In a new study, researchers found people whose diets included high levels of vitamin A had a 17% reduction in risk for common skin cancer compared to those who ate modest amounts of vitamin A.
The skin cancer is cutaneous squamous cell carcinoma. It is the second-most-common type of skin cancer among people with fair skin.
The research was conducted by a team from Brown University.
Vitamin A is known to be essential for the healthy growth and maturation of skin cells.
But previous studies on its effectiveness in reducing skin cancer risk have been mixed.
In the study, the team examined the diet and skin cancer results of participants in two large, long-term observational studies:
The Nurses’ Health Study, which followed 121,700 US women from 1984 to 2012, and the Health Professionals Follow-Up Study, which followed 51,529 US men from 1986 to 2012.
In the two studies, about 123,000 participants were white (and thus had a significant risk of developing skin cancer), and they completed the dietary reports multiple times.
The team found a total of 3,978 cases of squamous cell carcinoma were reported and verified within the 24- or 26-year follow-up periods.
Both studies also asked the participants about hair color, the number of severe sunburns they had received in their lifetime, and any family history of skin cancer.
But the studies did not ask participants about their avoidance of midday sun, a major risk factor for skin cancer.
The researchers found that people with the highest daily vitamin A intake were 17% less likely to get skin cancer than people with the lowest total vitamin A intake.
These people reported eating on average the amount of vitamin A equivalent to one medium baked sweet potato or two large carrots each day.
Those in the lowest vitamin A group reported eating a daily average amount of vitamin A equivalent to one-third cup of sweet potato fries or one small carrot, which is still above the US Recommended Dietary Allowance of vitamin A.
The team also found the majority of vitamin A came from the participants’ diets, particularly from fruits and vegetables, rather than from animal-based foods or vitamin supplements.
Plant-based sources of vitamin A include not only sweet potatoes and carrots but also leafy green vegetables and fruits like apricots and cantaloupe.
Milk, some types of fish, and liver are rich sources of animal-based vitamin A.
The team says the study provides another reason to eat lots of fruits and vegetables as part of a healthy diet.
Although skin cancer is hard to prevent, the findings suggest that eating a healthy diet rich in vitamin A may be a way to reduce the risk, in addition to wearing sunscreen and reducing sun exposure.
The researchers also caution that too much vitamin A, particularly from supplements and animal sources, can lead to nausea, liver toxicity, increased risk of osteoporosis, and hip fracture, and even birth defects.
But side effects from high levels of plant-based vitamin A are minimal.
The lead author of the study is Eunyoung Cho, an associate professor of dermatology and epidemiology at Brown University.
The study is published in the Journal of the American Medical Association Dermatology.
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