Melanesians, Non-Western Diet, And Cardiovascular Disease Risk

Why do some non-Western populations have low rates of stroke and heart disease?  Here is a paper looking at one such population.  Abstract (containing one spelling correction):

OBJECTIVES:

To compare cardiovascular risk factor levels between non-westernized Melanesians, apparently free from stroke and ischaemic heart disease, and healthy Swedish populations, and to analyse, among adult Melanesians, relations with age, sex and smoking status.

DESIGN:

Cross-sectional survey.

SUBJECTS:

(i) Traditional horticulturalists in Kitava, Trobriand Islands, Papua New Guinea, uninfluenced by western diet. this study tested 151 males and 69 females aged 14-87 years with 76% and 80% smokers over 20 years. (ii) Healthy Swedish reference populations.

MAIN OUTCOME MEASURES:

Sitting systolic and diastolic blood pressure, weight, height, body mass index, circumferences of waist, pelvis and mid upper arm, triceps skinfold thickness, fasting serum total cholesterol, triglycerides, high-density lipoprotein cholesterol, estimated low-density lipoprotein cholesterol, apolipoprotein B, apolipoprotein A1 and apolipoprotein (a).

RESULTS:

Compared to Sweden, diastolic blood pressure, body mass index and triceps skinfold thickness were substantially lower in Kitava, where all subjects > or = 40 years were below Swedish medians. Among males > or = 20 and females > or = 60 years systolic blood pressure was lower in Kitavans. Fasting serum total cholesterol, low-density lipoprotein cholesterol and apolipoprotein B were 10-30% lower in Kitavan males > or = 40 and females > or = 60 years. Triglycerides were higher in Kitavans aged 20-39. High-density lipoprotein cholesterol did not differ while apolipoprotein A1 was lower in Kitavans. Apolipoprotein (a) tended to be lower in Kitavans, but the differences were small.

CONCLUSIONS:

Of the analysed variables, leanness and low diastolic blood pressure seem to offer the best explanations for the apparent absence of stroke and ischaemic heart disease in Kitava. The lower serum cholesterol may provide some additional benefit. Differences in dietary habits may explain the findings.

So, dietary differences leading to lean body structure, lower blood pressure, and lower cholesterol levels may explain the better stroke/heart disease profile in Melanesians vs. Swedes.  Of course, genetic differences, not mentioned in this abstract, between the two populations may influence this as well.  What I would like to see is a study comparing people within each population, each group having a different diet.  For example, do Melanesians with a Western diet have higher rates to stroke and heart disease?  What about Swedes on a healthier diet?