This is the first study to explore the association between dietary patterns and blood minerals level. In the past 20 years, the nutritional status of children in China has greatly improved, but there are still unhealthy diets and insufficient intake of micronutrients [36]. Dietary patterns directly affect children’s nutritional and health status. Therefore, studying the current situation of dietary patterns and evaluating the association between dietary patterns and micronutrients will provide a practical solution to improve the nutritional intake of children.
This study aimed to identify dietary patterns within school-age children and to explore the correlation with blood minerals (calcium, iron, copper, magnesium, and zinc) concentration. In this sample of school-age children, three dietary patterns were identified – ‘Healthy-conscious’ dietary pattern; ‘Snacks/Beverages’ dietary pattern; ‘Cereals/Beans’ dietary pattern. One of the primary findings was that household income was associated with differences in pattern behavior. Children with higher family incomes tend to the ‘Healthy-conscious’ dietary pattern, and middle-income families tend to prefer the traditional ‘Cereals/Beans’ dietary pattern.
Income and food cost are the two most important determinants of dietary convergence in developing nations [37]. While globalization presents a chance for a greater intake of healthy and diverse foods in economies in transition, it also permits an increase in the consumption of inexpensive, energy-dense foods [38]. The observed positive association between household income and ‘Healthy’ dietary patterns was described in several studies [39, 40]. And cross-sectional studies found that the ‘Unhealthy’ dietary pattern was inversely associated with income [41, 42]. The inverse relationship could be due to the high cost of healthy diets. [43–45]. A study based on the China Health and Nutrition Survey revealed that an increase in family income boosts protein and fat intake, but has a negative correlation with carbohydrate consumption [46]. And individuals with higher salaries tend to consume a wider variety of foods. As expected, there is a large positive correlation between income and dietary knowledge, as higher-income persons are more health-conscious and have greater access to health information [47–49].
Another finding was that blood copper concentration was positively correlated with ‘Healthy-conscious’ dietary pattern scores and ‘Snacks/Beverages’ dietary pattern scores after accounting for confounders, although the regression coefficient is low (P < 0.05, β < 0.3). Copper metabolism is regulated by physiologic demand, but the mechanisms involved have not been elucidated to date. And copper deficiency does not occur frequently, it most often occurs in patients with Menkes disease (MD), a genetic disorder of impaired copper homeostasis. Excess copper has also been reported in humans, most often being associated with another, rare genetic disorder, Wilson’s disease (WD).
It is well known that none of the five minerals can be synthesized in the human body and can only be consumed through foods. The best dietary sources of copper are shellfish, seeds, nuts, organ meats, and bran cereal. High-loading nuts and homonemeae in the ‘Healthy-conscious’ pattern are rich in copper (> 2.4 µg/g). In addition, about 55% − 75% of dietary copper is absorbed, which is considerably higher than that of other minerals [50]. Therefore, we speculate that elevated blood copper levels are a short-term effect caused by high copper dietary intake. Moreover, mRNA levels for many proteins involved in copper homeostasis in mammals (e.g., CTR1, ATP7A, and ATP7B) do not change in response to dietary copper intake levels, demonstrating a lack of control at the level of gene transcription or transcript stability. Regulation of copper intake and efflux may instead be controlled at a posttranscriptional level, predominantly by protein trafficking, as exemplified by the copper-transporting ATPases moving from the TGN to either the enterocyte BLM (APT7A) or the canalicular membrane of hepatocytes (ATP7B) when copper is in excess [51]. Copper metabolism is best known to be influenced by iron. It has been suggested that iron can interfere with copper utilization, and high iron consumption can interfere with copper absorption in infants and adults [52]. Plant components in vegetables and tea (e.g., polyphenols, phytates), as well as soft drinks, inhibit iron absorption, which may also contribute to an indirect increase in blood copper levels [53].
Therefore, we propose that dietary patterns cannot reflect children’s long-term mineral needs. Firstly, the proportion of mineral elements in the blood is extremely low, resulting in the blood concentration being highly susceptible to a short-term diet. Meanwhile, the interaction of mineral elements also makes their concentration unpredictable. In August 2021, the National Health Commission of China issued a notice that trace elements testing of children shall not be carried out as a medical examination item unless the diagnosis and treatment needs. The blood concentration of trace elements in healthy individuals remains relatively stable because they are strictly regulated [54–62]. Evaluating the trace elements status in healthy children through blood concentration still needs further study.
There are several limitations to our study. First, the study participants were mainly school-age children, not fully representative of all age groups, and analyses were conducted in a single city, which may limit the generalizability of the findings. Second, the study participants were healthy individuals, but low blood levels due to element deficiency are usually accompanied by obvious clinical symptoms. Finally, we cannot exclude the possibility of residual confounding in the analysis due to unmeasured or imprecisely measured factors. It is possible, for example, that dietary intake is only one component of an overall lifestyle that affect the content of blood minerals. Such passive smoking [63, 64] and high-intensity exercise [65, 66] can lead to significant changes in blood minerals.
Mineral homeostasis is a complex and highly regulated process involving acquisition, utilization, storage, and efflux. Although some limitations may apply, blood mineral concentration is still used as the standard for evaluating trace elements status in patients. To comprehensively evaluate minerals status, both laboratory tests and the clinical assessment of trace elements deficit symptoms might be required.