Vitamin D: Additional Research on the Benefits

Summary: In a nested case-control study involving 224 women with epithelial ovarian cancer and 603 matched controls aged 34 to 73 years, a significant inverse association was observed between plasma 25-hydroxyvitamin D (a measure of overall vitamin D status) levels and risk of ovarian cancer among overweight and obese women. No significant associations were observed between plasma 25-hydroxyvitamin D levels or plasma 1,25-dihydroxyvitamin D (biologically active form) levels with ovarian cancer risk. However, in the subgroup of obese and overweight women, a significant inverse association was observed between plasma 25-hydroxyvitamin D levels with risk of ovarian cancer. Obese or overweight women in the highest quartile for plasma 25-hydroxyvitamin D levels showed a 61% reduced risk of ovarian cancer, compared to women in the lowest quartile.  Additionally, obese and overweight women with adequate 25-hydroxyvitamin D levels (32 ng/mL or more) showed a 36% reduced risk of serous ovarian cancer, compared to women with inadequate 25-hydroxyvitamin D levels. Thus, the authors of this study conclude, "Overall, our results do not suggest that plasma vitamin D levels are associated with risk of ovarian cancer. However, we observed significant associations in some subgroups, which should be evaluated further in other studies because increasing vitamin D intake is an easy preventive measure to adopt." 

 

Reference: "Plasma 25-hydroxyvitamin d and 1,25-dihydroxyvitamin d and risk of incident ovarian cancer," Tworoger SS, Lee IM, et al, Cancer Epidemiol Biomarkers Prev, 2007; 16(4): 783-8. (Address: Channing Laboratory, 3rd Floor, 181 Longwood Avenue, Boston, MA 02115, USA.)

 

Vitamin D deficiency is linked to an increased risk of cancer, researchers have told attendees at the annual meeting of the American Association for Cancer Research, with results from a clinical trial hoped to show benefits of high-dose vitamin D replacement in individuals with high risk of lung cancer. 

 

The link between vitamin D intake and protection from cancer dates from the 1940s when Frank Apperly demonstrated a link between latitude and deaths from cancer, and suggested that sunlight gave "a relative cancer immunity."

 

Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive. The latter is derived from plants and only enters the body via the diet.

 

Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.

 

Donald L. Trump, president and CEO of Roswell Park Cancer Institute told attendees at the American Association for Cancer Research centennial meeting that substantial epidemiological data indicate a link between low vitamin D levels and an increased risk of a number of cancers.

 

Trump said that no large-scale prospective trials have been conducted to test the hypothesis that aggressive vitamin D supplementation may influence cancer risk, and Roswell Park Cancer Institute recently initiated a clinical trial of high-dose vitamin D3 in individuals with high risk of lung cancer.

 

"The goal of this study is to delineate the biologic effects of 1,25(OH)2D supplementation in high-risk patients," said Trump.

 

Preclinical studies have demonstrated an anti-proliferative and pro-differentiative effects of high-dose 1,25(OH)2D in vitro and in vivo, said Trump, with all tumour models sensitive to vitamin D.

 

"While preclinical data and limited clinical data strongly suggest that 1,25(OH)2D… has a role in the suppression of established cancer, there are numerous unanswered questions about optimal dose, schedule and formulation of 1,25(OH)2D," said Trump.

 

Calls to increase vitamin D intake have been growing. Indeed, only recently fifteen experts from universities, research institutes, and university hospitals around the world called for international agencies to "reassess as a matter of high priority" dietary recommendations for vitamin D because current advice is outdated and puts the public at risk of deficiency (The American Journal of Clinical Nutrition, Vol. 85, pp. 860-868).

 

A recent review of the science reported that the tolerable upper intake level for oral vitamin D3 should be increased five-fold, from the current tolerable upper intake level (UL) in Europe and the US of 2000 International Units (IU), equivalent to 50 micrograms per day, to 10,000 IU (250 micrograms per day).

 

Source: Annual meeting of the American Association for Cancer Research 16 April 2007, Abstract "Vitamin D: Sunshine, Diet and Supplements - Cancer Prevention and Therapy"

Authors: D.L. Trump, M. Fakih, I. Chung, C.S. Johnson

 

Summary: In a multiethnic cohort study involving 85,903 men and 105,108 women aged 45 years or older at baseline, results suggest that calcium, vitamin D and dairy exert a protective effect against colorectal cancer.  During 5-8 years of follow-up, 1,138 men and 972 women developed colorectal cancer. Using Cox proportional hazards models adjusted for potential confounders, an inverse association was observed between total calcium intake (diet plus supplements) and risk of colorectal cancer in both men and women. Men and women in the highest quintiles of total calcium intake showed 30% and 36% reduced risks of colorectal cancer, respectively, compared to men and women in the lowest quintiles of intake. Similarly, men and women in the highest quintiles for intake of dairy products showed 23% and 34% reduced risks of colorectal cancer, respectively. On the other hand, an inverse association was observed between total vitamin D intake and risk of colorectal cancer in men alone. Men in the highest quintile of total vitamin D intake showed a 28% reduced risk of colorectal cancer, compared to men in the lowest quintile. Thus, the authors of this study conclude, "The findings support the hypothesis of protective roles for calcium, vitamin D, and dairy products in the risk of colorectal cancer."

 

Reference:  "Calcium and vitamin D intake and risk of colorectal cancer: the multiethnic cohort study," Park SY, Murphy SP, et al, Am J Epidemiol, 2007; 165(7): 784-93. (Address: Dr. Song-Yi Park, Cancer Epidemiology Program, Cancer Research Center of Hawaii, University of Hawaii, 1236 Lauhala Street, Honolulu, HI 96813, USA.)