To our knowledge, no previous study has prospectively evaluated the associations of calcium intake with incident adenoma, metachronous adenoma, and incident cancer in the same cohort using the same food frequency questionnaire, which minimises misclassification that can occur when combining dietary estimates from multiple studies with different food frequency questionnaire instruments. One weakness is that the PLCO is a sigmoidoscopy-based randomised trial, which only screened the distal colorectal region. Thus, incident adenoma cases mainly included adenomas from the left side of the bowel although metachronous adenoma and incident CRC cases included cases from both proximal and distal regions. However, it is interesting that reports found that colonoscopy was linked to reduced deaths from the distal colorectal region, but not the right. 41,42 Similarly another report from the PLCO observed sigmoidoscopic screenings only reduced distal, but not proximal CRC mortality. 25 Further, sigmoidoscopic screenings also significantly reduced both distal and proximal CRC incidence in the PLCO. 25 Thus, the PLCO provides a unique opportunity to test whether calcium intake confers additional protection against proximal and distal CRC among those receiving sigmoidoscopic screening(s). Similar to other nutritional epidemiological studies using food frequency questionnaires, there are possibly non-differential measurement errors which usually bias the results to the null. In addition, despite the relatively large sample sizes in our study, our investigations between calcium intake and colorectal carcinogenesis were constrained when evaluating by Ca:Mg ratio strata. The number of cases for some sub-categories of calcium intake in the <1.7 Ca:Mg ratio stratum were few and in some instances zero, making inferences relating to trends difficult in this stratum. Furthermore, to maintain relatively balanced number of cases in calcium categories in the largest Ca:Mg ratio stratum, we choose 2.5, the median in the data set, as one of the Ca:Mg ratio cut-offs, instead of 2.6 as investigated in previous studies. Finally, considering investigation of three main outcomes, several sub-group analyses and tests for effect modification, it is possible that findings reported in this study may be due to chance. We found different calcium intake distribution between intervention arm and control arm shown in Supplementary Table 1. The reason is not clear, and it may be due to different food frequency questionnaires were in two arms. However, we found the association pattern between calcium intake and CRC risk is similar in the intervention arm and control arm.
Overall performance
The outcome from our data are in contract which includes before composed studies, however in argument with people. Each other cohort education and you may before intervention products found high calcium supplements intake otherwise supplementation is actually pertaining to moderately reduced risks of adenoma, metachronous adenoma and CRC. seven,8,9,10,eleven,a dozen,fifteen,32 But not, the outcomes of a massive-scale randomised clinical test (WHI) don’t service an effect of calcium together with nutritional D supplements into the chance away from CRC immediately https://datingranking.net/cs/korean-cupid-recenze following 7 several years of go after-right up. sixteen You will be able that the realize-upwards months in WHI may not have become for a lengthy period to have a safety effect to be obvious. Actually, the study of your own Nurses’ Wellness Investigation and you can Medical researchers Go after-upwards Analysis just exhibited an enthusiastic inverse relationship ranging from calcium supplements intake and you will CRC and in addition indicated that the latest connectivity turned into more and more more powerful with growing periods from latency, and you will is actually most effective into the twelve–sixteen decades realize-up several months. 33 With an average follow-upwards months a great deal more in this way research compared to the WHI, we too report similar point rates due to the fact Zhang ainsi que al., which have a healthier inverse association to own distal CRC however to have proximal CRC. 33 A pooled-research away from 10 cohort education as well as claimed the newest inverse relationship ranging from milk products and you can CRC try limited to cancer of your own distal, not new proximal anus. 15 Therefore accumulating proof consistently implies calcium supplements intake is of the less risk of distal CRC.
Metachronous colorectal adenoma (recurrent adenoma)
It’s distinguished whenever i evaluated the combined relationships away from California intake having Milligrams consumption categorised from the RDA level for a few different types of colorectal neoplasia chance (incident adenoma, event CRC otherwise event distal CRC), we receive equivalent style like in our first analyses where the inverse relationships to have California consumption regarding these types of outcomes was all the more powerful having Milligrams intake during the or over the RDA compared to help you Mg intake lower than this new RDA (Second Tables cuatro–6). Although not, not one of the evaluation for telecommunications was statistically significant on the other hand to your evaluating to possess communications i observed on the California:Mg rates. This might be consistent with earlier findings inside the Eastern Asian communities when you look at the that relations have been mathematically tall ranging from Ca:Mg percentages with calcium supplements intake, however ranging from magnesium intake having calcium supplements intake. 19 To put it differently, the communications that have California:Mg percentages can’t be informed me by magnesium intake by yourself.