Search Methods
To find information about nutrients effects, we search online for systematic reviews and meta analyses of randomized controlled trials and large observational studies published in:
Grading System and Criteria
We use the following grade system to describe the effectiveness of nutrients:
EFFECTIVE (high evidence). We believe a nutrient is effective when the results of at least one quality systematic review of randomized clinical trials have shown it helped to prevent or treat a certain health disorder in at least 75% of treated individuals and has provided more benefits than harms, when there is a clear cause-effect relationship between a nutrient and the health effect and when a nutrient has not been shown to be ineffective in any other quality systematic review.
POSSIBLY EFFECTIVE (moderate evidence). We consider a nutrient possibly effective when it has been shown to be effective (according to above criteria) in 25%-75% of treated individuals, or when it has been shown effective in more than 75% of individuals but long-term effects were evaluated by short-term studies (<1 year), when less than 100 participants were involved or when practical importance of the effect seems to be low.
POSSIBLY INEFFECTIVE (low evidence). We consider a nutrient possibly ineffective, when no quality systematic review of randomized controlled trials has shown convincing evidence or most systematic reviews show no evidence a nutrient can help to prevent or treat a certain health disorder.
INSUFFICIENT EVIDENCE. We think there is insufficient evidence about effectiveness of a nutrient when it has not been evaluated by any quality systematic review or when results of different systematic reviews are conflicting.
Nutrients Review team
