Unfair comparison

Lots of missing people

Look out for comparisons of nutrition interventions where what happened was not measured in most or all people in the study.

Sometimes, outcomes were not measured in all or most people that were allocated to nutrition interventions being compared. When lots of people are left out of the results of a study, or there is a big difference between the comparison groups in how many people were left out of each group, the results can make the effects of a nutrition intervention seem bigger or smaller than they are.

For example, people may stop taking part in a study comparing different foods, drinks, diets or nutrition supplements because the specific intervention they got was not helping them, or because it was making them worse. If those people’s outcomes are excluded from the results, it can make the effects of that intervention seem bigger than they really are.

REMEMBER: Think about whether the results of lots of people who started out in a study comparing different nutrition interventions, are missing.