Nutritional Renaissance and Public Health Policy

The science of nutrition has long been entrapped in reductionist interpretation of details, a source of great confusion. However, if nutrition is defined as the integration of countless nutrient factors, metabolic reactions and outcomes, biologically orchestrated as in symphony, its relevance for personal and public health would be less confusing and more productive. This more wholistic interpretation may be observed at the cellular and physiological levels and may be described, in part, by the concept of pleiotropy (multiple cell-based effects from one nutrient source), together with its more expansive cousin, epitropy (multiple cell-based effects from multiple nutrients). There are many consequences. First, wholistic interpretation helps to explain the profound but little-known health benefits of whole plant-based foods (not vegan or vegetarian) when compared with whole animal-based foods and/or with the nutritionally variable convenience foods (generally high in fat, salt, refined carbohydrates and low in complex carbohydrates). Second, wholistic interpretation explains why the U.S. Dietary Guidelines and related public policies, which are primarily conceived from reductionist reasoning, serve political agendas so effectively. If diet and health advisories were to acknowledge the biological complexity of nutrition, then make greater use of deductive (top down) instead of inductive (bottom up) reasoning, there would be less confusion. Third, wholistic nutrition, if acknowledged, could greatly help to resolve the highly-polarized, virtually intractable political debate on health care. And fourth, this definition tells why nutrition is rarely if ever offered in medical school training, is not one of the 130 or so medical specialties, and does not have a dedicated research institute at U.S. National Institutes of Health. Nutrition is a wholistic science whereas medical practice is reductionist, a serious mismatch that causes biased judgement of nutrition. But this dichotomy would not exist if the medical practice profession were to understand and adopt wholistic interpretation. Reductionist research, however, is crucially important because its findings provide the granular structure for wholistic interpretation-these two philosophies are inescapably interdependent. Evidence obtained in this manner lends strong support to the suggestion that nutrition is more efficacious and far more affordable in maintaining and restoring (treating) health than all the pills and procedures combined. Admittedly, this is a challenging paradigm for the domain of medical science itself.

Medically supervised water-only fasting in the treatment of hypertension

BACKGROUND

Hypertension-related diseases are the leading cause of morbidity and mortality in industrially developed societies. Although antihypertensive drugs are extensively used, dietary and lifestyle modifications also are effective in the treatment of patients with hypertension. One such lifestyle intervention is the use of medically supervised, water-only fasting as a safe and effective means of normalizing blood pressure and initiating health-promoting behavioral changes.

METHODS

One hundred seventy-four consecutive hypertensive patients with blood pressure in excess of 140 mm Hg systolic, 90 mm Hg diastolic (140/90 mm Hg), or both were treated in an inpatient setting under medical supervision. The treatment program consisted of a short prefasting period (approximately 2 to 3 days on average) during which food consumption was limited to fruits and vegetables, followed by medically supervised water-only fasting (approximately 10 to 11 days on average) and a refeeding period (approximately 6 to 7 days on average) introducing a low-fat, low-sodium, vegan diet.

RESULTS

Almost 90% of the subjects achieved blood pressure less than 140/90 mm Hg by the end of the treatment program. The average reduction in blood pressure was 37/13 mm Hg, with the greatest decrease being observed for subjects with the most severe hypertension. Patients with stage 3 hypertension (those with systolic blood pressure greater than 180 mg Hg, diastolic blood pressure greater than 110 mg Hg, or both) had an average reduction of 60/17 mm Hg at the conclusion of treatment. All of the subjects who were taking antihypertensive medication at entry (6.3% of the total sample) successfully discontinued the use of medication.

CONCLUSION

Medically supervised water-only fasting appears to be a safe and effective means of normalizing blood pressure and may assist in motivating health-promoting diet and lifestyle changes.

Energy balance: interpretation of data from rural China

Data used for this analysis are pertinent to the issue of energy balance and body-weight control. They were obtained, in a comprehensive study of human diet, lifestyle, and disease mortality, from 65 counties (130 villages, 6500 adults) of rural China (Chen et al., 1990). After adjusting the food intake data to represent a reference male adult involved in the least physical activity and representing the same body weight, total calorie intake (40.6 kcal/kg body weight) was about 30% higher in China when compared with an average adult American male (30.6 kcal/kg bw). However, the body mass index for the Chinese male was about 25% lower (20.5 vs. 25.8 kg bw/m2). Diets in rural China were low in fat (14.5% of energy), relatively low in protein (65.8 g/day), and high in fiber (33 g/day), representing a diet unusually rich in plant-based foods (e.g., including about 90% of the total protein). It is believed that the excess energy intake among the Chinese is mostly attributed to their greater physical activity. However, some unknown but significant, and probably difficult to measure, amount could be due to increased energy expenditure associated with non-post-prandial basal metabolism. This hypothesis is based, in part, on evidence from experimental animal data from this and other laboratories showing that laboratory rats fed diets comprised of substantially reduced intakes of protein consume more energy, but gain less weight. They also exhibit increased thermogenesis, due both to enhanced metabolic body heat and to diet-driven physical activity, while sharply reducing blood cholesterol concentrations and tumor development.

The promotion effect of anorectic drugs on aflatoxin B(1)-induced hepatic preneoplastic foci

The ability of three extensively used anorectic drugs, namely fenfluramine (FN), fluoxetine (FX) and amphetamine (AM), to alter the development of aflatoxin B(1) (AFB(1))-induced gamma-glutamyl-positive (GGT(+)) preneoplastic liver foci was investigated in 135 male weanling F344 rats. Following AFB(1) administration, 15 rats were killed, while the rest were divided into four groups and fed diets containing either FN, FX, AM or control diet, with half of the animals in each group subsequently being killed at 4 weeks and half at 10 weeks. All three anorectic drugs as expected suppressed initial food intake, growth rate, body weight gain and food efficiency. They also tended to suppress body fat mass and to decrease plasma levels of T(3) and T(4). FN significantly (P < 0.05) increased GGT(+) foci number/cm(2) and number/cm(3), while FX significantly increased GGT(+) foci number/cm(2) and the volume fraction of foci. Histopathological staining also revealed that FN- and FX-treated animals had more serious morphological alterations in their liver tissue. In contrast, foci development was, if anything, suppressed by AM feeding. These results indicate that serotoninergic drugs (FN and FX), as opposed to dopaminergic drugs (AM), may have tumor promoter activity, at least for liver tissue.

Iron status of middle-aged women in five counties of rural China

OBJECTIVE

To determine the relationships of dietary iron sources, other dietary factors, and lifestyle to iron status among premenopausal and recently postmenopausal Chinese women with widely varying regional dietary patterns.

DESIGN

Cross-sectional. Subjects were interviewed, blood samples were drawn, and dietary intakes were measured by a 3-day dietary survey for subjects in the five survey counties.

SETTING

Rural China.

SUBJECTS

About 80 randomly selected subjects per county among women aged 32 66 y.

