Is the degree of food processing and convenience linked with the nutritional quality of foods purchased by US households?

Abstract

Background: "Processed foods" are defined as any foods other than raw agricultural commodities and can be categorized by the extent of changes occurring in foods as a result of processing. Conclusions about the association between the degree of food processing and nutritional quality are discrepant.

Objective: We aimed to determine 2000-2012 trends in the contribution of processed and convenience food categories to purchases by US households and to compare saturated fat, sugar, and sodium content of purchases across levels of processing and convenience.

Design: We analyzed purchases of consumer packaged goods for 157,142 households from the 2000-2012 Homescan Panel. We explicitly defined categories for classifying products by degree of industrial processing and separately by convenience of preparation. We classified >1.2 million products through use of barcode-specific descriptions and ingredient lists. Median saturated fat, sugar, and sodium content and the likelihood that purchases exceeded maximum daily intake recommendations for these components were compared across levels of processing or convenience by using quantile and logistic regression.

Results: More than three-fourths of energy in purchases by US households came from moderately (15.9%) and highly processed (61.0%) foods and beverages in 2012 (939 kcal/d per capita). Trends between 2000 and 2012 were stable. When classifying foods by convenience, ready-to-eat (68.1%) and ready-to-heat (15.2%) products supplied the majority of energy in purchases. The adjusted proportion of household-level food purchases exceeding 10% kcal from saturated fat, 15% kcal from sugar, and 2400 mg sodium/2000 kcal simultaneously was significantly higher for highly processed (60.4%) and ready-to-eat (27.1%) food purchases than for purchases of less-processed foods (5.6%) or foods requiring cooking/preparation (4.9%).

Conclusions: Highly processed food purchases are a dominant, unshifting part of US purchasing patterns, but highly processed foods may have higher saturated fat, sugar, and sodium content than less-processed foods. Wide variation in nutrient content suggests food choices within categories may be important.

Keywords: convenience food; diet; food processing; processed food; ultra-processed.

FIGURE 1

Trends in US household food and beverage purchases categorized by the degree of industrial processing and level of convenience, Homescan 2000–2012. Weighted unadjusted mean per capita kcal/d and % kcal purchased from each category defined by (A) degree of processing and (B) convenience by year. Each uniquely barcoded food or beverage was classified into a mutually exclusive category for (A) degree of processing based on the extent to which a food was altered from its natural state by industrial food processing and the purpose of these processes and (B) convenience based on the amount of food preparation required by the consumer before a product can be eaten. Data from the 2000–2012 Homescan longitudinal panel of household purchases of consumer packaged goods. All values are weighted to be nationally representative. Percentages labeled within the graph represent estimates in 2000, 2004, 2008, and 2012. Number of year-level observations and households: foods and beverages: n = 656,184 (157,142 households); foods: n = 656,172 (157,139 households); and beverages: n = 655,833 (157,114 households). Moderately processed grain products represented ≤0.2% kcal purchased and therefore do not appear in the figure. *Significant linear trend in the contribution of a given category of processing or convenience to purchases (% kcal), determined by using survey-weighted linear regression models accounting for market-level clustering. P < 0.001 to account for multiple comparisons and sample size.

FIGURE 2

Adjusted proportion of household-level food purchases exceeding saturated fat, sugar, and sodium recommendations by degree of processing and level of convenience, Homescan 2012. Weighted adjusted percentage of household-level food purchases within a category defined by (A) degree of processing or (B) convenience that have >10% kcal saturated fat, >15% kcal sugar, >2400 mg sodium/2000 kcal, or exceed all 3 DGA/FDA-recommended limits. The 95% CIs are indicated by brackets. Nutrient content was calculated at the household level for all food purchases in 2012 within a category of processing or convenience. Determined from survey-weighted adjusted logistic regression models regressing the binary outcome of exceeding recommendations on processing or convenience level (dummy variables), with adjustment for the % kcal from food groups (quartiles) and with market-level clustering. Stata’s “margins” command was used to determine the predicted probability that purchases in each category exceeded DGA/FDA-recommended limits. Data from the 2012 Homescan panel of household purchases of consumer packaged goods: (A) n = 177,726 household-level purchases of processed foods (less processed: n = 59,175; moderately processed: n = 59,267; highly processed: n = 59,284); (B) n = 177,566 household-level purchases of convenience foods (requires cooking and/or preparation: n = 59,043; ready-to-heat: n = 59,240; ready-to-eat: n = 59,283). “Less processed” includes minimally processed and basic processed products. “Ready-to-heat” includes products requiring minimal preparation. *Significantly different from less-processed foods (Figure 2A) or foods requiring cooking and/or preparation (Figure 2B). Wald test with P < 0.001 to account for multiple comparisons and sample size. DGA, Dietary Guidelines for Americans.