There is a constant influx of information always being thrown at us. When it comes to nutrition or lifestyle, it’s usually in the form of eat this, not that, or do this exercise, not that one, etc. But is it true? In this article I am going to break down the different types of research studies and trials into easy, understandable language so going forward, you can look a little closer at the latest trend and decide for yourself!
Meta-Analysis or Systematic Reviews
“Meta-analysis is a quantitative, formal, epidemiological study design used to systematically assess previous research studies to derive conclusions about that body of research.”1 Let’s break that great definition down! A meta-analysis is a formal study looking at an amount of data (quantitative), from many previous studies on the same subject, to determine how and when a disease may occur in a population of people or animals (epidemiology).
“Outcomes from a meta-analysis may include a more precise estimate of the effect of treatment or risk factor for disease, or other outcomes, than any individual study contributing to the pooled analysis. The benefits of meta-analysis include a consolidated and quantitative review of a large, and often complex, sometimes apparently conflicting, body of literature. Rigorously conducted meta-analyses are useful tools in evidence-based medicine.”1
Meta-analysis analyzes studies (randomized controlled trials or a type of observational study) from many countries and from different medical/research associations. This increases the number of total participants and outcomes that are looked at. Due to looking at such large bodies of research, they offer the best conclusions on a given subject.
Now we will look at individual trials or studies.
Randomized Controlled Trials (RCTs) are considered experimental research
“If you want to know how effective a treatment or diagnostic test is, randomized trials provide the most reliable answers. Because the effect of the treatment is often compared with “no treatment” (or a different treatment), they can also show what happens if you opt to not have the treatment or diagnostic test.
When planning this type of study, a research question is stipulated first. This involves deciding what exactly should be tested and in what group of people. Randomized controlled trials provide the best results when trying to find out if there is a cause-and-effect relationship. RCTs can answer questions such as these:
- Is the new drug A better than the standard treatment for medical condition X?
- Does regular physical activity speed up recovery after a slipped disk when compared to passive waiting?” 2
Randomized controlled trials are more expensive to operate; however, they can give more information as more variables are controlled.
Pure Example: One group may be eating a low-fat diet (control group) and the other group is eating a regular amount of fat (placebo group), but both think they are eating low fat diets. The studies are usually also blind (the participants do not know if they are in the group eating low fat or not) or double blind (neither the participants nor the researchers know which group is eating low fat). This helps so that the conclusions are not swayed one way or another but is simply drawn from the data collected.
Caveat. Let’s say one of the conditions of the study is that both groups are to eat the same number of calories. (This way, data collected is not skewed by perhaps one group eating less calories than the other) What if the group eating low fat is now eating more carbs to cover the caloric gap and have added benefits from the fruits and veggies they are eating. Is the data they are receiving real because they are eating low fat, or the benefits of eating more plant matter? Research can get tricky! (This is where meta-analysis or systematic reviews of RCTs are very good at helping to discern the results of trials.)
Cohort Studies, Case Control Studies and Cross-Sectional Studies are all in the category of observational (trend) studies.
In observational studies, not all the variable factors of the participant are controlled (if any) and the variables themselves could also be the reason for the findings. The data collected is based on what the participant reports via an interview, survey or analysis of their medical records. Conclusions are drawn based on these findings. These studies are usually quick and inexpensive.
Example: Recently a study came out stating eggs are “associated with” an increased risk of heart disease. Being that it was an observational study, the participants just simply gave the number of eggs they ate on which days during the study. They were not told how many eggs to eat each day. (They may have eaten two eggs on Monday and three eggs on Friday). Here is where we need to ask, what does the rest of the diet look like? Are they eating a plentiful amount of fruits and veggies, or the Standard American Diet (SAD) with high amounts of processed food? Because of this, they real only conclusion that can be made is that eggs are “associated with” an increased risk of heart disease but are not the sole cause of heart disease itself.
- Do not believe everything you see, read or hear without knowing all the information
- Know the type of research study that was done (Meta- Analysis vs RCTs vs Observational)
- Meta-Analysis or Systematic reviews are the best studies to look at for evidence-based
- Remember that “associated with” does not mean causation
- Ask yourself, what other variables in the trial may also account for the conclusion
You can always ask your health coach, medical practitioner etc. to help you understand the latest trends and research.
Here’s to getting Healthy on Purpose my friends!
- Haidich A. B. (2010). Meta-analysis in medical research. Hippokratia, 14(Suppl 1), 29–37. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049418/
- InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. What types of studies are there? 2016 Jun 15 [Updated 2016 Sep 8]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK390304/
Infographic Image is from Precision Nutrition.