Written by Joyce Smith, BS. This study found an inverse association between vitamin A and carotenoid intake and risk of squamous cell carcinoma of the skin.
The greatest risk factors for squamous cell carcinoma (SSC) of the skin are age, fair skin and ultraviolet sunlight (ultraviolet light) exposure 1. Today, an increasing number (seven to eleven percent) of fair-skinned people in the U.S. develop SCC, with the most frequent sites being the face and head. Vitamin A comprises a large number of related compounds known as retinols (e.g., retinol, retinal, and retinoic acid) 2. Vitamin A from animal-based foods is called retinol, a precursor of retinoic acid. The vitamin A found in fruits and vegetables includes beta carotene, alpha carotene, and beta cryptoxanthin, and can be converted into retinol in the body. Most carotenoids are non-provitamin A and include lutein, zeaxanthin, and lycopene 3; however, alpha and beta carotenoids and beta cryptoaxanthin convert to retinol, thereby adding to vitamin A’s skin protection 4. They also act as antioxidants to block ultraviolet light-induced free radicals from damaged skin 5.
Epidemiologic data on vitamin A intake and risk of SCC are limited, thus prompting Kim et al to examine whether vitamin A intake is associated with a reduction in SCC risk. In a recent large perspective cohort study 6, the research team, using Food Frequency Questionnaires (FFQs), examined the diets and prevalence of SCC of the skin in 121,700 U.S. women in the Nurses’ Health Study from 1984 to 2012 and 51,529 U.S. men in the Health Professionals Follow-Up Study from 1986 to 2012. Dietary vitamin A, retinol, and carotenoids were assessed repeatedly throughout the study via a validated food frequency questionnaire and SCC risk was confirmed by SCC pathology reports.
During a follow-up period of more than 26 years, researchers found that a higher total (dietary and supplemental) vitamin A intake was associated with a reduction in cutaneous SCC risk, suggesting a protective role of vitamin A against the development of SCC. The study participants consisted of 123,000 white females who, because of their ethnicity, had a significant risk of developing skin cancer. They had no prior history of cancer and completed the dietary reports multiple times. Among these individuals included in the team’s subsequent analysis, a total of 3,978 cases of squamous cell carcinoma were reported and verified within the 24- or 26-year follow-up periods.
Participants with higher intake of total vitamin A tended to be older, more physically active and more likely to be non-smokers and abstainers of alcohol and caffeine. Women with a higher intake of total vitamin A were more likely to use postmenopausal hormones. After grouping the study participants into quintiles (five categories) of increasing vitamin A intake levels, the researchers found that people in the quintile with the highest average daily total vitamin A intake had a 17 % reduced risk of developing skin cancer than those in the quintile with the lowest total vitamin A intake (P < .001 for trend). Higher intakes of retinol and some carotenoids were also associated with a reduction in SCC risk. Comparing the highest quintiles to the lowest quintiles revealed the following trends: (P = 0.001 for trend) for total retinol; (P= 0.001 for trend) for beta cryptoxanthin; (P < 0.001 for trend) for lycopene; and (P = 0.02 for trend) for lutein and zeaxanthin. The US Recommended Daily Allowance (RDA) of Vitamin A is 3000 IU for adult males and 2331 IU for adult women 7. The median vitamin A intake was higher than the RDA in all five quintiles. Food intake, especially vegetable sources of carotenoids, contributed to a large proportion of the participants’ vitamin A intake. More research is needed to understand the appropriate level of vitamin A intake required for maximum health benefits.
Study limitations include the homogenous population of well-educated, white health care professionals which limits generalization of the study results. Skin cancer is not prevalent among non-whites. Also, ultraviolet radiation cannot be accurately measured and FFQs are subject to bias recall and potential misclassification of Vitamin A.
While study results support an inverse association between vitamin A and carotenoid intake and risk of skin SCC, and demonstrate a beneficial and protective role of vitamin A against SCC development, future studies exploring vitamin A’s role in the prevention of SCC are warranted.
Source: Kim, Jongwoo, Min Kyung Park, Wen-Qing Li, Abrar A. Qureshi, and Eunyoung Cho. “Association of Vitamin A Intake With Cutaneous Squamous Cell Carcinoma Risk in the United States.” JAMA dermatology 155, no. 11 (2019): 1260-1268.
© 2020 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley. This is an open access article under the terms of the Creative Commons Attribution-Non Commercial-No Derivs License.
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Posted June 8, 2020.
Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.
References:
- Li WQ, Cho E, Weinstock MA, Mashfiq H, Qureshi AA. Epidemiological Assessments of Skin Outcomes in the Nurses’ Health Studies. Am J Public Health. 2016;106(9):1677-1683.
- van Berkel TJ. Bringing retinoid metabolism into the 21st century. J Lipid Res. 2009;50(12):2337-2339.
- Asgari MM, Brasky TM, White E. Association of vitamin A and carotenoid intake with melanoma risk in a large prospective cohort. The Journal of investigative dermatology. 2012;132(6):1573-1582.
- Britton G. Structure and properties of carotenoids in relation to function. FASEB journal : official publication of the Federation of American Societies for Experimental Biology. 1995;9(15):1551-1558.
- Stahl W, Sies H. β-Carotene and other carotenoids in protection from sunlight. Am J Clin Nutr. 2012;96(5):1179s-1184s.
- Kim J, Park MK, Li WQ, Qureshi AA, Cho E. Association of Vitamin A Intake With Cutaneous Squamous Cell Carcinoma Risk in the United States. JAMA Dermatol. 2019;155(11):1260-1268.
- Insitute of Medicine, Panel on Micronutrients, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: The National Academies Press; 2001.
