Nutrition Science: Reading Beyond the Headlines
“Fruits and vegetables don’t protect against cancer”; “calcium supplements cause heart attacks”—just two examples of recent headlines that appeared in the popular press. Thanks to the swelling public interest in the prevention of disease through diet, just about every magazine, newspaper and website reports on nutrition science. But sometimes this glut of nutrition news is conflicting and confusing, leaving you to wonder, “What am I supposed to eat?”
“Ten or twenty years ago, health research was mostly reported through medical journals that were mainly read by health and research professionals who issued the final word on a topic. Now people get access to the initial studies instead of the final word,” says nutrition researcher Howard Sesso, Sc.D., Associate Epidemiologist at Brigham and Women’s Hospital and Associate Professor of Medicine at Harvard Medical School. “In nutrition science, you don’t always have the same results in study after study. This is problematic; people may then begin to distrust the sometimes conflicting findings they hear.”
Nutrition Science 101
In order to determine whether that vitamin C study you just read about is meaningful, let’s step back for a refresher course on the principles of research. Nutrition research starts with posing a great question (known as a hypothesis,) and then sets out to discover facts that help answer it through observation or experimentation, collection of data, and analysis. There are different types of research—here’s a brief look at the basics.
Observational research investigates the relationships between factors in groups of subjects with regard to health. For example, an observational study might look at the relationship between heart disease and vitamin C intake in a group of females.
Experimental research studies subjects—whether human or animal—that are randomly assigned to either an experimental group (given the treatment) or a control group (given placebo or no treatment.) The difference in the results between the two groups can then be attributed to the treatment. Experimental research is divided into two general types: basic research and clinical trials.
Basic research, which may be conducted in vitro (in test tubes) or with animals, investigates biochemical substances or biological processes, usually to understand how a particular process works. For example, an experiment might be conducted on rats that studies how vitamin C might help reduce oxidation, which plays a role in heart disease.
Clinical trials are studies of human subjects that involve the measurement of variables compared to a control group. For example, a clinical trial might investigate the results of vitamin C supplements on oxidation levels in a group of adults, compared with a similar group that receives no vitamin C supplements.
The “gold standard” in research is a randomized, double-blind, placebo-controlled study, which uses random assignment of subjects to experimental and control groups; neither the subjects nor the persons administering the experiment know the critical aspects of the experiment, so as not to create a bias.
The Nutrition Science Path
According to Sesso, nutrition research typically follows a course: scientists notice a relationship between diet and health through observational research that generates a hypothesis, they investigate the mechanism behind this relationship in test tubes and animals, and then they bring it to human clinical trials—starting with smaller groups of subjects and moving to larger groups. The research that occurs before it gets to the human trial phase is important—it establishes a fundamental understanding—but it is preliminary; you can’t “hang your hat” on the evidence just yet. And then there’s the little detail of publishing research; it must be published in a journal that is peer-reviewed—that means a group of qualified individuals in the same field has evaluated it. Scientific consensus from government and health organizations, such as the U.S. Food and Drug Administration or the American Dietetic Association, comes when a large enough volume of research has been published, which can take a long time.
“You can take vitamin D as an example; there are lots of good mechanistic and observational studies, but there haven’t been a lot of large-scale clinical trials targeting vitamin D. The Institute of Medicine issued a report on vitamin D that was middle of the road—suggestive of benefits, but warning consumers to not take mega-doses until there were more clinical trials,” reports Sesso.
Putting Nutrition Science into Perspective
Nutrition science expert, Howard Sesso, Sc.D., offers tips on how to put those nutrition science headlines into perspective.
- Remember, one study doesn’t decide the truth. No matter how large and expensive the study, a single research finding should not be the basis of changing your diet.
- Consider less specific research findings first. Instead of focusing on research that looks at single foods or nutrients, look at research findings on a dietary pattern, like the Mediterranean diet.
- No single change can make all the difference. In all likelihood, there’s no one pill, one nutrient, or one food that will cure every disease.
- Trust clinical trials more than animal studies. Look beyond the headlines to the study design—if it’s animal research it may not be definitive.
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Written by Sharon Palmer, MSFS, RDN on October 6, 2011; Updated on November 6, 2019.
Image: farmers market, Sharon Palmer, MSFS, RDN