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Many observational studies have found that dietary calcium intake is inversely related to body weight and body fat mass. It has been suggested that one possible physiological mechanism behind this is that dietary calcium increases faecal fat excretion. To examine the effect of calcium from dietary supplements or dairy products on quantitative faecal fat excretion, the authors performed a systematic review with meta-analysis. They included randomized, controlled trials administering extra calcium (supplements or dairy) in healthy subjects, where faecal fat excretion was measured. Thirteen research papers were found to be eligible for inclusion in the analysis.
As a consequence of the rigorous statistical analyses, it is now evident that dietary calcium does impair the absorption of dietary fat and increase faecal fat excretion. The authors found a large inconsistency in the results of trials using calcium supplements, whereas the trials that gave extra calcium in the form of dairy products consistently found an increase in fat excretion. The authors estimate that an increase in daily dairy intake of 1,200 mg. can be expected to result in a 5.2 g. per day increase in faecal fat excretion, or about 45 kcal. per day or 2 kg. body weight over a year.
However, though the effect was statistically highly significant, its importance for daily energy balance and body-weight regulation may be minor. Christensen and colleagues conclude that “dietary calcium has the potential to increase faecal fat excretion to an extent that could be relevant for prevention of weight (re-)gain. Long-term studies are required to establish its quantitative contribution to weight control over time.”
The project was initiated by the Danish obesity specialist Professor Arne Astrup, and was funded by unrestricted grants from the Oak Foundation and the Global Dairy Platform LLC, Chicago, USA.