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.
The outcome from your research come into agreement with before published degree, however in conflict with people. Both cohort education and you will before intervention examples discover higher calcium consumption or supplements was about modestly less dangers of adenoma, metachronous adenoma and you can CRC. 7,8,9,10,eleven,twelve,15,32 Yet not, the outcomes regarding a huge-measure randomised clinical test (WHI) do chemistry not service an aftereffect of calcium and additionally supplement D supplements with the occurrence from CRC after seven years of pursue-up. 16 It is possible that the follow-up several months within the WHI may not have been for enough time to possess a protective impact are obvious. Indeed, the study of Nurses’ Fitness Study and Health professionals Go after-right up Study not merely demonstrated a keen inverse relationship ranging from calcium supplements consumption and CRC and also indicated that the newest associations turned increasingly stronger with growing symptoms off latency, and you will is actually strongest on 12–sixteen ages follow-up period. 33 Which have an average go after-up months significantly more along these lines research compared to the WHI, i as well report comparable part quotes given that Zhang ainsi que al., having a healthier inverse connection to own distal CRC although not to own proximal CRC. 33 A beneficial pooled-study out of 10 cohort degree plus said the brand new inverse connection anywhere between milk and you may CRC are limited by malignant tumors of the distal, not the fresh proximal anus. 15 Hence accumulating proof constantly indicates calcium supplements consumption are in the reduced threat of distal CRC.
Metachronous colorectal adenoma (perennial adenoma)
It’s notable if we evaluated the newest joint connectivity from California intake with Mg consumption classified by the RDA peak for three different varieties of colorectal neoplasia chance (experience adenoma, incident CRC or incident distal CRC), we found comparable fashion like in the first analyses where the inverse relationships having Ca intake when it comes to these types of effects was indeed all of the stronger having Milligrams consumption on otherwise above the RDA opposed in order to Mg consumption below the brand new RDA (Supplementary Dining tables 4–6). Yet not, none of testing to have correspondence was in fact statistically extreme having said that towards examination to have communication we observed toward California:Milligrams percentages. It is consistent with earlier findings into the Eastern Asian populations for the that the connections have been mathematically extreme between Ca:Milligrams rates that have calcium supplements intake, not ranging from magnesium intake which have calcium intake. 19 Quite simply, the latest telecommunications that have California:Mg percentages can’t be explained of the magnesium consumption alone.