This study sought to evaluate macro- and micronutrient intakes in an Iranian adult population concerning dietary recommendations across adulthood and the elderly according to gender and geographical status. Overall, energy intakes were below the levels recommended by the Iranian Desirable Food Basket. While carbohydrate and protein intakes were within the recommended ranges, excessive intakes of total fat and saturated fat were observed in both adults and elderly participants. Among micronutrients, insufficient intakes of iron, selenium, retinol, folate, and vitamin D were markedly evident.

The mean energy intake of our 19–60-year-old participants was 2,321.64 ± 33.16 Kcal, while in the elderly, the mean energy intake was 1,987.81 ± 55.81 kcal/day. Considering gender differences, the mean energy intake was 2,386.7 ± 989.6 kcal/day for men and 1,996.2 ± 835.5 kcal/day for women. Compared to the Iranian Desirable Food Basket, which recommends 2,554- 2,669 kcal/day for adults and 2,182 kcal/day for the elderly [22], our study population’s energy consumption was below the recommended level. In a recently published meta-analysis from the Eastern Mediterranean Region (EMR) on the 18-64-year-old population, the mean energy intake was reported to be 2,287 kcal/ay, ranging from 1,805 to 2,870. The mean energy intake of Iranians in this report was 2,166.3 kcal/day, closely matching our results [22, 23]. Considering the increasing prevalence of overweight and obesity in Iran [24], low reported energy intake in this study may be attributed to reporting bias. Besides, the lack of a local food composition table influences the results.

Carbohydrate intake contributed to 50.46% of total energy in adults and 52.98% in the elderly, which was within the recommended guidelines range (40–60%). Similarly, the results of a systematic review in 2021 revealed that the contribution of carbohydrates to energy was 55.3% in the Iranian population [23]. In 2019, the Isfahan Cohort Study (ICS) results indicated that 60% of total energy was supplied from carbohydrates, which was higher than our results, but still in the recommended range [25]. Similar to our findings, a large prospective cohort study in 18 countries showed that carbohydrate intake was about 53% in the Middle East, consistent with our findings [26]. Iranian cuisine is characterized by its reliance on carbohydrate-rich staples, with rice and bread forming the foundation of traditional meals [27]. Moreover, dietary shifts in Iran indicate a growing reliance on refined carbohydrates, particularly processed grains and sugars, which may contribute to metabolic disorders [14].

Carbohydrate intake was higher in men than in women in both age groups, but the difference was not statistically significant in the elderly. Research indicates that gender-related variations in carbohydrate consumption tend to emerge during early childhood and may be influenced by metabolic factors, dietary habits, and cultural influences [28, 29]. A prospective cohort study and meta-analysis revealed that both lower and higher intakes of carbohydrates are associated with an increased risk of mortality, and the minimal risk was observed at carbohydrate levels of 50–55% [30]. As carbohydrate intake trends continue to evolve, a balanced, evidence-based approach is essential to mitigate metabolic disease risks and improve overall dietary quality in Iran.

In the present study, the contribution of total fat and saturated fat to total energy intake was 38.3% and 14.5% in adults, and 35.8% and 12.5% in the elderly, which exceed dietary guidelines (20–35% for total fat, and < 10% for SFA). This trend contrasts with previous reports from Iran [25, 31, 32], including the Tehran lipid and glucose study (2006–2017), which documented a decline in total and saturated fat intake from 31.6% and 10.6–29.1% and 9.3%, respectively [33]. In the PURE cohort study, fat consumption was lower in Europe and North America (30.5%), the Middle East (30.3%), and Southeast Asia (29%) [26], suggesting that dietary patterns in Iran may be shifting toward higher fat consumption. Higher fat intakes observed in this study may be attributed to socioeconomic changes in Iran’s population due to the severe sanctions and COVID-19 crisis, leading to poverty growth, food insecurity, and unhealthy food habits [11, 12]. According to previous studies, it is believed that lower socioeconomic status is associated with a higher intake of fat and refined sugar [34, 35].

