Poor diet quality is a leading determinant of chronic noncommunicable diseases, which account for most of the mortality and morbidity in Spain1 and worldwide.2 This has prompted the formulation of national dietary guidelines that provide evidence-based food consumption recommendations to help individuals select foods that ensure optimal nutrient intake, promote health, and prevent diet-related chronic diseases.3,4 Concurrently, the environmental impact of food has garnered significant attention.5 Transforming food production systems and dietary choices is necessary to achieve the 2030 Agenda for Sustainable Development and the United Nations’ Sustainable Development Goals. This transformation aims to promote diets that are protective of ecosystems, culturally acceptable, affordable, nutritionally adequate, safe, and healthy.6

To this end, the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) updated the Spanish dietary guidelines, incorporating the latest information on the impact of diet on health while considering sustainability.3 Published in December 2022, the healthy and sustainable dietary recommendations for the Spanish population provide food-based recommendations for a healthy and sustainable diet, within the Mediterranean diet, emphasizing the consumption of fruits, vegetables, whole grains, plant-based protein, fish, olive oil as the main fat, and water as the beverage of choice, while moderating the intake of potatoes, eggs, dairy products, and meat. They also advise limiting the consumption of processed foods, saturated fats, salt, and sugary drinks.3

Several dietary indices have been developed to quantify adherence to national food-based dietary guidelines.7 These indices can help to assess the diet quality of specific populations, monitor changes over time, and promote culturally rooted dietary practices. They also serve as valuable tools for nutritional education, public health policies, and clinical practice.7,8 Furthermore, such indices enable researchers to investigate associations between dietary adherence and health outcomes in population-based studies, especially at the national level, providing valuable insight for future guideline updates.8

Therefore, the main objectives of this study were firstly, to develop the healthy and sustainable dietary recommendations for the Spanish population index (HS-DRSI) and estimate the degree of adherence to these guidelines in the adult population of Spain, and secondly, to examine the association between the HS-DRSI and all-cause mortality in this population.

The baseline characteristics of study participants are shown in table 2. The mean age±SE was 46.9±0.3 years, and 50.5% were female. The distribution of adherence to the HS-DRSI is depicted in figure 2 of the supplementary data; only 22.8% of participants had an adherence score ≥9 points (moderate adherence). Compared with participants with the lowest adherence to the guidelines (HS-DRSI ≤5), those in the highest quartile (HS-DRSI ≥9) were older, more frequently female, had lower educational attainment, lived in larger municipalities, were less often current smokers, had a higher BMI, slept fewer hours at night, and had a higher prevalence of morbidities.

When food and nutrient intake was examined among quartiles of the HS-DRSI, a higher quartile was associated with greater intake of vegetables, fruits, whole grains, legumes, nuts, fish, white meat, olive oil, fiber, protein, omega-3 fatty acids, and several vitamins and minerals, including vitamins A, C, D, folic acid, calcium, potassium, and zinc (table 3). Conversely, higher adherence to the HS-DRSI was associated with lower intake of total energy, potatoes and other tubers, cereals, eggs, dairy products, total meat, processed meat, sweetened beverages, energy drinks, alcohol, sugars, and saturated fats (table 3). The prevalence of inadequate nutrient intake was lower in the higher quartiles of adherence to the score, except for iodine (table 2 of the supplementary data).

During a median follow-up of 12.9 years, 939 deaths (7.89%) were recorded. A higher HS-DRSI score was associated with lower all-cause mortality after adjustment for sociodemographic factors (model 2, quartile 4 vs quartile 1: HR, 0.76; 95%CI, 0.60-0.94; P for trend=.01) (table 4). In model 3, the estimate for the comparison between the highest and the lowest quartiles of HS-DRSI remained similar (HR, 0.76; 95%CI, 0.60-0.96; P for trend=.02). The HR of mortality for a 2-point increment in the score was 0.93 (95%CI, 0.86-1.00) (table 4). Among participants without chronic conditions at baseline, the magnitude of the association after adjustment for the main sociodemographic and lifestyle factors was somewhat stronger than in the population with diseases at baseline (quartile 4 vs quartile 1: HR, 0.48; 95%CI, 0.31-0.72; P for trend=.003) and per 2-point increment (HR, 0.80; 95%CI, 0.70-0.92) (table 4). We observed a dose-response relationship when modeling the association with restricted cubic splines (figure 3A,B of the supplementary data) (P for nonlinear trend=.05 and 0.03, respectively).

Table 5 shows compliance with individual dietary recommendations and all-cause mortality. The recommendations with the highest compliance were using olive oil for cooking and food dressing (88.7%), minimizing salt consumption (84.1%), and consuming ≤3 servings/d of dairy (80.7%). Conversely, those with the lowest compliance were: eating at least 3 servings of vegetables from the total of vegetable and fruit intake (2.75%), and including at least 1 serving of plant-based protein foods in daily main meals (4.01%). We found significant inverse associations with mortality for meeting the recommendations for nuts (≥3servings/wk), dairy (≤3 servings/d) and sweetened and energy drinks (<1 serving/wk): the corresponding HR were 0.73 (95%CI, 0.59-0.90), 0.80 (95%CI, 0.66-0.97), and 0.81 (95%CI, 0.67-0.97), respectively. Among participants without chronic conditions at baseline, significant associations were found for consuming at least 3 servings of vegetables from the total for vegetable and fruit intake (HR, 0.17; 95%CI, 0.05-0.58) and minimizing processed meat consumption (HR, 0.68; 95%CI, 0.47-0.97) (table 5).

