Intake of antioxidants and risk of type 2 diabetes in a cohort of male smokers

Abstract

Background/Objectives: Oxidative stress may induce insulin resistance in peripheral tissues and impair insulin secretion from pancreatic b-cells. Antioxidants are suggested to decrease the risk of diabetes through reduction of oxidative stress. However, only a few studies exist on dietary antioxidants and the risk of type 2 diabetes. We investigated the association of dietary antioxidants with incident type 2 diabetes in the a-Tocopherol, b-Carotene Cancer Prevention Study cohort. Subject/Methods: The study cohort included 29 133 male smokers aged 50-69 years. During a median follow-up of 10.2 years 660 incident cases of diabetes were observed among the 25 505 men with a completed baseline food frequency questionnaire. Results: Dietary a-tocopherol, b-tocopherol and b-tocotrienol were positively associated with the risk of diabetes when adjusted for age and supplementation (relative risk (RR) 1.17 (95% confidence interval (CI) 0.91-1.51) P for trend 0.02; RR 1.31 (95% CI 1.02-1.68) P for trend 0.01; RR 1.28 (95% CI 1.00-1.63) P for trend 0.01, respectively), but the association disappeared after multivariate adjustment (RR 0.92 (95% CI 0.71-1.19) P for trend 0.97; RR 1.06 (95% CI 0.82-1.36) P for trend 0.48; RR 1.04 (95% CI 0.80-1.35) P for trend 0.46, respectively). Other tocopherols and tocotrienols as well as vitamin C, carotenoids, flavonols and flavones had no association with risk of diabetes. Conclusions: Dietary antioxidants were not associated with a decreased risk of incident diabetes in middle-aged male smokers.

Dietary intake of carotenoids and risk of type 2 diabetes

“…Moreover, previous research suggests that smoking increases oxidative stress [16], and that smokers may need a higher intake of carotenoids in comparison with non-smokers to reduce their diabetes risk [9]. One study indeed found reduced diabetes risk with higher serum b-carotene and total carotenoid values in nonsmokers only [9], and a study among male smokers reported no associations of dietary [8] or supplementary [14] b-carotene with diabetes risk. However, two other studies did not confirm such an interaction with dietary carotenoids [7] or supplementary b-carotene [12].…”

“…For dietary lycopene, three cohort studies showed no association with diabetes [7,8,15]. Very little research has been performed on other individual dietary carotenoids such as a-carotene, b-cryptoxanthin, lutein, zeaxanthin and the total of carotenoids, and therefore no conclusions can yet be drawn on such intakes [7,8].…”

“…So far, b-carotene has been studied most often, with two observational studies reporting an inverse association of dietary b-carotene with diabetes [6,7] and another reporting no association among male smokers [8]. In addition, studies that addressed serum or plasma b-carotene values in association with diabetes risk showed inconsistent results [6,9e11].…”

“…Randomized controlled trials with b-carotene supplementation consistently showed no effect on diabetes among women with a history of cardiovascular disease [12], generally healthy men [13] and among male smokers [14]. For dietary lycopene, three cohort studies showed no association with diabetes [7,8,15]. Very little research has been performed on other individual dietary carotenoids such as a-carotene, b-cryptoxanthin, lutein, zeaxanthin and the total of carotenoids, and therefore no conclusions can yet be drawn on such intakes [7,8].…”

Lutein intake at the age of 1 year and cardiometabolic health at the age of 6 years: the Generation R Study

“…Studies assessing lutein in relation to metabolic syndrome were all cross-sectional, and thus the inverse relationships that were observed could potentially be explained by reverse causation. Prospective studies in adults that investigated lutein (levels or intake) in relation to risk of type 2 diabetes found inconsistent results (30)(31)(32)(33) , and these studies all had a follow-up period of >10 years, and are thus less prone to risk of reverse causation.…”