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Masters Core Fitness
Be your own nutrition sleuth

Research Design

Be your own nutrition sleuth

Posted on February 09, 2015 at 04:59 AM

You may have read the headlines — Tomato-rich diet ‘reduces prostate cancer risk’ or Overweight people ‘live longer,’ study claims.
Headlines like these might pique your interest to read more and follow the advice to achieve a healthier you.

But flashy headlines like these are often deficient in providing the real truth.

Truth be told, I am often overwhelmed by the storm of health-related topics and their contradictory conclusions and recommendations. Should I completely chuck trans fats from my diet? What should I believe about salt?

Even after vetting a study’s research design — sample size, methodologies and conclusions — I’ve come to side with Ben Goldacre, author of Bad Science: Quacks, Hacks, and Big Pharma Flacks, who writes: “The most important take-home message with diet and health is that anyone who ever expresses anything with certainty is basically wrong, because the evidence for cause and effect in this area is almost always weak and circumstantial.”

Indeed. Researchers often think they deserve a chance to fluff, and honestly that’s human nature.

A go-to guide that puts fluff into perspective is Behind the Headlines, a guide featured by the U.S. National Library of Medicine. This feature, which explains the science behind health stories in the news, examined the article about the purported benefits of a tomato-rich diet, which emanated from a U.K study published in a peer-reviewed medical journal.

While the media generally got it right, they used wildly different figures for the number of study participants, from 1,800 to 20,000. Reason: Of the 23,720 men who were initially included in the study, a great many of them were excluded because of missing questionnaires. Getting the sample size wrong may not sound like a biggie, but sample size will affect the value of a study.

While the U.K researchers concluded that eating more than 10 portions of tomatoes per week is associated with an 18 percent reduced risk of prostate cancer, the study did not provide enough evidence to change the current dietary recommendations for reducing the risk of prostate cancer: Eat a healthy, balanced diet; get regular exercise and stop smoking, rather than rely on eating one exclusive food, such as tomatoes, according to the Behind the Headlines review.

Moreover, the tomato study was a case controlled study, and this type of research design does not prove cause and effect. In other words, the study didn’t prove that eating more tomatoes prevents prostate cancer even though the association is biologically plausible, because the lycopene in tomatoes is a nutrient thought to protect against cell damage. However, the jury is still out on whether it really does protect cells.

Nonetheless, there appears to be a bias toward reporting positive research findings. The best thing you can do to promote your health it to promote your knowledge about how to interpret research articles noted in the news. The basic premise is to keep asking questions and seek more detailed answers. Here are some factors to consider:

  • Pay attention to the type of research design. That will tell you a lot. All research is based on a particular design, and they all serve a purpose. But only randomized controlled clinical trials can provide sound evidence of cause and effect because they are carefully planned experiments and include methodologies that reduce the potential for bias between patients who are in a control group and those who are not. In contrast, case studies, while fascinating, don’t use control groups to compare outcomes and have little statistical validity. Other studies, such as meta-analysis studies, merge data from multiple studies and mathematically combine the results using accepted statistical methodology to report the results as if it were one large study. Again, doesn’t prove cause and effect but may help identify future research questions, a good thing.
  • Review the subjects. Who was involved in the study — males, females or both; perhaps just animals? How many and how old were the subjects? Were they healthy or afflicted with a particular condition or disease?
  • Consider the time frame. Was the study conducted over several months or years? Was the time frame long enough to detect changes?
  • Check the measurement tools. Did researchers use reliable and valid tools to accurately answer the research question?
  • Compare the reported results with the findings. Do they stack up, or did the results go beyond the findings?
  • Check for conflict of interest. I’m always skeptical of studies that find positive results and are funded by a concern that would benefit financially. Knowing who sponsored the research and whether it was peer reviewed is critical when evaluating studies.
  • Look for other research on this topic area. How does the other research compare?

Ultimately, your best source of advice and knowledge is to check in with a medical professional — your doctor or a specialist in the area that concerns your health. After all, it’s your body, and isn’t that the truth?


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