Differences in dietary habits, serum fatty acid compositions and other coronary risk characteristics between freshmen and fourth-year male university students

Westernization of lifestyles among Japanese, in particular among young generations, is a matter of concern for future increase in coronary heart disease. We surveyed a total of 349 male university students to examine changes in lifestyles and coronary risk factors in campus life. We compared dietary habits and serum fatty acid compositions as well as other coronary risk characteristics between freshmen (n=171) and fourth-year (senior) students (n=178). Serum fatty acid compositions and dietary intakes of selected foods as well as serum lipids, blood pressures and physical characteristics were examined at the 1996 and 1997 annual health examinations.Compared to freshmen, senior students had a lower frequency of fish, vegetable, milk and egg intake, and a higher frequency of oil and fat intake. The proportions of serum saturated and monounsaturated fatty acids were significantly higher among senior students than among freshmen, whereas the proportion of serum polyunsaturated fatty acids was significantly lower among senior students than among freshmen. Senior students also had higher systolic and diastolic blood pressures, percent body fat, smoking rate and alcohol usage than freshmen. Mean body weight and mean body mass index were not different between the two groups.Senior students generally showed Westernized dietary habits and higher coronary risk profiles than freshmen as indicated by the change of serum fatty acid compositions. Modification of these dietary habits and lifestyles may be important for the prevention of future CHD among Japanese young adults.

[The effects of fish supplementation of platelet function, count and metabolism in healthy Japanese]

To investigate changes in platelet function, count and metabolism following fish intake among Japanese, we conducted an experimental intervention study of seven healthy Japanese volunteers (4 males and 3 females) aged 28-58 years. We supplemented their diets with an approximate daily intake of 200-400 g fish which is equivalent to about 10 g n3-polyunsaturated fatty acids (about 3.5 g eicosapentaenoic acid plus 5.0 g docosahexaenoic acid) during the 17 days. The study continued until the 23rd day after returning to an ad libitum diet. The proportion of serum n3-polyunsaturated fatty acids increased two-fold on 5th day and three-fold on 15th day of fish supplementation, but decreased to one and a half-fold on the 2nd day and returned to the level before fish supplementation on the 12th day after returning to an ad libitum diet. The proportion of serum n6-polyunsaturated fatty acids decreased by 17% to the level before fish supplementation on the 5th day, 33% on the 15th day of fish supplementation. However, the decrease was only 10% on the 2nd day and the proportion returned to the same level as before fish supplementation on the 12th day after returning to an ad libitum diet. As a result, the serum n3/n6 polyunsaturated fatty acid ratio increased four-fold on the 15th day of fish supplementation, and returned to the baseline level on the 12th day after returning to an ad libitum diet. Platelet counts decreased and the mean platelet volume increased during fish supplementation. Both parameters returned to the level before fish supplementation on the 12th day after returning to an ad libitum diet. The counts and proportion of large type platelets increased significantly during fish supplementation. Although platelet aggregation by ADP (adenosine 5'-diphosphate) did not change significantly, platelet aggregation by collagen tended to decrease during fish supplementation. Platelet factor 4, one of the indices of platelet activity, decreased significantly during fish supplementation. The mean serum triglyceride level declined during fish supplementation, but returned to the level just before fish supplementation on the 2nd day after returning to an ad libitum diet. The mean plasma fibrinogen level tended to decline during fish supplementation and remained lower until the 12th day after returning to an ad libitum diet. Habitual fish intake may attenuate the development of atherosclerosis and prevent ischemic heart disease through suppression of platelet activity, and by reducing platelet counts and serum triglyceride levels.

