Level of Evidence

Definition

A classification of the reliability and quality of scientific studies based on their methodology, allowing the evaluation of the strength of nutritional conclusions.

How it works

The level of evidence is a standardized scale evaluating the confidence that can be placed in a study's results. At the bottom of the scale are expert opinions and uncontrolled observational studies, while at the top are meta-analyses of randomized controlled clinical trials.

Role

Allows health professionals and consumers to evaluate the reliability of nutritional recommendations and health claims.

Examples

• Level 1: Meta-analysis of randomized trials on statins and cholesterol
• Level 2: Randomized clinical trial on the effects of fiber on glycemia
• Level 3: Observational study on the link between coffee and cardiovascular diseases
• Level 5: Expert nutritionist opinion

Recommendations

Base your nutritional decisions on the evidence of the highest available level. Be aware that recommendations can change with the accumulation of new evidence of better quality.

Key takeaway

Meta-analyses and randomized controlled trials are the most reliable forms of evidence, while opinions and anecdotes should be considered with caution.

Related terms