the effects of plant flavonoids on mammalian cells have been of substantial recent interest , with attention focused on the implications of these agents for cardiovascular disease and for cancer 1 . some epidemiological studies designed to examine a possible protective effect of flavonoids in cardiovascular disease
inconsistencies may be due to measurement error because foods that are flavanol - rich , such as grapes , red wine , or cocoa and chocolate shows remarkable variability in the flavonoid content , largely reflecting processing 16 - 18 .
the kuna indians of panama are known for their low blood pressure levels and little rise in blood pressure with age 19 - 21 .
our interest began with a search for protective genes , but the protection was environmental rather than genetic 20 .
as no environmental factor identified to date will reduce blood pressure levels to 110/70 mm hg -- the average found in the kuna , even those over 65 years of age -- identification of potential environmental factors was of considerable interest .
we learned that kuna still residing in their indigenous location in the san blas islands drank cocoa , all locally grown , as their major source of fluid .
the flavonoids were shown to cause the activation of nitric oxide synthase in healthy volunteers and patients with atherosclerosis 23 , 24 .
the very high flavonoid intake taken by virtually all kuna indians residing in their indigenous home area , enjoying what is almost certainly the highest flavanoid intake of any community , has created an opportunity to examine the possible role of a sustained high flavonoid intake on cardiovascular disease and cancer -- two major contributors to morbidity and mortality 1 .
there are also reasons for suspecting that flavonoids could protect against diabetes mellitus , as they improve sensitivity to insulin 25 .
we employed death certificates mandated by the republic of panama for all deaths within the republic .
as only kuna indians can own land in the san blas and all but a very small fraction of the residents are kuna indians , this allowed us to compare a population characterized by a very high sustained flavonoid intake with another population in which flavonoid intake is more variable , on average much lower .
cocoa obtained in the mainland from grocery stores is flavanol - poor 18 , 22 . because there are many risk factors for each of these processes and because death certificates contain little information on risk beyond age and to avoid potentially spurious evidence on risk , we prespecified that a significant outcome from this study would demonstrate a lower frequency of 4 processes in the san blas -- ischemic heart disease , stroke , diabetes mellitus , and cancer .
these complex processes have little in common other than the possibility that flavanols might influence their development and progression 1 .
death certificates for the years 2000 to 2004 were available for 77,375 in mainland panama and 548 individuals in the san blas .
a single cause of death was listed by either the attending physician or by a local health authority .
all of the data were submitted to the panamanian ministry of health in panama city and were available for analysis .
the code of the specific cause of death was based on the detailed list of the international class of occasional statistics of diseases and problems related health problems ( cid 9 and 10 ) .
the age distribution in the san blas and in the panama mainland was obtained from the most recent census information obtained in the year 2004 .
frequency of deaths per hundred thousand population were tabulated for various causes of death , both with and without age - adjustment and relative risk and 95 percent confidence interval were calculated .
we used the student 's t - test and chi square to compare the frequency of cause - specific deaths in mainland panama and the san blas .
in mainland panama , the most common cause of death was diseases of the circulation with a frequency of 119/100,000/year ( table 1 ) .
this was made up almost equally of ischemic heart disease with a frequency of 43.94/100,000/year and stroke with a frequency of 41.34/100,000/year .
the frequency was somewhat greater in males , 132/100,000/year , than in females , 106/100,000/year , and as expected showed a striking increase with age , reaching a peak of 1,193/100,000/year in those over 60 years of age .
the frequency in males ( 77.6/100,000/yr ) exceeded only slightly the frequency in females ( 71.8/100,000/yr ) .
diabetes mellitus was sixth in frequency with an average of 24.4 deaths/100,000 with a frequency significantly higher in women than in men .
the frequency peaked at 237.6/100,000/yr in those over 60 years of age . in the san blas ,
the most common cause of death in the san blas was infections with a frequency of 80.5/100,000/yr .
