How well do Europeans eat compared to recommended diets?
The following section describes the metrics on Food Based Dietary Guidelines that was embedded in Deliverable 6.3.
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Performance metric 1: Food based dietary guidelines
The first performance metric for balanced and sufficient diets is positioned around foods-based dietary guidelines, that provide advice on foods, food groups and dietary patterns to promote overall health and prevent chronic diseases. The food-based approach was primarily chosen because increasing evidence points out that specific foods and dietary patterns have a substantial role in the prevention of chronic diseases (Mozaffarian, 2010). The food-based dietary guidelines are usually defined at the national level and therefore differ across Europe. We first established a common set of food-based dietary guidelines that align food choices of European population groups (Table 2).
Individual variables: ‘intake of foods products’
Individual variables are the mean intake of food products (gram/day). We made use of the FoodEx2 exposure hierarchy from the European Food Safety Authority (EFSA) to consistently classify the food consumption data obtained from national food consumption surveys.
Derived variables: ‘Adherence to the guidelines for food groups.’
All these individual food products are aggregated into food groups that are aligned with the food based dietary guidelines (see protocol 2.2 SUSFANS). Several food groups are classified as ‘healthy’ food groups, e.g., foods that require a minimum intake (vegetables, legumes, nuts and seeds, fruits, fish, dairy) and, some food groups are classified as ‘unhealthy’ food items, e.g., foods for which a maximum intake is recommended (red- and processed meat, hard cheese, sugar sweetened beverages, alcohol and salt). For each of these derived variables, individual goals, e.g. per food groups, were set to be able to calculate the population adherence to these individual food groups guidelines (Table 2).
The percentage of population that adheres to these goals is calculated using not only the average consumption of the population, but also the distribution of consumption in that population. In general adherence to individual guidelines is expected to be low. We evaluated the dietary intakes, adjusted to a 2000 kcal per day diet, to assess diet quality independently of diet quantity. This also reduces measurement error within and across surveys (Willett, 2012).
Performance metric
To derive a performance metric, we constructed a score for the overall dietary pattern for the selected 5 key foods (fruits, vegetables, fish, red- and processed meat, and sugar sweetened beverages). Intake of foods, rather than macronutrients or micronutrients, may be most relevant for non-communicable disease risk (Micha, 2015). Foods and food groups that are mostly included (on different aggregation levels) in dietary quality indices, are fruits, vegetables, staple foods, sugar, dairy products, and protein sources such as meat, eggs and plant based proteins (Trijsburg, not published). The Global Burden of Diseases Nutrition and Diseases Expert Group published their rational to include a selection of foods related to non-communicable diseases (Micha, 2015). They included fruit and vegetable intake as these are associated with the reduced risks of Coronary Heart Disease (CHD), stroke, oesophageal cancer and lung cancer. Fish intake was included because it reduces the risks of CHD and stroke. Red and processed meat intake are related to increased risk of CHD, diabetes and colorectal cancer. Sugar sweetened beverages are associated with increased risks diabetes and increase in BMI (Micha, 2012). They also included nuts and seeds and whole grains in their list of key foods. However, we excluded those because nuts and seeds are often eaten salted, and with the current assessment method we could not distinguish between salted and unsalted nuts. Furthermore, we did not include whole grain products as these are difficult to classify and compare between countries. However, if assessment methods will improve in the future and can quantify whole grain consumption better, we advise to include whole grain intake in this diet quality index. For now, dietary fibre intake, which is highly correlated with whole grain intake will be included in the nutrient based performance metric. Finally, we did not include milk, which is highly correlated with calcium intake, and will therefore be included in the nutrient based performance metric.
To derive a summary score for the five key foods, we use previously set cut-offs for each food item. Capping of intake will be applied to avoid crediting of overconsumption (Drewnowski, 2009), and also vice versa for foods that should be limited. Therefore food intake is set equal to the cut-off value if intake exceeds the cut-off value. The dietary scores are calculated for each individual. Subsequently, these individual scores are averaged to calculate the population mean. A continuous score between 0 and 10 points is calculated based on the average intake of two assessment days. Similar to the Healthy Eating Index, the five indicators are weighted equally (1/5) in the total score.
We calculated the scores based on the five indicators (Table 3) with the following formulas:
- If vegetable intake ≥ 200 g then score is 10; if<200 g then score is g vegetable/200*10
- If fruit intake ≥ 200 g then score is 10; if <200 g then score is g fruit/200*10
- If fish intake ≥ 20 g then score is 10; if <20 g then score is g fish/20*10
- If meat intake ≤ 70 g then score is 10; if >70 g then score is 70/g meat*10
- If Sugar Sweetened Beverage (SSB) intake ≤ 70 g then score is 10; if >70 g then score is 70/g SSB*10
For example, consumption of 100 g/d of fruits (standardized to 2000 kcal/d) will give a score of ‘5’ for the component ‘Fruits’. Eating more than the recommended intake for fruits, vegetable, and fish will not give a higher score. Each component has a maximum score of 10 points. Scores for each food item will be summed up and multiplied by 2 to derive at a total score with a maximum of 100. A score of ‘100’ represents complete adherence to the food-based dietary guidelines that are included.
This food-based performance metric can be used for total populations, e.g. national surveys, but also for population subgroups. National surveys consist of individual based data that include several demographic characteristics. These can be used to stratify the population according subgroups (age, sex, BMI, educational level).
** Disclaimer **
For use in the SUSFANS project, national dietary survey data were standardized based on populations’ age and sex distributions (year 2010), daily energy intake (2000 kcal for women and 2500 kcal for men), and number of dietary assessment days. Therefore, data presented here may differ from national dietary survey data published elsewhere.