Bone mineral density (BMD) is a crucial indicator of bone mass per unit volume or area, serving as a significant predictor of fracture risk, an essential diagnostic parameter for osteoporosis and osteopenia, and a prevalent metric for evaluating bone health (1). It is of great concern that individuals with low BMD face a significantly elevated risk of developing osteoporosis and sustaining fractures. Osteoporosis results in a reduction in bone strength and resilience, rendering even minor traumas sufficient to cause fractures, particularly in the hip, spine, and wrist. Among these, hip fractures are of particular concern, as they often necessitate surgical intervention and carry a high mortality rate (2). A significant increase in mortality is observed in elderly patients within the first year after a hip fracture, largely due to complications from surgery and prolonged bed rest, such as infections, blood clots, and cardiorespiratory failure (3).

In the 21st century, osteoporosis due to low BMD has emerged as one of the top five global diseases, with a prevalence of 23.1% in women and 11.7% in m en. This condition has become a significant public health concern, imposing substantial economic burdens on many countries (4). In the United States alone, approximately 2 million fractures are attributed to osteoporosis annually, with projected healthcare costs reaching $25.3 billion by 2025 (5). Furthermore, there is evidence that BMD among United States adults has been declining over the past decade, which may have a detrimental impact on the situation (6).

The development of BMD is influenced by a number of factors, including biological genetics, metabolic processes, and habits (7). It is noteworthy that dietary nutritional intake plays a pivotal role in the presence and development of low BMD and is a factor that can be readily modified (8). The research evidence is clear that an adequate intake of essential nutrients, including protein, calcium, vitamin D, vitamin K, magnesium, and phosphorus, is essential for maintaining bone health and reducing the risk of low BMD (9). This underscores the potential of dietary modifications to mitigate bone loss.

As societies progress, dietary patterns become increasingly intricate. Traditional research often isolates the effects of individual nutrients or foods on diseases, but such approaches fail to capture the interactions among various nutrients. Consequently, dietary pattern analysis has emerged as a supplementary methodology for investigating the association between diet and the risk of developing chronic diseases (10). Previous studies have identified representative dietary patterns, including the Mediterranean diet, which is rich in meat, eggs, milk, nuts, and olive oil, and the Nordic diet, which is characterized by whole grains, root vegetables, and berries (11–13). Despite the 2015 United States Dietary Guidelines Advisory Committee’s emphasis on considering nutrient amounts, proportions, types, combinations, and consumption frequency in dietary patterns, there remains a dearth of nutrient-based studies examining the relationship between dietary patterns and disease (11–14). Although food patterns can predict certain disease risks, the specific mechanisms remain unclear; however, the combination of nutrients may exert a more significant effect on disease than individual nutrients, suggesting that studying dietary patterns could offer deeper insights into the underlying biological mechanisms and new perspectives on disease etiology, while nutrient-based analyses allow for comparisons of nutritional status across diverse populations irrespective of behavioral, cultural, or geographical differences (15–17). A number of studies have employed nutrients as a means of investigating the relationship between dietary patterns and disease, including obesity, psychological disorders, metabolic syndrome, and certain cancers (15, 18–20). However, fewer studies have been conducted on the association between dietary patterns and bone health (21).

A review of the literature revealed that factor analysis and cluster analysis are the most commonly used methods in dietary pattern analysis. Factor analysis yields factor scores, which are subsequently categorized into quartiles to depict dietary patterns. However, this method may result in a loss of statistical information (22). Cluster analysis, which encompasses Q-type (sample clustering) and R-type (variable clustering), offers distinct advantages. Q-type clustering categorizes dietary variables but fails to elucidate intra-group dietary patterns. In contrast, R-type clustering excels at distinguishing populations, although the complexity and icorrelation of dietary items challenge the interpretability of the results (23).

In this study, we will integrate factor analysis and cluster analysis methods to explore the relationship between dietary patterns based on nutrient intake and BMD. Initially, factor analysis will extract factor scores representing nutrient intake from participants, thereby identifying distinct dietary patterns. Subsequently, cluster analysis will effectively classify the study population, maximizing the retention of raw dietary information and distinguishing populations with different dietary patterns. Finally, we will analyze the correlations between these dietary patterns and participants’ BMD, specifically examining how nutrient combinations collectively affect BMD. Our findings aim to inform the development of nutrient-based dietary interventions to prevent and minimize low BMD and osteoporosis. Through our innovative approach and comprehensive analysis, we hope to contribute new perspectives and methodological advancements to the field of diet and BMD research, providing empirical support for future studies.

