- It’s an Observational Study: Think of
these types of studies as circumstantial evidence. In some areas of science,
like climate change, this type of data is more useful and meaningful. But in
the area of nutrition, they're bordering on useless particularly when they study a single food or nutrient. Observational studies cannot show cause and effect. The only thing they can show is that there may be some sort of relationship between two things - like juice and cancer.
- It's Self-Reported Data: How well do you remember what you ate yesterday? Or last month?
- An 18% increased risk is weak. While it may sound like a lot, it’s not. To give you some perspective, smoking 25 cigarettes a day increases the risk of lung cancer by 900%. That’s a strong relative risk. Not 18%. And this weak 18% would only hold true if the juice was the actual cause – which this study cannot show.
Beth Kitchin PhD RDN
Assistant Professor Nutrition Sciences
University of Alabama at Birmingham