Studies in areas of health are likely to confuse, as the evidence they provide is contradictory.
How certain can we be about the benefits or harms of dieting, exercising, drinking alcohol, and smoking? What can we do to protect ourselves from conditions such as obesity, heart disease, diabetes? The evidence is far from clear.
Has health research deliberately tried to confuse us? It’s possible! Some research studies are biased, or even fraudulent, because it is bound by funding or ideology.
Other research is correlational. Here are some examples of correlational studies:
Studies that report people’s views – say, from questionnaires
Studies that report clinicians’ observations
Studies that draw conclusions form archives
Correlational studies can provide evidence for anything under the sun. Correlation is not causation!
Causation is best inferred from experimental studies, such as those conducted in labs, but even high quality experiments, such as randomized controlled trials (RCTs), can provide contradictory evidence.
So what can we do? How many studies should we read to get a good enough idea of what is beneficial or harmful to our health?
The answer is ... just ONE (1) study, if it is a meta-analysis. This is because a meta-analysis is a “study of studies”. One meta-analysis may have synthesized ALL available evidence on a topic, and can therefore provide the best evidence and advice on that topic. Here’s more on meta-analyses: Meta-analysis - an overview | ScienceDirect Topics
Why get lost in the labyrinth of Dr Google when we are better off reading just ONE meta-analysis on a topic of interest...?
Caveats! Only a small number of meta-analyses (or any studies for that matter) can be freely accessed over the internet. The majority of full-text meta-analyses are “locked” in university libraries, available to those who have a university membership. To make matters worse, meta-analyses are written in “stiff” language that may put off readers, including ‘seasoned’ academics.
My health meta blog presents results of key meta-analyses, in a simple and succinct form. My entries are < 500 words and provide the evidence from one meta-analysis covering a topic pertinent to health.
Three criteria guide my choice of meta-analyses.
1. The meta-analysis should be ‘recently’ published, in order to provide comprehensive coverage of the evidence.
2. The meta-analysis should summarize evidence of experimental studies, if available, as experiments provide ‘stronger’ evidence.
3. The authors of the meta-analysis should report no conflicts of interest (e.g., financial or other associations with industry that could bias their research).
Disclaimer! As is the case with all types of studies, some meta-analyses may be seen as “better” than others. While I choose meta-analyses from reputable, peer-reviewed, scientific journals, I do not make decisions based on purported quality. Besides, to be published, 'higher quality' studies are expected to report limitations.