Impact of Dietary Behaviors on Dyslipidemia in Japanese Male Workers

Research Article

Ann Transl Med Epidemiol. 2014;1(1): 1003.

Impact of Dietary Behaviors on Dyslipidemia in Japanese Male Workers

Arai K1, Maeda E1, Iwata T1, Tanaka O1, Murata K 1* and Sakamoto M2

1Department of Environmental Health Sciences, Akita University Graduate School of Medicine, Japan

2Department of Epidemiology, National Institute for Minamata Disease, Japan

*Corresponding author: Murata K, Departmentof Environmental Health Sciences, Akita University Graduate School of Medicine, 1-1-1 Hondo, Akita 010- 8543, Japan

Received: October 06, 2014; Accepted: October 31, 2014; Published: November 01, 2014


Dyslipidemia such as hypercholesterolemia and hypertriglyceridemia, affecting atherosclerosis, is known to be induced by dietary behaviors including high-fat diets, but little is known about what kind of dietary behavior is associated with dyslipidemia. We explored which of lunch patterns such as box lunch, meals at restaurants, instant noodles, and rice-balls was more strongly connected with dyslipidemia. Data on dietary behaviors (e.g., breakfast-skipping, snacking, lunch patterns, dinner time irregularity, and daily ethanol intake) and the possible confounders (age, body mass index, sleep duration, smoking habit, regular exercise, and work stress), along with fasting serum levels of triglycerides, LDL-cholesterol and HDL-cholesterol, were collected from 1,582 male workers belonging to a health insurance union of automobile dealerships in Japan. Proportions of dyslipidemia among the workers were 17.3% for hypertriglyceridemia (≤ 150 mg/dl), 18.9% for hyper- LDL cholesterolemia (≥ 140 mg/dl), and 4.7% for hypo-HDL cholesterolemia (< 40 mg/dl). Given a multiple regression analysis with adjustment for possible confounders, the contribution ratio of lunch to lipid variations was between 0.1% and 0.8%. Also, habitual instant noodle ingestion showed a significant relation to triglycerides. Odds ratios of habitual instant noodle ingestion, after adjustment for the possible confounders, were 1.575 (95% confidence interval, 1.120 to 2.215) for hypertriglyceridemia and 2.039 (1.148 to 3.623) for hypo- HDL cholesterolemia; and, the former showed a dose-dependent relationship. Despite the small contribution of lunch to total food intake, it is suggested that habitual ingestion of instant noodles can lead to hypertriglyceridemia and hypo- HDL cholesterolemia in male workers.

Keywords: Dyslipidemia; Instant noodles; Triglycerides; Cholesterol; Lunch patterns


LDL-C: Low-Density Lipoprotein Cholesterol; HDL-C: High- Density Lipoprotein Cholesterol; BMI: Body Mass Index; ALT: Alanine Aminotransferase; TG: Triglyceride; AST: Asparate Aminotransferase; GGT: γ-Glutamyltransferase; SD: Standard Deviation; OR: Odds Ratio; CI: Confidence Interval


Hypercholesterolemia and hypertriglyceridemia are mainly induced by dietary behaviors including high-fat diets [1], and such dyslipidemias elevate the risk of atherosclerotic cardiovascular disease [2]. In addition, overaccumulation of saturated fatty acids in the liver has been suggested to trigger hepatocellular apoptosis or inflammation [3,4], which seems to result in elevated Alanine Aminotransferase (ALT) involved in nonalcoholic fatty liver disease [5,6]. For promoting the primary prevention of atherosclerosis and fatty liver, accordingly, it is crucial to identify dietary behaviors that are strongly associated with dyslipidemia.

In Korean men, a noodle-bread dietary pattern showing greater intake of noodles and bread has been reported to be in close association with hypercholesterolemia and abdominal obesity [7]. Also, snacking, a common feature in the Western diet, contributes to hepatic steatosis and obesity [8]. In Japanese workers, lunch patterns (e.g., box lunch, meals at restaurants, instant noodles like cup ramen, and rice-balls) seem to be generally unchanged while dinner pattern differs daily among the Japanese, Chinese and Western diets or in seasonal ingredients of fish and vegetables; for this reason, it may be easy to examine the lunch pattern. We formulated a hypothesis about dietary behaviors that a certain lunch pattern might lead to dyslipidemia in Japanese male workers and drew up a project designed to test it. In addition, we explored the extent of contributions of lunch to serum levels of Triglyceride (TG), Low-Density Lipoprotein Cholesterol (LDL-C) and High-Density Lipoprotein Cholesterol (HDL-C) and the strength of relationships between the lipid levels and liver markers such as ALT in the same subjects, because it has been demonstrated recently that ALT elevation is associated with habitual ingestion of instant noodles for lunch [9].