Plasma fibrinogen, tissue plasminogen activator, plasminogen activator inhibitor 1, and their related factors in three Japanese population samples

To examine population mean variations in plasma fibrinogen and fibrinolytic variables, and their rela tions with cardiovascular risk characteristics among Japanese middle-aged men, a cross-sectional study was conducted for a total of 245 men aged 50-59 years in three population-based samples: residents in rural communities of northeast and central Japan and urban white-collar workers. Age-adjusted mean value of plasma fibrinogen, tissue plasminogen activator antigen (t-PA antigen), plasminogen activator inhibitor 1 antigen (PAI-1 antigen) did not differ significantly among the populations. Mean value of tissue plasminogen activator activity (t-PA activity) was lower in central rural residents than in northeast rural men. According to multiple linear regression analyses, there were positive associations of t-PA and PAI-1 antigens with serum triglyceride levels, serum insulin and waist-hip ratio within each population and the total samples. A positive association between these fibrinolytic variables and usual ethanol intake was also observed. Smoking was significantly associated with plasma fibrinogen and PAI-1 antigen but not with t-PA antigen or activity. Activity of t-PA was inversely associated with body mass index, and a mean difference in t-PA activity was in part explained by a mean difference in body mass index. In conclusion, population mean values of plasma fibrinogen and fibrinolytic variables did not differ among three Japanese populations except for mean t-PA activity. Reduced fibrinolysis expressed as increased PAI-1 antigen was associated with smoking and the status of insulin resistance, such as high levels of serum insulin, serum triglycerides and waist-hip ratio.

[Effectiveness of a health education class to increase fish intake evaluated by serum fatty acid compositions]

For prevention of cardiovascular disease, we recommended increased fish intake for 50 middle-aged women and men of 40-83 years old at a three-month community-based health education program in an inland farming community. The effectiveness of the education program was evaluated by examining changes in serum lipids and serum fatty acid compositions. For comparison, we selected 48 men and women of 38-82 years old did not participated in the program. Before education, there was no significant difference in the dietary frequency of fish, meat, egg and dishes prepared with oil, mean values of serum lipids or serum fatty acid compositions except for saturated fatty acid, gamma-linolenic acid, dihomo-gamma-linolenic acid and alpha-linolenic acid. After three months, the frequency of fish intake of one or more times per day increased from 33% to 43% in the education group while the frequency of fish intake did not change in the control group. In the education group, serum n3 polyunsaturated fatty acid composition increased from 8.8% to 10.6%. This fatty acid increase was primarily observed in eicosapentaenoic acid and docosahexaenoic acid. The n3/n6 ratio increased from 0.21 to 0.31. In the control group, no change was observed in n3 polyunsaturated fatty acids. This study suggests that the community-based dietary education increased fish intake and serum n3 polyunsaturated fatty acids in women and men of 40 years old or older.

[Relation of serum fatty acids with serum lipids and blood pressure in women]

We studied the correlation of serum fatty acids, a potential coronary risk factor, with serum lipids and blood pressure. The subjects were women aged 40-69 of four Japanese populations (fishing, coastal farming, inland farming and urban populations) and a Caucasian population in which different dietary habits have been reported. Within populations, the total cholesterol level was not correlated with serum fatty acids. HDL-cholesterol was inversely correlated with saturated fatty acids and monounsaturated fatty acids, and positively correlated with polyunsaturated fatty acids although not significantly so in all populations. LDL-cholesterol was not correlated with saturated fatty acids and mono polyunsaturated fatty acids, but was positively correlated with polyunsaturated fatty acids. Triglyceride was positively correlated with saturated fatty acids and monounsaturated fatty acids, and inversely correlated with polyunsaturated fatty acids for all populations. Blood pressure correlated positively with saturated fatty acids, and inversely with polyunsaturated fatty acids although these associations were not statistically significant.

[Dietary habits and serum fatty acid compositions of women college students--changes in serum lipids and fatty acids by dietary education]

