Table 3 | Strengths and weaknesses..

Dietary index	Strengths	Weaknesses
HEI	Based on dietary guidelines^a. Energy intakes based on sex and age taken into account. Has a dietary variety component. Updated in 2000 and 2005. Score ranges from 0 to 100, which is beneficial for statistical analysis. Ten components. Components are food and nutrients. Has been used to make alternate scores (AHEI and CHEI). Component scores range from 0 to 10 depending on extent to which they meet guidelines (other indices are just given a score of 0 or 1 for each component).	Same weighting for each component – all components do not have the same health impact^b. Meat is scored positively^c. Score changes depending on items in the FFQ used^d. Uses servings per day in calculation of the score. Size of servings is not defined, and using grams per day is preferred.
RFS	Based on dietary guidelines^a. Only food items, therefore easy to communicate to the public. Has a corresponding NRFS. Has been used to make alternate scores (RFBS).	Same weighting for each component – all components do not have the same health impact^b. Score changes depending on items in the FFQ used^d. Energy intake not taken into account. No dietary variety component. Only food items included. No quantities or serving sizes used, only number of foods deemed to be beneficial which are consumed over a certain period. No specific period over which foods eaten are counted, changes for each study.
HDI	Based on dietary guidelines^a. Energy intake taken into account. Nine components. Components are food and nutrients. Ranges used for intakes instead of single cut off values.	Same weighting for each component – all components do not have the same health impact^b. Score changes depending on items in the FFQ used^d. No dietary variety component.
MeDi	Energy intake taken into account. Nine components. Combination of food groups and fat intake. Mostly food based, easy to communicate to the public. Can use study medians or specific designated medians as cut offs^e. Both non-consumers and excessive consumers of alcohol have a low score^c. Has been used to make alternate scores (aMED). Score is not based on dietary guidelines, but on a traditional diet^f.	Same weighting for each component – all components do not have the same health impact^b. Meat and dairy are scored negatively^c. Score changes depending on items in the FFQ used^d. No dietary variety component. A range rather than a simple cut off is more beneficial to give extent to which dietary guideline is met.

^aAlso a negative point as it reflects nutritional knowledge and guidelines at the time and requires updating regularly as nutritional knowledge and guidelines are updated.
^bComponents that affect health to a greater extent should have a greater weight in the score, weighing is based on current dietary knowledge so requires regular updating and there may controversy between researchers on suitable weighing for each component.
^cModerate amounts of meat consumption is beneficial. Excessive and no consumption is unfavourable. Therefore a single cut off cannot be used to categorize consumption of meat. The HEI rewards all levels of consumption, and the MeDi rewards no and low consumption only. Both excessive and non-consumers should have a low score and only moderate consumption a high score. This is the same for alcohol and dairy.
^dThere is choice in which items from the FFQ should be included in each of the component scores; these ‘choices’ will cause differences in the scores, making it harder to compare results between studies, as researchers reach different conclusions about which items are included.
^eStudy specific medians have disadvantages, for example, the median might not reflect a healthy intake level and will differ between populations and studies, but it does mean that half the cohort will have a positive score and half negative. Specific designated medians have a disadvantage in that intake of a particular component may be below the cut off level for almost all subjects, causing the component be omitted from the score as it will not add value.
^fCould also be argued as a negative point.
Abbreviations: MeDi, Mediterranean diet; aMED, alternate Mediterranean diet; HEI, healthy eating index; AHEI, alternate healthy eating index; CHEI, Canadian healthy eating index; HDI, healthy diet indicator; RFS, recommended food score; NRFS, non recommended food score; RFBS, recommended food and behaviour score; FFQ, food frequency questionnaire;

Table 3: Strengths and weaknesses of dietary indices.

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