Investigation of oxidative stress and dietary habits in Mongolian people, compared to Japanese people

Abstract

Background: The average life span of Mongolians is 62 years for males and 69 years for females. This life span is about 16 years shorter than that of Japanese. Mongolian people generally eat meat, fat and diary products but less vegetables or fruit. Thus, we investigated the state of oxidative stress and dietary habits of Mongolians.

Methods: The investigation was performed in Murun city in the northwest area of Mongolia. A total of 164 healthy subjects (24-66 y) were enrolled. As a marker of reactive oxygen species, the levels of reactive oxygen metabolites (ROM) were measured using the d-ROM test. Interviews about dietary habits were performed using the Food Frequency Questionnaire established by the Kagawa Nutrition University.

Results: ROM levels were 429.7 +/- 95.2 Carr U for Murun subjects, whereas Japanese people (n = 220, 21-98 y) showed 335.3 +/- 59.8 (p < 0.001). The levels of serum malondialdehyde-modified low-density lipoprotein-cholesterol and urinary 8-hydroxydeoxyguanosine were also high. ROM levels correlated with body fat ratio and inversely correlated with handgrip strength. Handgrip strength in the subjects over 45 years decreased more rapidly than that of age-matched Japanese. Murun subjects ate larger amounts of meat, fat, milk and flour and dairy products than Japanese, but less vegetables or fruit. Serum vitamin A and E levels were the same as Japanese references, but vitamin C levels were lower.

Conclusion: Murun subjects may be in high oxidative stress, which may have a relationship with early ageing and several diseases, ultimately resulting in their short life span. In order to increase antioxidant capacity and suppress overproduction of ROM, antioxidant food intake is recommended.

Figure 1

Comparison of daily food intake (g/day) among Murun, Ulaanbaatar Group A and Japanese subjects. Murun subjects seldom eat vegetables or fruit. Ulaanbaatar Group A subjects lived by urbane-styles and ate high amounts of fruits.

Figure 2

Relation of ROM levels with age. a: Japanese subjects, b: Murun subjects, c: Murun subjects without contraceptive pill users. Japanese young subjects showed low ROM levels, and the levels increased with age. But Murun subjects did not show this tendency. The levels were very high even in young ages.

Figure 3

Comparison of body weight between Murun subjects and Japanese people Generally, Murun subjects showed higher body weight than age-matched Japanese people.

Figure 4

Comparison of BMI between Murun subjects and Japanese people. Murun subjects showed higher BMI levels than age-matched Japanese people. In males, the difference became clear in those over aged 50.

Figure 5

Comparison of %BF between males and females (a) and correlation of ROM levels with %BF (b). a: Females showed higher levels of %BF than males. b: This finding suggests that ROM production may have a relation with lipid accumulation.

Figure 6

Comparison of handgrip strength between Murun subjects and Japanese people people. Handgrip strength of Murun subjects decreased earlier than that of age-matched Japanese. This finding suggests that ageing of Murun subjects may progress faster than that of Japanese people.

Figure 7

Comparison of handgrip strength between Ulaanbaatar Group A and Group B people (a and b), and correlation of ROM levels with handgrip strength in Murun subjects (c). These findings suggest that ROM production may influence the ageing process.

Figure 8

Relation of MDA levels with LDL levels (a) and SOD activities with ROM levels (b) in Murun subjects. MDA levels correlated with LDL levels significantly. SOD activities did not correlate with ROM levels, and a few subjects showed high SOD activities.