Dietary vitamin A and prevalence of bronchial metaplasia in asbestos-exposed workers

Abstract

The purpose of this investigation was to examine the association between dietary intake of vitamin A in the form of retinol and provitamin A carotenoids and the prevalence of bronchial squamous metaplasia in a sample of asbestos workers from an industrial clinic. Bronchial biopsies were obtained from 49 asbestos workers. Pulmonary function testing was done and in-person interviews were conducted to estimate dietary intake of retinol and provitamin A carotenoids, tobacco exposure, and asbestos exposure. Results indicated that workers with metaplasia reported consuming a significantly lower intake of total vitamin A [2000 retinol equivalents (RE)/d] than did subjects without metaplasia (2710 RE/d, P = 0.02). Logistic regression analyses showed that higher intakes of retinol [odds ratio (OR): 0.31; 95% CI: 0.04, 2.44], provitamin A carotenoids (OR: 0.31; 95% CI: 0.03, 2.84), and total vitamin A (OR: 0.29; 95% CI: 0.03, 2.49) were associated with a nonsignificant reduction in the OR for metaplasia (highest quartile compared with lowest quartile, adjusted ORs). Current smoking (OR: 5.25; 95% CI: 0.50, 55.1) and former smoking (OR: 2.95; 95% CI: 0.31, 28.1) were associated with a nonsignificant increase in the OR for bronchial metaplasia compared with never smoking. Greater airway obstruction [decreased forced expiratory volume in 1 s (FEV 1 )/forced vital capacity (FVC)] was associated with an increased OR for metaplasia (OR: 2.86; 95% CI: 1.09, 7.69). These results suggest that a higher (ie, above the median) intake of vitamin A from foods decreases the risk of bronchial metaplasia in workers occupationally exposed to asbestos.Am J Clin Nutr 1998;68:630-5.

Adverse effects of antioxidative vitamins

“…Similar results were noted for the supplementation of patients occupationally exposed to asbestos [39,55]. An increase in the frequency of intracerebral haemorrhage cases in supplemented alcoholics was also found [36].…”

The Concept of Cyclical Nutritional Therapy for Hair Growth which can be Applied for Wellness

“…Vitamin A has been found to damage bone and increase incidence of hip fractures at just marginally higher doses without signs of hypervitaminosis [35][36][37]. Excess β-carotene which is an effective antioxidant at low partial pressure of oxygen (pO 2 ) as in peripheral tissues becomes pro oxidant at high pO 2 as in lungs even leading to DNA (Deoxyribonucleic acid) damage [38][39][40][41]. Regular supplements of β-carotene could not protect patients with lung asbestosis.…”

“…Regular supplements of β-carotene could not protect patients with lung asbestosis. β-carotene increased the incidence of lung cancer in smokers by 18% and caused intra cerebral hemorrhage in alcoholics [38,42,43]. Vitamin A stores are depleted with high intake of vitamin E [41].…”

Subclinical vitamin A deficiency does not increase development of tumors in irradiated or unirradiated lungs

“…16,17 In humans, low vitamin A intake and/ or reduced serum retinol levels, common in developing countries, are associated with increased risk of infection, reduced night vision, anemia, reduced lung function and risk of injury from environmental agents such as asbestos. 16,18 – 20 The prevalence of the milder, subclinical vitamin A nutritional deficits seen in developed countries is unclear, as serum retinol levels are not a good predictor of tissue stores. A number of studies suggest that subclinical vitamin A deficiency or suboptimal vitamin A nutritional status may be common, especially in certain patient populations, including patients with chronic liver disease, obesity, postbariatric surgery, the elderly and those who avoid liver products and vitamin A-supplemented foods.…”