Discussion

From the results, we could conclude that there are statistically significant differences in dietary nutrients intake and lifestyle between the case group and the control group. These diabetic patients were in the early stage of their clinical practice. The reason was that the case group had relatively higher BMI but with less total energy intake. Obesity (BMI≥28.0 kg/m²) is associated with diabetes [18]. Patients often lose weight after a period of diabetes. Compared with the control group, diabetics had lower carbohydrate intake, as well as higher fat and protein intake significantly. These results may be related to the diabetics consciously improving their diet structure after diagnosis. It may be beneficial for patients to reduce their carbohydrate intake. In clinical practice, adopting LCD is an active treatment option for diabetic patients [19]. A Case Study in China revealed that ketogenic diets may potentially reverse T2DM [20]. Under a 12-week continuous professional remote care intervention, an overweight T2DM patient restricted carbohydrate intake by ketogenic diets, and adjusted his diabetes medication under monitoring. Related biomarkers became normal after the intervention. It suggested that LCD may have a significant effect on preventing and treating diabetes in China. Furthermore, LCD can normalize impaired fasting glucose (IGT) patients’ blood glucose and prevent them from progressing to become T2DM patients [21].

Nevertheless, its health negative effects also need to be highlighted, including the deficiency of vitamin and dietary fiber, an increased risk of renal dysfunction by high protein intake [22]. Also, our study has shown the deficiency of vitamin and insoluble fiber.

At the same time, diabetic patients in the early stages had also shown a tendency to change their living habits, such as quitted smoking and limited alcohol. The smoking and drinking condition in case group was better than that in control group. Alcohol can affect the secretion of islets, which may lead to an inadequate response of pancreatic cancer β to glucose, finally resulting in insulin resistance and the increased risk of T2DM [23]. Exposed to cigarette smoke can result in pancreatic β-cell dysfunction and impair insulin secretion, too [24]. Even the never-smoking, long-term exposure to second-hand smoke also increases the risk of diabetes. A prospective study conducted by the Japan Public Health Center illustrated that the never-smoking woman who was in a higher percentage of passive smoking environment from her spouse would have an elevated risk of diabetes. Occupational exposure could also lead to similar outcomes [11]. Therefore, strengthening health education on quitting smoking and limiting alcohol can not only benefit diabetic patients, but also help the surroundings stay healthy.

When people are aware of controlling their illness after diagnosis, their first reaction is to stop smoking and limiting alcohol. However, as for dietary therapy, they just realize to reduce carbohydrate intake, whereas they are at a loss when confronted with the elimination of adverse effects of LCD. It is difficult for them to make some complicated improvements, such as paying attention to the supplement of micronutrients. In our study, the intake of insoluble fiber and vitamins in the case group was relatively lower. Higher intake level of dietary fiber is negatively associated with T2DM [25]. Producing a sense of fullness to delay hunger, disturbing the absorption of carbohydrate to lower blood sugar, and reducing the amount of cholesterol absorbed by the intestine, which are all included in the physiological properties of dietary fiber [26]. Compared with the meaningless pectin fiber, cereal fiber has a protective effect on T2DM, it works through these three pathways: increasing glucose tolerance, decreasing inflammation and changing immune response [27]. In our research, for insoluble fiber and vitamin A, B1, B2, the intake of participants was almost less than RNI. Then, it could be seen that is closer to RNI and has a lower risk of diabetes. For the vitamin B3, C and E which intake roughly reached RNI, the risk of diabetes in the lower-RNI group was significantly higher than that in the RNI group, while no significant difference between the higher group and RNI group. The association between diabetes and vitamin A is still relatively vague. There was a Randomized Clinical Trial (RCT) demonstrating that high intake level of vitamin A, E plus zinc may improve blood glucose control, β-cell function, and insulin secretion in diabetic patients [28]. On the contrary, the other, which contradicted the former one, insisted that further researches were needed to verify whether the deficiency of Vitamin A was positively associated with the pathogenesis of diabetes [29]. Instead, the effect of antioxidant vitamins is clear. RCT proved that the supplement of vitamin C and vitamin E, could benefit T2DM on preventing diabetes, improving clinical conditions and avoiding complications [30]. Adults who were diagnosed with prediabetes or diabetes will have greater demand for vitamin C [31]. In addition to the inherent health concept, it is imperative to carry out a more profound health education of balanced diet on diabetic patients.

In addition to the above nutrients, we can also focus on biochemical indicators. Dyslipidaemia is very common in T2DM and it is associated with increased risk of cardiovascular diseases [32]. Compared with the control group, the level of case group on GLU, HbA1c, TG, INS and FER was much higher. The results of our research indicated that the TC level in diabetics was 1.85mmol/L, while that in normal people was 1.55mmol/L. A diabetes survey conducted in Mexico City revealed that only less than 5% of patients aware of their illness had achieved treatment targets for LDL-C [33]. The lower rate of diabetes awareness and the poor level of index control highlight the urgent need of strengthening diabetes care, as well as health education. For diabetic patients, lipid-lowering therapy must be considered as a primary measure to prevent coronary heart disease that includes both lifestyle intervention and medical therapy [34]. Nowadays, the NCEP ATP III guidelines recommend that an optimal goal for LDL cholesterol is <70 mg/dl, whereas <100 mg/dl is considered as the lowest target [35].

