A new study led by scientists at Stanford has found that a daily supplement of 1,000 mg of calcium plus 400 IU of vitamin D3 lowered the risk of getting melanoma by 57% in women with a history of other skin cancers, but did not affect the incidence of melanoma in women with no history of skin cancer.
The new study, conducted by Jean Y. Tang, MD, PhD of the Department of Dermatology, Stanford University School of Medicine, and colleagues, was published in the June 27, 2011 issue of the Journal of Clinical Oncology.
In the study, the researchers analyzed data on 36,282 postmenopausal women, 50 to 79 years old, who took part in the Women’s Health Initiative study. In testing to see if calcium plus vitamin D had any effect on hip fractures or colon cancer, the Women’s Health Initiative Study assigned the women randomly to a test group taking daily supplements of 1,000 milligrams of calcium and 400 IU of vitamin D, or a control group given a placebo.
The women were followed over a period of approximately seven years. The study authors examined the data on incidence of melanomas in both groups, during this period.
Overall, 176 cases of melanoma developed over the seven years of follow-up.
Analysis showed that, neither incidence of non-melanoma skin cancer nor melanoma rates differed significantly between the group assigned to take the supplements (hazard ratio [HR], 1.02; 95% CI, 0.95 to 1.07) and the placebo group (HR, 0.86; 95% CI, 0.64 to 1.16), when considered as a whole.
However, when the study participants were broken down into those with a history of non-melanoma skin cancer and those without a history of skin cancer, the researchers found that the women with a history of non-melanoma skin cancer who were assigned to take the calcium + vitamin D supplements had a reduced risk of melanoma versus those receiving the placebo (HR, 0.43; 95% CI, 0.21 to 0.90; Pinteraction = .038). This means that the women with a history of non-melanoma skin cancer were 57% less likely to develop melanoma over the seven year follow up period if they were taking the calcium + vitamin D supplements, rather than the placebo.
No difference in rate of melanoma was observed in women without a history of skin cancer, whether they took the supplements or the placebo.
In conclusion, the authors wrote, “Vitamin D supplementation at a relatively low dose plus calcium did not reduce the overall incidence of NMSC [non-melanoma skin cancer] or melanoma. However, in women with history of NMSC, CaD [calcium + vitamin D] supplementation reduced melanoma risk, suggesting a potential role for calcium and vitamin D supplements in this high-risk group. Results from this post hoc subgroup analysis should be interpreted with caution but warrant additional investigation.”
The researchers noted that the women most at risk of developing life-threatening melanoma skin cancer are those who have had a previous non-melanoma form of skin cancer, such as basal cell or squamous cell cancer.
Vitamin D and calcium are well-known for their roles in bone growth, but they also affect other cells in the body, the authors observed. Some previous studies have shown that vitamin D and calcium are associated with lower risk of colon, breast, prostate and other cancers, the researchers said.
Dr. Tang suggested to HealthDay that cancer cells lurking in the skin of women who have had a previous skin cancer may be waiting to develop into melanoma, “but if they take calcium and vitamin D that reduces the risk of developing an actual tumor.”
She pointed out that the study only tested for supplements composed of a combination of 1,000 milligrams of calcium and 400 IU of vitamin D; the study data did not allow the researchers to break out the potential effect of either calcium or vitamin D alone. More study needs to be done in breaking out the potential effects of calcium or vitamin D alone, as well as to test the results in other population groups, Dr. Tang said.
“More studies need to be done, because we want to make sure these results are true in other communities,” Tang said. However, she noted that an earlier study led by her did also find a benefit from vitamin D in reducing the risk of melanoma among older men.
Other scientists have confirmed that a combination of Vitamin D and calcium seems to have an effect in lowering risk of melanoma, but whether calcium or vitamin D alone may also play a role is not known. As explained by Dr. Michael Holick, professor of medicine, physiology and biophysics at Boston University School of Medicine, to HealthDay, “We don’t know whether vitamin D can have its effect in the absence of calcium or vice versa; there’s rationale for both,” he said.
Dr Tang has indicated that her team next plans to test each of vitamin D and calcium directly on cancer cells, in an effort to further understand and explain why vitamin D and/or calcium may be beneficial.
Health & Diet Implications
According to the U.S. National Cancer Institute, more than 68,000 cases of melanoma in adults are diagnosed In the United States each year.
If taking supplements of calcium + vitamin D is able to reduce this risk, at least among post-menopausal women with a history of other types of skin cancer, this could have a significant positive health benefit.
According to Dr. Holick, quoted above, people can get vitamin D from diet, from supplements, and even from sun exposure. Two dietary sources of vitamin D are fatty fish and fortified dairy products.
Dr. Holick recommended to HealthDay that children take 1,000 IU of vitamin D a day and adults, 2,000 IU.
For more information on skin cancer, see MedlinePlus by the U.S. National Library of Medicine, National Institutes of Health.
And, see HelpingYouCare™’s resource pages on Skin Cancers, including:
Copyright © 2011 Care-Help LLC