This cohort study prospectively examined intake of vitamin A and carotenoids and SCC risk in the Nurses’ Health Study (1984-2012) and the Health Professionals Follow-up Study (1986-2012). Diet was assessed repeatedly. Incident SCC was confirmed by pathologic reports. Data analysis was performed from Jun. 21, 2017 to Dec. 4, 2018.
Vitamin A encompasses a large number of related compounds, known as retinoids, (e.g., retinol, retinal, and retinoic acid). They can be differentiated into two groups depending on whether the food source is animal or plant. Vitamin A derived from animal-based foods is retinol (also called preformed vitamin A), which is a yellow, fat-soluble compound that is the precursor of the most active form of vitamin A (retinoic acid) used in the body.
The form of vitamin A found in fruits and vegetables is called provitamin A carotenoid, which includes beta-carotene, alpha-carotene, and beta-cryptoxanthin and can be converted into retinol in the body. However, most carotenoids are non-provitamin A and include lutein, zeaxanthin, and lycopene.
Retinol and its derivatives are essential for growth, differentiation, and maintenance of normal epithelial cells.
A total of 3978 SCC cases in 75,170 women in the Nurses’ Health Study and 48,400 men in the Health Professionals Follow-up Study were documented. The results indicated people with more vitamin A were generally older in age and did more physical activity. Likewise, these participants were less likely to smoke, drink alcohol and caffeine.
The cohort study used information from the Nurses’ Health Study with 121,700 U.S. female registered nurses aged 30 to 55 years and details from the Health Professionals Follow-up Study with 51,529 U.S. working men aged 40-75 years. Participants in both cohorts completed a questionnaire on their medical history and lifestyle and have been followed up biennially, with follow-up rates generally exceeding 90%.
Researchers found that higher intake of total vitamin A, retinol, and several individual carotenoids, including beta cryptoxanthin, lycopene, and lutein and zeaxanthin, was associated with lower risk of SCC. The results were generally consistent between men and women. The inverse associations appeared to be more prominent among those with moles and those with burn or blistering sunburn reaction as children or adolescents.
Overall, researchers found an inverse association between intake of vitamin A and carotenoids and risk of cutaneous SCC, supporting the protective role of vitamin A against SCC development. Data further support the contention that supplemental and dietary vitamin A may be beneficial in preventing SCC, researchers concluded.