Inflammation is involved in the progression of atherosclerosis and cardiovascular disease (CVD) [1,2]. Several studies have reported that an increased level of hsCRP, a marker for low grade inflammation, is associated with an increased CVD risk among various populations across the world [3,4,5]. CVD mortality is twice as high in a group with hsCRP > 3 mg/L, a level considered high risk by the American Heart Association (AHA) and the Center for Disease Control and Prevention (CDC) [6], compared to those with < 1 mg/L (low risk) [7].

hsCRP is a strong independent predictor for future CVD outcomes. Among apparently healthy non-smoking, normoglycemic, normolipidemic, premenopausal women participating in the Women's Health Study, the risk of future cardiovascular events was four times higher in those with the highest hsCRP than in those with the lowest hsCRP [8]. hsCRP has also been proposed as a more powerful predictor of cardiovascular events than other markers of inflammation or lipids in the plasma such as amyloid A, soluble intercellular adhesion molecule, interleukin-6, homocysteine [9], and even low-density lipoprotein cholesterol, a well-established conventional risk factor for CVD [10].

Several studies have reported a significant association between hsCRP and various dietary factors, suggesting that hsCRP can be modifiable by manipulating the diet. hsCRP level is higher in subjects who consume high quantities of meat, total fat, saturated fat, and cholesterol [11,12,13], and is lower in those who consume high quantities of fruits and vegetables, fish and poultry [14], and dietary fiber [15]. Furthermore, a healthy pattern (high intake of fruits, vegetables, tomatoes, poultry, legumes, tea, fruit juices, and whole grains) is inversely associated, whereas a western pattern (high intake of refined grains, red meat, butter, processed meat, high-fat dairy, sweets and desserts, pizza, potato, eggs, hydrogenated fats, and soft drinks) is positively associated with high hsCRP [16].

Vietnam is undergoing a rapid change in economic development, urbanization, and diet transition with an increasing trend in the number of people with CVD risk factors [17,18]. CVD mortality in Vietnam now accounts for nearly 40% of the mortality due to noncommunicable diseases [19]. The prevalence of some CVD risk factors such as obesity and dyslipidemia has been reported for Vietnamese women [20,21], but not for serum hsCRP levels, which might be a better predictor of future CVD risk. Although many studies have demonstrated an association between hsCRP and dietary intake, very few studies have investigated such a relationship in young women in their 20s and 30s [11]. Given that hsCRP is a powerful predictor of future CVD events, and that its level can be modified by diet, studies on the relationship between hsCRP and diet may help develop core messages for dietary intervention strategies. Therefore, we investigated the relationship between serum hsCRP and diet in healthy Vietnamese young women.

In this study of apparently healthy Vietnamese women, the high risk group (serum hsCRP > 3 mg/L) consumed fewer fruits and vegetables and less potassium and folate than those in the low and average risk groups. We found an inverse association between serum hsCRP and fruit and vegetable, total plant food, total food, potassium, and folate consumption after adjusting for age, BMI, total energy intake, alcohol consumption, dietary supplement use and exercise. A multiple regression analysis after adjusting for covariates revealed a significant negative association between hsCRP and fruit and vegetable consumption, confirming the results of other investigators [25,26].

Previous studies on the relationship between hsCRP and dietary intake have reported that hsCRP levels are inversely associated with fruit and vegetable intake [25], and that the risk of high hsCRP (> 3 mg/L) increases with low consumption of fruits and vegetables [26]. Among nutrients, hsCRP is inversely associated with dietary intake of vitamin C [27], folate [28], and dietary fiber [15], for all of which nutrients fruits and vegetables are great sources. Most of these studies were conducted in middle-aged or elderly women in western populations (England, Portugal, Sweden, and Iran). Only one study is available in young Indian women in their 20s and 30s, which was similar to our study subjects, and that study reported a decreased hsCRP level in the group that consumed many fruits and vegetables compared to that of low consumption. This suggests that the beneficial role of fruits and vegetables against hsCRP may be universal across many population groups including eastern countries and also several age groups including young adults [11] despite differences in baseline hsCRP level and fruit and vegetable consumption. A healthy or prudent diet pattern with high fruit and vegetable consumption is inversely associated with hsCRP in diverse ethnic populations including those participated in the Nurses' Health Study [14] and Japanese [29]).

