ARCHIVED - Methodology Used to Develop the 2008 National Nutritious Food Basket
The contents of the 2008 National Nutritious Food Basket are based on the food choices reported by Canadians during the 2004 Canadian Community Health Survey Cycle 2.2, Nutrition (CCHS 2.2). More than 35,000 Canadians participated in the CCHS 2.2 by providing, among other information, detailed descriptions of the foods and beverages they consumed throughout the course of one day.
Food Categories and Popularity Ranking
The foods and beverages reported were classified into five categories following the principles of Canada's Food Guide ("vegetables and fruit", "grain products", "milk and alternatives", "meat and alternatives", and "unsaturated fats and oils"). The foods were ranked in order of their popularity within their respective category. Popularity was based on the number of servings consumed. For example, if a total of 100 servings of "grain products" were reported in the CCHS 2.2 and 25 were breakfast cereals and 30 were rice, then breakfast cereals would have a popularity of 25% and rice, 30%. For foods that were consumed in slightly different formats (not different enough to significantly alter their nutrient content), the servings of these different formats were combined. For instance, servings of boiled potatoes and baked potatoes were combined to estimate the popularity of potatoes. In other cases, servings of similar types of foods were combined to provide one estimate of popularity. For example, the popularity of cantaloupe, honeydew melon, and watermelon were combined. Cantaloupe was selected to represent all types of melon consumed since it was the most popular kind of melon in the grouping. Minor adjustments were made to the popularity of whole-grain grain products and unsaturated fats and oils to facilitate the achievement of nutrient goals. Briefly, whole-wheat flour was attributed the same popularity as all-purpose flour whereas a portion of the popularity of mayonnaise and salad dressing was transferred to canola oil.
The popularity of foods was used to create one kilogram composites. The kilogram was chosen as the base unit since most foods in the basket are purchased by weight. The composite is calculated using information on the popularity of each food in the group and the amount of each food that is considered one serving. A one kilogram composite was created for the following groups (listed in alphabetical order):
- dark green vegetables;
- meat, poultry and meat alternatives;
- non-whole-grain grain products;
- orange vegetables;
- other vegetables and fruit;
- unsaturated fats and oils; and
- whole-grain grain products.
Composites were also created for eggs and for milk and alternatives. The composite for eggs was expressed in units (number of individual eggs) instead of on a one kilogram basis since they are purchased as units (dozen, half-dozen), not by weight. The composite for milk and alternatives was developed based on the calcium equivalent of 1 litre of 2% milk in order to take into account the fact that foods in this group are sold by volume (litres, millilitres) and weight (grams). The equivalence approach allows products to be represented on a similar basis. This approach was carried over from the methodology used to develop the previous National Nutritious Food Basket. The nutrient content of the foods included in the 2008 basket was obtained from version 2007b of the Canadian Nutrient File.
Determining the Amount of Food in the Basket
The next step was determining the amount of food in the basket in order to satisfy the food and nutrient goals. The food goals were based on Eating Well with Canada's Food Guide and included:
- providing one serving of dark green vegetables and one of orange vegetables per day;
- providing at least half of all grain products as whole-grain grain products;
- providing 2 cups of milk per day; and
- providing at least two servings of fish per week.
The Dietary Reference Intakes (DRIs) values were used as the nutrient goals. The Recommended Dietary Allowance (RDA) was the goal in the case of folate, iron, magnesium, niacin, phosphorus, riboflavin, thiamin, vitamin A, B6, B12 and C, and zinc. Because food composites provide a single, representative nutrient profile for a cluster of foods, determining the amount of food in the basket was like creating a single diet for an individual in each age and gender group. In this situation the Institute of Medicine recommends using the RDA for planning in order to reach a nutrient level that will be acceptable for almost all individuals in an age and gender group. It considers the Estimated Average Requirement (EAR) an inappropriate goal for planning in this situation. The Adequate Intake (AI) was the goal for calcium, fibre, potassium, sodium, and vitamin D whereas the Acceptable Macronutrient Distribution Range (AMDR) was the goal for percent of energy from carbohydrates, protein, and total fat. The average estimated energy requirements (EER) within each DRI age-sex group was used as a target level; the EERs were calculated using measured heights and weights of individuals within the normal Body Mass Index (BMI) range who participated in the CCHS 2.2. The physical activity was set at "low active".
The quantity of food in the basket was considered acceptable when the food goals were achieved and when the amounts of nutrients reached at least 95% of the goal amounts. It was assumed that adults aged 50 years and older take a daily vitamin D supplement of 10 µg (400 IU) as recommended in Canada's Food Guide. It was also assumed that pregnant and breastfeeding women take a daily multivitamin containing folic acid (and iron in the case of pregnant women).
Goals were met for all but two nutrients: potassium and sodium. The amount of potassium in the basket corresponded to between 59% and 87% of the goal (in other words, the AI). It should be noted that an AI is based on much less data than an RDA and incorporates substantially more judgment than other DRI values. It is also worthwhile to note that the amount of potassium in the basket is higher than the current intakes of Canadians in nearly all age and gender groups. As for sodium, the amount in the basket exceeded the goal (AI) in all age and gender groups. The content was also greater than the Tolerable Upper Intake Level for male aged 14 years and older as well as for pregnant and lactating woman. However, the sodium content of the basket is up to 40% lower than what Canadians consume.
Converting Edible Quantities of Food into As Purchased Quantities
The final step was to convert the amounts of food from an edible amount to an as purchased quantity since this is the format in which the prices of foods are collected. Conversion factors were obtained from the Canadian Nutrient File. For most foods, the conversion yielded larger as purchased quantities than edible quantities given that a proportion of the food is wasted during preparation. For instance, to obtain 100g of edible (cooked) lean ground beef one must purchase 133g. On the other hand, to obtain 100g of edible (cooked) oatmeal one only has to purchase 17g. For certain foods (for example bread, cheese and yogurt), converting from edible to as purchased was not necessary since the foods could be consumed as purchased, without significant waste or change in weight/volume.
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