beta-carotene and Keratosis

This review deals with topical and systemic approaches for protection of human skin against the harmful effects of solar radiation. Two concerns about the deleterious effects of sun exposure involve: (1) acute effects (e.g., sunburn and drug-induced phototoxicity) and (2) potential long-term risks of repeated sun exposures leading to development of solar elastosis, keratoses, induction of both nonmelanoma and melanoma skin cancer, and alteration of immune responses and functions. Action spectra of normal and abnormal reactions of human skin to acute and chronic effects of solar radiation are presented with a view to helping the physician prescribe the appropriate sunscreens. Factors that influence acute effects of sunburn are reviewed. Various artificial methods effective in minimizing or preventing harmful effects of solar radiation, both in normal individuals and in patients with photosensitivity-related problems, are discussed. Emphasis is placed on the commercially available chemical sunscreens and their properties. Sun protection factor (SPF) values of several brand-name formulations determined with a solar simulator under indoor conditions (laboratory) and with solar radiation under natural, field conditions are presented. Factors responsible for variations of SPF values observed under indoor and outdoor conditions are reviewed. Systemic photoprotective agents and their limitations are outlined. The photobiology of melanin pigmentation (the tanning reaction) is briefly discussed, with emphasis on the dangers of using quick-tanning lotions for stimulation of the tanning reaction.

Topics: 5-Methoxypsoralen; Administration, Oral; Administration, Topical; beta Carotene; Carotenoids; Chloroquine; Dermatitis, Contact; Furocoumarins; Humans; Keratosis; Melanins; Methoxsalen; Nonprescription Drugs; Photosensitivity Disorders; Skin Neoplasms; Skin Pigmentation; Sunburn; Sunscreening Agents; Ultraviolet Rays

Solar keratoses (SKs) are among the strongest determinants of skin cancer, but little is known about the success of measures to control these common skin tumors.. To determine whether daily sunscreen application and/or beta carotene supplementation retards the rate of occurrence of SKs in adults in the medium term.. Randomized controlled trial conducted between February 1992 and August 1996.. General community of the subtropical township of Nambour, Australia (latitude, 26 degrees south).. A total of 1621 adults aged 25 to 74 years. Interventions Participants were randomized to daily use of sunscreen (application of a high-protection sunscreen to their head, neck, arms, and hands every morning) or application of sunscreen at their usual discretionary rate. They were also randomly assigned to take either one 30-mg tablet of beta carotene or one placebo tablet each day.. Change in the prevalent number of SKs in the intervention group relative to change in the control group.. The ratio of SK counts in 1994 relative to 1992 was lower in people randomized to daily sunscreen use (1.20; 95% confidence interval, 1.04-1.39) than in those randomized to discretionary sunscreen use (1.57; 95% confidence interval, 1.35-1.84). This 24% reduction is equivalent to the prevention of an average of 1 additional SK per person over that time. A reduction in the rate of change of SK prevalence was also seen in the sunscreen intervention group relative to the discretionary sunscreen group between 1994 and 1996, but it was not significant. No effect on the rate of change of prevalent SK counts was seen among those taking beta carotene supplements relative to those taking placebo tablets.. Daily application of sunscreen retarded the rate of SK acquisition among adults in a subtropical environment, while a beta carotene supplementation of 30 mg/d had no influence on the occurrence of SKs.

Topics: Adult; Aged; beta Carotene; Humans; Keratosis; Middle Aged; Sunlight; Sunscreening Agents

The baseline, intra-, and interindividual variability as well as storage stability of carotenoids, tocopherols, and retinoids in human buccal mucosal cells were determined because this information is lacking. All the buccal mucosal cell samples were collected after an overnight fast. In the variability study, 154 subjects (median age 57.5 y) provided three samples each at 7-10-d intervals over a 1-mo period. In the stability study, 13 young volunteers provided four samples each before and during the 11 d of oral administration of beta-carotene, alpha-tocopherol, and vegetable juice; the cells were pooled and stored as a pellet at -80 degrees C. Eleven micronutrients were analyzed simultaneously with HPLC. The results indicated that 1) lycopene and beta-carotene were the two major carotenoids, retinol was not detected in most cell samples; 2) the intra-individual variability was small, but the interindividual variability was very large; 3) two measurements of micronutrient concentration in fasting buccal mucosal cells should be adequate to establish a representative baseline for each micronutrient; and 4) the micronutrients under the storage conditions were stable for > or = 8 mo.

Topics: Administration, Oral; Adult; Aged; beta Carotene; Carotenoids; Female; Humans; Keratosis; Leukoplakia; Male; Middle Aged; Mouth Mucosa; Precancerous Conditions; Reference Values; Retinoids; Uterine Cervical Dysplasia; Vegetables; Vitamin E

Topics: beta Carotene; Canthaxanthin; Carcinoma, Basal Cell; Carcinoma, Squamous Cell; Carotenoids; Child; Child, Preschool; Drug Combinations; Drug Therapy, Combination; Etretinate; Humans; Keratosis; Male; Skin Neoplasms; Xeroderma Pigmentosum