Increased hsCRP levels due to inflammation lead to a risk for endothelial dysfunction [30] and cause progression of atherosclerosis and cardiovascular disease [31]. Fruits and vegetables or nutrients such as vitamin C, folate, and potassium, which are found in high concentrations in those food groups, may directly and indirectly influence serum hsCRP levels, inflammation, and endothelial function. The mechanisms associated with dietary factors that influence hsCRP levels and inflammation are still unclear. However, high consumption of fruits and vegetables, which are good sources of antioxidant vitamins and folate, has beneficial effects on endothelial function [32,33]. Antioxidant vitamins contribute to endothelial function by reducing LDL oxidation [34], and folate by reducing plasma homocysteine concentration which can increase platelet aggregation, thrombosis [35] and decrease nitric-oxide (NO) production [36]. Potassium, another nutrient found in high concentrations in fruits and vegetables, improves vascular function by softening endothelial cells and stimulating NO release [37,38].

The mean hsCRP of the subjects was 1.3 ± 2.9 mg/L, and 9.8% of the subjects were in the high risk hsCRP group, which was similar to the level in young Indian (mean hsCRP levels, 1.3 ± 2.5 mg/L, 12.8% of subjects belonged to the high risk group) [11], but higher than that of other Asian young women [39,40] and Turkish women [41] as well as young women in European countries (mean hsCRP levels, 0.67-0.89 mg/L) [42,43]. In our subjects, hsCRP was highly correlated with many of the metabolic disease parameters such as BMI, WHR, body fat, blood pressure, white blood cell count, triglycerides, and HDL cholesterol, confirming the results of other studies, mostly in middle-aged populations [44,45]. We found such a relationship between hsCRP and metabolic disease parameters in Vietnamese young women as well.

Due to limited data, it is difficult to compare our results to those of other studies conducted among Vietnamese young women of same age, geographical or socioeconomic groups. The BMI of our subjects (mean 20.0 ± 2.4) was higher to that reported in women (mean of BMI 19.5 ± 1.9) of Thai Nguyen's 9 districts, rural region (n = 4,983; mean age, 26.2 ± 4.6 years) [46] and lower than that of women of reproductive age (mean of BMI 21.1 ± 0.1) of urban region (n = 730; mean age, 32.7 ± 0.4 years) [47]. The energy intake in our subjects was about 1,728 kcal/day (data not shown), which was lower than that reported in young women living in the rural area (2,196 kcal/day) [46] and those in the urban area (1,899 kcal/day) [48]. The differences in energy intake may have been partly due to differences in food intake survey methods, a 24-hour recall method in our study, semiquantitative food frequency method in rural areas [46], and 24-hour recall combined with controlled food weighing method in urban areas [48].

Vietnam is undergoing a rapid change in economic development, urbanization, and diet transition with an increasing trend in the number of people with CVD risk factors [17,18]. The CVD mortality in Vietnam now accounts for nearly 40% of mortality due to noncommunicable diseases [19]. A high CVD risk is particularly noticeable in urban areas of Vietnam, similar to this study area. The prevalence of diabetes and having a cluster of (≥ 2/4) metabolic CVD risk factors (hypertension, dyslipidaemia, diabetes, and obesity) in women in urban areas is approximately 1.4 and 2.6 times higher, respectively than that in rural areas [20,49]. The prevalence of some CVD risk factors in Vietnamese women such as obesity, dyslipidemia, diabetes has been reported [20,21], but not for serum hsCRP levels, which might be a better predictor of future CVD risk.

Although many studies have demonstrated an association between hsCRP level and dietary intake, very few studies have investigated such a relationship in young women in their 20s and 30s. If intervention is implemented early enough, the impact of diet and lifestyle interventions can be maximized. Given that hsCRP is a powerful predictor for future CVD, and that hsCRP level might be modifiable by dietary factors, studies on the relationship between hsCRP level and diet are important for developing diet intervention strategies.

This study has several limitations. First, a 1-day 24-hour recall may be insufficient to assess typical daily intake due to potentially large intra-individual variability in food and nutrient intake. However, our dietary interviewers were well-trained, which minimized potential errors when assessing dietary intake. Second, nearly 70% of our subjects were college students; therefore, our data may not be extrapolated to most women in Vietnam. Third, we cannot infer causality because of the cross-sectional nature of the study. Therefore, a prospective study should be conducted to explore the association between hsCRP and dietary intake in Vietnamese women. Nevertheless, our study had certain strengths. This is the first study on the relationship between hsCRP and diet in young Vietnamese adult women. This study was the International Collaboration Study for the Construction of Asian Cohort of the Korean Genome and Epidemiology Study (KoGES) performed on a large scale, and information on the identified and potential confounding factors was included in the analysis.

In conclusion, we found that hsCRP level was closely related to dietary intake in healthy Vietnamese women. Fruit and vegetable, potassium, and folate intake were inversely associated with hsCRP level. Therefore, to prevent the occurrence of future CVD by reducing hsCRP levels, it is necessary to increase consumption of fruits, vegetables, and all plant foods.

This study protocol was approved by the Human Investigation Review Board of Ewha Womans University College of Medicine (ECT 200-18 200-19).