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Calcium Supplement Claims

Calcium supplement advertising claims can appear confusing, calcium-supplement-claims | Articlewith good reason. Sometimes the claims may be simply wrong or represent special subgroup results of a clinical study, not the overall outcome.

Two current calcium supplement claims serve as examples. One leading calcium pill claims to be “proven to reduce the risk of hip fractures by 29%.”  This claim comes from a large clinical study entitled “Calcium plus Vitamin D Supplementation and the Risk of Fractures” published in the New Journal of Medicine in 2006.  The study involved 36,282 postmenopausal women taking either 1000 mg of calcium carbonate plus 400 IU of vitamin D daily or a placebo over 7 years.  The authors concluded that “among healthy postmenopausal women, calcium with vitamin D supplementation resulted in a small but significant improvement in hip bone density, did not significantly reduce hip fracture, and increased the risk of kidney stones.”

Then why does this particular pill claim to reduce fractures by 29%?  The answer lies in a sensitivity analysis done by the authors afterwards of highly compliant calcium supplement users. That subgroup recorded a 29% reduction in average fractures (or 4 fewer fractures per 10,000 patients) as compared to the placebo group.  The claim is accurate but not reflective of results of what the average calcium carbonate and vitamin D user experienced in the study.

Because subgroups can be created after the fact, many researchers are cautious about making sweeping conclusions on their results. That applies to calcium supplement research or any intervention subjected to randomized, controlled clinical trial (RCT).

The second example of claim confusion also involves another calcium carbonate brand, this one under the brand name of Algaecal.  According to the company website, “In just six months (180 Days), participants experienced a significant average INCREASE in bone mineral density of 2.8% as evidenced by before and after DEXA scans. Highly compliant participants experienced an INCREASE in bone mineral density by an incredible 3.7%."

Realities of Misleading Claims
This particular calcium supplement trial is unpublished but an executive summary dated April 3, 2008 was posted online by the supplier.  As with the prior example, the company emphasizes highly compliant subgroup results over the average outcome in the study. More importantly, the results appear to be inflated.  The 2.8% and 3.7% bone changes come from calcium-supplement-claims | Articlefigure 2 of the executive summary. The 2.8% figure represents the change from a made-up placebo. The only “real” increase in the study was from baseline, 2.18%. Moreover, the executive summary authors clearly state that figure 2 percentages are annualized, meaning the 6-month actual results were doubled.  As such, the true average improvement in bone density from the beginning is 1.09% after 6 months, not 2.8 %.  The highly compliant subgroup increase at 6 month is not 3.7% but 1.85%!

How do you know which claims to believe? Start by reviewing the abstract of a study that serves as the basis of a claim. Not finding similar language as the claim in the abstract should trigger a red flag.  If the study is not referenced by the company or not even published, be extra cautious. Somebody may be pushing too hard to sell you a calcium supplement.