T. Colin Campbell

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.

Nutrition and drug-metabolizing enzymes.

The role played by nutrition and nutritional status in drug metabolism, as distinct from the effects of diet plus nonnutrient components on these reactions, is discussed. The cytochrome P‐450‐dependent mixed‐function oxidation (MFO) activity, primarily located in the liver, and such other reactions involving the transferases and hydrases which, on theoretic grounds, may become rate limiting during nutritional alteration determine the degree of the biologic response. This is exemplified by the relationship between dietary protein deficiency which decreases MFO activity and increases the duration of action of barbiturates by decreasing their rates of metabolism and tissue clearance. Male Sprague‐Dawley weanling rats were fed on a deficient diet of 5% protein and compared with controls on 20% protein. In the protein‐deficient animals, the liver cells were larger, there were fewer per liver weight as demonstrated by DNA content, the cells were higher in lipid content, and the liver contained less protein per unit weight than that of control animals. Preliminary experiments to examine a possible relationship between protein intake and certain types of cancer were undertaken. The effect of protein deficiency on the proportion of a 3H‐AFB1 dose which binds critical macromolecules in liver nuclei was studied. An important finding was that protein‐deficient diets depressed the binding to DNA by 70%. If, indeed, as recently postulated, 80 to 90% of human cancers are due to environmental chemicals and chemical carcinogens require metabolic activation, the question is posed whether nutritional manipUlation, particularly of the amount of dietary protein, may modify carcinogenic susceptibility. Similarly, nutritional status could also significantly affect pharmacologic response and environmental chemical insult.

The effect of protein deficiency on the in vivo binding of aflatoxin B1 to rat liver macromolecules

Abstract Male, weanling rats divided into three groups were maintained for 15 days on a semipurified diet containing either 5% casein fed ad libitum (group 1), 20% casein pair-fed to group 1 (group 2), or 20% casein fed ad libitum (group 3). Animals on day 16 were injected i.p. with 3H-AFB1 (1.90 mg/kg) and were sacrificed six hours later. In both the control and protein deficient animals, binding of AFB1 to DNA was greater than that for chromatin protein. In the protein deficient animals, there was a consistent decrease (70%) in binding to chromatin, DNA and chromatin protein. The decrease in binding to nuclear macromolecules in protein deficient animals is correlated with carcinogenicity and mixed function oxidase (MFO) enzyme activity, and the relationships between carcinogenicity, MFO activity, and binding are discussed.

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 Peoples 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.

Effects of low dietary protein and dietary aflatoxin on hepatic glutathione levels in F-344 rats

Abstract In order to investigate the effects of low dietary protein and dietary aflatoxin (AFB 1 ) on hepatic glutathione (GSH) levels, groups of male and female F-344 (60–100 g) rats were fed 5 and 20% casein diets with/without 2.5–5 ppm AFB 1 for 6 weeks. Animals were sacrificed at selected times between 0 hr to 6 weeks, and GSH contents were determined in liver homogenates. Whereas in males, low protein diets caused a marked retardation in growth, females grew equally well on both protein diets. Low protein diets caused a reduction in hepatic GSH within hours of feeding which remained low for the duration of the study. Dietary AFB 1 increased hepatic GSH regardless of dietary protein level and animal sex. Histologic examinations revealed that AFB 1 caused more acute lesions in males although lesions in both sexes were much more pronounced in the high protein groups. It should be noted that no simple relationship between GSH levels and protection against hepatic lesions was observed.

Fish consumption, blood docosahexaenoic acid and chronic diseases in Chinese rural populations

The Chinese traditional diet is low in fat. However, there is regional variability in the amount, type of fat consumed and the pattern of chronic diseases. An epidemiological survey of 65 rural counties in China (6500 subjects) was conducted in the 1980s. We have re-examined the red blood cell fatty acid and antioxidant composition, with fish consumption. Fish consumption correlated significantly with the levels of docosahexaenoic acid (DHA) in red blood cells (RBC) (r=0.640, P<0.001), selenium (r=0.467, P<0.001) and glutathione peroxidase (r=0.333, P<0.01) in plasma. The proportion of DHA in RBC was inversely associated with total plasma triglyceride concentrations. A strong inverse correlation between DHA in RBC and cardiovascular disease (CVD) was found. The strongest correlation was the combination of DHA and oleic acid. RBC docosahexaenoic acid itself also correlated negatively and significantly with most chronic diseases and appeared to be more protective than either eicosapentaenoic or the omega3 docosapenataenoic acids. These results demonstrate the protective nature of fish consumption and DHA, found in high fat Western diets, operates at a low level of fat. This finding suggests the protective effect of fish consumption as validated by red cell DHA is universal. The protective effect is, therefore, most likely to be due to the fundamental properties of docosahexaenoic acid in cell function.

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.

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.

Interrelationships of dietary protein level, aflatoxin B1 metabolism, and hepatic microsomal epoxide hydrase activity

Abstract In a continuation of studies on protein intake and aflatoxin B 1 (AFB 1 ) metabolism, weanling rats were fed semipurified diets containing either 20% casein or 5% casein for two weeks to determine the effect of dietary protein level on hepatic microsomal epoxide hydrase activity and AFB 1 metabolism in an effort to evaluate the role of protein intake on the formation and degradation of the reactive metabolite of AFB 1 . Styrene oxide was used as substrate for epoxide hydrase since the hypothetical AFB 1 2,3-epoxide (AFB-epox) cannot be synthesized because of its lability. Two groups of animals were fed 20% casein diets; one was fed ad libitum and the second was pair fed to the 5% casein group in order to control the effects of total feed intake. The depression of epoxide hydrase activities caused by the 5% casein diets was approximately equivalent to that previously seen with hepatic microsomal mixed function oxidase (MFO) activities with the identical protocol. Similarly, the metabolism of AFB 1 to AFQ 1 and AFM 1 was depressed by the 5% casein diets, with an increase in the production of chromatographically more polar material. The relationship of the MFO and epoxide hydrase activities to AFB 1 metabolism and formation of macromolecular adducts is discussed.

Influence of Nutrition on Metabolism of Carcinogens

The recognition that nutrition has an important bearing on the determination of cancer risk has received support in many quarters in the last few years. Moreover, foods which supply these nutrients may also contain a large variety of nonnutrient, adventitious components, some of which may be carcinogenic. Various epidemiological estimates during the last ten years have generally agreed that 80–90% of all human cancers are associated with the environment and/or ingestion of carcinogenic chemicals (Doll, 1967; Boyland, 1967; Higginson, 1969). However, we know very little about the fundamental mechanisms which account for these relationships. One hypothesis that should be considered is the possibility that nutritional status may play a role through modification of enzyme activities which are responsible for carcinogen metabolism.