Theses Doctoral

Mexicans' Consumption of Taxed Sugar-Sweetened Beverages and the Psychosocial Determinants of Consumption in the Context of the 2014 Sugar-Sweetened Beverage Tax - A Mixed Methods Study

Alvarez Sanchez, Cristina

In Mexico about 73 percent adults and 33 percent children have overweight or obesity; and nearly 14 percent adults are estimated to have Type 2 diabetes, being the principal cause of mortality. Obesity and diabetes rates rose sharply starting in the 1980's and 1990's, coinciding with the globalization processes that Mexico underwent resulting in a higher availability and consumption of energy-dense and nutrient-poor ultra-processed foods. Sugar-sweetened beverages (SSBs), carbonated cola beverages such as Coca-Cola in particular, are widely consumed and well integrated into Mexico's cultural fabric and constitute the major source of added sugars in the Mexican diet. High intake of SSBs is associated with weight gain, type 2 diabetes, coronary heart disease, and metabolic syndrome,
In 2014, the Mexican government introduced a 1-peso-per-liter (approx. US 8 cents; about 10 percent of the pre-tax price) on industrialized SSBs along with many other public health measures in an attempt to curb rising obesity rates. Two years into the SSB tax, purchases of sugary beverages in stores decreased by 7.6 percent on average. This decrease in purchases is remarkable, nevertheless, based on the existing cross-sectional data, the change cannot be s attributable solely to the effect of the taxation. Moreover, there are many other concurrent factors that might have affected demand and purchases of SSBs: like an 8 percent ad valorem tax imposed on discretionary energy-dense food in 2014, the regulation of foods and beverages in schools, and the regulation of food and beverage marketing on TV targeted to children.
Further, it may be plausible for the SSB tax to have exerted effect via other mechanisms, such as increasing awareness of negative health outcomes. There is evidence from other countries that junk food and SSB taxes imposed with public health goals contribute to enhancing people's awareness about the negative health consequences of unhealthy foods.
The purpose of this study was to explore what are Mexicans' beliefs, attitudes, social norms, and behaviors in relation to SSBs in the context of the SSB tax, and why and how behaviors have been modified. This purpose was addressed using a sequential explanatory mixed methods design, starting with a quantitative survey with a nationally representative sample, followed by a qualitative study with parents and construction workers.
Quantitative study. The first phase of the study consisted of closed-ended questions (designed to ask about awareness of and opinion about the effectiveness of the tax, psychosocial determinants of SSB consumption, and perception of change in SSB consumption since the year the tax was implemented) that were developed and inserted into a new questionnaire of the 2016 National Health and Nutrition Survey (ENSANUT) carried out by the Mexican INSP. The questionnaire was administered face-to-face to 6,650 Mexican adults 20-59 years old, providing a representative sample at the national, urban and rural, and regional levels. The two principal statistical analysis conducted were: (a) Logistic regression, used to evaluate the probability of a person reporting a decrease in SSB consumption, given their awareness of the tax, opinion about its effectiveness, psychosocial (SSB health-related beliefs, self-efficacy, and liking of SSBs) and environmental (availability of potable water) determinants, after controlling for covariates; (b) Multiple linear regression analysis, utilized to examine the association between the same factors and current consumption of taxed SSBs. Results showed that compared with adults not aware, adults who were aware of the SSB tax were more likely (OR=1.30) to report a decrease in SSB consumption (p=.012). In urban areas, adults aware of the tax drank a significantly lower amount of taxed SSBs (-15.7%; p=.023) than those not aware. Self-efficacy and liking of SSBs were significantly associated with a reported decrease in consumption and with current consumption (p<.001), while health beliefs and availability of potable water were not significantly associated with either reported change in SSB consumption or current consumption of taxed SSBs. We conclude that implementation of an SSB tax accompanied by highly visible campaigns may further influence the impact of taxes on SSBs consumption.
Qualitative study. The second phase consisted of a qualitative multi-case study involving interviews and focus groups with parents of children 9 years old or younger and construction workers that assisted in interpreting the findings of the quantitative study. This study also expanded upon the quantitative findings particularly in relation to the ways people modified (or not) their purchasing and consumption behaviors after the imposition of the SSB tax and the reasons why. The analysis was informed by the Reasoned Action Approach and the hyperbolic (future) discounting concept from behavioral economics theory. The main findings of the study with parents are that most reported drinking less soda than in the two-four years prior and that they largely are trying to reduce their children's consumption of SSBs and encourage water consumption. Changes in parents' behaviors and practices were precipitated by health concerns and not necessarily by price increases (although these were of concern). Half of the participants knew about the tax and its purpose; and it seems like the debate around the tax might have contributed to increasing awareness about the detrimental health consequences of taxed beverages. We conclude that for many of these parents the current taxation of SSBs may have had a mild effect on SSB consumption; a higher level of the tax (20 percent) may impose an additional constraint. The main findings of the study with construction workers are that they consume a high amount of both soda and water during their work days (approx. 1.25. liters and 4 liters, respectively). They associate consumption of soda to pause and meal breaks, and consumption of water to the times when they are working. Nevertheless, their identity as construction workers is constructed in relation to their soda consumption. While they are aware of the health consequences that a high soda consumption can entail, it seems like they had never contemplated the need and/or possibility of changing their practices. Construction workers have not (permanently) altered their patterns of soda consumption in the context of the tax. Presence of an illness (i.e., kidney problems) triggered changes in some, but they were only temporary. We conclude that a 1 peso-per-liter (10 percent) tax is not enough to trigger changes in practices in this group, and that the government should consider a higher level of the tax to have an effect on these consumers.
In this dissertation, the interpretation of the quantitative and the qualitative results in combination yields a better understanding about the potential influence of the SSB tax on Mexicans SSB-related behaviors and psychosocial factors. The key conclusions of this work are that: 1) A considerable number of the Mexican adult population is aware of the tax on SSBs, but that awareness differs by socio-demographic characteristics; 2) A large majority of the population beliefs that the tax is not reducing consumption of taxed SSBs meaningfully; 3) having been exposed to debates/campaigns in relation the tax, combined withto the price increase, may have contributed to increasing health awareness and/or rethinking beverage choices in some population groups that are more sensitive to diet/nutrition and health (e.g., parents in their role as caregivers) but not of others (e.g., construction workers); 4) the most salient determinants of SSB consumption are: social norms, liking for SSBs, perceived behavioral control, and the beverage environment; 5) Mexican adults are knowledgeable about the health consequences of a high consumption of industrialized SSBs, however, while knowledge is necessary, it might not be sufficient to result in large behavioral changes.
This study contributes to the fields of public health and food and nutrition policy by suggesting an alternative pathway through which health taxes may exert an impact on people's behavior. It also highlights the complexity of food choice and behavior change and the need for comprehensive approaches, grounded in research of psychosocial determinants, to have a meaningful impact on changing consumers' behaviors.
The findings of this dissertation suggest that in the future, governments could consider accompanying public health taxes with comprehensive and targeted education campaigns in an attempt to create synergy between both approaches. In addition, future nutrition education and public health campaigns might focus more on teaching self-regulation skills, after motivation has been established, and on shifting social norms around SSB drinking.

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More About This Work

Academic Units
Behavioral Nutrition
Thesis Advisors
Contento, Isobel R.
Ph.D., Columbia University
Published Here
June 10, 2018