MAIN OUTCOME MEASURES

Blood hemoglobin, plasma ferritin, and plasma iron.

RESULTS

Total iron intake was relatively high (15-29 mg/d) compared to developed counties. Heme iron intake was negligible in two of the study counties. Overall levels of iron deficiency anemia were relatively low in these generally iron-stressed women. There was no clear statistical relationship between iron intake and physiological iron status. Although several measures of dietary intake (heme iron, dietary calcium, animal protein) were correlated with several measures of iron status before adjusting for survey county, only dietary animal protein was significantly positively correlated with plasma ferritin after adjusting for the possibly confounding factor of the survey county (r= 0.15, P = 0.009). Intakes of potential inhibitors of iron absorption, such as tea, even in very high amounts, were not correlated to iron status. Plasma ferritin was positively correlated with plasma retinol (P = 0.024) and cholesterol (P = 0.007). Systemic inflammatory response, as indicated by high plasma C-reactive protein levels, was shown to be raised in a group of subjects with apparently contradictory high levels of ferritin and low levels of hemoglobin (P = 0.03).

CONCLUSIONS

Iron nutriture in these areas of rural China seemed more related to physiological factors such as inflammatory response, menses, plasma vitamin A and cholesterol, than to dietary factors.

Determinants of plasma retinol concentrations of middle-aged women in rural China

The purpose of this study was to assess the correlates and possible determinants of plasma vitamin A among middle-aged women in rural China. The vitamin A adequacy of the different diets at the five widely varying survey sites was also assessed. Patterns of correlations among dietary and biochemical measurements were strikingly different from previous studies in Western subjects. Plasma beta-carotene was uncorrelated with beta-carotene intake even after adjusting for potential confounders. In counties with low preformed vitamin A intake, plasma retinol correlated with plasma copper (P = 0.007), which in turn was correlated with dietary intake of copper (P = 0.007). In these counties plasma retinol was correlated with plasma beta-carotene (P = 0.001) and was increased 10% in women in the first 2 y of menopause (P = 0.028). Plasma retinol and C-reactive protein levels are inversely correlated (r = -0.15, P < 0.001), indicating that vitamin A status and inflammatory response may be related but the causal direction is unknown. Despite low intake of vitamin A (county averages of 13-78% of recommended daily allowance [RDA]), and particularly of preformed vitamin A, only 3% of these women had plasma retinol levels below 0.7 mumol/L, considered to indicate possible marginal deficiency. Plasma levels of retinol and beta-carotene were more influenced by intrinsic factors such as menopause, lipid status, retinol requirements, and possibly copper status and inflammation than by extrinsic factors such as diet and lifestyle.

Diet, lifestyle, and the etiology of coronary artery disease: the Cornell China study

Investigators collected and analyzed mortality data for >50 diseases, including 7 different cancers, from 65 counties and 130 villages in rural mainland China. Blood, urine, food samples, and detailed dietary data were collected from 50 adults in each village and analyzed for a variety of nutritional, viral, hormonal, and toxic chemical factors. In rural China, fat intake was less than half that in the United States, and fiber intake was 3 times higher. Animal protein intake was very low, only about 10% of the US intake. Mean serum total cholesterol was 127 mg/dL in rural China versus 203 mg/dL for adults aged 20-74 years in the United States. Coronary artery disease mortality was 16.7-fold greater for US men and 5.6-fold greater for US women than for their Chinese counterparts. The combined coronary artery disease mortality rates for both genders in rural China were inversely associated with the frequency of intake of green vegetables and plasma erythrocyte monounsaturated fatty acids, but positively associated with a combined index of salt intake plus urinary sodium and plasma apolipoprotein B. These apolipoproteins, in turn, are positively associated with animal protein intake and the frequency of meat intake and inversely associated with plant protein, legume, and light-colored vegetable intake. Rates of other diseases were also correlated with dietary factors. There was no evidence of a threshold beyond which further benefits did not accrue with increasing proportions of plant-based foods in the diet.

Emerging tobacco hazards in China: 1. Retrospective proportional mortality study of one million deaths

OBJECTIVE

To assess the hazards at an early phase of the growing epidemic of deaths from tobacco in China.

DESIGN

Smoking habits before 1980 (obtained from family or other informants) of 0.7 million adults who had died of neoplastic, respiratory, or vascular causes were compared with those of a reference group of 0.2 million who had died of other causes.

SETTING

24 urban and 74 rural areas of China.

SUBJECTS

One million people who had died during 1986-8 and whose families could be interviewed.

MAIN OUTCOME MEASURES

Tobacco attributable mortality in middle or old age from neoplastic, respiratory, or vascular disease.

RESULTS

Among male smokers aged 35-69 there was a 51% (SE 2) excess of neoplastic deaths, a 31% (2) excess of respiratory deaths, and a 15% (2) excess of vascular deaths. All three excesses were significant (P<0.0001). Among male smokers aged >/70 there was a 39% (3) excess of neoplastic deaths, a 54% (2) excess of respiratory deaths, and a 6% (2) excess of vascular deaths. Fewer women smoked, but those who did had tobacco attributable risks of lung cancer and respiratory disease about the same as men. For both sexes, the lung cancer rates at ages 35-69 were about three times as great in smokers as in non-smokers, but because the rates among non-smokers in different parts of China varied widely the absolute excesses of lung cancer in smokers also varied. Of all deaths attributed to tobacco, 45% were due to chronic obstructive pulmonary disease and 15% to lung cancer; oesophageal cancer, stomach cancer, liver cancer, tuberculosis, stroke, and ischaemic heart disease each caused 5-8%. Tobacco caused about 0.6 million Chinese deaths in 1990 (0.5 million men). This will rise to 0.8 million in 2000 (0.4 million at ages 35-69) or to more if the tobacco attributed fractions increase.

CONCLUSIONS

At current age specific death rates in smokers and non-smokers one in four smokers would be killed by tobacco, but as the epidemic grows this proportion will roughly double. If current smoking uptake rates persist in China (where about two thirds of men but few women become smokers) tobacco will kill about 100 million of the 0.3 billion males now aged 0-29, with half these deaths in middle age and half in old age.

Dietary vitamin C intake and lung function in rural China

The relation between dietary vitamin C intake and pulmonary function was investigated in a cross-sectional study carried out in 69 counties in rural China in 1989. Within each of the 69 counties, 120 subjects aged 35-64 years were identified using a three-stage random clustering procedure. Each subject underwent pulmonary function testing, completed a detailed questionnaire, and provided a blood sample. Dietary vitamin C intakes were estimated among half of the subjects using a 3-day weighed record of household food intake. Plasma vitamin C was measured in sex-specific blood pools created from individual samples in each geographic area. Among the 3,085 subjects for whom there were complete data, dietary intake of vitamin C (151 mg/day (standard deviation, 111)) was significantly related to forced expiratory volume in the first second (FEV1) and forced vital capacity after adjustment for sex, age, height, weight, total caloric intake, tobacco smoking, and education. An increase of 100 mg/day in vitamin C intake was associated with an increase of 21.6 ml (95% confidence interval -0.4 to 43.5) in FEV1 and an increase of 24.9 ml (95% confidence interval 0.2 to 49.6) in forced vital capacity. No significant interaction with smoking status was observed. A significant positive association was also observed at the geographic level, between county-pooled plasma vitamin C and mean FEV1. These data support the hypothesis that dietary vitamin C may protect against the loss of pulmonary function.

