Dietary patterns and their association with the components of metabolic syndrome: A cross-sectional study of adults from northeast Thailand

Introduction

Public health in most low- and middle-income countries is challenged, in addition to infectious diseases, by chronic or non-communicable diseases (NCDs)¹. This situation coincides with economic development, demographic transition, and epidemiological changes in a population, which leads to a shift in dietary behaviours and physical activity, also known as nutrition transition². The underlying dietary changes have been highlighted for Asia, including Thailand³. A high consumption of red meat, processed meat, and refined sugar has increased in high- and low-income countries substantially. The changes in dietary intake are aggravated by hyper-palatable processed food high in fat, salt, or sugar⁴. As an after-effect, NCDs such as cardiovascular diseases, especially type 2 diabetes mellitus (T2DM), have emerged as a pressing health problem because obesity and T2DM are closely related⁵. Thailand, as a high middle-income country, was not spared from these developments and faced a rapidly increasing T2DM prevalence; the prevalence of T2DM among Thai adults has risen from 2.3% in 1991⁶ to 8.0% in 2015⁷. Thailand is divided into four major regions, and the northeast seems to have a higher prevalence of T2DM than other regions⁸. Particular regional dietary habits might be linked to the nutritional status and subsequently, to health risks such as T2DM. Sticky or glutinous rice is a staple food and more popular in the northeastern region, whereas ordinary rice is a favourite in the other regions of Thailand⁴. Metabolic syndrome (MetS), a cluster of metabolic abnormalities, such as impaired blood glucose, dyslipidemia, abdominal obesity, and high blood pressure, is known as a major precursor to T2DM and cardiovascular disease (CVD)^9,10 A systematic review study reported that the prevalence of MetS ranged from 11% to 40% among adults in countries of the Asia-Pacific region¹¹. The fourth National Health Examination Survey in Thailand, in 2009, reported that the prevalence of MetS was 23.2%¹², which was somewhat higher than in other Asian countries¹³.

In nutritional epidemiology, the analysis of dietary patterns is based on the concept of the overall food consumption and this approach was used to determine the relationship between diet and the risk of chronic diseases^14,15. However, dietary patterns cannot be measured directly, thus the use of statistical methods to identify dietary patterns is necessary. Factor analysis based on intercorrelations between dietary items is the predominant method to identify dietary patterns¹⁶. Several studies of dietary pattern analysis found that dietary patterns characterized by a high intake of meat, high-fat foods and refined carbohydrates were positively associated with an increase in risk of MetS and its components^17–19, whereas a dietary pattern characterized by a high consumption of whole grains, fish, vegetables, and fruits was found to be protective against MetS and its components^20,21. One previous investigation in Thailand identified a dietary pattern consisting of a high intake of carbohydrate in the form of sticky rice, fermented fish, chili paste and bamboo shoots that was associated with MetS and its individual components¹⁷. However, the studies to determine dietary patterns in the Thai population are limited. It has remained unclear whether the traditional Thai diet or a changed pattern resulting from the nutrition transition is associated with the risk of MetS. The objective of this study was to identify dietary patterns derived from factor analysis and to determine the association between dietary patterns and MetS and its components.

Methods

Results

Characteristics of the study participants are presented in Table 1. Females, at 69.7%, were in the majority compared with 30.3% of males. The age range of women and men was not significantly different, with a mean of 49.1 ± 6.4 years. A higher proportion of females were obese (50.9%) than men (36.6%). Most of the participants were married and had finished elementary school. Men’s income exceeded that of women. Physical activity seemed to be on a vigorous level (53.2%; 68.3% in men and 46.6% in women). Only a few women smoked (1.0%), but 64.1% of the men did so. Within the group of women, 49.7% indicated that a first-degree relative had a history of diabetes, hypertension or dyslipidemia, but the proportion (36.6%) was less frequent for men. Only a minority of study participants, less than 10%, regularly took medicine for diabetes, high blood pressure, or dyslipidemia. Total energy intake and the distribution intake of carbohydrate, protein, and fat of men were significantly above that of women, but the intake of defined nutrients such as fiber, cholesterol, and sugar did not differ between the sexes.

