calcium and critical thinking

by Sarah Luna

Each week, the nutrition department hosts a seminar where the grad students present a scientific article. I’ve been greatly disappointed in these types of seminars in the past. Luckily, Cornell seems to do them right.

Today my grad buddy (kind of like a grad SA) presented the findings of a calcium study done in 2006. This randomized, double blind, placebo study analyzed the effects of calcium and vitamin D supplementation in 38,000 postmenopausal women over seven years–one group got the calcium, the other got the placebo. Ok, even if you’re not familiar with study design at all, 38,000 people yield a lot of data.

Oddly enough, the study found no effect of supplementation on the number of hip fractures these women experienced. This was alarming because calcium and bone health seem inextricably linked in health classes and popular thinking. Isn’t calcium supplementation supposed to help?

Well, it’s complicated.

These women were not deficient in calcium or vitamin D. The mean age was 62 in both groups. The mean BMI was 29. I read that and was deeply saddened–the average woman in this study was borderline obese. They had a very low activity level.

So calcium supplementation in a non-deficient population did not reduce the risk of hip fracture.

In the Q&A session, it was brought up that perhaps a deficient population would be helped by supplementation. That calcium is effective up to a certain amount.

This caused us to look at the history of calcium studies and their effects on public policy. In the 90s, studies showed that calcium supplementation did reduce the risk of hip fractures. This led to the widespread calcium fortification of foods (like orange juice). This fortification has resulted in a less deficient population, which now responds less to additional calcium supplementation.

This study also found that supplemental calcium significantly increased the risk of kidney stones. Ouch. Other studies corroborate this finding and add that dietary calcium does not.

I took the following from this article and discussion:

  1. Calcium supplementation in a non-deficient population has no effect on hip fracture risk (no clinical significance) and increased risk of kidney stones; therefore, blanket calcium supplementation should not be attempted.
  2. Nutrition research spurs public policy (fortification) which then changes research outcomes.
  3. Over-consumption (of anything) causes problems just like deficiency does.
  4. Dietary sources are more desirable than supplemental sources.

Many women do benefit from calcium supplementation. The important thing is not to overshoot your individual needs. If you’re deficient, supplement as needed. If not, leave it alone.

I love when classes inspire me to think.