung and prostate cancers, and lymphocytic leukemia/chronic lymphocytic lymphoma, Hodgkin's lymphoma and non-Hodgkin's lymphoma.
Also reviewed were 37 studies that examined cancer mortality rate disparities not explained by known factors for 25 types of cancer occurring among African Americans and Caucasians. "Statistically significant disparities emerged for cancer-specific survival rates for 13 types of cancer: bladder, breast, colon, endometrial, lung (non-small cell, stage III, IV), ovarian (advanced), pancreatic, prostate, rectal, testicular, vaginal cancer, Hodgkin lymphoma, stage II, and melanoma," the authors report. "All cancers for which a disparity in cancer-specific survival was reported also have evidence for a beneficial role of vitamin D, as do most of those for which we found disparities for all-cause survival."
Because cancer takes years to reach a stage in which it can be detected, high serum vitamin D concentrations over the course of a lifetime are needed to reduce risk, the authors note.
Once the disease has been diagnosed, vitamin D improves survival via antiangiogenic and antimetastatic mechanisms, as well as by other factors.
In addition to reduced production of vitamin D by the skin, obesity (which occurs more often among African Americans compared to Caucasians) could also account for some of the lower levels of vitamin D that occur in this population, since having a higher body mass index has been correlated with decreased vitamin D status.
"Lower serum 25(OH)D concentrations among African Americans than white Americans may explain many of the cancer survival disparities after consideration of socioeconomic status, stage at time of diagnosis, and treatment," the authors conclude. "If substantially correct, programs to increase serum 25(OH)D concentrations among African Americans could reduce the cancer disparities."Deficient vitamin D levels in African-American women linked to elevated breast cancer risk
The Third American Association for Cancer Research Conference on the Science of Cancer Health Disparities was the site of a presentation by University of South Carolina associate professor of epidemiology Susan Steck, PhD, MPH of a greater incidence of vitamin D deficiency among African-American women, which was associated with an increased likelihood of aggressive breast cancer.
"We know that darker skin pigmentation acts somewhat as a block to producing vitamin D when exposed to sunlight, which is the primary source of vitamin D in most people," noted Dr Steck.
Vitamin D has been found to help inhibit cell proliferation and induce programmed cell death and differentiation in normal and cancerous breast cells. Dr Steck and her associates measured serum 25-hydroxyvitamin D levels in 60 African-American and 47 Caucasian women aged 33 to 84 who were diagnosed with breast cancer during the previous 5 years. Vitamin D levels among African American women averaged 19.3 nanograms per milliliter, compared to 29.8 ng/mL in Caucasians. Deficiency, defined as 25-hydroxyvitamin D levels lower than 20 ng/mL occurred in 60 percent of African-American participants, and just 15 percent of Caucasian women.
The researchers found an association between the lowest vitamin D levels and a greater risk of triple-negative breast cancer, which is not responsive to estrogen and progesterone. Additionally, women who were deficient in vitamin D were more than 8 times likelier than nondeficient women to have aggressive disease.
“This study corroborates other research showing racial differences in vitamin D status and provides further support for a protective role of vitamin D in breast cancer, particularly for highly aggressive disease,” the authors conclude. “The prevalence of vitamin D deficiency and insufficiency was high, suggesting the need for monitoring of vitamin D levels among breast cancer patients.
Further Information on Vitamin D Recommended Dosage from Life Extension
Vitamin D3 can be synthesized by humans in the skin upon exposure to ultraviolet-B (UVB) radiation from sunlight. But, due to the winter season, weather conditions, and sun block, the body’s ability to produce optimal vitamin D levels may be inhibited.73 These factors point to the value of taking a daily vitamin D supplement.
Vitamin D has long provided significant support for healthy bone density.74-79
However, scientists have also validated the critical role that vitamin D plays in regulating healthy cell division and differentiation, and its profound effects on human immunity.80-87
These findings link a deficiency of vitamin D to a host of common age-related problems.
The current RDA is only 600 IU. As a result of startling evidence of a widespread vitamin D deficiency, prominent nutritional scientists are calling on Americans to increase their vitamin D intake to 1,000 IU per day and higher.
Currently, most experts in the field believe that intakes of between 1,000 and 10,000 IU for adults will lead to serum 25(OH)D levels above those indicative of vitamin D deficient levels, at approximately 80 nmol/L or 32 ng/mL.
Vitamin D in the amount of 2,000 IU is contained in the multi-nutrient Life Extension Mix and the multivitamin Two-Per-Day Tablets. A vitamin D blood test can help you determine the additional amount of vitamin D you may need to supplement to achieve an optimal level.
For those who need to take higher doses of vitamin D3 and are under a physician’s supervision, Life Extension now makes available a 5,000 IU vitamin D3 supplement. Regular CBC/Chemistry blood tests are suggested when taking this 5,000 IU vitamin D3 supplement.
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