How to Better Understand Scientific Research: Interview with Rosanne Rust, MS, RD, LDN

BY ON OCTOBER 22, 2012

English: Flowchart of the steps in the Scientific Method (Photo credit: Wikipedia)

Prior to starting here at the CRA, I mostly depended on experts and science writers to explain scientific studies appearing in the media. I accessed studies and read them, but truly did not understand how to look for methodology errors or how to evaluate conclusions.

Since working at CRA, I have learned the media often times does not get the science right. Although I know more now than I did before about analyzing studies, I still don’t have the expert-level understanding that researchers, registered dietitians (RD), doctors, or specialists have. I do, however, have access to these experts—a fortunate opportunity not everyone has.

To help others better understand what experts look for when analyzing studies, especially with the many health topics being discussed in the media today, I sat down with Rosanne Rust, MS, RD, LDN, to learn exactly what she looks for when analyzing a study. Rosanne is a registered, licensed dietitian with 25 years of experience in the field of Dietetics and she holds a master’s degree in clinical nutrition.

During our interview, I asked her to weigh in on the questions that are asked the most. You’ll see that we reference a few studies discussed previously on this blog in the discussion and link to additional information. Here is what she had to say:

Therese: What are the steps to the Scientific Method?

Rosanne: The scientific method is a logical and rational order of steps taken by scientists so they may come to conclusions about the world around them. The steps to the Scientific Method include:

Observation/Research (could include reviewing current research)
Hypothesis
Predictions
Experimentation
Conclusions

Therese: How do I understand what the researcher’s hypothesis was?

Rosanne: The hypothesis is generally stated at the beginning of the research article or in the abstract (the summary paragraph, called as such, that precedes the entire research paper) or in the Introduction. If you take a look at the Melanson study on HFCS and sucrose consumption, for example, you'll see at the end of the Introduction section the statement:

"The aim was to investigate whether HFCS may have more deleterious effects on measured indicators of energy balance control as compared with sucrose."

A scientist comes up with his or her hypothesis after studying the subject or problem. The hypothesis is a statement that may describe what you think the outcome of the study will be or what you are observing. It may also be viewed as what the group has set out to try to "prove" or "disprove".

The Introduction section of the paper usually provides additional background and statistics about the problem.

Therese: How do I understand the methodology they used to test that hypothesis?

Rosanne: The type (age, gender) and number of subjects (people), the "tests" that participants are to undergo, and the way in which data was gathered, are all part of what is called the "methodology". In the Melanson study, these are listed as "Materials and Methods." There are several types of experimental design, choosing what's right for the hypothesis is important. The design methods should be well communicated in the paper for anyone to be able to evaluate the research properly.

Good research controls for a variety of factors. For instance, in this study subjects range in age from 20-60, but are all women who meet a set of criteria. They are all initially evaluated in the same way (body composition, dietary history). For a study to really show cause and effect human subjects are captive—that is, they sleep, eat and live at the facility while they are under scientific observation. In the case of measuring metabolic changes, a variety of scientific and medical equipment is used.

Since the purpose of the study was to determine the metabolic effects of drinks sweetened with HFCS in the Melanson study, every aspect of the subjects diet and metabolism was controlled for (meaning all subjects were given the same nutrients and calories at the same times) so that any effect of HFCS can be visible.

"Reading through a research paper is challenging, which is why you may want to consult with the experts in that field (in the case of nutrition studies this would be the scientists and researchers themselves who work on such studies, PhD nutritionists, registered dietitians)."

Therese: How do I locate the findings and implications and how can I tell if there are obvious inconsistencies?

Rosanne: Findings are found under the section of the paper usually called "results" or "conclusions".

As you read the findings, consider how they actually tie into the original hypothesis.

For example, in the Princeton study on HFCS and obesity, HFCS was given to rats at an 8% solution (Nature's Flavors®, Formula 55, v/v dissolved in tap water, 0.24 kcal/mL), and sucrose was given as a 10% solution (Domino® Granulated Pure Cane Sugar, w/v, dissolved in tap water, 0.4 kcal/mL). The researchers concluded that the rats given HFCS gained more weight than the rats given sucrose. They did not control for the amount of rat chow rats ate (both groups had unlimited access to chow), nor did they control the sugar solutions. Why didn't they compare the same type of sugar solution that provided the same amount of calories per milliliter?

The second part of this experiment was very poorly controlled and looked at male rats in three groups who were given either a HFCS solution, that was offered either 24 hours a day, 12 hours a day, or not at all. In all cases, male rats were allowed unlimited access to rat chow. There was no control for sucrose. The researchers then used a completely different protocol for the female rats (group one was given the same as males, but the second group was offered 12 hours of HFCS solution, and 12 hours of chow, and group 3 was given 12 hours of sucrose solution, along with 12 hours chow).

One could conclude that if you give rats an unlimited supply of any food or drink, 24 hours day, they'll gain more weight than rats who have access to less food for only 12 hours a day. Yet the researchers concluded that it is HFCS that caused the weight gain. What about the unlimited chow? Why not compare it to equal amounts of sucrose in the same doses?

The lack of controls and equivalent comparisons in this study, have led scientists and nutrition experts to essentially "throw away the evidence”, as you can see here, here and here.

If you are interested in reading peer-reviewed research on HCFS and sugar, you can locate that in our science section.

If you have additional questions around a specific study or health topic, here are respected writers who cover science and nutrition that may have written on your area of interest.

Rust is a licensed, registered dietitian, nutrition communications consultant, author and member of the CRA RD Panel. She’s co-authored Hypertension Cookbook For Dummies, Restaurant Calorie Counter for Dummies®, 2nd ed (2011), Calorie Counter Journal for Dummies® and The Glycemic Index Cookbook for Dummies® (Dec 2010). To learn more, visit: www.rustnutrition.com Members of the RD Panel are paid consultants to the Corn Refiners Association (CRA), but their statements and opinions are their own.

RD Panel members provide general dietary information, but you should consult your own physician or dietitian for advice concerning your particular circumstance.