Repression of hepatitis B virus (HBV) transgene and HBV-induced liver injury by low protein diet

Persistent infection with hepatitis B virus (HBV) is one of the primary risk factors for human hepatocellular carcinoma (HCC). In a human ecological study, we have shown that, in addition to HBV, animal food consumption also significantly contributes to the variance of HCC. To test the interacting effect of HBV and animal food consumption on the development of HCC, we investigated HBV expression in HBV transgenic mice fed three levels of casein diet. HBV expression in transgenic animals was substantially inhibited when dietary casein was reduced from the traditional level of 22% to the level of 6%. Northern analysis revealed that suppression of HBV was derived from both the upstream albumin promoter and the internal HBV promoter. Immunochemical staining of liver sections indicated that only a few hepatocytes around the central vein expressed viral surface antigen (HBsAg) in the 6% casein animals, whereas virtually all hepatocytes stained positively for HBsAg in the 22% dietary casein animals. Serum HBsAg concentrations at 4 months were increased by 1.6-, 2.1-, and 5.1- fold over baseline for animals fed the 6%, 14%, and 22% casein diets, respectively. Correspondingly, liver injury was much less severe in animals fed 6% casein diet than in those fed 14% and 22% casein diets. These results demonstrate that a low casein diet is a potent suppresser of HBV transgene and HBV-induced liver injury, suggesting that diet management may be a practical means to aid in the control HBV infection.

Inhibition of hepatocellular carcinoma development in hepatitis B virus transfected mice by low dietary casein

In a comprehensive human ecological study, primary liver cancer has been shown to be highly significantly associated with 1) the prevalence of persistent infection with hepatitis B virus (HBV) and 2) plasma cholesterol concentrations that are, in turn, associated with the consumption of animal based foods. In rat studies, aflatoxin-induced hepatocellular carcinoma is substantially prevented by decreasing the intake of animal based protein (casein), a hypercholesterolemic nutrient. Thus the development of primary liver cancer associated with persistent HBV infection or with aflatoxin exposure may be controlled by reduced intake of animal-based proteins. Transgenic mice transfected with an HBV gene fragment containing the viral transactivator of hepatis B virus, HBx, which induces the formation of hepatocellular carcinoma, were used to examine the ability of dietary casein to modify tumor formation. Reducing the concentration of dietary casein to 6% from the traditional level of 22% markedly inhibited (by 75%) hepatic tumor formation in these transgenic mice. Tumor development also was substantially altered by interchanging dietary casein concentration well after tumor development had begun (at 8 months), increasing by 173% from the expected yield when casein intake was increased and decreasing by 99% when casein was reduced. These findings suggest that the development of liver tumor formation among individuals persistently infected with HBV may be controlled by minimizing or eliminating the intake of animal protein-based foods.

Dissimilarity in aflatoxin dose-response relationships between DNA adduct formation and development of preneoplastic foci in rat liver

Earlier work in this laboratory and that carried out by others demonstrated that after a single dose of aflatoxin B1 (AFB) the resulting liver AFB-DNA adduct levels were directly proportional to dose. Earlier work also showed that after ten daily doses the AFB dose-response relationship with gamma-glutamyl transpeptidase (GGT) positive preneoplastic foci measured at 3 months was sublinear, with a threshold at a dose of about 150 micrograms/kg body weight/day. The objective of this study is to determine the factors influencing the shift in AFB dose-response between AFB-DNA adducts and GGT foci. Male Fisher 344 weanling rats were orally administered one or ten doses of AFB ranging from 50 to 350 micrograms/kg body weight/day. The animals were killed 2 or 24 h after the first AFB dose, or after the tenth AFB dose. The first and tenth doses were tritiated in these animals and 3H-AFB-guanine adducts isolated from liver DNA were measured by HPLC. Another group was killed 3 months after receiving ten doses in order to measure GGT foci development. AFB-guanine adduct levels were directly proportional to dose after the first dose, but after the tenth dose were much lower in the 200-350 micrograms/kg groups than after a single dose. The GGT foci response confirmed earlier work concerning a sublinear response. Among the individual animals in the 200-350 micrograms/kg groups there was a positive relationship, after controlling for dose, between GGT foci development and weight gained both during dosing (P = 0.018) and also to a lesser extent during the early promotional period (P = 0.066). Enzyme activity levels of GGT in liver homogenates were higher in the highest dose groups and reflected biliary proliferation rather than histological GGT stained foci. Urinary levels of AFB metabolites changed proportions in the high dosage multiply dosed animals reflecting alteration in AFB metabolism or excretion. The differences between the linear adduct and the sublinear foci dose-response curves may be the result of non-adduct effects of higher multiple AFB doses on foci formation including acute cytotoxicity, altered AFB metabolism and disposition, enhanced weight gains, or shortened foci latency but not through enhanced guanine adduct levels. Other studies that showed a linear relationship between AFB dose and liver tumor development used continuous feeding of maximal doses an order of magnitude less than the lowest dose in this study and thus avoided acutely toxic effects. We hypothesize that liver tumor development may mirror foci response in a 10-dose AFB regimen with doses above 100 micrograms/kg due to acute toxicity effects.

Evaluation of the FIRI (Fasting Insulin Resistance Index) and selected plasma parameters associated with insulin resistance as predictors of cardiovascular mortality in rural Chinese women

Insulin Resistance Syndrome (IRS) refers to a cluster of pathologies including hypercholesterolaemia, diabetes, hypertension and cardiovascular disease indicating that these diseases share a common aetiology in insulin resistance and hyperinsulinaemia. Recently a simple index of insulin resistance referred to as the Fasting Insulin Resistance Index (FIRI) was proposed by Duncan et al, for use in clinical practice and epidemiologic investigations of disease FIRI is estimated as the product of fasting plasma glucose and fasting plasma insulin divided by 25 (FIRI = (glucose x insulin/25). This communication evaluates the utility of FIRI using data from a large comprehensive ecologic study on diet and disease in rural counties in the People's Republic of China and provides support for the use of this biomarker/index in epidemiologic studies on disease states associated with IRS.