the frequency of death due to infections was substantially greater in men ( 130.1/100,000/yr ) than in women ( 61/100,000/yr ) .
an early peak in those under 10 years of age was dominated by diarrheal illness in the very young .
the common infections , in addition to diarrhea were tuberculosis , malaria , influenza , and hiv . in the conditions of interest ( table 2 ) ,
heart disease showed a frequency of only 8.3/100,000/yr and stroke was even lower , with a frequency of 3.2/100,000/yr .
cancer and diabetes were equally low with a frequency of 3.7/100,000/yr ( table 2 ) .
four conditions were predetermined before the analysis to be specific targets for effectiveness of flavanols , heart disease , stroke , cancer , and diabetes mellitus .
the year - by - year findings in panama and in the san blas for those four conditions are shown in table 3 .
the stability year - by - year for each diagnosis in panama was evident . in the case of cancer , the frequency over the five years ranged from 64.2 to 72.2/100,000/yr with a mean of 68.41.60 .
in san blas during the same interval four of five years showed no cancers , and one year showed a peak of 22/100,000/yr with a mean of 4.44.4 in san blas : the difference in frequency is highly significant ( p<0.001 ) . a similar pattern exists for ischemic heart disease and stroke , each relatively stable in panama and showing more variation in san blas : the frequency in san blas for both was significantly lower than in mainland panama ( p<0.001 ) . in the case of diabetes ( table 3 ) the same consistent difference
was found , but the difference was smaller : the frequency in san blas was 39 percent of that in panama .
the data are presented by age for these 4 conditions for the most recent year in which data are available , 2004 ( table 4 ) .
four conditions were predetermined before the analysis to be specific targets for effectiveness of flavanols , heart disease , stroke , cancer , and diabetes mellitus .
the year - by - year findings in panama and in the san blas for those four conditions are shown in table 3 .
in the case of cancer , the frequency over the five years ranged from 64.2 to 72.2/100,000/yr with a mean of 68.41.60 . in san blas during the same interval four of five years showed no cancers , and one year showed a peak of 22/100,000/yr with a mean of 4.44.4 in san blas : the difference in frequency is highly significant ( p<0.001 ) . a similar pattern exists for ischemic heart disease and stroke , each relatively stable in panama and showing more variation in san blas : the frequency in san blas for both was significantly lower than in mainland panama ( p<0.001 ) . in the case of diabetes ( table 3 ) the same consistent difference was found , but the difference was smaller : the frequency in san blas was 39 percent of that in panama .
the data are presented by age for these 4 conditions for the most recent year in which data are available , 2004 ( table 4 ) .
death from trauma was also more frequent in the mainland than in the indigenous island location , largely reflecting the influence of motor vehicle accidents .
in the san blas , there are neither roads nor automobiles , and death from this source was zero .
an increase in risk in the san blas was associated with perinatal medical problems , infections , and all other causes .
the average age of the kuna in the islands was very much influenced by the mortality in the very young , primarily due to diarrhea .
as an index of aging , we examined the age distribution on the mainland and in the islands ( table 5 ) .
about 12 percent of both males and females in the san blas were 55 years of age or older , about double the 6 percent over that age in the panama mainland ( chi square = 11.04 ; p<0.001 ) .
in panama , as in much of the western world , diseases of the circulation are the most common cause of death , and cancer is second .
the difference in risk of death due to these two classes of illness , cancer and heart disease , between san blas and mainland panama was very large .
our original hypothesis was that this would be the case if flavanol - rich cocoa and its influence on nitric oxide synthesis had implications for disease pathogenesis , as has been suggested 26 .
we could explain this extraordinary difference in the risk of death by proposing either a better prognosis or a lower incidence of these illnesses in san blas .
a reduced incidence is the most likely explanation , but both a better prognosis and a reduced incidence could have a similar explanation .
the san blas is the oldest indigenous district in the republic of panama , having a relatively homogeneous population both biologically and ethnically .
it exhibits one of the highest levels of poverty and economic and social exclusion in panama .
