- Research indicates a healthy base tan protects the skin against melanoma.
- Outdoor workers have lower rates of melanoma than do indoor and night shift workers.
Melanoma is a type of cancer originating in the melanocytes. Melanocytes are cells that produce melanin, which gives skin its pigment (color).
Each year in the United States, melanoma affects about 70,000 and kills about 9,000. Melanoma affects 33% more males than female; 50% more males than females die from the disease.
A number of genetic risk factors for melanoma have been identified:
- Red or blonde hair
- Blue or green eyes
- Lighter skin.
Diet may play a role in the risk of melanoma. Dietary fat and alcohol may be associated with increased risk of the disease.
On the other hand, carbohydrates, protein, and some antioxidant vitamins may be linked to reduced melanoma risk.
Sunlight exposure and melanoma risk
There are two ultraviolet (UV) regions of interest regarding melanoma:
- The UVB region (short wave UV) produces vitamin D. Too much UVB exposure also causes sunburn.
- The UVA region (long wave UV) does neither. But UVA generates free radicals, which can alter the DNA in melanocytes. This may lead to melanoma.
Eumelanin is the dark pigment produced by melaninocytes. Darker skin pigmentation reduces the risk of melanoma. Darker skin reduces the penetration of UV in the skin. It also repairs DNA damage caused by UV. Pheomelanin is the reddish melanin more common in those with red hair and freckles. Pheomelanin does not protect against melanoma.
Europeans who live farther from the equator have lighter skin and increased rates of melanoma. Countries at higher latitudes have less sun. With increasing latitude, UVB decreases more rapidly than UVA. However, for fair-skinned Europeans living outside of Europe, living closer to the equator is associated with increased risk of melanoma since the light pigment does not provide adequate protection at higher UV levels than in their home countries.
According to many studies, the risk of melanoma increases with recreational UV exposure. But melanoma risk does not increase with chronic UV exposure such as from outdoor occupations. People who participate in recreational UV exposure often go in the sun just a few times a year. Their skin has not been prepared for higher UV doses.
However, when the skin is exposed to UV gradually, such as a few minutes longer each day in the spring, the skin develops a protection factor. This protection doubles or quadruples the time of sun exposure without burning. In addition, over a number of years, the skin wrinkles through a process called elastosis. Melanoma has a harder time growing in wrinkled skin. Thus, melanoma often develops on the face and hands in older people.
When sunscreens are used specifically to protect against sunburns, they also protect against melanoma. But when sunscreens are used routinely (when there is no or little danger of sunburning), they are linked to increased risk of melanoma. The reason is that sunscreens do not protect well against UVA and people spend more time in the sun with sunscreen.
Vitamin D and melanoma
Vitamin D levels
A recent study from the Women’s Health Initiative found: “Vitamin D supplementation at a relatively low dose (400 IU/d) plus calcium (1500 mg/d) did not reduce the overall incidence of nonmelanoma skin cancer (NMSC) or melanoma. However, in women with history of NMSC, CaD supplementation reduced melanoma risk, suggesting a potential role for calcium and vitamin D supplements in this high-risk group.”
There are also findings for vitamin D and breast, colon, and rectal cancer. The rates of these cancers decrease rapidly as vitamin D levels increase from very low levels [less than 10 ng/mL (25 nmol/L) to 30 ng/mL (75 nmol/L). Cancer rates decrease slowly after that. It is assumed that the results for melanoma would be similar.
How vitamin D works
Vitamin D has been shown to block the growth of cancer tumors. The active form of vitamin D, calcitriol, provides numerous benefits against cancer. This form of vitamin D encourages cells to either adapt to their organ or commit apoptosis (cell suicide). Calcitriol also limits blood supply to the tumor and reduces the spread of cancer.
There is some evidence that dietary vitamin D reduces the risk of melanoma. Based on results for other cancers, raising vitamin D levels to 40 ng/mL (100 nmol/L) might lower the risk of melanoma. The rule of thumb is that vitamin D levels rise by 6–10 ng/mL (15–25 nmol/L) for each 1000 IU (25 mcg)/day of vitamin D3. Vitamin D3 is the active form of vitamin D produced by the skin. However, there is considerable person-to-person variability. Thus, people taking large doses should have their vitamin D levels measured before and three months after taking supplements.
Researchers in the United Kingdom studied the effects of vitamin D on melanoma recurrence. People taking vitamin D supplements and having higher vitamin D blood levels had slightly lower rates of disease recurrence. Vitamin D receptors, which affect gene expression or messages, also played a role. However, this study provides only weak evidence that vitamin D is useful for treating melanoma.
Find out more…
Do you want to find out more and see the research upon which this summary is based? Read our detailed evidence summary on Melanoma.
Page last edited: 05 August 2011