Beyond the Headlines

Sorting Out Nutrition Science

As sports dietitian—a registered dietitian who specializes in sports nutrition—not a day goes by that I’m not dealing with science: biology, biochemistry, physiology, exercise science, medicine, nutrition ... the list goes on and on.

As a runner looking to improve your performance, you too need to deal with the science. No, you don’t need to make a career out of it, but learning how to interpret and make sense of scientific information that impacts your daily eating and training habits is imperative. Otherwise, you are doomed to worrying needlessly about every "breaking" nutrition and health-related story, as well as to falling victim to erroneous advice about supplements and fad diets.

Understanding the Scientific Process

To the non-scientist, diet and health-related scientific news is often frustrating. Almost daily, we read or hear about what appears to be contradictory information about performance-enhancing supplements or the best diet to follow. Do carbohydrates give you energy or do they really make you fat? Should runners be following the classic high-carbohydrate, low-fat, moderate-protein diet (and what is high carbohydrate by the way—55% of your total calories, 60%, 70%?) or would eating more protein and fewer carbs help us drop those last stubborn pounds and pick up some new PRs? Will a pill a day give us more energy?

The scientific process—how studies are designed, conducted and reported—is a road of discovery, a road that is not necessarily straight. Spend an evening with a group of runners describing the ideal training schedule for a marathon or what constitutes the "best" running shoe and you have the idea. The scientific process hinges on gaining knowledge about a subject through observing measurable evidence. To uncover facts, researchers often need to explore in different directions, causing the road to twist, turn and sometimes even backtrack. As is often the case with food and health-related information, these facts may still be only part of a larger, partially understood phenomena, thus requiring even more research be conducted before answers can be found. The refrain "two steps forward, one step back" is common in the scientific world.

As a result, the scientific process generates a great deal of debate. Tracking the debate, which can take considerable time and effort, is the key to putting new research into context.

First, new findings as published in scientific journals should be viewed as discussions among scientists. Almost no one gets the final word in these discussions, as it’s rare that any one study provides a final, complete answer. In other words, researchers publish their results (the gold standard is in a peer-reviewed journal) expecting that debate will ensue. Other scientists trying to duplicate the results will confirm or contradict the results. This process is crucial in adding to the body of literature on a subject as well as in shaping future research.

Second, keep in mind that certainties only emerge through repeated research and analysis—like a runner having to try out several sports drinks before finally settling on one that works consistently. Coming up with certainties for an entire population as a whole (e.g., the ideal sports drink for all runners) takes even more time and effort. It’s also possible that old, accepted research results will be revisited and discussed again and even seen in a new way as new information or technology comes to light.

The Role of the Media in Reporting Food and Health-Related Scientific Studies

The media functions as one of the prime gatekeepers of food and health information. Unfortunately, the media thrives on delivering "breaking news" such as the latest research or the results of a single new study. This information makes for great headlines that attract our attention, such as "Atkins’ Diet Catapults Body into a State of Fat Meltdown." Coupled with the fact that most adults haven’t had a basic physiology or nutrition class since ninth grade (if at all) it’s not surprising that health and performance-conscious runners are often tripped up by scientific jargon or outsmarted by complicated pseudoscience masquerading as real research.

The biggest problem is that the media often reports nutrition and health-related news as factual and definitive—as the "final word." (If you don’t see the problem with this, re-read the above section.) Reporters, however, often fail to provide the proper context for the information or they rely on news releases and study abstracts, which are not credible substitutes for original research. Abstracts and news releases don’t provide enough information to make judgments about the merits of the study, or for accurately reporting the results. This means it’s often up to you to figure out what the results mean, or if they even mean anything at all.

As for the Atkins Diet, the scientific community remains unconvinced (so far) of many of it’s purported health benefits. Despite Dr. Atkins’ New Diet Revolution being firmly ensconced on the New York Times best-seller’s list for four-plus years, it lacks solid scientific support. Atkins relies heavily on rhetoric, speculation and personal testimonials of his patients—none of which can prove that his is the healthier diet. Well-designed clinical trials are now underway. (See "Measuring the Merits.")

Interpreting Nutrition and Health-Related News

To keep from feeling frustrated or overwhelmed by the daily barrage of food, exercise and health news, put the following strategies into practice.

Strategy #1: Pay attention to the context.