Use of an improved method for analysis of urinary aflatoxin M1 in a survey of mainland China and Taiwan

An improved monoclonal antibody immunoaffinity chromatography/high-pressure liquid chromatography/ fluorescence detection method was developed to measure aflatoxin (AF) exposure by quantifying AFM1 in human and rat urine samples. Analysis of different amounts of various AF metabolites showed that the immunoaffinity resin was highly selective for aflatoxin B1 (AFB1), AFB2, and AFM1. Recovery of added AFs increased with the amount of immunoaffinity resin and was virtually complete within the range of 0.01-10 ng of AFM1 by using 7 ml of resin. The detection limit of this method is 0.5 pg/ml urine. Rats dosed with tritiated AFB1 excreted in their urine tritiated AFM1, among other AF metabolites, as indicated by chemical derivative confirmation and cochromatography with authentic AFM1 and agreement of radioactivity and fluorescence quantitation. A linear dose-response relationship was found over the range of 0.05-50 micrograms/kg of body weight/day. Two humans dosed with 1.0 microgram of pure AFB1 excreted 6-7% of the dose as urinary AFM1 over 5-7 days. Pooled urine samples from 30 men from each of 69 rural counties in mainland China and 16 survey areas in Taiwan, with two villages per county or area, were analyzed with this improved method (170 villages total). The correlation coefficient of urinary excretion of AFM1 compared between villages within all 85 survey areas was 0.50 (P < 0.001). Sixty-five % of the samples contained detectable concentrations of AFM1 with an average excretion of 3.1 ng/12 h. Assuming an excretion rate of 2-6%, this AFM1 excretion corresponds to a very low average daily AF consumption of 0.1-0.3 microgram/day (possible range, 0-11 micrograms/day). Patterns of urinary excretion of AFM1 were similar in mainland China and Taiwan.

Effects of carotenoid-rich food extracts on the development of preneoplastic lesions in rat liver and on in vivo and in vitro antioxidant status

The effect of dietary carotenoid-rich extracts of carrots, tomatoes, and orange juice on rat liver gamma-glutamyl transpeptidase-positive preneoplastic foci induced by aflatoxin B1 was investigated. Organic extracts were prepared from the foods, dissolved in tricaprylin oil to equivalent concentrations of the major food-specific carotenoids, and fed by intubation to Fischer 344 male rats. The extracts were administered during the 2-week aflatoxin-dosing (initiation) period of the study or during the subsequent 12-week post-dosing (promotion) period. Vitamin status and antioxidant activities were measured in blood and liver. Extract feeding caused an accumulation of carotenoids in the liver, a substantial decrease in spontaneous erythrocyte hemolysis, and lowered plasma glutathione, blood superoxide dismutase, and blood catalase. Differences in foci development among the three extracts were not as consistent or profound as differences between initiation and promotion dosing. The number of gamma-glutamyl transpeptidase-positive foci was decreased by extract feeding during the initiation period, whereas extract feeding during the promotion period caused a decrease in the average diameter of the foci. The total volume of foci was markedly reduced by extract feeding during either period. Extracts were compared with purified carotenoids and alpha-tocopherol in their ability to affect in vitro antioxidation activity and were nearly as effective as the pure compounds. In summary, carotenoid-rich extracts of these three foods substantially inhibited biochemical and cellular events thought to play a role in the early stages of hepatocarcinogenesis.

Vitamin A and carotenoid status in rural China

Vitamin A status of 260 groups of twenty-five males or twenty-five females, aged 35-64 years, surveyed in twenty-four provinces of the People's Republic of China, was assessed by measuring plasma retinol. retinol-binding protein and beta-carotene concentrations. Direct measurements of food intake over a 3 d period and questionnaire data on the frequency of consumption of vegetables, fruits, animal products and other dietary items were also used. Vitamin A status appeared to be low only in specific counties but in general was satisfactory or only marginally deficient. Plasma beta-carotene levels were strikingly low in comparison with Western levels despite generous vegetable consumption suggesting that intake of vitamin A precursors may have been adequate but not abundant enough to maintain high circulating plasma levels of beta-carotene. Plasma beta-carotene, for both males and females, was significantly correlated with the frequency of consumption of green vegetables. Plasma retinol, for males, was highly correlated with meat, fish, oil and alcohol consumption expressed both in quantity or frequency of consumption. Higher levels of plasma retinol, together with lower levels of plasma beta-carotene in males compared with females, suggest that men consume more animal products or may have higher retinol requirements and therefore a higher rate of conversion of beta-carotene to retinol.

Assessment of zinc nutritional status in rural China

Zinc nutriture was assessed in 6500 adults aged 35-64 years old in 65 mostly rural counties (two communes per county) in China on the basis of plasma zinc levels and dietary zinc intakes. In addition, the use of plasma albumin and red blood cell superoxide dismutase (SOD) for assessing zinc nutritional status was evaluated. Plasma levels of zinc and albumin were highly correlated between sexes (p<0.001) and between neighbouring communes in the same county (p<0.005), indicating a high degree of data reliability as assessed by this measure of "within county" homogeneity. Zinc deficiency, defined as plasma zinc values less than 70 μg/dL, was not observed for the populations in any of the 65 counties included in the survey. Dietary zinc intake was estimated on the basis of the newly revised Chinese food composition tables in conjunction with a 3-day household dietary survey of approximately 2000 households in the same study. Average dietary zinc intake was 11.9 mg/day, with a wide variability (7.4-34.9 mg/day) across the sample of 65 counties. The average levels of plasma zinc and dietary zinc intake observed in this adult rural Chinese population were comparable to those reported in healthy U.S. subjects, suggesting that zinc deficiency may not be a cause for concern in rural Chinese adults. However, marginal zinc deficiency may be prevalent in some rural areas.

Association of dietary factors and selected plasma variables with sex hormone-binding globulin in rural Chinese women

Sex hormone-binding globulin (SHBG) is an important regulator of plasma sex steroids as well as a sensitive indicator of insulin resistance. SHBG may be an important diagnostic measure of risk for pathologies associated with insulin resistance syndrome (IRS) such as non-insulin-dependent diabetes mellitus (NIDDM), obesity, hypertension, dyslipidemia, and atherosclerotic cardiovascular disease. In women, SHBG is also implicated in diverse pathologies such as cancers of steroid-sensitive tissues and hirsutism. Data from an ongoing ecological study linking diet and health in rural China were analyzed to determine the relation of selected plasma variables and diet to plasma concentrations of SHBG. All data represent county mean values, pooled by age and sex, to assess the relation between biochemical and lifestyle characteristics and disease-specific mortality rates at the county level. The study sample consisted of 3250 Chinese women between the ages of 35 and 64 y living in 65 widely dispersed rural counties. Consumption patterns for 21 different food groups were derived from a food-frequency questionnaire and a 3-d dietary survey and subsequently compared. Correlation analyses of county mean values demonstrated a significant association between SHBG and insulin, testosterone, triacylglycerols, body mass index, age at menarche, and several foods. In regression analyses, after adjustments, the strongest predictors of SHBG concentrations were the dietary intake of rice (beta = 0.42, P < 0.01), fish (beta = 0.34, P < 0.05), millet (beta = -0.27, P < 0.01), and wheat (beta = -0.34, P < 0.01). When insulin, testosterone, and triacylglycerols were added to the model only triacylglycerols (beta = -0.26, P < 0.05) remained a significant independent predictor of SHBG. Additional analyses suggested that the consumption of green vegetables was modestly positively correlated with SHBG and negatively with insulin values. Consumption of rice and fish in particular appeared to favorably influence the principle plasma variables associated with a reduction in the risk for IRS pathologies.

