Division
of Nutritional Sciences
Cornell University
Savage Hall
Ithaca, NY 14850
email: bjp1@cornell.edu
Cornell University
Savage Hall
Ithaca, NY 14850
email: bjp1@cornell.edu
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Division
of Nutritional Sciences
Cornell University Savage Hall Ithaca, NY 14850 email: bjp1@cornell.edu |
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ComprehensiveEpidemiological Transition | Aggregate Findings | Socioeconomic
SpecificA variety of specific disease, nutrient and biomarker associations have been investigated. Virtually all support the idea that nutrients usually present in plant based foods minimize the occurrence of chronic degenerative diseases.
Epidemiological TransitionAbout four dozen different disease categories were available for investigation, including both the chronic degenerative diseases (e.g., cancers, cardiovascular diseases, diabetes) and the communicable, infectious diseases (e.g., tuberculosis, pneumonia, gastrointestinal).When their geographic distributions were sought, it was found that the degenerative diseases tended to cluster in the more urbanized, industrialized counties while the communicable diseases were primarily found in the more agricultural counties. The 'dietary and lifestyle' factors chiefly associated with the 'degenerative disease' counties included metabolic and dietary factors which characterize diets richer in animal products and higher in total fat. These findings suggested that only small additions of animal based foods to an otherwise all plant based diet could elevate blood cholesterol (both total and LDL), thence to elevate the risk for the chronic degenerative diseases.
Aggregate FindingsComparison of diets in rural China with average American diets shows that Chinese diets are much lower in total fat (6-24% of calories, except for certain nomadic groups in northern China), much higher in dietary fiber (10-77 g/day), about 30% higher in total calorie intake and substantially lower in foods of animal origin.These diets are much different from the average American diets, containing only about 0-20% animal based foods, while the average American diet is comprised of about 60-80% animal based foods. Disease patterns in much of rural China tend to reflect those prior to the industrial revolution in the U.S., when cancers and cardiovascular diseases were much less prevalent. The major comprehensive dietary factor responsible for disease rates of pre-industrialized societies changing to those of post-industrialized societies is the decision to consume much larger quantities of animal based foods.
SocioeconomicChina is in the midst of an economic revolution which has had a direct impact on every aspect of Chinese society and culture including the traditional Chinese dietary pattern and the health profile of the population. The results of the dietary surveys document dramatic dietary changes in rural China between 1983 and 1989 with large increases in the consumption of total fat and animal foods and these nutritional changes undoubtedly have serious health implications for the population. This 'dietary transition' is directly linked to the socioeconomic environment, specifically to increases in the purchasing power and discretionary cash income of households, increased food availability and access to food variety in the marketplace, as well as to effects of cultural diffusion and assimilation, particularly increased exposure to more-western values and lifestyles.Increased industrialization and urbanization also have a direct effect on the health and disease profile of the population. The detailed information available on health facilities, educational institutions, agricultural patterns and other environmental factors allow for analyses in the context of disease patterns.
Breast CancerThis disease is much less common in rural China. It is significantly associated with dietary fat and higher levels of reproductive hormones such as estrogen and testosterone (yes, there is a small amount of testosterone among women), both of which typify meat and dairy rich diets characteristically found in Western countries. These findings also support the idea that young girls who are encouraged to grow as fast as they can, reach menarche more quickly, sustain higher levels of steroid hormones during their reproductive years, extend their time for menopause, and incur a higher risk of breast cancer.
Large Bowel CancerLarge bowel cancer in China (colon, rectum) is much less common than in the U.S. It is associated with lower intakes of a wide variety of dietary fiber components only found in plant based foods. It is also associated with the prevalence of schistosomiasis, an intestinal parasite once very common in China, but now largely brought under control.
Stomach CancerStomach cancer is much more common in China than in the U.S., in spite of their higher intakes of plant based foods. Evidence from this study suggests that it is because of the more damaging effects of Heliocobacter pylori infection upon the stomach wall, resulting from the ingestion of fermented and salted foods and the destruction of the acid producing ability of the stomach. Therefore, there is a much higher proportion of people who are 'programmed' to get stomach cancer. Actually, those who eat more vegetables and sustain more B-carotene in their blood have a lower risk of this cancer.
