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Careful account of vitamin D study closes with questionable recommendation on testing

Weight loss plus vitamin D reduces inflammation linked to cancer, chronic disease

Our Review Summary

vitamin DThis news release describes a randomized, controlled clinical trial designed to learn whether adding vitamin D supplements to substantial weight loss regimens would have a synergistic effect in reducing inflammatory chemicals in the bodies of overweight, older women with levels of vitamin D considered too low. The study, published in Cancer Prevention Research, has potential relevance for cancer prevention because inflammatory cytokines have been implicated in the genesis and progression of some cancers, as well as heart disease and other disorders. The release offers substantial details about the design, metrics and outcomes of the clinical trial and does a pretty good job of defining the possible reasons for the effects of chronic inflammation and weight loss on cancer development. It goes to some lengths to narrowly define the results and avoid overstatement. That said, the release ends on a sour note by encouraging readers to talk to their doctors about vitamin D testing — a recommendation not consistent with U.S. Preventive Services Task Force guidelines and which is not supported by this research. Readers might also have been better informed if the release had offered more context regarding the many conflicting and sometimes confusing studies that have previously looked for links among vitamin D, inflammatory responses, diet, overweight, sun exposure and cancer.

 

Why This Matters

News releases that include the words “diet,” “overweight,” “vitamin,” and “cancer” are almost narrative nuclear events, often guaranteeing an explosion of coverage, souped up vitamin sales pitches, and lots of negative fallout whose half-life seems forever. Cancer remains the second biggest killer disease overall of Americans, and some experts believe that it will soon push heart disease and stroke out of first place. Thus cancer prevention is a deservedly hot topic, and it is no surprise that Americans are eager for information about ways to limit their risk. News releases that describe research on these topics have enormous power to inform and misinform.

Criteria

Does the news release adequately discuss the costs of the intervention?

Not Satisfactory

There was no mention of the potential costs of screening women for vitamin D levels (as encouraged in the release in a statement from the principal investigator) or the cost of supplementation.

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?

Satisfactory

The release does a good job of comparing data and providing explanations for the measurements used. We’ll award a Satisfactory for that precision, but as noted below under “Evidence,” there was no explicit caution regarding the fact that measurements of interleukin-6 (IL-6) are only surrogates for the effects of weight loss and vitamin D on clinical outcomes related to inflammation (e.g. cancer diagnoses). IL-6 levels dropped in both the placebo and vitamin D arms, and it’s not clear whether the statistically significant additional decline in IL-6 observed in the vitamin D group is clinically important.

Does the news release adequately explain/quantify the harms of the intervention?

Not Satisfactory

Because some of the participants were vitamin D-deficient and the dose of vitamin D provided was modest (2000 IU/d), this was a tough call. But supplementation is often so misunderstood, overhyped and oversold that some statement cautioning readers to pay attention to the specifics of this study and not apply its recommendations to everyone seems prudent.

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

For the most part, the release provides a cautious and accurate description of what appears to be a well-conducted clinical trial in a well-defined population. For example, it notes that weight loss and vitamin D lowered inflammation LINKED to cancer — not that these things reduced cancer risk itself (something this study couldn’t establish). But as noted above, we would have appreciated an explicit acknowledgment that IL-6 is a surrogate marker for the clinical outcomes that people care about. And more importantly, we’re concerned about the closing comment that women should talk to their doctors about measuring their vitamin D levels to determine the most appropriate dose. The problem is there is no evidence supporting screening or treating to a level — and certainly not from this study. The US Preventive Services Task Force has concluded that evidence is insufficient to recommend routine vitamin D screening and the IOM has said that while there are data supporting the benefits of vitamin D supplementation with bone health and fall prevention, there is no evidence supporting benefits for cancer. While testing may be warranted in those with signs or symptoms of clinical deficiency, the statement made here implies that everyone should be tested so that an appropriate dose of vitamin D can be selected. That goes beyond the available evidence.

Does the news release commit disease-mongering?

Satisfactory

It’s hard to argue that overweight, vitamin deficiency, chronic inflammation and cancer are not real threats, so no mongering apparent here.

Does the news release compare the new approach with existing alternatives?

Not Applicable

The study didn’t discuss alternative preventive measures or genetic causes of increased cancer risks. But this is such a broad and expansive topic that we don’t think the release should have been expected to address those myriad issues. We’ll rate this Not Applicable.

Does the news release establish the availability of the treatment/test/product/procedure?

Satisfactory

Primary care physicians and other health providers are well positioned to monitor blood levels of vitamin D, along with dietary and exercise regimens. The news release makes that clear, albeit indirectly. As noted above, we think the release goes too far in suggesting that people ask their doctors about having their vitamin D levels checked. But we’ve already docked points for that, so we’ll award a Satisfactory rating here.

Does the news release establish the true novelty of the approach?

Satisfactory

The release makes a case for this being the first clinical trial of its kind; although it’s always difficult to make that statement absolutely, the writer of the release attributes the statement to the study author. As a general rule, it’s probably best to say “believed to be the first.”  While the release meets our standard here, we also wish it had delved a bit into the background of previous vitamin D research and the conflicting and confusing messages that research has generated. Without that context, the typical reader might wrongly jump to the conclusion, based on the wording of the lede and other parts of the release, that this study of vitamin D supplementation — because it was a controlled clinical trial — has somehow settled the important questions about the role of vitamin D and inflammation in cancer risk. The debate remains alive and well. 

Total Score: 6 of 9 Satisfactory

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