Materials and Methods

Study population

In February-March 2012, a self-reported questionnaire was distributed to approximately 2,200 male employees belonging to a health insurance union of motor vehicle dealerships in a prefecture of northeast Japan, including salesmen, mechanics, and office clerks, but excluding the managerial class [9]. Of them, 1,857 consented to our proposal and returned the forms to the occupational health nurse of the union (response rate = 84%). Two hundreds and seventy-five respondents were excluded: those who did not undergo the mandatory health checkup, conducted under the Industrial Safety and Health Law in Japan, in April-July 2012; those whose fasting blood could not be taken; those who suffered from ischemic heart disease, chronic renal failure, alcoholic dependency diagnosed by a psychiatrist, liver cirrhosis, or cancer; those whose serological tests for hepatitis B or C infection were positive; those who took antihyperlipidemic agent; and, those whose reported questionnaire forms contained imperfect information. The study population consisted of 1,582 male workers aged 19-29 years (28.1%), 30-39 years (39.4%), 40-49 years (20.2%), and 50-67 years (12.3%). Some mechanics in this study had underwent the specific health examination for organic solvent workers under the Industrial Safety and Health Law annually, but such workers had neither symptoms/signs of organic solvent poisoning nor abnormal findings in urinalysis. This study was conducted in accordance with the Declaration of Helsinki of 1964 as revised in 2000, after our study protocol was approved by the Ethical Review Committee of the Akita University Graduate School of Medicine.

Exposure and outcome variables

Breakfast, lunch, snack, and dinner, as well as smoking and drinking habits, regular exercise, stress at work, and sleep duration, were inquired via the questionnaire made for this study on lifestyle behaviors. For instance, each subject reported whether he felt any stress at work (yes/no). Habits of breakfast-skipping/snacking during work hours and dinner time irregularity were scored as “absence”=0 and “presence”=1. What each subject ate at lunch time on workdays, i.e., a home-made or takeout box lunch, meals at restaurants, instant noodles, rice-balls (onigiri, i.e., a ball of cooked rice usually formed by hand), and others, was also asked by a method of multiple responses. In addition, one more question about how often each ate instant noodles in a week was posed to the subjects who indicated that they did consume such noodles for lunch. Nocturnal sleep duration (min) was computed as the difference between bedtime and wake time on workdays. The weekly amount of each type of alcoholic beverage consumed was also asked as described previously [10,11]; e.g., “How many 180 ml-cups (or 1,800 ml-bottles) of sake do you drink in a week?” and “How many 350 ml-cans (500 ml-cans, or 633 ml-bottles) of beer do you drink in a week?” Types of alcoholic beverages listed were sake, beer, shochu (a Japanese distilled alcoholic beverage primarily made from barley or sweet potatoes), whisky, wine, and others (e.g., plum wine, brandy, gin, or vodka). A total of 100% ethanol equivalent dose (g/d) was calculated for each subject. Smoking habit was scored as “nonsmoker” = 0 and “current smoker” = 1. Regular exercise was defined as at least one 30-min session at least once per week. The responses of exercise and work stress were scored as “absence” = 0 or “presence” = 1.

Data on lipid markers, i.e., fasting serum TGs, LDL-C, and HDL-C, along with ALT, Asparate Aminotransferase (AST), γ-Glutamyltransferase (GGT), and body mass index (BMI, kg/m2), were obtained for each subject from the annual health checkup record. These lipids and liver markers were measured by the Akita Foundation for Healthcare, according to the principles recommended by the Japan Society of Clinical Chemistry [12]. Based on conventional values recommended by the Japan Atherosclerosis Society [13], TGs of 150 mg/dl or more, LDL-C of 140 mg/dl or more, and HDL-C of less than 40 mg/dl were defined as hypertriglyceridemia, hyper-LDL cholesterolemia, and hypo-HDL cholesterolemia, respectively.

Statistical analysis

Since TGs, LDL-C, HDL-C, ALT, AST, and GGT did not show a normal distribution, they were logarithmically transformed in using the Pearson product-moment and partial correlation coefficients and multiple regression analysis, and the median, minimum and maximum, but not mean ± Standard Deviation (SD), were employed in the tables. The relations of lifestyle behaviors (sleep duration, breakfast-skipping, snacking, irregularity of dinner time, smoking, daily ethanol intake, regular exercise, and work stress), lunch patterns (box lunch, meals at restaurants, instant noodles, and rice-balls), and confounders (age and BMI) to serum lipid levels were analyzed by multiple regression analysis. Multiple logistic regression analysis with adjustment for lifestyle behaviors and confounders was also used to calculate Odds Ratio (OR) and 95% Confidence Interval (CI) of lunch patterns on dichotomous data of hypertriglyceridemia, hyper- LDL cholesterolemia, and hypo-HDL cholesterolemia, which could avoid the overestimate resulting from extremely high TGs (> 400 mg/ dl). All analyses with two-sided P values were performed using the Statistical Package for the Biosciences (SPBS Ver. 9.65) [14] and the significance level was set at P < 0.05.


Background characteristics of 1,582 male workers are shown in Table 1. Proportions of dyslipidemia among them were 17.3% for hypertriglyceridemia, 18.9% for hyper-LDL cholesterolemia, and 4.7% for hypo-HDL cholesterolemia. Given a linear regression, all regression coefficients of these lipid markers on age and BMI, except for that of HDL-C on age, were statistically significant (Figure 1), implying that age and BMI are essential confounders for the assessment of serum lipids. After adjusting for age, BMI, and daily ethanol intake, TGs were positively correlated with ALT, AST, and GGT (Table 2). Likewise, LDL-C was positively correlated with ALT and GGT; but, HDL-C was negatively correlated with ALT.