Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.
''Eat more fiber.''
''Eat more meat.''
There seems to be so much nutritional advice out there, and a lot of it tends to be contradictory. It can lead us to wonder, ''where do they even come up with this stuff?!''
While there may not be a rhyme or reason to how non-scientists or entrepreneurs interpret the results, professional nutritionists develop their recommendations based on nutritional research. Learning how to evaluate nutritional research and its different design processes can help someone determine for themselves whether or not the nutritional advice is sound.
Good nutritional research follows the scientific method. The scientific method follows the following steps:
- Ask a question
- Formulate a hypothesis
- Design and perform an experiment
- Analyze the experiment results
- Draw up conclusions and share results
Coming up with a good question and developing the hypothesis are important steps. These steps need to be based on prior research and gaps in current knowledge. Once these steps have been developed, an experiment needs to be designed.
In nutritional research, primary or secondary research can be conducted. Primary research occurs when scientists gather their own data to analyze. Secondary research occurs when scientists analyze the results from other research, and make conclusions based on the results from other researchers. Secondary research can be really important in order to summarize data and help draw conclusions when results from different studies seem to be contradictory. Typically, however, researchers want to focus on primary research.
There are four main types of primary research for nutrition:
- Animal or laboratory
Types of research
Animal and laboratory studies are when the effects of a nutrient or food are examined in animals or cells in a test tube. These types of studies are frequently done in nutrition because it is difficult to ethically perform randomized studies on humans. For example, nutritionists cannot set up a study and tell one group of people to not eat protein because if the study went on for too long, those participants would die or suffer serious health consequences. So, the next best thing is to do the study on animals and hope the results translate in a similar way to humans.
Case-control studies take a group of people who have a specific condition or outcome, such as diabetes or successful lost weight. The studies then compare that group to a group who doesn't have that condition or outcome. Researchers ask questions about the behavior of the group members. For example, nutritionists may ask how many servings of fruits and vegetables did members from each group eat a day. This type of study is helpful because we are actually using people. However, a shortcoming is that we are relying on people to remember what they have done in the past and to accurately report it.
Cohort studies gather a large group of people and follow them for an extended period of time. This can even be for 20 or more years! Throughout the course of the study, data will be collected on the participants. For example, participants may need to keep a food journal detailing what they have eaten each day. At the end of the study (and often during certain check points throughout the study) each participant will be tested for a variety of health conditions. The foods eaten can then be compared to the health conditions that participants have. This type of study is better than case-control because researchers are not relying on participants to recall past events. These studies are limited, however, because there is still no randomization.
Randomized trials are ideal in many ways because the researchers can control many aspects of the study. Researchers do, however, need to be careful with ethical issues with this type of study. For example, if research has begun to show that one treatment may be harmful to participants, then that treatment needs to be stopped. These studies are randomized because groups are randomly split up, and given different treatments. Since we are dealing with humans in these cases it can often be difficult to ensure that participants will follow the treatment. So while this is an ideal study, there are still shortcomings associated with this type of research.
When looking at the results of nutritional research, it is important to determine what type of research was performed. If it was animal or laboratory research, take the results with a grain of salt. The results might be applicable to humans, but we do not know for sure.
When looking at case-control results, examine what questions researchers asked, and how far in the past participants were expected to recall events and what they ate.
When looking at cohort studies, it is important to examine how many controls researchers accounted for. For example, if the research concludes that ''people who ate more apples resulted in better mental health'', you may want to examine if researchers accounted for differences in exercise, other foods, mental health history etc. Perhaps people who exercise just tend to eat more apples than those who don't exercise, so maybe the exercise is affecting the mental health more than the apples.
When looking at randomized studies, you need to examine whether the treatments would have been easy or difficult to follow. How likely is it that participants actually followed the prescribed treatment?
Good nutritional advice will be based upon good nutritional research. We can tell that nutritional research is good when it follows the scientific method. The type of experiment is important to examine, this can be primary or secondary research. Primary research includes laboratory/animal, case-control, cohort, and randomized studies. Each type of research has specific limitations that need to be considered.
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