Significant positive correlations were found between all dietary scores (table 3 of the supplementary data). The HS-DRSI was moderately correlated with the AHEI (r=0.56), DASH (r=0.56), and MEDAS (r=0.59), and these scores were moderately to strongly correlated with each other (r=0.54-0.73). We found protective associations of similar magnitude to that found for the HS-DRSI per 1-standard deviation increment in the AHEI (HR, 0.90; 95%CI, 0.83-0.98), GDQS (HR, 0.91; 95%CI 0.84-0.98), MEDAS (HR, 0.89; 95%CI, 0.82-0.97), and MDS (HR, 0.91; 95%CI, 0.84-0.99) (table 4 of the supplementary data). The results for the DASH-style diet were in the same direction but did not reach statistical significance.

Lastly, no significant differences in the associations with mortality were found between the HS-DRSI and any of the stratification variables (P for interaction>.05 in all cases) (table 5 of the supplementary data). Excluding deaths in the first 2-years of follow-up yielded results consistent with the main analyses (HR quartile 4 vs quartile 1: 0.74; 95%CI, 0.58-0.94; P for trend=.02).

In this retrospective cohort study, the HS-DRSI was developed to measure adherence to the 2022 healthy and sustainable dietary recommendations for the Spanish population. Higher adherence to the guidelines reflected optimal intake of key nutrients and was associated with a lower risk of all-cause mortality in a representative cohort of Spanish adults, including all participants and those without chronic morbidities at baseline (figure 1). Although significant results were found only for an HS-DRSI score of ≥ 9 points, the association appeared to be linear. The protective association was consistent across the main population subgroups and was of similar magnitude to that found for other well-known healthy dietary indices. Among the individual components of the HS-DRSI, meeting the recommended intake of nuts, dairy, and sweetened beverages, was inversely associated with all-cause mortality.

Figure 1.

Central illustration. The healthy and sustainable dietary recommendations for the Spanish population index was developed to measure agreement with the 2022 healthy and sustainable dietary recommendations for the Spanish population.

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A major characteristic of the guidelines used to derive the HS-DRSI is the consideration of both the environmental and health impacts of food choices. This is mainly reflected in the prioritization of healthy plant-based foods while reducing animal food sources.5 Accordingly, we included a specific target of at least 1 serving of plant protein in the main meals. Gradually, other countries have started incorporating sustainability aspects into their dietary guidelines, yet only a minority comprehensively address the environmental impact of food choices.12 The HS-DRSI includes 16 components that reflect recommendations for consumption for the 6 food groups included in the guidelines (fruit and vegetables, potatoes and other tubers, cereals, sources of vegetable and animal protein, olive oil, and water), as well as 4 components based on additional food groups proposed to be minimized or limited (processed meat, other processed foods, salt, and unhealthy beverages). The HS-DRSI shares common components with other well-established dietary indices, giving positive scores for higher consumption of fruits, vegetables, nuts, and legumes, and lower consumption of red and processed meats, salt, and sweetened beverages.13–15 Consumption of fish and seafood, preference for white meat, and olive oil as the fat of choice are characteristic targets of the Mediterranean pattern.13 Although the scoring systems vary among different indices, both the HS-DRSI and the MEDAS are based on dichotomous scoring with defined cutoffs for food consumption. A dichotomous scoring system was chosen over a more complex approach to facilitate interpretation and implementation beyond research (eg, in clinical settings).

The results from this study show that compliance with the dietary guidelines was poor, with only 22.8% of the participants meeting 9 or more of the recommendations. This is not surprising, as previous evidence suggested that adherence to the Mediterranean diet declined in the past decades in Spain.16,17 These findings highlight the significant potential for improving diet through clinical and public health interventions, specifically, targeting population groups with poorer adherence, as well as emphasizing the recommendations with the lowest adherence, which are those related to a healthy plant-based dietary pattern, ie, increasing consumption of vegetables, including at least 1 serving of plant-based protein foods at main meals, prioritizing whole grain products, and reducing consumption of meat.

