BACKGROUND: Adequate calcium intake is known to protect the skeleton. However, studies that have reported adverse effects of calcium supplementation on vascular events have raised widespread concern. OBJECTIVE: We assessed the association between calcium intake (from diet and supplements) and coronary artery calcification, which is a measure of atherosclerosis that predicts risk of ischemic heart disease independent of other risk factors. DESIGN: This was an observational, prospective cohort study. Participants included 690 women and 588 men in the Framingham Offspring Study (mean age: 60 y; range: 36-83 y) who attended clinic visits and completed food-frequency questionnaires in 1998-2001 and underwent computed tomography scans 4 y later in 2002-2005. RESULTS: The mean age-adjusted coronary artery-calcification Agatston score decreased with increasing total calcium intake, and the trend was not significant after adjustment for age, BMI, smoking, alcohol consumption, vitamin D-supplement use, energy intake, and, for women, menopause status and estrogen use. Multivariable-adjusted mean Agatston scores were 2.36, 2.52, 2.16, and 2.39 (P-trend = 0.74) with an increasing quartile of total calcium intake in women and 4.32, 4.39, 4.19, and 4.37 (P-trend = 0.94) in men, respectively. Results were similar for dietary calcium and calcium supplement use. CONCLUSIONS: Our study does not support the hypothesis that high calcium intake increases coronary artery calcification, which is an important measure of atherosclerosis burden. The evidence is not sufficient to modify current recommendations for calcium intake to protect skeletal health with respect to vascular calcification risk.
"Also, even in individuals with normal kidney function, the effect of supplemental calcium on cardiovascular health has emerged as equivocal or even slightly negative in some recent studies   . This is a bit surprising in light of calcium's ability to decrease PTH and inhibit GI phosphate absorption, and evidence that calcium intake is not a determinant of risk for coronary artery calcification in the general population ; it has been proposed that supplemental calcium may up-regulate renin production by decreasing serum calcitriol   . Arguably, the optimal approach to moderating PTH in support of vascular and bone health may be to employ effective vitamin D supplementation, while keeping calcium intake moderate so that relatively high serum levels of both calcitriol and calcidiol are maintained. "
[Show abstract][Hide abstract] ABSTRACT: Increased fasting serum phosphate within the normal physiological range has been linked to increased cardiovascular risk in prospective epidemiology; increased production of fibroblast growth factor 23 (FGF23), and direct vascular effects of phosphate, may mediate this risk. Although dietary phosphate intake does not clearly influence fasting serum phosphate in those with normal renal function, increased phosphate intake can provoke an increase in FGF23, and in diurnal phosphate levels, and hence may adversely influence vascular health. Dietary phosphate absorption can be moderated by emphasizing plant-based dietary choices (which provide phosphate in less-bioavailable forms), avoidance of processed foods containing inorganic phosphate food additives, and by ingestion of phosphate-binder drugs, magnesium supplements, or niacin, which precipitate phosphate or suppress its gastrointestinal absorption. The propensity of dietary phosphate to promote vascular calcification may be opposed by optimal intakes of magnesium, vitamin K, and vitamin D; the latter should also counter the tendency of phosphate to elevate parathyroid hormone.
[Show abstract][Hide abstract] ABSTRACT: Through a systematic search in Pubmed for literature, on links between calcium malnutrition and risk of chronic diseases, we found the highest degree of evidence for osteoporosis, colorectal and breast cancer, as well as for hypertension, as the only major cardiovascular risk factor. Low calcium intake apparently has some impact also on cardiovascular events and disease outcome. Calcium malnutrition can causally be related to low activity of the extracellular calcium-sensing receptor (CaSR). This member of the family of 7-TM G-protein coupled receptors allows extracellular Ca2+ to function as a "first messenger" for various intracellular signaling cascades. Evidence demonstrates that Ca2+/CaSR signaling in functional linkage with vitamin D receptor (VDR)-activated pathways (i) promotes osteoblast differentiation and formation of mineralized bone; (ii) targets downstream effectors of the canonical and non-canonical Wnt pathway to inhibit proliferation and induce differentiation of colorectal cancer cells; (iii) evokes Ca2+ influx into breast cancer cells, thereby activating pro-apoptotic intracellular signaling. Furthermore, Ca2+/CaSR signaling opens Ca2+-sensitive K+ conductance channels in vascular endothelial cells, and also participates in IP(3)-dependent regulation of cytoplasmic Ca2+, the key intermediate of cardiomyocyte functions. Consequently, impairment of Ca2+/CaSR signaling may contribute to inadequate bone formation, tumor progression, hypertension, vascular calcification and, probably, cardiovascular disease.
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