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| Version | Summary | Created by | Modification | Content Size | Created at | Operation |
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| 1 | Jiaqi Yang | + 1139 word(s) | 1139 | 2022-03-21 11:00:56 | | | |
| 2 | Lindsay Dong | + 2 word(s) | 1141 | 2022-03-22 03:07:55 | | | | |
| 3 | Lindsay Dong | + 2 word(s) | 1141 | 2022-03-22 03:09:03 | | |
β-carotene is widely available in plant-based foods. β-carotene supplementation had no beneficial effects on cardiovascular disease (CVD) incidence and potential harmful effects on CVD mortality.
β-carotene showed a 4% increased risk on overall CVD incidence and a 17% risk increment of β-carotene supplements for total stroke among adults compared with the placebo or controlled group. However, no effects were shown for major CVD events, other CVD, or myocardial infarction separately, which were in accordance with previous meta-analyses [7][9][10][11]. There is a 9% increased risk of CVD in the male population, while no effect was shown among female individuals; thus, gender might play a role in β-carotene’s efficacy on cardiovascular incidence. There is an increased risk of total stroke among male smokers and intracerebral hemorrhage among male heavy drinkers [16][17]. However, in the Women’s Health Study, no significant benefit or harm on stroke was observed among smokers (13% of female population at the baseline) [18]. Still, there was a possibility of random findings because of the small sample size. In addition, the gender differences may also be caused by the different health behaviors between men and women. Both cigarette smoking and heavy alcohol intake are established risk factors for stroke. Tobacco use facilitates the development of free radicals and atherosclerotic process [19]. It also increases the stroke risk by decreasing cerebral blood flow [19]. Studies also showed that, under certain conditions such as high oxygen concentration, β-carotene switched to a pro-oxidant effect [20][21][22]. This pro-oxidant mechanism generates the β-carotene radical cation, which requires vitamin C to repair. However, due to the low serum level of vitamin C in smokers, the β-carotene radical may lead to an increased risk of cardiovascular disease [21]. Heavy alcohol consumption (more than 3 to 4 drinks per day) causes harmful physiological responses and is associated with higher cardiovascular risk, which is apparent in both men and women [20]. Since smoking and drinking rates among male individuals are generally higher than female, these differences in proportion may lead to the discrepancy of β-carotene’s efficacy on stroke or CVD incidence in sex groups. In general, the risk increment of CVD among smoking populations is 14%.
Results also indicated an increased risk of CVD in the subgroups of low-dose and single treatment of β-carotene. This result conflicts with previous meta-analyses which showed null effects [9]. However, this finding can be explained by previous literature. A previous study manifested that, besides the oxygen tension, the β-carotene concentration and interactions with other antioxidants also influenced the pro-oxidant effect of β-carotene [22]. Animal studies suggested that excess dietary intake of β-carotene facilitated the peroxidation in vivo, especially in an α-tocopherol-deficient diet since the presence of other antioxidants in the body might attenuate the pro-oxidant effect of β-carotene [22][23][24].
β-carotene was consistently associated with increased risk of mortality, including CVD mortality and all-cause mortality. Harmful effects were also observed in the single-treatment subgroup. Previous studies also indicated that high-dose, single or combined intervention of β-carotene increased the risk of all-cause mortality [8][9]. In at-risk and smoking populations, there are positive associations between β-carotene and CVD mortality. The USPSTF report also identified an increased risk of lung cancer in the high-risk population or smokers and hypothesized that the single supplementation of vitamins affected the physiologic system in an implicated way which could be either ineffective or could dose-harm to a certain disease risk [7].