The results showed that 13.45% of energy in adults and 13.9% in the elderly was supplied by protein, which is in the recommended range of 10–35%. All our participants had sufficient intakes of protein. However, the source of this protein—whether from animal or plant origin—is not specified. In the EMR, protein contribution to energy was reported to be 13.9% overall and 16.2% in Iran [23]. Among Iranian middle-aged and elderly, protein intake was slightly higher ranging from 17.42 to 17.51%, suggesting age-related dietary shifts. Lower intakes of proteins in our study may be attributed to the increased costs of protein sources, especially animal sources, due to the COVID-19 crisis and imposed sanctions. The results of a nationwide survey revealed that 33% of the households reduced their weekly red meat consumption, while 14.2% decreased egg consumption following COVID-19 pandemic [36, 37]. These trends highlight growing food insecurity, particularly among lower-income groups, reinforcing the need for policy interventions to ensure adequate protein access.

Our results show that iron intakes are far below the recommended guidelines in adult females (10.31 ± 0.15 mg/day), with 97.0% of participants having insufficient intake [23]. A cross-sectional study in 2017 reported a mean daily iron intake of 17.5 mg/day among Iranian reproductive-age women, with 26.6% consuming less than 75% of the RDA, and 4.3% affected by Iron Deficiency Anemia (IDA) [38]. Historical data suggests moderate improvements in anemia prevalence, with rates declining from 33% in 2001 to 16% in 2015 and 13.8% in 2013 [39,40,41]. However, anemia remains a major public health concern, particularly given economic barriers to accessing iron-rich foods [42]. Considering the socioeconomic changes in Iran and the increased cost of animal sources of iron, supplementation and fortification strategies should be taken into account to achieve the WHO nutritional goal of reducing anemia by 50% by 2030 [43].

Our findings reveal a concerning level of zinc insufficiency, with 55% of adult women and 90% of adult men failing to meet the RDA. In the elderly, the trend persists, with 52% of women and 90.6% of men experiencing inadequate zinc intake. These results suggest that men may be more vulnerable to zinc deficiency, likely due to higher physiological demands and dietary habits. The Tehran Lipid and Glucose Study (TLGS) documented fluctuations in zinc inadequacy, with an initial improvement before rising again in Phase 7, where 30.2% of women and 16.2% of men had insufficient intake [10]. Compared to the TLGS, our study presents a far higher prevalence of zinc deficiency, particularly among men, reinforcing concerns about declining dietary sufficiency in this demographic. A large cohort study in the Japanese population revealed that higher dietary zinc intake was inversely associated with coronary heart disease mortality in men but not women [44]. Given the significant zinc insufficiency observed among men in our study, this association highlights the critical role of adequate zinc intake in supporting cardiovascular health.

Among vitamins, insufficient intakes of retinol, vitamin D, and folate were remarkable in all participants in both adults and the elderly. This aligns with trends observed in the EMR, where mean daily vitamin D intake was reported to be very low (3.1 µg/day) [23], although still higher than our results. Vitamin D deficiency appears to be a global concern, with Greece reporting 100% insufficiency across all ages and sexes [45]. Similarly, in the USA, vitamin D intake falls below estimated average requirements, ranging from 64.1% in food-secure regions to 79.2% in food-insecure areas [46]. Vitamin D naturally exists in animal sources, and the richest are fish liver oils, cod liver oil, and egg yolk [47]. As these sources are rare in daily diets, the lack of a fortification policy may explain the observed deficiencies [48, 49]. A study assessing Finland’s vitamin D fortification policy between 2000 and 2011 demonstrated a substantial improvement in the vitamin D status of Finnish adults over the study period [50]. Additionally, unlike vitamin D, folate inadequacy was not observed in the USA [46] — likely due to mandatory fortification policies that ensure adequate intake across populations. This highlights the importance of fortification strategies, particularly in regions where dietary sources of essential vitamins remain limited.

According to our results, excessive sodium intake was more commonly reported in men, as 72.0% of male adults and 76.0% of the male elderly consumed sodium above the recommended level. Consistent with our findings, a recent report from Shiraz, Iran indicated that 70.0% of the general population consumed sodium above the upper limit [9]. The first national report on salt intake in Iran showed that the mean daily intake was 9.5 g, with 41% of the population consuming twice the WHO-recommended amount [51]. The main sources of salt intake in Iran are added salt, bread, and cheese [52]. Decreasing salt intake in traditional bread— the main source of energy among the Iranian population— may play a crucial role in salt reduction. While it is important to note that the FFQ used in this study does not specifically assess salt as a distinct item, the study does report sodium intake from foods.

