One thing not up for debate is that nutrition is an important part of overall good health. But that’s where agreement seems to end – at least according to reports in the media. Eat more protein; but all red meat is risky. Eggs send bad cholesterol levels through the roof; no wait, now it’s OK to eat them again. And recently, news about whether supplements, including calcium and vitamin D, protect us or actually cause harm has been fodder for headlines. So how do you parse the contradictory messages?
I recently sat down with Shivani Sahni, Ph.D., Nutrition Program scientist in the Institute for Aging Research (IFAR) to provide some insight into what’s behind the calcium supplement controversy. What I learned is that the science of nutrition is extremely intricate and complicated, and research study results must be understood in a context that lay audiences and even science journalists do not have the expertise to fully appreciate and weigh before formulating simple conclusions. And, most importantly, research is a painstaking and lengthy process taking years to complete. One study builds on another, always discovering a stone unturned that influences earlier and subsequent study outcomes.
Jennifer Davis: According to an NBC News report last September, “Findings, reported in the British Medical Journal's online publication BMJ.com, support what U.S. health officials have been telling Americans for a few years now — taking calcium supplements is not just a waste of time, but it could be harmful.” How does this report square with your research?
Shivani Sahni: There were actually two studies – one on calcium and how it impacts bone mineral density (BMD) and the other on the relationship between calcium and fractures. The paper quoted in this news report focused on the fracture study. It concluded that there is no benefit to increasing calcium intake whether from supplements or diets on fracture outcomes. So it is interesting to figure out where we go from there.
Even though these papers made huge headlines, I don’t think they will really change the standard of care right now. The reason for that is because findings were based on a meta-analysis, which pulled data from a number of studies to look at the association between calcium and fracture. So the results are very dependent on which studies went into this meta-analysis.
It’s important to understand how each study was structured to fully understand the outcomes. For example the biggest study they used was from the Women’s Health Initiative study, which looked at women and the use of calcium supplements and vitamin D and found no benefit. But the important catch is if they had looked at subsequent analysis looking at people who actually adhered to supplement treatment, rather than a population at large, it could have actually made those weaker findings a bit stronger.
I’m concerned that the overall message reported from the BMJ paper is that there is no benefit to dietary calcium, whereas our studies have found significant results with dairy foods, which is an important contributor of dietary calcium. The message that calcium supplements should be avoided also minimizes the benefit of the interaction of vitamins and minerals contained within a healthy diet that keeps bones healthy. So for example we found milk is beneficial not only for supplying calcium, but protein as well, which IFAR studies have shown impacts BMD. Dairy products also contain potassium and magnesium, also essential to bone health. So we’re talking about a very complex system of nutrients within a food. I am very cautious when it comes to endorsing the results of meta-analysis studies. When it comes to diet and understanding what does or does not benefit our health, we shouldn’t consider just a single nutrient.
When you talk about calcium you can’t talk about it alone. You have to talk about vitamin D. You have to take that into consideration and a lot of previous studies for one reason or another were unable to do that. For example, Dr. Douglas Kiel, IFAR’s Director of Musculoskeletal Research contributed to a meta – analysis of research that studied vitamin D and fracture. The findings from that study were null except for a result from a study that included a subgroup of older men. But even in that case, the researchers acknowledged that they did not look at calcium and vitamin D together. It is a problem if initial studies included in a meta-analysis don’t have everything in place to reliably validate the meta-analysis conclusion. It’s complicated.
One study never decides standard of care. In general over-supplementation should be avoided, and the tendency to take supplements in place of getting nutrition from diet is not a good approach to nutritional health. Reliance on supplements should be minimal, based on genuine need and discussed with your doctor.
A final note from the author – A study published in JAMA Internal Medicine made headlines in January suggesting that high doses of vitamin D increase the risk of falls and fractures in older adults. Dr. Kiel was an author on an editorial in the same issue that put the study into perspective.
Dr. Kiel’s recommendation? “Until the safety of larger doses of vitamin D is established, it is better to either get enough vitamin D from diet or take more modest daily supplements if there is a deficiency.”