Dietary patterns have become a major public health concern, particularly in relation to the rising prevalence of obesity, anemia, and chronic diseases among adult women. Middle-aged women (40–65 years) represent a nutritionally vulnerable group due to menopausal transitions that influence body composition, metabolic function, and micronutrient status. Recent evidence suggests that this population is at increased risk of both excess body weight and iron-deficiency anemia, highlighting a complex dual burden of malnutrition (López-Moreno et al., 2025; World Health Organization, 2025). Furthermore, global estimates indicate that anemia remains highly prevalent, affecting approximately 30% of women of reproductive age, and showing a slight increasing trend in recent years (World Health Organization, 2025). Furthermore, the risk of chronic diseases such as cardiovascular disorders and hypertension increases significantly after age 40 (Rapsomaniki et al., 2014; Wang et al., 2020), underscoring the importance of maintaining optimal nutritional status and healthy lifestyle behaviors (Benjamin et al., 2019). In recent years, plant-based diets, including lacto-vegetarian diets, have gained popularity due to their perceived health benefits (Corrin & Papadopoulos, 2017). However, concerns remain regarding potential nutritional deficiencies, particularly iron deficiency anemia, which may compromise overall health.

Despite global health efforts, the prevalence of anemia among women of reproductive age remains persistently high. It has shown a slight increasing trend in recent years, rising from approximately 27.6% in 2012 to 30.7% in 2023 (Figure 1). This highlights a continuing global public health challenge, particularly among women at risk of nutritional deficiencies.

The urgency of this research lies in the need to better understand the dual impact of plant-based diets on health. While such diets are associated with reduced risk of chronic diseases and improved weight management, they may also lead to inadequate intake of essential nutrients such as iron and vitamin B12 if not properly planned. This issue is particularly relevant in developed regions such as California, where lifestyle behaviors and dietary trends are rapidly evolving.

Previous studies have reported that vegetarian diets are generally associated with lower body mass index (BMI) and improved metabolic profiles compared to omnivorous diets (Medawar et al., 2020). Furthermore, observational studies have shown that individuals following plant-based diets tend to have lower energy intake and reduced risk of cardiovascular diseases (Kennedy et al., 2024). However, other research has shown that vegetarians often have lower iron stores, increasing the risk of iron-deficiency anemia (López-Moreno et al., 2025). Similarly, studies in large populations have demonstrated significant associations between dietary patterns, BMI, and lifestyle factors such as physical activity and smoking (Azhar et al., 2023). In addition, comparative analyses of vegetarian and omnivorous populations have shown that while BMI and blood pressure may not differ significantly, differences in hematological parameters, particularly hemoglobin levels, remain evident (Heniková et al., 2025).

In the United States, the adoption of plant-based diets has increased substantially over the past decade, driven by health, environmental, and ethical considerations. Among these, lacto-vegetarian diets are commonly practiced due to their perceived balance between plant-based benefits and dairy-derived nutrient intake. However, while plant-based diets are consistently associated with lower body mass index (BMI) and improved cardiometabolic profiles, they may also increase the risk of micronutrient deficiencies, particularly iron and vitamin B12 (Kennedy et al., 2024; López-Moreno et al., 2025; Medawar et al., 2020).

California represents a particularly relevant setting for examining these dietary patterns, as it has one of the highest prevalences of plant-based diet adoption in the United States, supported by strong health-conscious lifestyles and diverse dietary practices. Despite this, empirical evidence focusing on middle-aged women in this region remains limited, especially regarding the simultaneous assessment of nutritional status and hematological outcomes.

Previous studies have largely examined either general populations or single health outcomes, such as BMI or anemia, without addressing their potential coexistence. This creates a critical knowledge gap in understanding the potential nutritional trade-off, where favorable weight status may coexist with increased anemia risk among individuals following plant-based diets.

Therefore, this study aims to examine the relationship between dietary patterns, nutritional status, lifestyle behaviors, and health outcomes among lacto-vegetarian and non-vegetarian women in California. The novelty of this study lies in its integrative approach, which simultaneously examines nutritional status, lifestyle behaviors, and health outcomes among lacto-vegetarian and non-vegetarian women in California. By focusing on a specific age group and combining multiple health indicators, this study provides a more holistic understanding of the health implications of dietary patterns.

Accordingly, the purpose of this study is to analyze the association between nutritional status, lifestyle behaviors, and health outcomes among lacto-vegetarian and non-vegetarian women in California. The findings of this study are expected to contribute to the development of evidence-based nutritional recommendations and public health strategies, particularly for midlife women, to promote optimal health and prevent nutritional deficiencies.

This section presents the findings of the study, including the characteristics of the participants, differences in lifestyle behaviors, nutritional status, and health outcomes between lacto-vegetarian and non-vegetarian women, as well as the associations among these variables. Descriptive statistics are used to summarize participant characteristics, followed by bivariate and correlation analyses to examine differences and relationships between variables. The results are presented in Tables 1–3 for clarity and systematic interpretation.

RR = risk ratio; CI = confidence interval. RR was calculated for dichotomous variables only

Regarding nutritional status, a higher proportion of lacto-vegetarians had a normal BMI (50%) compared to non-vegetarians (30%). In contrast, overweight and obesity were more prevalent among non-vegetarians (35% and 35%, respectively), with a statistically significant difference (p=0.04).

