Mortality in British vegetarians: review and preliminary results from EPIC-Oxford.

BACKGROUND: Three prospective studies have examined the mortality of vegetarians in Britain. OBJECTIVE: We describe these 3 studies and present preliminary results on mortality from the European Prospective Investigation into Cancer and Nutrition-Oxford (EPIC-Oxford). DESIGN: The Health Food Shoppers Study and the Oxford Vegetarian Study were established in the 1970s and 1980s, respectively; each included about 11 000 subjects and used a short questionnaire on diet and lifestyle. EPIC-Oxford was established in the 1990s and includes about 56 000 subjects who completed detailed food frequency questionnaires. Mortality in all 3 studies was followed though the National Health Service Central Register. RESULTS: Overall, the death rates of all the subjects in all 3 studies are much lower than average for the United Kingdom. Standardized mortality ratios (95% CIs) for all subjects were 59% (57%, 61%) in the Health Food Shoppers Study, 52% (49%, 56%) in the Oxford Vegetarian Study, and 39% (37%, 42%) in EPIC-Oxford. Comparing vegetarians with nonvegetarians within each cohort, the death rate ratios (DRRs), adjusted for age, sex and smoking, were 1.03 (0.95, 1.13) in the Health Food Shoppers Study, 1.01 (0.89, 1.14) in the Oxford Vegetarian Study, and 1.05 (0.86, 1.27) in EPIC-Oxford. DRRs for ischemic heart disease in vegetarians compared with nonvegetarians were 0.85 (0.71, 1.01) in the Health Food Shoppers Study, 0.86 (0.67, 1.12) in the Oxford Vegetarian Study, and 0.75 (0.41, 1.37) in EPIC-Oxford. CONCLUSIONS: The mortality of both the vegetarians and the nonvegetarians in these studies is low compared with national rates. Within the studies, mortality for major causes of death was not significantly different between vegetarians and nonvegetarians, but the nonsignificant reduction in mortality from ischemic heart disease among vegetarians was compatible with the significant reduction previously reported in a pooled analysis of mortality in Western vegetarians.

EPIC-Oxford: lifestyle characteristics and nutrient intakes in a cohort of 33 883 meat-eaters and 31 546 non meat-eaters in the UK.

OBJECTIVE: To describe the lifestyle characteristics and nutrient intakes of the Oxford cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC). DESIGN: Cohort of men and women recruited through general practices or by post to include a high proportion of non meat-eaters. Dietary, anthropometric and lifestyle data were collected at baseline and four diet groups were defined. SETTING: United Kingdom. PARTICIPANTS: In total, 65 429 men and women aged 20 to 97 years, comprising 33 883 meat-eaters, 10 110 fish-eaters, 18 840 lacto-ovo vegetarians and 2596 vegans. RESULTS: Nutrient intakes and lifestyle factors differed across the diet groups, with striking differences between meat-eaters and vegans, and fish-eaters and vegetarians usually having intermediate values. Mean fat intake in each diet group was below the UK dietary reference value of 33% of total energy intake. The mean intake of saturated fatty acids in vegans was approximately 5% of energy, less than half the mean intake among meat-eaters (10-11%). Vegans had the highest intakes of fibre, vitamin B1, folate, vitamin C, vitamin E, magnesium and iron, and the lowest intakes of retinol, vitamin B12, vitamin D, calcium and zinc. CONCLUSIONS: The EPIC-Oxford cohort includes 31 546 non meat-eaters and is one of the largest studies of vegetarians in the world. The average nutrient intakes in the whole cohort are close to those currently recommended for good health. Comparisons of the diet groups show wide ranges in the intakes of major nutrients such as saturated fat and dietary fibre. Such variation should increase the ability of the study to detect associations of diet with major cancers and causes of death.

Lifestyle determinants of serum insulin-like growth-factor-I (IGF-I), C-peptide and hormone binding protein levels in British women.

