Researchers find 17% reduction in risk for squamous cell carcinoma in those consuming higher amounts of vitamin A in their diet.
People whose diets include high levels of vitamin A, have a 17 percent reduction in risk for a common type of skin cancer, compared with those who ate modest amounts, finds a study from Brown University. Carotenoids from fruit and vegetable intake appeared more effective than retinol from animal sources. The findings were published in the Journal of the American Medical Association Dermatology..
The importance of squamous cell carcinoma
Squamous cell cancer is the second most common skin cancer worldwide and in the USA about 1 million cases occur each year according to the American Cancer Society. The main risks for developing this cancer are exposure to UV combined with a lighter skin and older age. Reducing sun exposure is the most is the most effective way of reducing the risk of this disease.
The role of vitamin A
Vitamin A is known to have a role in skin maintenance and its effects on cancer have been studied. According to the authors of this study synthetic retinoids have been used to prevent skin cancer in high risk groups but the treatment can have adverse effects. The effects of vitamin A from the diet on squamous cell cancer has not been extensively studied say the study authors.
Previous studies
Their study is based on an analysis of data from 2 large observational studies, the Nurses Health Study and the Health Professionals Follow-Up Study. The study follows up on one done in 2003 on the same two studies. At that time, with a shorter follow-up period of less than 20 years, no effect on cancer risk could be shown.
The findings
Eunyoung Cho an associate professor at Brown and colleagues analysed data for around 123,000 participants of the studies who were at risk of skin cancer but had no prior history of cancer. They used information from dietary questionnaires for each participant to work out their vitamin A intake and examined about 26 years of follow-up for cases of squamous cell carcinoma. They identified 3,978 cases of squamous cell carcinoma in that time period.
The researchers grouped the study participants into five categories by their vitamin A intake and examined their risk of cancer, based on the number of cases in each category. They found that the participants obtained most of their vitamin A from their diet rather than from supplements. Their daily intake varied from an equivalent of 2 large carrots in the high intake group to the equivalent of one small carrot in the lowest intake group. People in the category with the highest average daily total vitamin A intake were 17 percent less likely to get skin cancer than those in the category with the lowest total vitamin A intake.
Eunyoung Cho, said: “Skin cancer, including squamous cell carcinoma, is hard to prevent, but this study suggests that eating a healthy diet rich in vitamin A may be a way to reduce your risk, in addition to wearing sunscreen and reducing sun exposure.”
The next step could be clinical trials of vitamin A supplements.
Sources of vitamin A
In the diet, we get vitamin A from alpha and beta-carotene in leafy green vegetables, sweet potatoes and carrots and from retinyl palmitate in animal liver, milk, and fish. Both are converted into retinol in the body (see MedlinePlus for more information).
Search for more studies about vitamin A and squamous cell skin cancer:
("vitamin A" or retinol or carotene or "retinyl palmitate") and "squamous cell carcinoma" and skin
Reference
Association of Vitamin A Intake with cutaneous squamous cell carcinoma risk in the United States. Jongwoo Kim, Min Kyung Park, Wen-Qing Li, Abrar A. Qureshi, Eunyoung Cho. JAMA Dermatology Published online July 31, 2019. doi:10.1001/jamadermatol.2019.1937
Medline page on vitamin A