Abstract
Purpose
Diet may play an essential role in the aetiology of bladder cancer (BC). The B group complex vitamins involve diverse biological functions that could be influential in cancer prevention. The aim of the present study was to investigate the association between various components of the B group vitamin complex and BC risk.
Methods
Dietary data were pooled from four cohort studies. Food item intake was converted to daily intakes of B group vitamins and pooled multivariate hazard ratios (HRs), with corresponding 95% confidence intervals (CIs), were obtained using Cox-regression models. Dose–response relationships were examined using a nonparametric test for trend.
Results
In total, 2915 BC cases and 530,012 non-cases were included in the analyses. The present study showed an increased BC risk for moderate intake of vitamin B1 (HRB1: 1.13, 95% CI: 1.00–1.20). In men, moderate intake of the vitamins B1, B2, energy-related vitamins and high intake of vitamin B1 were associated with an increased BC risk (HR (95% CI): 1.13 (1.02–1.26), 1.14 (1.02–1.26), 1.13 (1.02–1.26; 1.13 (1.02–1.26), respectively). In women, high intake of all vitamins and vitamin combinations, except for the entire complex, showed an inverse association (HR (95% CI): 0.80 (0.67–0.97), 0.83 (0.70–1.00); 0.77 (0.63–0.93), 0.73 (0.61–0.88), 0.82 (0.68–0.99), 0.79 (0.66–0.95), 0.80 (0.66–0.96), 0.74 (0.62–0.89), 0.76 (0.63–0.92), respectively). Dose–response analyses showed an increased BC risk for higher intake of vitamin B1 and B12.
Conclusion
Our findings highlight the importance of future research on the food sources of B group vitamins in the context of the overall and sex-stratified diet.
Introduction
With an estimated 549,393 new cases and 199,922 deaths in 2018, bladder cancer (BC) is the tenth most common cancer worldwide [1]. More than half of all BC cases occur in higher income countries, with the highest incidence rates in North America and Europe and the lowest in Africa. Due to high recurrence rates, BC is an expensive malignancy to treat from diagnosis to death, with estimated costs ranging from USD 89,287 to USD 202,203 per patient [2]. In fact, bladder cancer is the most expensive malignancy to treat of all cancers [3]. Therefore, BC is an important public health problem.
BC is a complex disease not only influenced by genetic predisposition, but also lifestyle, environmental, and occupational exposures could potentially play an important role in the development of this disease [4]. The more established risk factors associated with the development of BC include smoking and deleterious occupational exposure [5, 6] and male gender [5, 7]. Since the bladder is an important excretion organ through which dietary metabolites are filtered, diet may play an essential role in the development of BC. According to the United States National Cancer institute, one third of all BC cases could have been prevented by adherence to dietary recommendations, hence the salient need to investigate potential associations between foods, nutrients and BC [8].
Previous epidemiological research on diet and BC reported that high amount of fluid, fruit, vegetable, yogurt, whole grain and dietary fiber intake were associated with a reduced risk of BC [9,10,11], while higher intake of barbecued meat, pork, and total fat may increase BC risk [8]. At last, organ meat consumption has also been associated with BC development [12].
Although these findings for individual food items lead to useful dietary recommendations, it remains unclear what nutrients or bioactive compounds are responsible for the observed effects on BC risk [13].
The B group complex vitamins are found in a variety of foods, including meat, whole grains, and are especially in rich supply in fruits and vegetables [14]. The B group complex vitamins include (1) thiamine (B1), (2) riboflavin (B2) and (3) niacin (B3), which mainly play a role in energy metabolism [15,16,17], (4) pyridoxine (B6), which reduces oxidative stress (as does vitamin B2), thereby preventing DNA damage [18, 19], (5) folate (B9), and (6) cyanocobalamin (B12), which play a significant role in protecting and maintaining the stability of the human genome by the maintenance of one-carbon metabolism (i.e. a set of interconnected biochemical pathways driven by both vitamin B9 and B12 to generate methyl groups for DNA methylation [20]), thereby possessing the potential to lower the chance of a neoplastic events [14, 21]. However, despite the biological plausibility that these B group vitamins play a role in cancer prevention, epidemiological evidence on the effect of these B group vitamin compounds on BC development is lacking or inconclusive [4, 14, 22]. Inverse associations with BC risk have only been reported for high intake of the vitamins B9, B12 and B6 [4, 23, 24]. A meta-analysis, however, concluded that the evidence for this protective effect is limited [14].
This lack of evidence could be due to the small sample sizes of previous studies and their consequent lack of statistical power to detect associations. The present study, therefore, aims to provide a more precise quantitative estimate for the associations between the various components of the B group complex vitamins and BC risk by pooling data from four cohort studies.
Find the complete article under this link: https://link.springer.com/article/10.1007/s00394-022-02805-2
Editorial published on Springer link, in The European Journal of Nutrition, February 7, 2022