The distribution of the components of MetS within the group of participants without MetS and those with MetS are given in Table 2. The proportion of individual components of MetS varies between the two groups as given in the table. Of the 248 participants with abdominal obesity, 62.1% falls into the group of MetS, but a considerable proportion of those with this component, 37.9%, were not in the MetS group. Likewise, the proportion of participants without MetS but with FBG above the cut-off point was18.6%; for low HDL-C, it was 45.6%; for high blood pressure was 32.4%; and for high triglyceride was 31.3%.

Two dietary patterns, named traditional and mixed, were identified by using factor analysis (Table 3). The two patterns together explained 26.9% of the total variance. The variance for the mixed pattern was 14.2% and the variance for the traditional pattern was 12.7%. The mixed pattern was characterized by the consumption of a variety of foods consisting of fruits, noodles and bread, milk and yogurt, soybean and soybean products, vegetables, eggs, sweet beverages, bakery and snacks, processed meat, legumes and nuts, seafood, and white rice. The traditional pattern included a high intake of sticky rice and animal source foods consisting of internal organs of animals, freshwater animals (frogs, pond snails, and small shrimps), poultry, processed meat (Thai sausage, fermented pork sausage, hot dog sausage, and pork cracking), insects, red meat, fish, and seafood as well as energy drinks. Alcohol was not included into both the mixed pattern and traditional pattern because of a very low factor loading.

The distribution of age, sex, MetS and the five components of MetS according to tertile scores of the two dietary patterns are presented in Table 4. The proportions of men and women were significantly different according to tertiles of each dietary pattern. Participants in the highest tertile of mixed pattern were women more than men. Participants with MetS did not differ in the highest tertile of each dietary pattern score comparing to the lowest tertile score. The proportions of those participants in the second and third tertile score who were found to consume the traditional dietary pattern were significantly associated with high triglyceride levels in comparison with those falling into the first tertile. A reversed feature evolved for low HDL-C in those preferring the traditional pattern. The proportion within the tertiles of the mixed pattern did not differ significantly as far as the five components of MetS were concerned.

Table 5 shows the relationship of the mixed and traditional dietary patterns with MetS and each component of MetS after applying a multiple logistic regression, controlling for other covariates. The lowest tertile of each dietary pattern was considered as reference. By using this approach, neither the mixed nor the traditional pattern was associated with MetS. Comparing the lowest tertile score of the mixed and traditional patterns with the highest tertile score, the mixed pattern was inversely associated with abdominal obesity (adjusted OR=0.49, 95% CI: 0.30–0.81). Increasing consumption of the traditional pattern was likely to be associated with high TG (adjusted OR= 1.74, 95% CI: 1.10–2.88).

Discussion

Two prominent dietary patterns of this cross-sectional study among northeast Thai people in the context of nutritional transition were generated by using the factor analysis, namely, the mixed pattern and the traditional pattern. A positive association was found between the traditional pattern and high TG, whereas a negative association was observed between the mixed pattern and abdominal obesity.

The traditional pattern as assessed through this study showed that a distinctive pattern still follows a traditional way of food intake such as eating more sticky rice and animal source foods. The consumption of freshwater animals (frogs, pond snails, and small shrimps), internal organs of animals, and insects of various kinds have long been recognised as ingredients of the northeast diet⁴. Following the classification of a diet as traditional, sticky rice as a staple food can be rightly considered a traditional food. Previous studies reported that an ethnic-specific diet, characterized by high consumption of rice, legumes, and vegetables, was positively related to MetS and its components (low HDL-C)³¹, while another study did not find the association with MetS and its components³². The traditional pattern in this study, although not associated with MetS, nevertheless was significantly associated with high triglycerides. This finding might be explained by the intake of high amounts of sticky rice in the traditional pattern. Sticky rice (Oryzaglutinosa) has a high glycemic index³³ and stimulates high serum triglyceride levels³⁴. Recently, the Fourth Thai National Health Examination Survey found that “carbohydrate dietary pattern” characterized by consumption of sticky rice, fermented fish, chili paste and bamboo shoots was associated with the risk of MetS and its components such as high TG and low HDL-C¹⁷. A study from the Korean National Health and Nutrition Examination Survey also showed that the high intake of rice-oriented pattern was significantly correlated with a higher prevalence of high TG and low HDL-C³⁵. Traditional patterns in this study not only included a high intake of sticky rice but also a high intake of animal source foods. Meat is an important source of total visible and invisible fat intake, particularly saturated fat. Several studies showed that dietary saturated fat consumption is associated with the risk of CVD due to increasing plasma lipid and lipoprotein^36,37. However, the intake of several animal source foods in this pattern, comprising insects, freshwater animals (frogs, pond snails, small shrimps) and fish, are good sources of protein and are typically low in fat. This may explain the lack of association between the traditional pattern and the MetS, but this pattern was related to high TG.

