Supplementation with calcium and vitamin D, alone or together, leads to increases in serum calcium (S-Ca) concentration with a peak 4 h after each ingestion and a more long-lasting elevation in serum 25-hydroxyvitamin D (S-25(OH)D), the marker metabolite for vitamin D status. Whether regular calcium supplementation elevates S-Ca after several months of use is debatable but this question has great importance for the understanding of the effects of calcium supplementation and S-Ca on health outcomes since continued use for many years is recommended.

A meta-analysis by Karolinska Institute researchers published in npj Genomic Medicine last 14th October 2021 indicated that calcium and calcium plus vitamin D supplementation increased fasting S-Ca concentrations over 1–4
years of use. MR analyses showed that genetically predictedlifelong increases of S-Ca concentrations were associated with lower odds of longevity and with an increased risk of cardiovascular disease. There was no evidence supporting associations of S-Ca with cancer and of S-25(OH)D with longevity, cardiovascular disease, or cancer.

Calcium supplementation (1000 mg dose) leads to an acute elevation of S-Ca with a peak of about 0.09 mmol/L increase after 4 h. S-Ca is homeostatically regulated and the effect of prolonged calcium supplementation on fasting S-Ca has not previously been comprehensively assessed. Researchers conducted a meta-analysis to address this question and found that both calcium and calcium plus vitamin D supplementation led to increased fasting S-Ca after several years of supplement use.

In the current study, it has been shown that predispositions to lifelong elevated calcium levels in the blood are linked to a higher risk of coronary heart disease and heart attack with shortening of life expectancy.