The first question you should ask yourself is, "So what? Does this ‘news’ mean I ought to do something or not?" Your job is to find out how this latest information fits with what is already known on the subject. This means reserving judgment about the latest "miracle food" or promising supplement until you put it into context. Does it confirm previous findings or is it a radical departure from current thinking? Because it takes time and effort to understand research, remind yourself that results only directly apply if you share the same characteristics as the group being studied. For example, if a study focused on untrained runners and you’ve been running religiously for the past 10 years, the results won’t directly apply to you.

Check with reputable sources—those that provide a balanced perspective, not just one side of the story. In other words, choose sources (like websites, magazines and newscasts) and experts (like health care providers) that reveal pros and cons, benefits and risks, and clearly delineate between their beliefs/opinions and known facts. Scientists often reach different conclusions from the same or similar data, so it’s prudent to check with more than one expert. Finally, be wary of "expert" advice from those who serve to profit from the results, such as the sales clerk selling supplements at your local health food store, or a doctor on the payroll of the company that makes the product he or she is endorsing.

The bottom line: Do your homework. An educated consumer knows that the results of a single study rarely warrant a change in behavior.

Strategy #2: Learn to distinguish between different types of studies—observational research and controlled experiments.

It’s important to know a bit about how studies are designed, as this directly relates to what their results do—and don’t—mean. An observational study entails examining specific factors in a defined group of people. The purpose is to investigate relationships between these factors and aspects of health, illness or performance. For example, an observational study may focus on healthy male runners ages 30 to 45 who take Supplement X and its relationship to how they perform in a marathon.

From a scientific viewpoint, observational research can only suggest relationships or associations—it cannot determine cause and effect. In other words, researchers may find that taking Supplement X appears to be associated or correlated with faster performances in the marathon, but that does not prove that Supplement X causes better performances. (The fastest marathoners in the group may simply run more miles each week or do more interval workouts than their counterparts.)

Epidemiologic or population-based studies, which are often the source of nutrition news, look at very large groups of people and are also observational by nature. For example, an epidemiologic study looking at the habits of Kenyan distance runners over the last 20 years could find that those runners who ate greater amounts of ugali (carbohydrate-rich stew) each day had a better chance of winning an Olympic medal. That is, the study found an association between eating more ugali and winning a medal. These results, from observing hundreds or even thousands of Kenyan runners, however, do not prove that eating more ugali was the cause of winning a medal.

Only controlled experiments can determine cause and effect. Here, study subjects are selected according to particular characteristics and then randomly assigned to either a control group or an experimental group. This random assignment is paramount as it helps ensure that variables that may affect the outcome of the study are distributed equally among the groups. In our case, male marathoners ages 30-45 would be recruited, screened and then randomly assigned to one of two groups; half would be given Supplement X and half would serve as the control group (they would be given a placebo: a sugar pill or fake treatment). The men themselves would be "blind," that is, they would not know to which group they have been assigned.

To further strengthen the results of the study, the researcher wouldn’t know which group was getting what until all the data had been gathered and analyzed, thus eliminating (as much as possible) researcher bias. This gold standard in research is called a double blind, placebo-controlled randomized clinical trial. Unfortunately these types of trials aren’t always feasible. For example, it may be hard to hide the fact that one group is getting a certain food compared to the control group, or what workouts they are doing. In our case, if the fastest male marathoners turn out to have taken supplement X, we can then more confidently claim that running faster in the marathon (the effect) can be attributed to taking Supplement X (the cause).

Bottom line: Because two things are related, it does not mean that one is the cause and the other the effect. Observing what someone else does and reporting on it can only reveal associations—it cannot prove cause and effect.

Strategy #3: Understand what the numbers really mean.

For people who live by the numbers, runners often get thrown off course by percentages, statistics and proportions related to risk. It’s important to differentiate between the relative numbers in terms of the risk (or success) for a particular outcome and the actual (raw) data. For example, when estimating the absolute risk of a healthy woman developing breast cancer, the statistic often quoted is 1 out of 8. This "high" 12.5% risk of developing cancer causes much anxiety among women of all ages and running abilities. However, this is the lifetime risk for a woman who lives to be 90! Your absolute risk depends on your age: 1 in 2,500 in your 20s, 1 in 232 in your 30s, 1 in 55 in your 40s and so on.

Bottom line: Get past the attention-grabbing headlines and sensational statistics. Although the relative risk (or success) of a particular outcome may appear high, check what the actual numbers show.

Suzanne Girard Eberle, M.S., R.D., author of Endurance Sports Nutrition, lives and runs in Portland, OR.