the district has two hospitals , six health centers , and eleven health posts , which do not guarantee access to all levels of service .
about 40,000 inhabitants are spread over forty - nine communities that are widely dispersed along the entire caribbean coast of panama .
the profile of health of the kuna residing in the san blas revealed substantial premature death due to infections : infectious and parasitic diseases made a contribution more than 4-fold higher than in the rest of the country .
the principle reasons were diarrhea , tuberculosis , aids , influenza , and malaria . one major limitation of our findings involves how the diagnosis on the death certificates was established .
medical diagnosis follows a well - defined sequence in which suspicion is raised from findings obtained from a medical history and physical examination , followed up with specific tests designed to establish the diagnosis . in the case of cancer , for example ,
examination of tissue obtained at biopsy is required for diagnosis . in the case of heart disease
, the diagnosis will be established through some combination of medical history and physical findings supplemented by the results of tests , including x - ray , angiography , ultrasound examination , the electrocardiogram , and occasionally a biopsy .
the availability of the laboratory examination probably differs in the san blas and the mainland , but the difference is relative , not absolute . in the hospital in ailigandi , for example , an electrocardiogram machine has been available for more than fifteen years , and the physicians who staff the hospital have worked in panama city and know how to diagnose myocardial infarction . during those fifteen years , there have been no cases of myocardial infarction diagnosed on ailigandi ( personal communication ) .
differences in the ability to establish a diagnosis may have played a larger role in the frequency of cancer diagnosis than in the frequency with which heart disease was diagnosed , although thousands of pap smears and biopsies are performed annually in the san blas . in 4 of 5 years , no cases of cervical cancer were diagnosed .
age of the communities at risk is important . as both diseases of the circulation and cancer increase in frequency with age , death at an earlier age from infection could have influenced the outcome .
in fact , the communities living in san blas are not younger : the percentage of kuna who are over the age of 55 years is substantially and statistically higher than in mainland communities .
adjustment for age served to enhance the difference in the frequency with which disease of the circulation or cancer led to death in the san blas versus the mainland .
although compatible with the possibility that a diet extraordinarily rich in flavonoids contributed to the low frequency of circulatory disease and cancer , it is obvious that other possibilities exist .
these include especially different patterns of diagnosis discussed above . as another alternative to flavanoid intake to account for the difference in disease frequency
as the difference was so very large , and the explanation is so important , follow - up population - based studies will be important to examine these risk factors prospectively .
until such data are available , the results of this study should be interpreted with great caution .
stress is commonly suspected to be lower on the islands than on the mainland ( commonly by people who have actually never visited the islands ) .
we have assessed stress in the panamanian mainland and islands , and there is a difference favoring the islands , but it is small 30 .
we and others have examined the diet in the san blas and kuna living in the panamanian mainland carefully and although several differences are noted , the most remarkable is cocoa intake 14 .
however , we have no information on diet and the frequency of other risk factors in non - kuna living in the panamanian mainland .
there is very probably less exposure to pollutants in the water and in the air in the san blas compared to the mainland , especially for those inhabitants that live in the city .
tobacco use by kuna is limited both in the indigenous island site and the mainland .
one common practice among the kuna involves working on the mainland on a job for a salary for many years , followed by retirement to the san blas indigenous island life where life is less stressful , and less expensive . to the extent that occurred , and
if twenty or thirty years of life on the panamanian mainland do not lead to changes that can not be reversed by return to the island , differences between the two locations may have been underestimated .
our hypothesis was that in the case of vascular disease the responsible pathway could involve stimulation of nitric oxide synthesis and thereby reversal of endothelial dysfunction 23 , 24 .
alternative possibilities , also possibly related to nitric oxide , include improvements in insulin sensitivity 25 , improvements in platelet function 15 , inhibition of ldl oxidation 28 , and an increase in plasma hdl cholesterol concentration 29 .
the influence of nitric oxide on insulin sensitivity would also provide an explanation for the difference in the frequency of diabetes mellitus 25 in the san blas and the mainland 1 .