A pronounced difference was observed in anemia status. The prevalence of anemia was substantially higher in the lacto-vegetarian group (70%) compared to the non-vegetarian group (10%), corresponding to a markedly increased risk (RR = 7.00; 95% CI: 1.90–25.60; p=0.001).

In contrast, no significant difference in hypertension prevalence was observed between the two groups (35% vs 40%; RR = 0.88; 95% CI: 0.41–1.90; p=0.60), indicating no meaningful association between dietary pattern and blood pressure status in this sample.

Based on blood pressure, most participants in both groups were classified as normal. The prevalence of hypertension was slightly higher in the non-vegetarian group (40%) compared to the lacto-vegetarian group (35%), although this difference was not statistically significant (p=0.60). Furthermore, no significant associations were observed between lifestyle behaviors and nutritional or health outcomes in either group (p>0.05). Although some weak positive or negative trends were identified, none reached statistical significance, likely due to the limited sample size and reduced data variability.

This study examined the association between dietary patterns, nutritional status, lifestyle behaviors, and health outcomes among lacto-vegetarian and non-vegetarian women in California. The findings indicate a clear contrast between metabolic and hematological outcomes. While lacto-vegetarian participants were more likely to have a normal BMI, non-vegetarians showed higher proportions of overweight and obesity. In contrast, anemia was substantially more prevalent among lacto-vegetarian participants, with a markedly increased risk compared to non-vegetarians. No significant differences were observed in physical activity, smoking behavior, or blood pressure between the two groups, and no significant associations were found between lifestyle factors and health outcomes.

These findings highlight a potential nutritional trade-off associated with lacto-vegetarian diets. Plant-based dietary patterns are associated with more favorable body weight profiles, likely due to their lower energy density and higher fiber content, which promote satiety and reduce overall caloric intake. This is consistent with previous studies showing that vegetarian diets are linked to lower BMI and improved metabolic outcomes (Dinu et al., 2017). However, the markedly higher prevalence of anemia among lacto-vegetarians suggests a significant nutritional vulnerability, particularly regarding micronutrient adequacy.

The magnitude of the observed difference in anemia risk suggests a clinically meaningful disparity between dietary groups. This finding supports previous evidence indicating that vegetarian populations are at increased risk of iron deficiency anemia due to limited intake of heme iron and reduced bioavailability of non-heme iron (López-Moreno et al., 2025; Pawlak et al., 2018). In addition, inhibitors of iron absorption, such as phytates and polyphenols, may further reduce iron uptake, while inadequate vitamin B12 intake may impair erythropoiesis. Similarly, previous studies have reported lower iron stores and higher anemia prevalence among vegetarians compared to non-vegetarians (Alexy et al., 2021; Chai et al., 2019; Rahfiludin et al., 2021; Rammohan et al., 2012; Reis et al., 2025).

Interestingly, although coffee consumption was significantly higher among non-vegetarians—an established inhibitor of iron absorption—this group still demonstrated better hemoglobin status. This suggests that the presence of heme iron sources in non-vegetarian diets may outweigh the inhibitory effects of dietary factors such as coffee consumption, emphasizing the importance of overall dietary composition rather than isolated dietary behaviors.

The lack of significant associations between lifestyle behaviors and health outcomes may be explained by the limited sample size and reduced data variability, which may have constrained the statistical power to detect meaningful relationships. It is also possible that dietary patterns exert a stronger influence on nutritional and hematological outcomes than lifestyle factors within this specific population.

From a theoretical perspective, this study contributes to the literature by emphasizing that plant-based diets are not universally beneficial but involve trade-offs between metabolic advantages and micronutrient risks. This supports a more nuanced understanding of dietary patterns, highlighting the importance of dietary quality and nutrient adequacy rather than dietary classification alone.

From a public health perspective, these findings underscore the importance of targeted nutritional strategies for middle-aged women. While promoting plant-based diets for their metabolic benefits, it is equally important to ensure adequate intake of critical nutrients such as iron and vitamin B12. Strategies such as increasing consumption of iron-rich plant foods, enhancing absorption with vitamin C, and considering supplementation under professional guidance should be emphasized. Routine screening for anemia may also be particularly important in this population.

This study demonstrates a clear nutritional trade-off associated with lacto-vegetarian diets among middle-aged women, characterized by more favorable BMI profiles but a substantially higher risk of anemia. These findings suggest that the health benefits of plant-based diets are not uniform and depend critically on nutrient adequacy, particularly iron and vitamin B12 intake.

From a public health perspective, these results highlight the need to move beyond generalized dietary recommendations toward more targeted nutritional guidance. Health promotion strategies for plant-based diets should include specific interventions to prevent micronutrient deficiencies, such as dietary planning, food fortification, and appropriate supplementation. Routine screening for anemia should also be considered, particularly for women adhering to long-term vegetarian diets.

Future research should focus on larger, longitudinal studies to better understand causal relationships and develop evidence-based dietary guidelines that optimize both metabolic and hematological health outcomes.

The authors would like to express their sincere gratitude to all participants who voluntarily took part in this study. We also acknowledge the support of community networks and local health centers in California for their assistance in participant recruitment and data collection. Special thanks are extended to the research assistants for their contribution to data collection and management.

The data supporting the results of this study were gathered through field-based observations and have been recorded by the researcher. Although the dataset is not openly accessible, it can be shared by the corresponding author upon reasonable and well-justified request.

This research does not receive external funding.

The authors hereby declares that this research is free from conflicts of interest with any party.