Bone density and lifestyle characteristics in premenopausal and postmenopausal Chinese women

The relationships between bone health and various lifestyle factors were examined in a cross-sectional study in 775 Chinese women aged 35-75 years. Bone mass was significantly positively associated with body weight, height, body mass index (BMI) and duration of breastfeeding, but was not significantly associated with other lifestyle variables, including alcohol consumption, parity, age at menarche and age at menopause after adjusting for age and body weight. A positive association was observed in premenopausal women (but not in postmenopausal women) for bone density with current cigarette smoking and plasma and urinary cotinine (the major metabolite of smoking). However, the confounding effects of other unknown factors present in this cross-sectional study may not be excluded. Daily physical activity, as indicated by time spent working in the fields, was found consistently to be positively associated with bone mass (p < 0.0001). When these women were grouped into three physical activity levels on the basis of occupation and daily work intensity, those undertaking heavy labor also had significantly higher radial bone mass than women undertaking light or medium labor. These results suggest a protective effect of daily physical activity on bone health in both pre- and postmenopausal women.

Accuracy and reliability of total body electrical conductivity (TOBEC) for determining body composition of rats in experimental studies

Total body electrical conductivity (TOBEC) has been promoted as a noninvasive method to estimate body composition in small mammals. Validation of this method has primarily been under normative conditions and has generally been inadequate. This article reports on the reliability and accuracy of TOBEC methodology to assess gradual, physiologically induced changes in body composition in rats under different experimental conditions. Reliability of the index of electrical conductivity (EM number) was assessed by analyzing components of variance. Accuracy was assessed by comparing EM number to actual lean body mass (LBM, from carcass analysis), across different experimental conditions, within a particular experimental condition, and over time for a given set of animals. Reliable measurements were obtained by strictly adhering to a standard protocol. TOBEC was inaccurate across experimental conditions, within experimental conditions, and within a single experimental condition during the course of an experiment. This inaccuracy apparently stemmed from the lack of a direct relationship between EM number and LBM; EM number was more strongly correlated with body weight than with LBM. At the present time, TOBEC cannot be used in place of carcass analysis to accurately predict the body composition of rats during or following the administration of a variety of experimental conditions.

Assessment of a modified household food weighing method in a study of bone health in China

OBJECTIVE

A 'modified' household dietary method to estimate individual intakes from total household intakes was evaluated in comparison to the individual food weighing method, i.e. direct weighing of foods consumed by individuals.

DESIGN

Foods consumed by the household were weighed and recorded over a 3 day period and were proportionally allocated to a specific person in the household by using energy conversion factors based on age, gender and physical activity. The individual dietary intakes were standardized by body weight (ratio of individual body weight to reference body weight from Chinese Recommended Daily Allowances (Acta Nutr. Sin. 12, 1-9), and were compared with the estimates from the individual food weighing method for both accuracy and associations with bone density.

SETTING

The subjects were randomly selected from five rural countries in China, characterized by different dietary patterns.

SUBJECTS

A total of 712 women aged 35-75 years participated in the dietary and bone measurements.

RESULTS

Nutrient intakes estimated by the modified household method (adjusting for body weight were very similar to those obtained by the individual method (r = 0.53-0.78, P < 0.001), except for sodium which had the largest deviation from the individual methods (r = 0.23, P < 0.001). Calcium intakes were 405 +/- 271 and 409 +/- 323 mg/day, respectively, as estimated by the individual and modified household methods. A very similar degree of correlation with radial bone density also was obtained for both calcium estimates.

CONCLUSION

The results indicate that the modified household method is appropriate for assessing food intakes of individuals in large nutritional studies.

Diet and chronic degenerative diseases: perspectives from China

A comprehensive ecologic survey of dietary, life-style, and mortality characteristics of 65 counties in rural China showed that diets are substantially richer in foods of plant origin when compared with diets consumed in the more industrialized, Western societies. Mean intakes of animal protein (about one-tenth of the mean intake in the United States as energy percent), total fat (14.5% of energy), and dietary fiber (33.3 g/d) reflected a substantial preference for foods of plant origin. Mean plasma cholesterol concentration, at approximately 3.23-3.49 mmol/L, corresponds to this dietary life-style. The principal hypothesis under investigation in this paper is that chronic degenerative diseases are prevented by an aggregate effect of nutrients and nutrient-intake amounts that are commonly supplied by foods of plant origin. The breadth and consistency of evidence for this hypothesis was investigated with multiple intake-biomarker-disease associations, which were appropriately adjusted. There appears to be no threshold of plant-food enrichment or minimization of fat intake beyond which further disease prevention does not occur. These findings suggest that even small intakes of foods of animal origin are associated with significant increases in plasma cholesterol concentrations, which are associated, in turn, with significant increases in chronic degenerative disease mortality rates.

Long‐term intake of a low‐casein diet is associated with higher relative NK cell cytotoxic activity in F344 rats

Earlier studies in our laboratory showed that animals exposed to aflatoxin B1 (AFB1) develop fewer gamma-glutamyl transpeptidase-positive preneoplastic foci and tumors when fed 6% dietary casein than when fed 22% casein during promotion; mechanisms underlying this effect have not been elucidated. We examined natural killer (NK) cell activity, mitogenic responses, and lymphocyte surface antigen profiles in male Fischer 344 rats dosed with AFB1 or dosing vehicle alone and then fed 6% or 22% casein isocaloric diets for one year. Mean body weights and food intake did not differ significantly among the groups during the study. NK cells purified from peripheral blood of rats fed 6% casein mediated higher specific lysis (p < 0.0001) against YAC-1 target cells than cells obtained from animals fed 22% casein. Mitogenic responses of splenic lymphocytes to concanavalin A and lymphocyte subpopulations, identified by flow cytometry, did not differ significantly among dietary groups. Hepatic tumors were detected in 27% of the 22% casein AFB1-treated group and in 6% of animals in the 6% casein AFB1-treated group. The association between long-term intake of a 6% casein diet and higher relative NK cell cytotoxic activity suggests a potentially important mechanism that may help protect against the development of hepatocellular tumors. Further study of this mechanism as a causal factor in limiting tumor development is required.