Sample characteristics were described using mean and standard deviation (SD) for continuous variables and N (%) for categorical variables. The chi-square test or analysis of variance (ANOVA) was used to test the differences between groups for categorical or continuous variables. To investigate the correlation between femoral neck BMD and dietary patterns, multivariate linear regression and logistic regression were performed. Multivariate models were adjusted for demographic variables such as age, sex, and race. NHANES uses complex sampling designs, including multistage whole-cluster sampling and weighting methods, to oversample individuals in certain groups to ensure adequate statistical power. We constructed weights for the multi-period combined data by selecting sampling weights associated with the minimum subsample (MEC), as recommended by NHANES (31). All coefficients with 95% confidence intervals (CI) were recorded. p values less than 0.05 (two-sided) were considered statistically significant. All statistical analyses were performed using the R software (version 4.3.1).

In this study, women, higher age groups, and race were identified as risk factors for low bone mineral density (BMD). Numerous prior investigations have highlighted the significant influence of both gender and age on BMD. It was revealed that women are at a higher risk (OR = 3.33, 95% CI: 2.9–3.72, p < 0.001) of low BMD compared to men, while both the 55–70 age group (OR = 2.25, 95% CI: 1.96–2.59, p < 0.001) and the >70 age group (OR = 4.55, 95% CI: 3.86–5.36, p < 0.001) exhibited a higher risk of developing low BMD compared to the 40–55 age group. These findings corroborate earlier research indicating a progressive decline in BMD with advancing age, especially evident after 50 years, making middle-aged and elderly individuals more susceptible to osteoporosis. Additionally, existing literature has highlighted the rapid reduction in bone mass among women following menopause, attributable to declining estrogen levels. This phenomenon elucidates why middle-aged and elderly women exhibit a heightened vulnerability to osteoporosis compared to men of equivalent age (32).

Compared to Mexican Americans, Non-Hispanic White people have a higher risk of low BMD (OR = 1.28, 95% CI: 1.05–1.56, p = 0.015), as do Non-Hispanic Asians (OR = 1.56, 95% CI: 1.22–2.00, p < 0.001). Conversely, Non-Hispanic Black people have a lower risk of developing the condition (OR = 0.42, 95% CI: 0.34–0.53, p < 0.001). Previous studies have shown that, in general, Non-Hispanic Black adults tend to have the highest BMD and the lowest prevalence of bone loss compared to Hispanics, Mexican Americans, Non-Hispanic White people, and Non-Hispanic Asian adults (33, 34). The research findings indicate that polymorphism of the vitamin D receptor (VDR) may be associated with higher BMD in Non-Hispanic Black individuals compared to Non-Hispanic White individuals. Differences in VDR FokI genotypes suggest that allelic frequency differences between Non-Hispanic Black and Non-Hispanic White populations may contribute to BMD variation (35, 36). Additionally, genetic factors such as single nucleotide polymorphisms in TRPV6 and TRPV5 may result in more efficient calcium absorption in Non-Hispanic Black individuals (37, 38). Furthermore, cultural customs promoting physical activity and healthy lifestyles among Non-Hispanic Black populations may also contribute to their relatively higher BMD. In contrast, Non-Hispanic Asians tend to have lower BMD compared to other ethnicities, influenced by both genetic and lifestyle factors. This may be related to unfavorable VDR FokI and BsmI polymorphisms among Asians, which are associated with decreased BMD (39). Additionally, cultural factors such as dietary habits play a role in bone health. Traditional Asian diets typically include fewer dairy and calcium-rich foods, which may contribute to lower BMD (40).

This study also shows a positive correlation between BMI, physical activity, and bone mineral density (BMD). Both high BMI and high activity groups have a lower risk of low BMD, consistent with previous studies (41, 42). Firstly, mechanical loading on bones is greater with higher body weight (higher BMI) and more physical activity. This load generates stresses that activate osteoblasts, promoting bone formation and reducing bone resorption, thus increasing bone density. Physical activity also enhances bone health by increasing muscle strength and mass. Stronger muscles exert greater traction on bones during exercise, promoting bone growth and remodeling (43, 44). Secondly, hormonal regulation plays a role. Fat cells secrete hormones (e.g., estrogen), cytokines, and other signaling molecules that affect bone metabolism. Higher amounts of adipose tissue in obese (high BMI) individuals can alter these hormone levels, influencing bone density. Regular exercise increases levels of growth hormone and sex hormones (e.g., testosterone), crucial for bone metabolism. Additionally, BMI is an important indicator of nutritional status (45).

