br analyzing magnesium within specific
analyzing magnesium within specific cellular or tissue compartments. Interestingly, use of a reported dietary intake estimate suggested the Ca/Mg ratio was linked with prostate cancer risk, while results were weaker using the blood biomarker, perhaps suggesting that dietary intake estimates provide a more stable estimate of sustained calcium and magnesium exposure despite potential reporting errors. Alternatively, dietary reporting of the Ca/Mg ratio is potentially non-specific and thus may be reflecting some other correlated factor linked with prostate cancer risk.
There are several limitations to address in this analysis. As pre-viously discussed, food frequency questionnaires have known limita-tions . Our case-control study design does not remove reverse causation as an alternative explanation. For example, the ‘magnesium trap’ hypothesis developed by Wolf and colleagues suggests cancer Blasticidin S may pull magnesium from blood and retain high intracellular magne-sium levels necessary for cell proliferation . Since it is possible that metastasis to the bone could aﬀect circulating calcium and magnesium levels, we excluded men with known metastatic disease from analyses. Alternatives to the analysis of blood levels include a 24-h urine sample or nails, however these types of biospecimens were not available for this analysis. We did not have data on nonprescription and magnesium-rich medications (e.g., milk of magnesia), and we did not measure io-nized magnesium and calcium, vitamin D, insulin, blood cytokines, or other interesting biomarkers, but we may in the future . Race dif-ferences in magnesium levels reached a level of statistical significance, but the biological relevance of these diﬀerences in the context of car-diovascular disease or other morbidity is unclear.
In summary, we found a small but statistically significant diﬀer-ences in magnesium levels associated with race, such that black men had lower magnesium intake and lower blood magnesium levels than comparable white men. However, we found no evidence of a protective association between magnesium and prostate cancer in either black or white men.
Conflicts of interest
No author has a conflict of interest or any financial interests to disclose.
Appendix A. Supplementary data
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