Diet in the News – What to Believe?

From national newspapers to personal blogs, nutrition articles are everywhere. But such a constant stream of information can make it difficult for readers to distinguish reliable research from weak studies and sensational headlines. Nutrition research is complex, and is often oversimplified by the media. Writers may report on a single preliminary study that is unverified by additional research, or highlight a study because it contradicts current health recommendations – the goal being an attention-grabbing headline. A quick research reality-check:

  • Research is an ongoing process, with a steady stream of new studies published every month. Because dietary recommendations are made based on the best science available at that time, guidelines may change as new research becomes available.
  • Contradictions between published research papers may occur. They are an inevitable and healthy part of the scientific process.
  • Not all scientific studies are created equal. Some study types are more reliable than others.
  • Newer studies are not necessarily more reliable than older studies.

What’s missing from the increasingly fast-paced media world is context. Diet stories in the news often provide little information about how the newly reported results fit in with existing evidence on the topic, which may result in exaggerating the new study’s importance.

The research process may seem confusing to the public, as contradicting studies occasionally arise. However, when viewed in the proper context – something often overlooked in media coverage – readers can look behind the headline and decide whether a research study is reliable or not.

Here are seven questions that serve as a “reliability radar” to help determine which health and nutrition news stories are worth your time.

7 Questions to help put health news in context

  1. One of the most crucial things to keep in mind is how does a given study fit into the entire body of evidence on a topic? What is the weight of the evidence?
  1. Is the story reporting the results of a single study? A single study is rarely influential enough to warrant that people change their behaviors based on the results. It is important to consider how that study fits in with other studies on the topic. Some articles provide this background, but sometimes you may need to do more digging on your own.
  1. How large is the study? Take note of the study’s sample size, as large studies often provide more reliable results than smaller studies.
  1. Was the study done on animals or humans? Many important studies have been carried out on animals, but to best understand how food and nutrients affect human health they must be studied in humans.
  1. Did the study look at real disease endpoints, such as heart disease or osteoporosis? Chronic diseases, like heart disease and osteoporosis, often take many decades to develop. To avoid waiting that long, researchers will sometimes look at markers for these diseases, like narrowing of the arteries or bone density. However, these markers don’t always develop into the disease.
  1. How was diet assessed? Some methods of dietary assessment are better than others. Good studies will be able to show sound methodology.
  1. What type of study is it? Study types fall into different categories, including cohort studies, randomized controlled trials, meta-analyses, systematic reviews, case control studies, and animal studies. The Department of Nutrition’s Dr. Frank Hu sums up why some study types are considered more reliable than others:

The “gold standard” is randomized clinical trials of dietary interventions on hard endpoints such as cancer and heart disease. However, such trials are often infeasible due to high cost, low long-term compliance, and potential ethical issues. In the absence of evidence from such trials, the strongest study design would be well-designed prospective cohort studies, in which a large number of healthy participants are followed for years or decades for disease outcomes. Cohort studies are usually superior to retrospective case-control or cross-sectional studies, which are prone to biases due to recall of dietary factors and selection of control participants. Animal studies can help understand disease mechanisms but the results may not apply to humans. Smaller human dietary intervention trials on intermediate biomarkers such as blood glucose or cholesterol can also help to illuminate biological mechanisms, and evidence from such trials is complementary to that from large cohort studies. In the end, combined evidence from several types of studies—prospective cohort studies and human intervention trials in particular—can be used to inform dietary guidelines and policies. Summarizing evidence using meta-analyses or systematic reviews can be helpful, but meta-analyses should be conducted with caution and interpreted in light of the totality of the evidence.