The mixed pattern was characterized by a consumption of a wide variety of food items long known to be part of the Thai cuisine (such as white rice, fruits, and vegetables), mixed with food items marketed by the food industry (such as noodles of various brands and bread, milk and yogurt, bakery and snacks, sweet beverages, and soybean and soybean products). A previous study indicated that a dietary pattern consisting of a variety of foods (such as grains and starches, vegetables and fruits, fish and seafood, meat, poultry, eggs, legumes, and dairy products) was inversely associated with the incidence of MetS among Korean adults³⁸. Fruits, milk and yogurt, soybean and soybean products and vegetables, major foods characterising the mixed pattern, seem to constitute a beneficial diet^39,40. Fruits and vegetables constitute a high-fibre diet, which is associated with a decreased risk of obesity⁴⁰, potentially accounting for some of the association between the mixed pattern and decreased abdominal obesity in this study. The meta-analysis of randomized controlled trials (RCTs) showed that the consumption of dairy products may have a modest benefit in facilitating weight loss in short-term or energy-restricted RCTs³⁹.

As evident from Table 2, a rather high proportion of participants had one or two components of MetS (such as low HDL-C, abdominal obesity, high BP, and high TG), but they were not included in the MetS group. Thus, MetS as such could not be statistically associated with two dietary patterns, but some components of MetS, significant statistically, could be linked to dietary patterns. High triglycerides were significantly linked to the consumption of the traditional pattern, whereas participants with no abdominal obesity related to the mixed pattern. Interpreting the statistics with caution, the mixed pattern appears to be more beneficial for health than the traditional pattern. Fruits and vegetables have long been constituents of the overall Thai dietary intake, but white rice is still the staple food throughout the country⁴ and should not be considered unhealthy. What appears to be less beneficial in the traditional pattern is the intake of glutinous rice (Oryzaglutinosa) with a high glycemic index³³, which stimulates high serum triglyceride levels³⁶. Hypothetically, elevated triglyceride levels as linked to the traditional pattern here indicates the risk for consumers of this pattern to develop T2DM, and the mixed pattern might to a certain extent prevent consumers of this dietary intake from acquiring T2DM. High triglyceride blood levels have been found to be independent risk factors pointing toward the development of diabetes^41–43. A promising approach for further studies would be to include metabolic variables closely linked to T2DM, such as insulin resistance, found to occur in hypertriglyceridemia and seem to be a risk factor for T2DM⁴⁴.

Some limitations of this study should be considered. Dietary patterns by using factor analysis involves subjective decisions for instant the consolidation of food items into food groups, the number of dietary patterns to be retained and the identified dietary patterns could be different in case of the subjects due to different ethnicity or culture¹⁴. The other limitation of the cross-sectional study is not optimal for assessing causal relationship because the investigator measures the outcome and the exposures at a single period time.

Conclusion

Two different dietary patterns could be recognized; the traditional- and the mixed pattern. These dietary patterns were not found to be associated with MetS. Adherence to the traditional pattern among the northeast Thai adults, in the context of nutrition transition, was associated with high triglyceride levels and seemed to be less beneficial for the mixed pattern, which was inversely related to abdominal obesity. Our findings show that the consumption of a variety of foods may be beneficial for health outcomes. Further studies on a larger sample population, as part of a prospective study, will provide important insights into the associations of dietary patterns and the metabolic syndrome.

Data availability

Dataset 1: Raw data gathered from the questionnaire 10.5256/f1000research.15075.d207245⁴⁵