Lifelines participants filled in extensive Food Frequency Questionnaires to assess their diet and nutrient intake. The FFQ results in a large quantity of detailed raw data, which require extensive specialized processing and calculations to yield scientifically valid sum scores (section: secondary & linked variables).
There are multiple types of diet sum scores that can be derived from the FFQ. Lifelines offers two types:

1. The Lifelines Diet Score (LLDS), developed by the UMCG department of epidemiology, is a fully food-based and evidence-based tool to assess relative diet quality. Its highest scores represent diets expected to be most beneficial in light of the prevention of nutrition-related chronic diseases;
2. The Dutch Healthy Diet index (DHD), developed by the WUR department of human nutrition and health is a tool to assess participant's own diet quality and adherence to the 2015 Dutch dietary guidelines. Higher scores on this index indicate a better adherence to the DHD2015 guidelines.