in addition , a role in carcinogenesis may be hypothesized through nitric oxide cell - to - cell communication 1 .
death certificates provide core information , especially important at the national level 31 , 32 .
for example , if someone dies with both cancer and diabetes , the cancer is far more likely to be recorded 33
. this problem should not have influenced our findings , as heart attack , stroke , and cancer are likely to have been chosen from among a range of possible diagnoses , and there is no reason why the pattern should differ on the mainland and in the san blas . despite the other possible explanations for the large differences in deaths from cardiovascular disease and cancer with an array of possible confounding factors , it is improbable that these could abolish the cardiovascular and cancer protective effect observed among the san blas kuna as compared to the mainland . although the findings are compatible with effect of the flavanol - rich cocoa on health , clearly a large number of alternative possibilities exist involving diet , physical activity , stress and genetic factors .
indeed , only a randomized , controlled clinical trial in which all of these factors can be controlled will lead to a definitive conclusion .
all of these issues can be addressed , but that will take time and substantial resources .
death rate for panama per 100,000 : effect of gender and age death rates for the 15 most common causes of death in panama .
the leading causes of death are cardiovascular disease , cancer , and accidents as in much of the world .
death rate for san blas per 100,000 : by age and gender death rate for the san blas island chain per 100,000 .
a similar presentation to table 1 , but focused on the san blas islands off the caribbean coast .
note that cardiovascular disease , cancer , and diabetes are less than 10% of their frequency in the mainland .
age adjusted death rate/100,000 for selected causes in panama * ish = ischemic heart disease age adjusted death rates per 100,000 over 5 years for the 4 conditions specified in the hypothesis that a very high dietary intake of flavanoids might predict . note the remarkable year - to - year consistency in panama and the very much lower frequency each year in the san blas .
age adjusted death rate in panama and kuna yala for 2004 age - adjusted death rate in panama and kuna yala for one year , 2004 , for the 4 conditions specified in the hypothesis .
note that in panama each diagnosis shows an age - dependent frequency , and that this does not appear in the san blas .
p<0.001 age - distribution in the san blas and mainland panama from the census of 2004 .
note that there are more individuals over the age of 55 years among the kuna in the san blas than mainland panama , and the frequency is about double during each decade .
 substantial data suggest that flavonoid - rich food could help prevent cardiovascular disease and cancer . 
 cocoa is the richest source of flavonoids , but current processing reduces the content substantially . 
 the kuna living in the san blas drink a flavanol - rich cocoa as their main beverage , contributing more than 900 mg / day and thus probably have the most flavonoid - rich diet of any population . 
 we used diagnosis on death certificates to compare cause - specific death rates from year 2000 to 2004 in mainland and the san blas islands where only kuna live . 
 our hypothesis was that if the high flavanoid intake and consequent nitric oxide system activation were important the result would be a reduction in the frequency of ischemic heart disease , stroke , diabetes mellitus , and cancer  all nitric oxide sensitive processes . 
 there were 77,375 deaths in mainland panama and 558 deaths in the san blas . in mainland panama , as anticipated , cardiovascular disease was the leading cause of death ( 83.4  0.70 age adjusted deaths/100,000 ) and cancer was second ( 68.4  1.6 ) . 
 in contrast , the rate of cvd and cancer among island - dwelling kuna was much lower ( 9.2  3.1 ) and ( 4.4  4.4 ) respectively . 
 similarly deaths due to diabetes mellitus were much more common in the mainland ( 24.1  0.74 ) than in the san blas ( 6.6  1.94 ) . 
 this comparatively lower risk among kuna in the san blas from the most common causes of morbidity and mortality in much of the world , possibly reflects a very high flavanol intake and sustained nitric oxide synthesis activation . 
 however , there are many risk factors and an observational study can not provide definitive evidence . 
1. Introduction
2. Materials and methods
3. Results
4. Discussion
Figures and Tables