Dietary intakes and urinary excretion of calcium and acids: a cross-sectional study of women in China

The relationship between dietary intakes and urinary calcium was examined in a cross-sectional survey of 764 middle-aged and elderly women with markedly different dietary patterns and lifestyles. Urinary calcium was correlated positively with urinary acids, including titratable acid (r = 0.46, P < 0.0001), ammonia (r = 0.42, P < 0.0001), and sulfate (r = 0.52, P < 0.0001). Urinary excretions of calcium and acids were correlated positively with intakes of animal and nondairy animal protein but were correlated negatively with plant-protein intake, possibly because of the alkaline nature of plant foods. Further analyses showed that urinary calcium and acids were associated positively with acid-forming foods and were associated negatively with plant foods. These results indicate that under free-living conditions urinary calcium excretion is likely determined by the acid-base status of the total diet, including among other factors the contribution of sulfur amino acids to urinary acid production.

Dietary calcium and bone density among middle-aged and elderly women in China

Associations between dietary calcium and bone status were investigated in 843 Chinese women aged 35-75 y who were selected from five rural counties where dietary calcium varied considerably. Bone mineral content (BMC) and bone mineral density (BMD) at the radius were significantly higher in one of the pastoral counties with higher calcium intake than in the nonpastoral counties. Analysis by individual for all counties combined showed that BMC and BMD were correlated positively with total calcium (r = 0.27-0.38, P < 0.0001), dairy calcium (r = 0.34-0.40, P < 0.0001), and to a lesser extent with nondairy calcium (r = 0.06-0.12, P = 0.001-0.100), even after age and/or body weight were adjusted for. The results strongly indicated that dietary calcium, especially from dairy sources, increased bone mass in middle-aged and elderly women by facilitating optimal peak bone mass earlier in life.

Geographic association between urinary excretion of N-nitroso compounds and oesophageal cancer mortality in China

Overnight urine samples were collected from approximately 60 male adults in each of 69 counties of China in 1989. Two specimens were collected from each subject--one after a loading dose of proline and ascorbic acid and another after a loading dose of proline only. Levels of N-nitrosamino acids and nitrate were measured in urine samples and correlated with cumulative mortality rates for subjects aged between 0 and 64 years in the 1970s. Oesophageal cancer mortality rates were positively and significantly associated with (i) urinary levels of excreted N-nitrosoproline (NPRO) (after proline and ascorbic acid loading or proline loading only), (ii) N-nitrososarcosine levels, and (iii) nitrosation potential (the decrease in the amount of urinary NPRO after adding ascorbic acid to the proline load). There were also positive correlations between the urinary level of NPRO or other N-nitrosamino acids and that of nitrate. The urinary excretion of nitrate was associated with consumption of various nitrate-rich vegetables. The results suggest that N-nitroso compounds (NOC) or other nitrite-derived carcinogens are implicated in the aetiology of oesophageal cancer in China.

Prolonged infection with hepatitis B virus and association between low blood cholesterol concentration and liver cancer

OBJECTIVE

To determine whether prolonged infection with hepatitis B virus is associated with a lower blood cholesterol concentration.

DESIGN

Cross sectional study.

SETTING

81 villages in rural China with a high prevalence of chronic infection with hepatitis B virus.

SUBJECTS

1556 apparently healthy men aged 35-64 years, randomly selected.

MAIN OUTCOME MEASURES

Hepatitis B virus carrier state; plasma concentrations of cholesterol, apolipoprotein B, and apolipoprotein A I.

RESULTS

238 (15%) of the men were positive for hepatitis B surface antigen, indicating that they were chronic carriers. Plasma concentration of cholesterol was 4.2% (0.11 mmol/l) lower among carriers (that is, positive for hepatitis B surface antigen) than among non-carriers (95% confidence interval 0.6% to 8.0% (0.01 to 0.21 mmol/l), p < 0.05), and apolipoprotein B concentration was 7.0% (0.036 g/l) lower (2.8% to 11.2% (0.014 to 0.058 g/l), p < 0.001). In contrast, no association was observed between plasma concentrations of cholesterol or apolipoprotein and hepatitis B that had been eradicated (that is, patient positive for hepatitis B core antibody but negative for hepatitis B surface antigen).

CONCLUSIONS

Chronic hepatitis B virus infection, which usually starts in early childhood in China, seems to lead not only to a greatly increased risk of death from liver disease but also to a somewhat lower cholesterol concentration in adulthood. This common cause produces an inverse association between cholesterol concentration and risk of death from liver cancer or from other chronic liver diseases.

The effects of D-fenfluramine on the development of aflatoxin-B1 induced GGT+ hepatic foci in F344 rats

The role of total caloric intake and attained body weight in the carcinogenic process in rodents is controversial. In the present study we examined the development of hepatic pre-neoplastic foci in rats treated with aflatoxin-B1 (AFB) and given the drug D-fenfluramine (FEN). Ingestion of this drug leads to a reduction in body weight by increasing the thermogenic response to a meal and by transiently reducing food intake. Young male rats were dosed with AFB or vehicle alone and were then assigned to receive control diet (NO FEN) or control diet + FEN (FEN; 0.15 g/kg diet) for 12-14 weeks. Body weight gain and food intake were reduced among animals given FEN; brown adipose tissue weight (% body weight) was elevated in these groups. Indices of protein status, and concentrations of T3, T4 and insulin did not differ among the groups. All animals given FEN developed GGT+ hepatic foci. The number and volume fraction of foci were significantly larger in FEN relative to NO FEN animals. The mean diameter of foci was slightly enhanced among FEN animals. These results suggest that FEN promotes the development of AFB-induced hepatocellular foci, despite reduced food intake and lower body weight. Since FEN is widely used as a weight loss aid, these findings deserve further study.

The sustained development of preneoplastic lesions depends on high protein intake

The effects of sequential alterations in the feeding of two levels of dietary protein (5% and 20% casein) on the postinitiation development of aflatoxin B1- (AFB1) induced gamma-glutamyl transpeptidase-positive (GGT+) preneoplastic foci were examined. Weanling male Fischer 344 rats fed AIN-76A diet (20% protein) were administered 10 intragastric doses of AFB1 (1 dose/day during the 14-day dosing period excluding weekends) at 250 micrograms/kg body wt (initiation). After AFB1 tissue clearance, rats were randomly assigned to dietary treatment groups. During the next 12 weeks (promotion), they developed AFB1-induced GGT+ preneoplastic lesions. The 12-week promotion period was subdivided into four three-week periods, during which rats were fed isocaloric diets containing 20% casein during all four periods (20:20:20:20), 5% casein during all four periods (5:5:5:5), or sequentially altered casein levels (20:5:20:5 and 5:20:5:20). Rats were killed at 3,6,9, and 12 weeks to examine the dependence of GGT+ foci development on protein intake. Animals fed 5% casein diets developed significantly fewer (p < 0.01) GGT+ foci than animals fed 20% casein diets despite greater total caloric intake. Similarly, in the intervention groups, preneoplastic development was enhanced when the 20% casein diet was fed and inhibited when the 5% casein diet was fed. These results indicate that the sustained development of AFB1-induced preneoplastic foci depends on a high protein intake. Alternatively, these results suggest that low protein intake inhibits lesion development.