Our findings support those of previous population-based studies reporting inverse associations between adherence to the Mediterranean diet and mortality, wherein the guidelines are mainly circumscribed in both Mediterranean18,19 and non-Mediterranean regions.20 We observed a 24% reduction in mortality risk among participants in the highest vs lowest HS-DRSI quartiles. The magnitude of the association for a 1 standard deviation increment in adherence to the HS-DRSI (8%) was similar to that found for other indices not considering sustainability, such as the AHEI (10%), the GDQS (9%), the MEDAS (11%), and the MDS (9%). These results are in line with previous studies that have shown associations between individual healthy diet indices and lower mortality.21,22 Lastly, our study is consistent with previous research indicating that adherence to food-based recommendations is associated with lower all-cause mortality.23,24

Among the individual components of the HS-DRSI, meeting the recommendations for nuts, vegetables, processed meat, dairy, and sweetened beverages was associated with reduced mortality. Consumption of nuts and vegetables has been inversely associated with all-cause death in several prospective cohort studies25,26, while consumption of processed meat and sweetened beverages has been extensively associated with all-cause and cardiovascular mortality.27,28 Regarding dairy consumption, the evidence is mixed in relation to its impact on health, with 2 recent meta-analyses finding no evidence for a protective or detrimental association with all-cause mortality29,30; therefore, the new Spanish guidelines recommend reducing consumption of these products to <3 servings/d based only on their high environmental impact.

The strengths of this study include the use of a large cohort representative of the adult population of Spain, with long follow-up and a comprehensive assessment of usual food consumption using a validated dietary history. An advantage of dietary indices that comprise only food-based components over those including both foods and nutrients is that they capture the complexity of the food matrix, the interaction between nutrients, the presence of nonnutrients, and the synergies that occur through the combination of different dietary components, which are better captured by the overall dietary pattern.3,31 Moreover, they facilitate adaptation to easy dietary assessment tools for clinical settings.

Several limitations of the study should also be acknowledged. First, whereas “water as the drink of choice” was included in the conceptualization of the index, we could not ascertain adherence to this item due to the lack of data on water intake in this cohort. To provide a more comprehensive assessment of dietary intake, food frequency questionnaires and other tools for this purpose should be expanded to include water consumption; future updates or studies in other settings should consider extending the score to incorporate this core component. The guidelines also provide recommendations on physical activity over the lifespan that were not addressed in this study. Complementary studies could assess adherence to this dimension independently or as part of a lifestyle score.32

Second, the dietary guidelines do not include recommendations on alcoholic beverage consumption, which was therefore not considered a component in the index.

Third, diet was measured only at baseline; thus, potential changes in dietary habits that may have occurred during follow-up were not assessed, which could lead to misclassification and incorrect associations.

Fourth, inherent to self-reported information, a certain level of recall bias and misclassification in food consumption cannot be ruled out. Additionally, information on lifestyle behaviors and morbidity was also self-reported, entailing potential measurement error.

Fifth, due to a large decrease in sample size, analyses among healthy participants showed wide confidence intervals, suggesting less precise results. Nonetheless, estimates showed a clear protective effect, stronger than for those with chronic conditions at baseline, emphasizing the ability of HS-DRSI to prevent premature death. Similarly, since there were few participants with higher scores, characterization of the impact of high adherence on mortality was not properly addressed; more evidence is needed to understand whether a ceiling effect may occur and at what level of adherence.

Sixth, we could not assess cause-specific mortality due to the small number of cases in the study population. Despite adjustment for multiple confounders, residual confounding by unmeasured or imprecisely measured variables (eg, socioeconomic status, comorbidities) may persist; therefore replication of these analyses in other cohorts in Spain is recommended.

Lastly, while our findings provide valuable insight for the Spanish population, their generalizability is limited due to cultural, nutritional, and health differences in other countries.

We have designed a dietary index to assess adherence to the Dietary Recommendations for the Spanish population updated in 2022. In a nationally representative cohort of adults from Spain, higher adherence to the guidelines was associated with a lower risk of all-cause mortality in participants with and without chronic diseases. Efforts should be made to promote adherence to these guidelines, focusing on the recommendations with lower compliance (ie, consumption of fruits and vegetables, whole grains, plant-based protein foods, and reducing meat consumption) and evaluating their effectiveness in preventing major chronic health conditions in diverse population subgroups.

This work was supported by grants from the Instituto de Salud Carlos III, State Secretary of R+D+I of Spain ERDF/ESF (European Regional Development Fund/European Social Fund) (FIS 20/1040, 23/272). VVC holds a “Training of university professors - FPU” grant (FPU19/06572) from the Spanish Ministry for Universities. The funding agencies had no role in study design, data collection and analysis, interpretation of results, manuscript preparation, or the decision to submit this manuscript for publication.

Written informed consent was provided by all study participants. The study was approved by the Clinical Research Ethics Committee of La Paz University Hospital in Madrid and conducted in accordance with the Declaration of Helsinki for biomedical research. SAGER guidelines regarding potential sex/gender bias have been followed.

No artificial intelligence was used in the preparation of this article.

The authors’ contributions were as follows: V. Vega-Cabello and E. López-García designed the research; V. Vega-Cabello performed the statistical analyses; V. Vega-Cabello and E. López-García drafted the manuscript; E. López-García supervised the conduct of the research; all authors reviewed the manuscript for important intellectual content and read and approved the final manuscript; and V. Vega-Cabello and E. López-García had primary responsibility for final content.

None of the authors has a conflict of interest related to this work.