To obtain fundamental information for prevention of coronary heart disease in young adults, frequency of dietary intake, blood lipid and serum fatty acid compositions were examined for 114 female students. The relationship of selected food intake to serum fatty acid composition was also examined. Results of a nutritional survey were used to identify students who had a frequency of fish intake of "none" or "1-2 times/week" from whom random selection into two groups was accomplished: control group (n = 31) and education group (n = 31). The education group received a recommendation for increasing fish intake for 3 months. The effect of the education program was evaluated by examination of blood lipids, serum fatty acid compositions and frequency of dietary intake. Fifty-four percent of the students reported "none" or "1-2 times/week" for the frequency of fish intake, and 76% of them reported "1 and more times/day" for oil intake. The proportion of serum saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids were 28.9%, 24.4%, 46.8%, respectively. Of the polyunsaturated fraction, 41.4% was omega 6-polyunsaturated fatty acids, and that of omega 3-polyunsaturated fatty acids was 5.4%. The omega 3/omega 6 ratio was 0.13. Serum omega 3-polyunsaturated fatty acids was directly related to frequency of fish intake, and serum omega 6-polyunsaturated fatty acid, especially linoleic acid, was directly related to frequency of oil intake. After a 3-month education program, the frequency of fish intake and meat intake increased, while frequency of oil intake decreased in the education group. Serum omega 3-polyunsaturated fatty acid (in particular eicosapentaenoic acid, docosahexaenoic acid) increased in the education group, but not in the control group. The omega 3/omega 6 ratio increased from 0.13 to 0.18 in the education group. These results indicate that dietary education for fish intake is effective in increasing serum omega 3-polyunsaturated fatty acids, and the omega 3/omega 6 ratio for female students with initial low intake of fish and a high intake of omega 6-polyunsaturated fatty acids.

[Population-based comparative study on dietary habits and serum fatty acid compositions]

Appropriate dietary instruction on fat intake is required for Japanese to prevent coronary heart disease because there has been a consistent increase in fat intake during the past two decades. To gain fundamental information for dietary instruction, we examined the relation between dietary habits related to fat and serum fatty acid compositions in women aged 40-69 of four Japanese populations (fishing, coastal farming, inland farming and urban populations) and a Caucasian population in which different dietary habits have been reported. Among Japanese, dietary intake of monounsaturated and polyunsaturated fatty acids (in particular omega 6-polyunsaturated fatty acid) were higher in the urban population than in the other populations. Intake of omega 3-polyunsaturated fatty acids did not vary among the Japanese populations, but intakes of eicosapentaenoic acid and docosahexaenoic acid were higher in fishing and coastal farming populations than in the other two populations. Serum concentrations and compositions of omega 6-polyunsaturated fatty acids (mostly linoleic acid) were higher in the urban and inland farming populations than in the other two populations whereas those of omega 3-polyunsaturated fatty acids (in particular eicosapentaenoic acid) showed the opposite trend. The proportion of omega 6-polyunsaturated fatty acids was higher and that of omega 3-polyunsaturated fatty acids was lower in Caucasian women than in the Japanese populations. The ratio of omega 3 (polyunsaturated fatty acids) to omega 6 was highest in the fishing population (ratio = 0.38), intermediate in coastal farming (0.35), urban (0.27) and inland farming (0.24) populations, and lowest in Caucasians (0.07). Within populations, the percentage of serum omega 6-polyunsaturated fatty acids increased with the increase of frequency of meat intake and oil intake. The percentage of serum omega 3-polyunsaturated fatty acids increased with the increase in frequency of fish intake. Because there are evident associations between the frequency of fish, meat and oil intake and serum fatty acid compositions, a frequency questionnaire on these foods would be useful for dietary instruction in the prevention of coronary heart disease.

[The effect of storage on serum fatty acids]

To investigate the effect of storage on serum fatty acids, we examined the composition of serum fatty acids in samples from healthy men stored at different temperatures for various periods of time. The following experimental storage conditions were studied: 1) 4 degrees C for three weeks, 2) -20 degrees C for 12 months and 3) -80 degrees C for 24 months. The fatty acid composition did not change after two-week storage at 4 degrees C. At -20 degrees C, there was a decline in the content of docosapentaenoic acid (22: 5, omega 3) after one month, and docosahexaenoic acid (22: 6, omega 3) after three months. However, omega 3-polyunsaturated fatty acid as a whole did not show a significant change. At -80 degrees C, there was a decline of docosapentaenoic acid after three months, arachidonic acid (20: 4, omega 6) after 12 months, and linoleic acid (18: 2, omega 6) after 24 months. As a whole, omega 3-polyunsaturated fatty acids did not change. Omega 6-Polyunsaturated fatty acids significantly declined 5% after 24 months. Therefore, it is recommended that serum fatty acids be measured within two weeks at 4 degrees C, within a few months at -20 degrees C and within one year at -80 degrees C to estimate the composition of the major fatty acids.