Effects of breast cancer treatments on plasma nutrient levels: implications for epidemiological studies

The interpretation of case-control studies in which blood nutrient levels are examined as etiological factors in cancer is complicated by the possibility that either the disease or its treatment may alter these levels. Circulating levels of selected nutrients were examined prior to diagnostic biopsy and compared with levels 3 to 4 months after diagnosis among 71 women with breast cancer and 95 women with benign breast disease. Among women with benign breast disease or women with breast cancer who were not given postsurgical adjuvant drug therapy, levels of alpha-carotene, lycopene, alpha-tocopherol, cholesterol, and triglycerides did not change over time. In contrast, women who received chemotherapy had increased levels of cholesterol, retinol, and alpha- and gamma-tocopherol, and women on antiestrogen therapy showed increased levels of triglycerides and alpha-tocopherol. Overall, the concentrations of carotenoids (lycopene, alpha-carotene, and beta-carotene) did not change in breast cancer cases, although subgroup analyses showed increased levels of beta-carotene among cases not receiving drug treatment and decreased levels among those receiving antiestrogens. In summary, blood levels of some nutrients did not appear to be affected by breast cancer or its treatments, but changes were noted for levels of plasma lipids, tocopherols, retinol, and beta-carotene. Those investigating the etiological relationship between breast cancer and circulating nutrients need to consider these effects in designing and interpreting epidemiological studies.

Inhibition of aflatoxin B1-induced gamma-glutamyltranspeptidase positive (GGT+) hepatic preneoplastic foci and tumors by low protein diets: evidence that altered GGT+ foci indicate neoplastic potential

Previous studies in this laboratory with young Fischer 344 male rats have shown that the post-initiation development of aflatoxin B1 (AFB1)-induced gamma-glutamyltranspeptidase positive (GGT+) hepatic foci was markedly inhibited by low protein feeding, even though the energy intake was greater. This dietary effect, however, did not necessarily apply to hepatic tumor development. Thus, the present investigation was undertaken to examine this dietary effect upon the development of hepatic tumors and, is so doing, to determine the correlation of foci development with tumor development. Following AFB1 dosing (15 daily doses of 0.3 mg/kg each), animals were fed diets containing 6, 14 or 22% casein (5.2, 12.2, 19.1% protein) for 6, 12, 40, 58 and 100 weeks. Foci at 12 weeks and tumors at 40, 58 and 100 weeks developed dose-dependently to protein intake. Foci development, tumor incidence, tumor size and the number of tumors per animal were markedly reduced while the time to tumor emergence was increased with low protein feeding. Non-hepatic tumor incidence also was lower in the animals fed the lowest protein diet. Foci development indices (foci number, per cent liver volume occupied) were highly correlated with tumor incidence at 58 and 100 weeks (r = 0.90-1.00). Tumor and foci inhibition occurred in spite of the greater energy intake.

Attenuation of preneoplastic lesion development by dietary protein intervention: apparent persistence and regression

The effects of feeding high protein diets that promote the development of aflatoxin B1 (AFB1)-induced gamma-glutamyl transpeptidase positive (GGT+) preneoplastic lesions were examined in Fischer 344 (F344) rats. After administering AFB1 for 2 weeks (initiation), animals were fed diets over four successive 3-week periods (promotion). Either a low (5% casein) or high (20% casein) protein diet was fed for 3, 6, or 9 weeks before switching to the opposite diet to determine whether progressively longer periods of feeding the initial diet caused preneoplastic foci to become more refractory to the intervention effects of the second diet. The results from animals consuming the 20% casein diet for progressively longer periods suggest that longer exposure to the high protein diet progressively enhances the potential for future lesion growth. Results from animals consuming the 5% casein diet for progressively longer periods suggest that longer exposure to the inhibitory low protein diet progressively inhibits the potential for future lesion growth. These results suggest that a high protein diet is a potent promoter of preneoplastic growth and that progressively longer exposure to a particular promotive environment increasingly attenuates foci response to future dietary intervention.

Antioxidant status and cancer mortality in China

Sex-specific mortality rates for selected cancer sites (including oesophagus, stomach, liver, lung, colorectum, breast and cervix) and a variety of biochemical indicators of antioxidant status, enzyme activity and oxidative stress (including plasma levels of beta-carotene, alpha-tocopherol, ascorbic acid, selenium, glutathione peroxidase, catalase, superoxide dismutase, iron, copper, zinc, total cholesterol and lipid peroxide) were examined in an ecological study of 65 mostly rural counties in the People's Republic of China. The wide range of both mortality rates and biochemical values and the measurement of a comprehensive set of biochemical indicators permitted both simple correlational and multivariate analyses of the joint and relative effects of each factor on site-specific cancer mortality. Plasma levels of dietary antioxidants were consistently negatively correlated with cancer mortality rates. Ascorbic acid was most strongly negatively associated with most cancers and selenium with oesophageal and stomach cancers. beta-carotene was found to have a protective effect independent of retinol, particularly for stomach cancer.

Additional ecological evidence: lipids and breast cancer mortality among women aged 55 and over in China

That dietary fat increases breast cancer risk has been strongly supported by international data collected among developed countries during the past few decades. Population aggregates with elevated lipid intake have tended to report elevated breast cancer incidence and mortality. This study is an ecological analysis of the association of various indicators of lipid intake with breast cancer mortality in 65 county-wide population aggregates in the People's Republic of China. Although the result is consistent with a positive association between lipid intake and breast cancer risk, the observed association is weaker than the association previously observed. This finding provides only modest support for the possibility of a diet-breast cancer link.

High protein intake promotes the growth of hepatic preneoplastic foci in Fischer #344 rats: evidence that early remodeled foci retain the potential for future growth

The effects of successive administration, withdrawal and readministration of high protein diets (20% casein) on the promotional growth, remodeling and regrowth of aflatoxin B1-induced preneoplastic liver lesions (foci) were examined. Weanling male Fischer 344 rats were given 10 intragastric doses of aflatoxin B1 at a level of 250 micrograms/kg body weight over a 2-wk dosing period (initiation). The subsequent 12-wk period was subdivided into four feeding periods, each lasting 3 wk (promotion). Two groups of rats were fed either a 20 or 5% casein diet during all four periods; additional groups were alternately fed these diets in different sequences. Switching from the high protein diet to a low protein diet (5% casein) resulted in marked remodeling (regression) of the growing lesions to a response level similar to that in animals that did not receive the initial promotional stimulus of high protein feeding. However, refeeding the high protein diet caused significant reappearance of these lesions. The restimulated development of these remodeled lesions far exceeded lesion growth in animals receiving only the late promotional stimulus of high dietary protein. Thus, these data suggest that a second occurrence of high protein feeding promotes the growth of remodeled foci, thus demonstrating their potential for future promotional growth.