OBJECTIVE: This study aims to identify the lifestyle determinants of insulin-like growth factor-I (IGF-I) and its main binding proteins (IGFBPs), C-peptide, and sex hormone-binding globulin (SHBG) to help elucidate the mechanism through which lifestyle factors may affect cancer risk. METHODS: This study is based on a sample of 292 British women, aged 20-70 years, whose lifestyle characteristics were assessed using a self-administered questionnaire and whose serum hormone concentrations were measured using immunoassays. RESULTS: Age was a strong determinant of both IGF-I and IGFBP levels; women aged 65-70 years had significantly lower IGF-I and IGFBP-3 concentrations and significantly higher IGFBP-1 and IGFBP-2 concentrations than women aged 20-24 years. Body mass index (BMI) was not strongly associated with IGF-I, although women with a BMI of 26-27.9 kg/m2 had a higher IGF-I concentration compared with both lean (BMI <20 kg/m2) and obese (BMI 30+ kg/m2) women. However, obese women had a significantly higher C-peptide and IGFBP-3 concentration and a significantly lower IGFBP-1, IGFBP-2, and SHBG concentration compared with lean women. Increasing vigorous exercise was associated with a significantly lower C-peptide concentration and increasing leisure-time activity was associated with a significantly higher IGFBP-1 concentration. Other lifestyle factors such as job activity, smoking, and reproductive factors were not associated with any hormone. CONCLUSIONS: Our data show that age is a major determinant of both IGF-I and its main binding proteins in women. BMI has strong effects on IGFBPs, C-peptide, and SHBG, but its effects on IGF-I remain unclear. The possible effect of physical activity on IGFBP-1 requires further investigation.

The associations of diet with serum insulin-like growth factor I and its main binding proteins in 292 women meat-eaters, vegetarians, and vegans.

The lower rates of some cancers in Asian countries than in Western countries may be partly because of diet, although the mechanisms are unknown. The aim of this cross-sectional study was to determine whether a plant-based (vegan) diet is associated with a lower circulating level of insulin-like growth factor I (IGF-I) compared with a meat-eating or lacto-ovo-vegetarian diet among 292 British women, ages 20-70 years. The mean serum IGF-I concentration was 13% lower in 92 vegan women compared with 99 meat-eaters and 101 vegetarians (P = 0.0006). The mean concentrations of both serum IGF-binding protein (IGFBP)-1 and IGFBP-2 were 20-40% higher in vegan women compared with meat-eaters and vegetarians (P = 0.005 and P = 0.0008 for IGFBP-1 and IGFBP-2, respectively). There were no significant differences in IGFBP-3, C-peptide, or sex hormone-binding globulin concentrations between the diet groups. Intake of protein rich in essential amino acids was positively associated with serum IGF-I (Pearson partial correlation coefficient; r = 0.27; P < 0.0001) and explained most of the differences in IGF-I concentration between the diet groups. These data suggest that a plant-based diet is associated with lower circulating levels of total IGF-I and higher levels of IGFBP-1 and IGFBP-2.

Hypertension and blood pressure among meat eaters, fish eaters, vegetarians and vegans in EPIC-Oxford.

OBJECTIVE: To compare the prevalence of self-reported hypertension and mean systolic and diastolic blood pressures in four diet groups (meat eaters, fish eaters, vegetarians and vegans) and to investigate dietary and other lifestyle factors that might account for any differences observed between the groups. DESIGN: Analysis of cross-sectional data from participants in the Oxford cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). SETTING: United Kingdom. SUBJECTS: Eleven thousand and four British men and women aged 20-78 years at blood pressure measurement. RESULTS: The age-adjusted prevalence of self-reported hypertension was significantly different between the four diet groups, ranging from 15.0% in male meat eaters to 5.8% in male vegans, and from 12.1% in female meat eaters to 7.7% in female vegans, with fish eaters and vegetarians having similar and intermediate prevalences. Mean systolic and diastolic blood pressures were significantly different between the four diet groups, with meat eaters having the highest values and vegans the lowest values. The differences in age-adjusted mean blood pressure between meat eaters and vegans among participants with no self-reported hypertension were 4.2 and 2.6 mmHg systolic and 2.8 and 1.7 mmHg diastolic for men and women, respectively. Much of the variation was attributable to differences in body mass index between the diet groups. CONCLUSIONS: Non-meat eaters, especially vegans, have a lower prevalence of hypertension and lower systolic and diastolic blood pressures than meat eaters, largely because of differences in body mass index.