We extracted three dietary patterns, namely, the “LP-HDF-VitA-Mg” pattern, the “HM-Cho-Se” pattern, and the “LM-VitD-Ca” pattern, from the intake of 22 nutrients among 8,316 research subjects by combining factor analysis with cluster analysis. The proportions of the three dietary populations were 29.70, 30.91, and 39.39%, respectively, after clustering, with relatively balanced numbers of samples in the three categories. Significant differences in femoral neck densities were found between the groups (F = 31.788, p < 0.001). Factor analysis and cluster analysis are two post-hoc analysis methods commonly used in nutritional epidemiology to simplify data and reveal potential relationships between variables, helping to navigate the complex interrelationships among nutritional components and identify various dietary patterns. However, this process can be subject to considerable subjectivity in identifying common factors (46). Previous studies commonly divide factor scores into quartiles after extraction but erroneously assume that subjects with the highest scores represent the dietary pattern, leading to a loss of statistical information, as high scores in common factors merely indicate a tendency toward a specific dietary pattern (47). Cluster analysis complements factor analysis by dividing individuals into groups based on similarities in nutritional profiles, thus identifying subpopulations with similar dietary behaviors, providing a more nuanced view of nutritional patterns, and refining these patterns. In this study, factor analysis was used to identify dietary patterns based on participants’ nutrient intake factor scores, which were effectively categorized using cluster analysis to maximize the retention of original dietary information. Meanwhile, this study utilized the variance contribution ratio and scree plot for statistical analysis to capture the interconnections of nutrients and diverse dietary characteristics in the population.

Investigating the correlation between three dietary intake patterns and BMD, significant inter-group differences in BMD were initially found among the groups. Post-hoc pairwise comparisons revealed higher BMD in the “HM-Cho-Se” group compared to others. However, after adjusting for demographic variables, the difference in BMD between the “LM-VitD-Ca” pattern and the “LP-HDF-VitA-Mg” pattern group became nonsignificant. Yet, a positive correlation persisted with the “HM-Cho-Se” pattern, suggesting that it may mitigate the risk of low BMD.

Interesting findings from our study revealed a complex relationship between nutritional intake patterns and BMD. Higher BMD was observed in individuals who adhered to a dietary pattern rich in protein, carbohydrates, fats, choline, and selenium, emphasizing the potential synergistic effects of these nutrients on bone health. Protein is an essential component of the human diet and plays a key role in bone metabolism. Essential amino acids derived from dietary proteins are critical for the synthesis of collagen, a key structural protein in bone (48). The positive correlation between higher BMD and diets rich in carbohydrates and fats emphasizes the importance of energy availability in bone health. Carbohydrates serve as the body’s primary source of energy to fuel the metabolic processes required for optimal bone function. Similarly, dietary fat contributes to energy reserves and plays a role in hormone production, influencing bone metabolism (49). Choline and selenium, often overlooked in bone health discussions, emerged as potential contributors to higher BMD in our study. Although more research is needed to elucidate their specific mechanisms, choline is known to be involved in cell membrane synthesis, and selenium acts as an antioxidant that may protect bone tissue from oxidative stress (50, 51). The lack of significant differences in femoral BMD between individuals following a “LP-HDF-VitA-Mg” pattern and those adhering to a “LM-VitD-Ca” pattern suggests the need for further exploration. Differences in femoral BMD suggest that specific nutrients may interact in some way to counteract their individual effects on bone health in a given dietary pattern. This indicates the need for more in-depth research into the intricate interactions between nutrients and their combined effects on bone metabolism. At the same time, we need to recognize that individual differences, lifestyle factors, and physical activity levels are critical to the potential impact of study results. Individuals respond differently to various nutritional patterns, which, together with external factors such as exercise and lifestyle choices, may lead to variations in the relationship between diet and bone health.

Our study has several limitations. Firstly, since the NHANES femoral scans were conducted only on individuals aged 40 and above, our findings are not generalizable to a wider age range. Skeletal health is influenced by various factors throughout life, and limiting our sample to those over 40 may miss BMD changes in younger populations. Secondly, using femoral BMD as the sole outcome indicator diminishes the reliability of our results. While femoral BMD is an important measure of bone health, it does not fully represent overall skeletal health and may be affected by individual differences, measurement accuracy, and method consistency. Relying on a single metric may overlook other important aspects of bone health, limiting the study’s applicability and accuracy. Additionally, this study’s cross-sectional design makes it difficult to establish a causal relationship between nutritional patterns and BMD. A longitudinal study would better capture the temporal aspects of these associations and assess the impact of dietary changes on bone health over time. Lastly, factor analysis introduces potential subjectivity, affecting the reliability of identified dietary patterns and their relationship with BMD. Future studies should include diverse age groups, use a longitudinal design, adopt comprehensive covariates, and employ more objective data analysis measures to address these limitations.

In summary, our study shows that individuals adhering to a dietary regimen characterized by elevated levels of macronutrients, choline, and selenium demonstrate a diminished likelihood of experiencing low BMD. This suggests that the consumption of foods rich in these specific nutrients may confer benefits for skeletal health.