Our findings reveal an alarming prevalence of potassium insufficiency across all age groups, with 97.6% of elderly women and 95.8% of elderly men failing to meet the recommended intake levels. Similarly, among adults, 96.8% of women and 96.0% of men exhibited inadequate potassium consumption, highlighting a nationwide dietary concern. Despite Iran being reported as having the highest daily potassium intake of 3,226 mg in the EMR [23], our results indicate widespread potassium inadequacy, regardless of age and gender. Higher sodium intake and higher sodium to potassium ratio in the diet are associated with a higher risk of stroke [53], CVDs, and all-cause mortality [54]. Therefore, policymakers need to take action to reduce dietary sodium intake and increase potassium intake, such as decreasing the salt content of food products, implementing food labeling, public awareness and encouraging increased consumption of fruits and vegetables.

DQI-I is a helpful score to assess the healthfulness of diet within and across countries. Our population’s average DQI-I score was about 68, varying in different geographical zones. Another report from Iran also reported the average DQI-I score of 69.1 in the Iranian obese population [55]. In China and the USA, it was reported to be around 60.0 [16]. The Korean National Health and Nutrition Examination Surveys reported the DQI-I score as 66.7 in cerebrovascular and cardiovascular disease (CCVD) patients and 67.8 in the non-CCVD group [56]. In the subgroup of adequacy and variety, our participants gained high scores, similar to the USA results [16]. The high variety and adequacy score represents food availability in our population. While assessing adequacy, DQI-I considers vegetables, fruits, and grain servings; however, it does not account for the distinction between refined and whole grains or the adequacy of variously colored fruits and vegetables. Additionally, among micronutrients, DQI-I adequacy only includes iron, calcium, and vitamin C. Therefore, while DQI-I is useful for evaluating overall diet healthfulness, it cannot fully assess the sufficiency of all nutrient intakes. According to the low score of overall balance and moderation, it is clear that an imbalanced diet —with a high intake of total fat and saturated fat — is a major concern in Iran. These results can be applied to nutritional interventions and education programs aimed at diet improvement in our region.

The present study was a comprehensive study on a large population of young, middle-aged and older adults distributed in different geographical zones of Iran. This population was from rural, urban and sub-urban regions, comprising a representative sample of Iran, ensuring broad demographic coverage and enhancing the generalizability of our findings. This study has several limitations that must be considered when interpreting its findings. A major challenge is the absence of a national Dietary Reference Intake (DRI) framework and comprehensive food composition tables, which are essential for accurately evaluating macronutrient and micronutrient adequacy. Besides, this study utilized a validated 65-item Food Frequency Questionnaire (FFQ) using telephone interviews. So, recall bias may have influenced self-reported dietary intakes. Additionally, the study did not assess supplement intake, meaning reported deficiencies are solely based on food sources. As another limitation, seasonal variations in food availability and socioeconomic and cultural factors were not evaluated in this study. Moreover, as a cross-sectional study, this research cannot determine long-term dietary patterns. Although it should be considered that this study presents a cost-effective method for periodic surveillance of dietary intakes, offering longitudinal insights into nutritional trends. Supplement intake, seasonal variations, and socioeconomic and cultural factors should be assessed in future studies, while using national standards to interpret insufficiencies.

While this study primarily focuses on dietary intakes assessment, data privacy remains a fundamental aspect of nutrition surveillance. In this study, to ensure participant confidentiality, all collected data was anonymized and no identifiable information was accessible to third parties. Recent guidelines provide a comprehensive framework for balancing data openness with participant privacy, emphasizing, informed consent, anonymization, and secure storage techniques [57]. Future nutrition research should prioritize data privacy methodologies, such as encrypted data-sharing protocols, alongside standard dietary assessment methods, to enhance data accuracy, cross-study comparability, and public trust in nutrition surveillance.