Liver CancerLiver cancer, like stomach cancer, is about 30 times more common in China than the U.S. Also, like stomach cancer, it is due to a 50-100 fold higher proportion of people who are 'programmed' to get the disease, namely those who remain chronically infected with hepatitis B (and probably hepatitis C) viruses. And further, those who eat animal products and increase their relatively low blood cholesterol levels, incur a significantly higher level of cancer risk. We hypothesize that were the Chinese to consume a typical American diet, their rate of this disease would skyrocket to the expected 50-100 fold increase over American rates.
Lung CancerLung cancer at the time of the 1973-75 mortality survey, was modestly low. However, since this time, these rates have begun to increase, thus reflecting the rapidly increasing use of tobacco products. Our University of Oxford colleagues, who have chiefly developed these particular data, estimate that, of the living Chinese, approximately 50 million will die prematurely from tobacco related deaths, if current usage continues.
OsteoporosisThis disease is much less common in China even though calcium intakes are much lower. Findings from an ancillary study of the China Project indicate that even though dairy food intake may increase bone density, no further reduction of osteoporosis appears possible. It is thought that the relatively low intake of animal protein, the relatively high level of physical activity, and the adaptation to the prolonged use of low calcium diets reduce the risk of this disease which chiefly among post-menopausal women.
Dietary FatAverage intake of dietary fat in rural China in 1983 was substantially lower than the US (14% vs. 36% of calories) but was closing the gap in a second survey in 1989 (19% vs. 34%). This lower intake principally was associated with the lower consumption of animal based products. One of the chief findings was its significant correlation with breast cancer mortality over a range of 6-24% of calories, although we do not attribute this strictly to dietary fat, per se. More likely, it is related to the life-long use of diets based on plant derived foods.
Dietary FiberDietary fiber intakes were measured in about 14 different ways. Average dietary fiber intake, per se, was about 3 fold greater in rural China. Most of the fiber intake was contributed by cereal grains, and consistent reductions in cancers of the colon and rectum were found with higher intakes of these various fiber fractions. Our data did not allow us to distinguish any differences between the associations of specific fiber fractions.
Dietary ProteinAverage protein intake was only about 65% of the average intake in the US. But, more significantly, only about 10% of the protein was provided by animal based foods, whereas in the US, it is about 70%. Thus, on an energy intake basis, animal protein intake is about 10-fold higher in the US, thus causing major differences in many nutrient intakes. Probably one of the most significant findings is the positive association of animal protein with blood cholesterol (both total and LDL) and the inverse association with plant protein. Also, an increasing intake of plant protein is associated with ever increasing body stature (height) reached during adulthood. Thus, a good quality plant based diet can lead to 'big' people.
Dietary AntioxidantsThe principle antioxidant associations with disease risks in rural China are those of the blood levels of B-carotene and vitamin C. The most consistent and significant associations showed that the higher the levels of these vitamins in blood, the lower was the mortality rates for several cancers.
Dietary MineralsNutritional status for 10 minerals (Cu, Fe, K, Mg, P, Se, Zn, B, Ca, Na) and 4 heavy metals (As, Cd. Pb, Hg) were assessed either by blood levels and/ or by urine excretion. Probably the most notable findings to date are a) the positive relationship between blood Cu and several cancers, and b) the surprisingly good Fe status (measured 5 ways) among adults in China. Also there was no evidence of a negative effect of the high fiber intake upon iron status, as has been widely believed in previous studies. Also, a strong but unexplained association exists between urinary Cd and primary liver cancer.
Dietary CaloriesTotal energy intake in rural China was about 30% higher per kg of body weight than in the US. This quite surprising finding probably is mostly due to the greater physical activity of the Chinese, although these data are referenced for an average Chinese office worker. No particular association of energy intake with any disease was noted, although we do not believe that investigation of caloric intake effects, in isolation, are very meaningful.
Growth/Body Size/ObesityIn general, Chinese are of smaller stature than American counterparts. Even so, the increase in body stature since 1953 has been remarkably similar to Japan, and higher than the increase noted for Europe early in the twentieth century. Individuals in northern China are considerably taller than in southern China. Obesity is far less prevalent in China than in the US, even though they consume about 30% more total calories. |
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