Behind the paper: The link between water insecurity and diet-related chronic disease in Mexico

We speak with Kaela Connors and Teresa Shamah-Levy, authors of new research published in PLOS Water, “Water insecurity is associated with higher prevalence of self-reported diet-related noncommunicable disease outcomes in adults from the Mexican National Health and Nutritional Survey 2021–22“.

What motivated you to explore the topic and decide on this research question?

Mexico faces dual public health burden: a diet-related chronic disease epidemic (with some of the highest prevalences of diabetes and obesity, globally) and a high level of water insecurity. These crises disproportionately affect socially vulnerable populations in regions with deep structural and environmental inequities.

Emerging evidence suggests water insecurity may drive poor health through dietary behaviors, stress, and diet-related chronic disease risk factors like high blood pressure, obesity, and kidney disease. In the absence of a safe, reliable water source, individuals may opt for sugary beverages or may heavily rely on less water-intensive, ready-to-eat ultraprocessed foods – especially in an obesogenic food environment like Mexico’s.

While doing my PhD research at the Instituto Nacional de Salud Publica in Mexico, I collaborated with researchers at the institute and the WISE-LAC network to study these pressing public health questions. Specifically, we were motivated to understand whether household water insecurity was associated with diet-related chronic disease in Mexico, given the plausibility of this dietary shift towards less healthy but easier to prep foods in the Mexican context. We were also motivated by the fact that these linkages have not been studied in middle- to high- income contexts with a high burden of obesity like in Mexico.

Could you talk us through how you designed your study?

There are two things that are cool about the design of this study. First, we leveraged nationally representative data from the Mexican National Health and Nutrition Survey (ENSANUT 2021-22). Second, we measured household water insecurity using the Household Water Insecurity Experiences (HWISE) Scale. Unlike traditional infrastructure measures that solely focus on supply or quality, the HWISE scale captures multi-dimensional experiences with water availability, accessibility and sufficiency for diverse household uses. Even more cool is that ENSANUT began collecting this information annually in 2021, making Mexico the first country globally to integrate continuous, experiential water metrics into its national health surveillance. This not only enriches our understanding of water insecurity over time but also offers insights into the potential intersection with nutrition, chronic disease, and social inequities.

Collaborating directly with the architects of both ENSANUT and HWISE, we analyzed information from nearly 25,000 Mexican adults to assess whether household water insecurity was associated with self-reported diabetes, hypertension, high cholesterol, high triglycerides, obesity and cardiovascular events as diagnosed by a medical doctor. ENSANUT also collected anthropometric and biomarker information in a small subsample which allowed us to look at ‘total cases’, meaning those that had received a medical diagnosis or those that might have been unaware but clinically had the condition according to their measurements or blood work.

Did you encounter any challenges during your study?

ENSANUT collects exceptionally rich cross-sectional, national level data for public health surveillance in Mexico – one of highest quality surveys globally. The cross-sectional nature of the data, however, does not allow us to study these relationships in the same household or person over time, so we are limited in our ability to make causal claims. We measured water insecurity within the past four weeks, but we know that diet-related chronic disease develops over a longer period.

Another challenge is that our main analyses relied on self-reported medical diagnosis. Sometimes patients are not aware of the status of their medical condition if they have not received a medical diagnosis due to factors such as medical access or absence of symptoms. For this reason, the prevalence of clinically diagnosed diabetes based on blood samples is 18.3% compared to 12.6% of self-reported medically diagnosed diabetes in Mexico. However, we accounted for this in our analysis of ‘total cases’ to account for both self-reported and clinically defined cases for those who may be unaware of a diagnosis. But this information was available in a smaller sample, so less statistically powered.

What did you find most striking or surprising about your results?

Something that really stood out was the consistency of the associations between household water insecurity with self-reported and total cases of diet-related chronic diseases, including diabetes, hypertension, high cholesterol, high triglycerides, and cardiovascular events.

It was also interesting to see that individuals belonging to households that were both water and food insecure had a higher likelihood of being medically diagnosed with diabetes. This finding highlights how multiple forms of social deprivation may overlap and potentially compound existing health inequities. More research needs to be done to disentangle this relationship, but it supports our hypothesized dietary pathway as those that are food insecure tend to more heavily rely on cheaper, energy dense options like ultraprocessed foods.

How do you think this research will be used and who do you hope might benefit from these new insights?

Almost 20% of households in ENSANUT 2021-2022 experienced moderate- to high- water insecurity; that’s a high proportion considering that Mexico is one of the wealthiest countries in Latin America but with wide inequality. It’s also striking given that >99% of the population is estimated to have access to at-least basic drinking water services.  This issue is projected to worsen under climate change and infrastructure challenges.

Mexico also faces a persistent epidemic of diet-related chronic disease, as mentioned, which its addressed through policies tackling the sale and marketing of unhealthy foods and poverty reduction.

These findings shed light on the role of water insecurity as a potential environmental determinant of these health outcomes. Insights generated from this paper can guide policymakers, nutrition researchers, and government institutions in Mexico in designing and implementing targeted health and nutrition policies. Particularly, chronic disease-prevention efforts can incorporate strategies that mitigate water insecurity in regions with a high double burden of both water insecurity and chronic disease like in Northern Mexico. Or high-risk populations (i.e., low income, food insecure) that tend to experience higher levels of water insecurity and chronic disease to prevent widening health disparities. These results also suggest that strategies to prevent chronic disease should not exclusively focus on individual behaviors but also consider structural determinants such as access to safe and reliable water.

What further research questions need to be addressed in this area?

We found a relationship between water insecurity and diet-related chronic diseases, but more research needs to be done to understand why this is happening. For example, do water insecure households shift consumption to sugary beverages, ultraprocessed foods, or foods away from home? It would deepen our perspective to understand – qualitatively – how households are coping with water insecurity. This would allow us to parse out what’s driving these relationships. Lastly, studying these relationships over time in the same household and person would enable us to strengthen evidence of the temporal and potentially causal relationships underlying these associations.

Why did you choose PLOS Water as a venue for your article?

PLOS Water felt like a natural fit since it publishes a wide range of innovative research at the intersection of water and health. We also were drawn to the fact that it reaches a wide global audience of water experts, researchers and policymakers so these findings could directly inform policy and practitioner actions. We’re happy it found its home with the journal and that it’s received engagement from those committed to simultaneously addressing water insecurity and healthy equity.

Author biographies

Kaela Connors, PhD is a Postdoctoral Researcher at the University of North Carolina, Chapel Hill and has a longstanding interest in how climate and the environment influence diet, disease risk, and health disparities. She previously worked at the Instituto Nacional de Salud Publica in Mexico.

Teresa Shamah-Levy, PhD is a nutritionist with a Master’s in Health Sciences with Concentration Area in Epidemiology and a PhD in Public Health. She is the Director of the Center of Evaluation and Surveys of the National Institute of Public Health in Mexico. She is a member of the National Researchers System. She has been the coordinator of several National Health and Nutrition Surveys in Mexico (ENSANUT).

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