Could a Specific Dietary Intake Be a Risk Factor for Cutaneous Melanoma?

Potential confounding factors considered in the logistic regression model were sex; age; education level; skin, hair, and eye color; Fitzpatrick skin type; presence of freckles, solar lentigines, and actinic keratosis; history of nonmelanoma skin cancer; number of melanocytic nevi; family history of skin cancer; sunburns in adulthood (≥6 episodes a year); occupational sun exposure; and history of sunscreen use in adulthood.

Results

A total of 191 participants were enrolled in the study (95 [49.7%] cases; 96 [50.3%] controls). Most participants were female (60.0% of cases; 59.4% of controls). The mean age (SD) of cases and controls was 56.8 (13.9) years and 56.5 (13.2) years, respectively. Mean body mass index (SD) did not differ between cases (27.2 [4.6]) and controls (28.2 [6.5]). Education levels of 8 years or less predominated in both groups (64.2% of cases; 57.3% of controls). No statistical difference was found for sex, age, education, or body mass index. The most frequent anatomic sites of CM were the trunk (54.7%) and arms (20.0%), and the most frequent histological type was superficial spreading (62.8%). The median Breslow thickness was 0.90 mm. Ulceration was observed in 20.9% of the cases, and 67% of participants with CM had a high mitotic rate (≥1 mitosis per square millimeter).

Phenotypic characteristics associated with an increased risk for melanoma were light brown hair (OR, 6.73; 95% CI, 3.30-14.2), blonde/red hair (OR, 21.7; 95% CI, 7.51-63.1), light-colored eyes (eg, blue, gray, green)(OR, 13.2; 95% CI, 6.13-28.7), light brown eyes (OR, 5.01; 95% CI, 2.24-11.5), and Fitzpatrick skin types I and II (OR, 7.37; 95% CI, 2.90-26.1). Family history of skin cancer was associated with an increased risk for CM (OR, 4.31; 95% CI, 1.86-10.7) as well as sunburns in adulthood (OR, 1.64; 95% CI, 1.17-1.99). Regular sunscreen use in adulthood had a 5-fold increased risk for CM compared to not using sunscreen regularly (OR, 5.6; 95% CI, 2.85-10.7). Regarding pigmented lesions, the presence of solar lentigines (OR, 4.8; 95% CI, 2.2-11.2), 60 or more nevi (OR, 5.4; 95% CI, 2.4-12.7), and freckles (OR, 3.7; 95% CI, 1.82-7.64) were all associated with an increased risk for CM. Solar elastosis (OR, 2.5; 95% CI, 1.08-5.85), actinic keratosis (OR, 9.1, 95% CI, 3.97-20.84), and occupational exposure to sun (OR, 2.57; 95% CI, 1.23-5.38) also were associated with an increased risk for melanoma.

The intake of most of the foods and beverages included in the study showed no association with CM. High frequency of butter intake (more than daily) was a protective factor for CM (OR, 0.33; 95% CI, 0.16-0.70) compared to low-frequency consumption (daily and less than daily). Consumption of mussels (OR, 0.53; 95% CI, 0.29-0.97) and oregano (OR, 0.28; 95% CI, 0.12-0.66) also were shown to be protective against CM (OR, 0.53; 95% CI, 0.29-0.97). Regarding beverages, those in the highest categories of consumption—liquor (OR, 2.12; 95% CI, 1.09-4.12) and spirits (OR, 2.23; 95% CI, 1.16-4.68)—were associated with an increased risk for CM.

To identify the relationship between CM and the consumption of some foods that were relevant on bivariate analysis, we performed a multivariate model. When adjustments were made, the association remained for butter (OR, 0.141; 95% CI, 0.032-0.613) and oregano (OR, 0.176; 95% CI, 0.042-0.735), while the risk associated with the consumption of both liquor (OR, 1.511; 95% CI, 0.39-5.90) and spirits (OR, 0.755; 95% CI, 0.130-4.393) disappeared (Table).

Comment

Observational studies show that diets rich in fruits and vegetables are associated with a lower risk for different types of cancers.^7,8 According to some studies, more than 30% of cancers in adulthood could be prevented or delayed by appropriate dietary intake and physical activity.¹⁰ However, there are still limited data on some specific cancers such as CM.

Substantial differences in the incidence of CM among different populations have suggested that environmental factors may play an etiological role in the development of CM and diet could be one of the modifiable risk factors.^11-13

Initially, we assessed the already known risk factors for CM, and results showed a significantly increased risk for participants with light brown, blonde, or red hair (P<.0001); light-colored and light brown eyes (P<.0001); Fitzpatrick skin types I and II (P<.0001); positive family history of skin cancer (P=.001); the presence of solar lentigines (P<.001), freckles (P<.001), and actinic keratosis (P<.0001); and high number of nevi (P<.0001). Sunburns in adulthood (P<.001) were associated with an increased risk for CM, and our findings are in agreement with the literature.¹²

Besides confirming the well-known risk factors for CM, our study also showed that some foods (eg, butter, oregano) may act as important protective factors in CM. It could be argued that the increased risks associated with the well-known risk factors (eg, Fitzpatrick skin type, number of sunburns) might not be as strong and/or could be modulated by dietary factors. To further elucidate this critical issue, we analyzed our data by examining the joint relationship between dietary consumption, individual characteristics, sun exposure, and melanoma. We conducted a multivariable analysis controlling for the well-known risk factors and our findings suggest that both butter and oregano, foods that are rich in vitamins A and D, are independent and protective risk factors for melanoma.