In our research, the difference of TC level between diabetes group and control group was statistically significant, and so was HbA1C. Besides being a significant diagnostic marker for blood glucose control, HbA1c can also be treated as a positive predicted index of dyslipidaemia in T2DM [36]. Then, Sharen Lee demonstrated that high HbA1c and lipid variability were important predictors of the undesirable outcome in diabetes, such as peripheral vascular disease and ischemic heart disease, as well as atrial fibrillation and heart failure [37]. Therefore, in order to prevent adverse outcomes caused by dyslipidaemia in diabetes, paying attention to routine blood lipid indices, HbA1C can also be monitored.

Iron overload is a known risk factor for T2DM [38]. Our research indicated that the level of FER in case group was significantly higher than that in control group. FER can cause severe damage to the pancreatic cells through excessive oxidative stress, which may lead to the insulin resistance and diabetes complications. For example, it has been confirmed that high dietary iron intake was associated with the presence of diabetic peripheral neuropathy [39]. A Mendelian randomization study demonstrated that a causal relationship lied between increased systemic iron status and increased T2DM risk based on genetic evidence [40]. Meanwhile, with the improvement of people’s living standards, the intake of red meat is generally higher, followed by an increase in iron intake. As an additional risk factor for metabolic syndrome, the measurement of serum ferritin concentration determination is essential [41]. From what has been discussed above, early detection can recognize the dangerous signal to prevent further damage to patients.

Finally, we cannot neglect the role played by health education in the prevention and treatment of diabetes. If there was no sufficient action to deal with the pandemic, the estimated number of diabetic patients will be forecasted as 578 million by 2030, and jumping to an alarming 700 million by 2045 [3]. One of the reasons for the higher prevalence may come from the deficient rate of awareness of the diabetes [4]. A population based study in Shanghai, China showed that among their participants, 28.06% were aware of their diabetes, 25.85% were on medication, and only 12.42% had achieved the glycaemic control [42]. Lower awareness and worse control rate of the diabetes, which may be attributed to lacking of access to health care, has made the diabetes health education looming ahead. Our study had shown that the prevalence of diabetes was higher among people with a lower education level, and among those who lived in rural areas. Both the less educated and rural residents are with inadequate health literacy and deficient access to health services [43], so they seldom know how to improve their lifestyle to control the condition of health indicators and are placed at higher risk for diabetes complications [33]. Nowadays, Diabetes Self-Management Education (DSME) has been used to empower patients to manage their diabetes, which contains healthy eating, self-monitoring of blood glucose, diabetes complications risk decrease behavior, etc. [44]. With the popularity of mobile devices, mobile health can provide better data support for DSME, which means, details of patients’ lives can be aggregated on the web and analyzed comprehensively. For example, Frøisland DH developed and tested an app for capturing and visualizing adolescents’ nutrients intake [45]. Above all, there remained some shortness in our research. The data of nutrients were collected from the dietary intake, not the serum level. At the same time, the dietary intake was calculated from the recipes recorded by participants and couldn’t represent the actual intake level. Further research should focus on the actual dietary intake.

Conclusions

The changes in diet and behavior of diabetic patients after diagnosis are mainly reflected in reducing carbohydrate intake, smoking and alcohol intake, and relatively increasing fat and protein intake whereas still insufficient dietary fiber and vitamins intake. The overweight/obesity and metabolic syndrome have not been improved, indicating that enhancing the health education of diabetes, including improving lifestyle and diet structure, is of great use not only in preventing the complication, but also in protecting the health of pre-diabetic patients. Early diagnosis and control of diabetes can cut down the premature mortality and disability. Taking early intervention on these people will greatly improve people’s health standard and decrease the medical costs.

Acknowledgements

This research used data from China Health and Nutrition Survey (CHNS). We are grateful to research grant funding from the National Institute for Health (NIH), the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) for R01 HD30880, National Institute on Aging (NIA) for R01 AG065357, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) for R01DK104371 and R01HL108427, the NIH Fogarty grant D43 TW009077 since 1989, and the China-Japan Friendship Hospital, Ministry of Health for support for CHNS 2009, Chinese National Human Genome Center at Shanghai since 2009, and Beijing Municipal Center for Disease Prevention and Control since 2011. We thank the National Institute for Nutrition and Health, China Center for Disease Control and Prevention, Beijing Municipal Center for Disease Control and Prevention, and the Chinese National Human Genome Center at Shanghai.

Funding

This work was supported by the National Natural Science Foundation of China (no.81874263).

Availability of Data and Materials

Data described in the manuscript, code book, and analytic code will be made available upon request pending application.

Authors’ Contributions

The authors’ responsibilities were as follows—XXG, XQL carried out the study design, data analysis and writing of the paper; TYM and XQL provided the original idea of the paper and played a vital role in the revised submission; WYZ collected and organized data from CHNS; FL, DC, PW, SSW, ZRX, ZYH polished the article; All authors were involved in writing the paper and had final approval of the submitted and published versions.

Competing Interests

The authors declare that they have no competing interests.

Consent for publication: Not applicable.

Ethics Approval and Consent to Participate

The CHNS was approved by the institutional review boards of the University of North Carolina at Chapel Hill and Chinese Center for Disease Control and Prevention. Each participant provided the written informed consent before participating.

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