Thermogenesis, low-protein diets, and decreased development of AFB1-induced preneoplastic foci in rat liver

The development of hepatocellular, putatively preneoplastic, gamma-glutamyl transpeptidase positive (GGT+) foci and tumors induced by aflatoxin B1 (AFB1) has been shown to be reduced in male F344 rats fed a diet containing 6% protein (as casein). This reduction occurs despite increased energy intake, when compared with animals fed a diet containing 22% protein. Among its many effects, low protein intake is known to increase the proportion of energy intake expended in the form of heat (thermogenesis); thus, this investigation examined the association between the development of GGT+ foci and alterations in indices of thermogenesis induced by feeding varying levels of dietary protein. Five days following the completion of AFB1 dosing, animals were assigned to groups fed 4%, 8%, 12%, 16%, or 22% dietary protein for 6 weeks. Foci development (% liver volume occupied) was markedly reduced in animals fed the low-protein diet (4%, 8%), yet calorie consumption per 100 g body wt was greater. A modest negative linear trend was observed in oxygen consumption with increasing levels of dietary protein intake. Urinary norepinephrine levels were elevated in the groups fed 4% and 8% protein; urinary dopamine and norepinephrine turnover rates in brown adipose tissue were highest in animals fed 4% protein. These results suggest that GGT+ foci development occurs when a "critical level" (approx 12%) of dietary protein intake is reached. Inhibition of foci development at lower levels of protein intake is associated with several indicators of increased thermogenesis.

Associations between breast cancer, plasma triglycerides, and cholesterol

A case-control study investigating the association between plasma lipids and breast cancer was conducted among women aged 30-80 in Buffalo, NY. All eligible women from a large breast clinic and two area physicians' offices were requested to participate over a one-year period. Subjects completed a health questionnaire and donated a fasting blood sample prior to diagnostic breast biopsies. The 83 women found to have breast cancer (cases) had significantly higher plasma triglyceride values than did the 113 women found not to have breast cancer (controls). Lower plasma beta-carotene values were associated with breast cancer, but only in those women with elevated triglyceride or cholesterol. Plasma cholesterol values were lower in those breast cancer cases presenting with more advanced stages of cancer, suggesting that metabolic effects of clinical and preclinical breast cancer may lower cholesterol levels. Although the limitations of case-control studies are well-recognized, these data suggest an etiologic role for plasma triglycerides and beta-carotene or for related dietary factors.

Nonassociation of aflatoxin with primary liver cancer in a cross-sectional ecological survey in the People's Republic of China

A comprehensive cross-sectional survey was undertaken in The People's Republic of China of possible risk factors for primary liver cancer (PLC) to include 48 survey sites, an approximately 600-fold aflatoxin exposure range, a 39-fold range of PLC mortality rates, a 28-fold range of hepatitis B virus surface antigen (HBsAg+) carrier prevalence, and estimation of exposures for a large number of other nutritional, dietary, and life-style features. PLC mortality was unrelated to aflatoxin intake (r = -0.17) but was positively correlated with HBsAg+ prevalence (P less than 0.001), plasma cholesterol (P less than 0.01), frequency of liquor consumption (P less than 0.01), and mean daily intake of cadmium from foods of plant origin (P less than 0.01). Multiple regression analyses for various combinations of risk factors showed that aflatoxin exposure consistently remained unassociated with PLC mortality regardless of variable adjustment. In contrast, associations of PLC mortality with HBsAg+, plasma cholesterol, and cadmium intake remained, regardless of model specification, while the association with liquor consumption was markedly attenuated (was nonsignificant) with adjustment for plasma cholesterol. The sharp contrast between the findings of no aflatoxin effect upon PLC prevalence in this survey and the positive correlation reported for previous but more restricted surveys is discussed. Based on the results of this survey and the data of laboratory animal and in vitro studies, an explanatory model for the etiology of PLC is proposed, taking into consideration the role of nutrition in the etiology of this disease.

Geographic association of Helicobacter pylori antibody prevalence and gastric cancer mortality in rural China

To examine the geographic association between Helicobacter pylori infection and gastric cancer, we have assessed the prevalence of IgG antibodies to H. pylori in plasma samples taken in 1983 from 1882 men, aged 35-64 years, in 46 rural counties of the People's Republic of China. The gastric cancer mortality rates in these countries in 1973-75 varied from 3 per 1,000 (cumulative rate, 0-64 years) to 69 per 1,000, while the proportions of the population positive for H. pylori antibodies (based on an average of about 41 men per county) varied from 28% to 96%. After correction for the limited number of blood samples per county, the estimated correlation between H. pylori antibody prevalence and gastric cancer mortality was 40% (p = 0.02). No other type of cancer showed a significant association with H. pylori.

Urinary riboflavin excretion after a load test in rural China as a measure of possible riboflavin deficiency

Urinary excretion of riboflavin was measured in 3318 adults 4 h after an oral dose of riboflavin. Male and female subjects aged 35-64 years were selected from 65 mostly rural counties located in 24 provinces of China. Counties were selected to represent a range of seven of the most prevalent cancer mortality rates in China and within counties households were selected at random. Urinary riboflavin excretion levels after a load test, erythrocyte glutathione reductase activity coefficients (EGR-AC), dietary riboflavin intakes, and a large number of other biochemical, dietary, and environmental parameters were measured. Mean dietary intake of riboflavin was 75 per cent of the Chinese recommended dietary allowances (CRDA). Mean meat intake per reference man was very low (26.4 +/- 23.7 g/d) in comparison to Western standards and milk was not consumed at all in most counties. Mean EGR activity coefficients measured on 'blood pools' for both males (1.47 +/- 0.14) and females (1.48 +/- 0.16) indicated that more than two-thirds of the population surveyed was in the medium or high risk category of riboflavin deficiency. Using current reference standards of less than 1.4 mg for 4-h urinary excretion of riboflavin after a 5 mg load, more than 70 per cent of the individuals examined exhibited low levels usually associated with high risk of riboflavin deficiency. In view of the lack of specificity for clinical indications of riboflavin deficiency and the tentative validity of the present CRDA, the interpretation of the data is problematic. We suggest that the present CRDA for this vitamin is set too high and requires critical review and possibly some revision.

Questioning riboflavin recommendations on the basis of a survey in China

Riboflavin status was surveyed in adults aged 35-64 y in 65 counties (two communes per county) in the People's Republic of China by erythrocyte glutathione reductase activity coefficients (EGRACs), by urinary excretion of riboflavin 4 h after the oral administration of 5 mg riboflavin (one commune per county), and by direct measurement of food intake over a 3-d period (one commune per county). EGRAC data were highly correlated between sexes (p less than 0.001) and between neighboring communes within the same county (p less than 0.001) and with riboflavin intake (p less than 0.001). The urinary-riboflavin-load test data were not correlated either with EGRAC or with riboflavin intake. Approximately 90% of the survey subjects were found to be deficient by Western and Chinese reference standards and allowances. Upon reconsideration of the Western experimental data originally used to establish these recommendations, it is suggested that riboflavin allowances are set too high both in China and in Western countries.