Validity of self-reported height and weight in 4808 EPIC-Oxford participants.

OBJECTIVE: To assess the validity of self-reported height and weight by comparison with measured height and weight in a sample of middle-aged men and women, and to determine the extent of misclassification of body mass index (BMI) arising from differences between self-reported and measured values. DESIGN: Analysis of self-reported and measured height and weight data from participants in the Oxford cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). SUBJECTS: Four thousand eight hundred and eight British men and women aged 35-76 years. RESULTS: Spearman rank correlations between self-reported and measured height, weight and BMI were high (r > 0.9, P < 0.0001). Height was overestimated by a mean of 1.23 (95% confidence interval (CI) 1.11-1.34) cm in men and 0.60 (0.51-0.70) cm in women; the extent of overestimation was greater in older men and women, shorter men and heavier women. Weight was underestimated by a mean of 1.85 (1.72-1.99) kg in men and 1.40 (1.31-1.49) kg in women; the extent of underestimation was greater in heavier men and women, but did not vary with age or height. Using standard categories of BMI, 22.4% of men and 18.0% of women were classified incorrectly based on self-reported height and weight. After correcting the self-reported values using predictive equations derived from a 10% sample of subjects, misclassification decreased to 15.2% in men and 13.8% in women. CONCLUSIONS: Self-reported height and weight data are valid for identifying relationships in epidemiological studies. In analyses where anthropometric factors are the primary variables of interest, measurements in a representative sample of the study population can be used to improve the accuracy of estimates of height, weight and BMI.

Lifestyle and nutritional determinants of bioavailable androgens and related hormones in British men.

OBJECTIVE: To investigate the lifestyle and nutritional determinants of serum bioavailable androgens and their related hormones in men. METHODS: This study is based on a sample of 696 men with a wide range of nutrient intakes, whose diet and lifestyle characteristics were assessed with a questionnaire and serum sex hormones measured using immunoassays. RESULTS: Men aged 70 years or older had 12% lower testosterone and 40% lower free-testosterone (FT) and androstanediol glucuronide (A-diol-g) concentrations than men who were 20-29 years of age. Conversely, sex hormone-binding globulin (SHBG) and luteinizing hormone (LH) concentrations were 90% and 49% higher in the oldest age group compared with the lowest, respectively. Men who had a body mass index (BMI) of 30+ kg/m2 had 30% lower testosterone, 45% lower SHBG, 22% lower LH and 5% lower FT concentrations compared with men with a BMI of <20 kg/m2. Conversely, A-diol-g concentration was 15% higher in the highest BMI category compared with the lowest. A high waist circumference was further associated with a 12% lower testosterone and SHBG concentration, after adjusting for BMI. Compared with never-smokers, smoking 10+ cigarettes/day was associated with 15% higher testosterone, 22% higher SHBG and 17% higher LH concentrations; FT and A-diol-g were not associated with smoking. Compared with no exercise, vigorous exercise of 3+ hours/week was associated with 11% higher testosterone and 16% higher SHBG concentrations, whilst LH, FT, and A-diol-g were not associated with vigorous exercise. Dietary factors were not strongly associated with hormones, although saturated fat intake was negatively associated with SHBG (r = -0.10; p = 0.01) and alcohol intake was positively associated with A-diol-g (r = 0.11; p = 0.004). No dietary factors were associated with testosterone, FT, or LH. CONCLUSIONS: Age is the strongest determinant of serum bioavailable androgens. BMI and some lifestyle and dietary factors influence SHBG and testosterone concentrations, but have no strong association with FT, suggesting that homeostasis is effective. A-diol-g shows broadly similar associations to FT, with the exception of the effect of BMI and alcohol.