Search

Background: Vegans and other vegetarians who limit their intake of animal products may be at greater risk of vitamin D deficiency than nonvegetarians, because foods providing the highest amount of vitamin D per gram naturally are all from animal sources, and fortification with vitamin D currently occurs in few foods. Objective: We assessed serum 25-hydroxyvitamin D [s25(OH)D] concentrations and factors affecting them in vegetarians, partial vegetarians, and nonvegetarians in a sample of calibration study subjects from the Adventist Health Study-2. Design: Food-frequency questionnaires and sun-exposure data were obtained from 199 black and 229 non-Hispanic white adults. We compared s25(OH)D concentration, dietary and supplemental vitamin D intake, and sun exposure in the different dietary groups. Results: We found no significant difference in s25(OH)D by vegetarian status for either white or black subjects. Among whites, dietary vitamin D intake and sun behavior were different between vegetarian groups, but there was no difference in skin type distribution. Among blacks, no significant differences were observed for any of these variables between vegetarian groups. The mean ([+ or -] SD) s25(OH)D was higher in whites (77.1 [+ or -] 10.33 nmol/L) than in blacks (50.7 [+ or -] 27.4 nmol/L) (P < 0.0001). Conclusions: s25(OH)D concentrations were not associated with vegetarian status. Other factors, such as vitamin D supplementation, degree of skin pigmentation, and amount and intensity of sun exposure have greater influence on s25(OH)D than does diet.

A number of studies have evaluated the health of vegetarians. Others have studied the health effects of foods that are preferred or avoided by vegetarians. The purpose of this review is to look critically at the evidence on the health effects of vegetarian diets and to seek possible explanations where results appear to conflict. There is convincing evidence that vegetarians have lower rates of coronary heart disease, largely explained by low LDL cholesterol, probable lower rates of hypertension and diabetes mellitus, and lower prevalence of obesity. Overall, their cancer rates appear to be moderately lower than others living in the same communities, and life expectancy appears to be greater. However, results for specific cancers are much less convincing and require more study. There is evidence that risk of colorectal cancer is lower in vegetarians and in those who eat less meat; however, results from British vegetarians presently disagree, and this needs explanation. It is probable that using the label 'vegetarian' as a dietary category is too broad and that our understanding will be served well by dividing vegetarians into more descriptive subtypes. Although vegetarian diets are healthful and are associated with lower risk of several chronic diseases, different types of vegetarians may not experience the same effects on health.

Background: Saturated fatty acid (SFA) intake increases plasma LDL-cholesterol concentrations; therefore, intake should be reduced to prevent coronary heart disease (CHD). Lower habitual intakes of SFAs, however, require substitution of other macronutrients to maintain energy balance. Objective: We investigated associations between energy intake from monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), and carbohydrates and risk of CHD while assessing the potential effect-modifying role of sex and age. Using substitution models, our aim was to clarify whether energy from unsaturated fatty acids or carbohydrates should replace energy from SFAs to prevent CHD. Design: This was a follow-up study in which data from 11 American and European cohort studies were pooled. The outcome measure was incident CHD. Results: During 4-10 y of follow-up, 5249 coronary events and 2155 coronary deaths occurred among 344,696 persons. For a 5% lower energy intake from SFAs and a concomitant higher energy intake from PUFAs, there was a significant inverse association between PUFAs and risk of coronary events (hazard ratio: 0.87; 95% CI: 0.77, 0.97); the hazard ratio for coronary deaths was 0.74 (95% CI: 0.61, 0.89). For a 5% lower energy intake from SFAs and a concomitant higher energy intake from carbohydrates, there was a modest significant direct association between carbohydrates and coronary events (hazard ratio: 1.07; 95% CI: 1.01, 1.14); the hazard ratio for coronary deaths was 0.96 (95% CI: 0.82, 1.13). MUFA intake was not associated with CHD. No effect modification by sex or age was found. Conclusion: The associations suggest that replacing SFAs with PUFAs rather than MUFAs or carbohydrates prevents CHD over a wide range of intakes.

Background: Evidence of the benefits of soy on cancer risk in Western populations is inconsistent, in part because of the low intake of soy in these groups. Objective: We assessed the validity of soy protein estimates from food-frequency questionnaires (FFQs) in a sample of Adventist Health Study-2 participants with a wide range of soy intakes. Design: We obtained dietary intake data from 100 men and women (43 blacks and 57 nonblacks). Soy protein estimates from FFQs were compared against repeated 24-h recalls and urinary excretion of daidzein, genistein, total isoflavonoids (TIFLs), and equol (measured by HPLC/photodiode array/mass spectrometry) as reference criteria. We calculated Pearson and Spearman correlation coefficients (with 95% CIs) for FFQ-24-h recall, 24 h-recall-urinary excretion, and FFQ-urinary excretion pairs. Results: Among soy users, mean ([+ or -] SD) soy protein values were 12.12 [+ or -] 10.80 g/d from 24-h recalls and 9.43 [+ or -] 7.83 g/d from FFQs. The unattenuated correlation (95% CI) between soy protein estimates from 24-h recalls and FFQs was 0.57 (0.32, 0.75). Correlation coefficients between soy protein intake from 24-h recalls and urinary isoflavonoids were 0.72 (0.43, 0.96) for daidzein, 0.67 (0.43, 0.91) for genistein, and 0.72 (0.47, 0.98) for TIFLs. Between FFQs and urinary excretion, these were 0.50 (0.32, 0.65), 0.48 (0.29, 0.61), and 0.50 (0.32, 0.64) for daidzein, genistein, and TIFLs, respectively. Conclusions: Soy protein estimates from questionnaire were significantly correlated with soy protein from 24-h recalls and urinary excretion of daidzein, genistein, and TIFLs. The Adventist Health Study-2 FFQ is a valid instrument for assessing soy protein in a population with a wide range of soy intakes.

Background: Epidemiologic studies have suggested a lower risk of coronary heart disease (CHD) at higher intakes of fruit, vegetables, and whole grain. Whether this association is due to antioxidant vitamins or some other factors remains unclear. Objective: We studied the relation between the intake of antioxidant vitamins and CHD risk. Design: A cohort study pooling 9 prospective studies that included information on intakes of vitamin E, carotenoids, and vitamin C and that met specific criteria was carried out. During a 10-y follow-up, 4647 major incident CHD events occurred in 293 172 subjects who were tree of CHD at baseline. Results: Dietary intake of antioxidant vitamins was only weakly related to a reduced CHD risk after adjustment for potential nondietary and dietary confounding factors. Compared with subjects in the lowest dietary intake quintiles for vitamins E and C, those in the highest intake quintiles had relative risks of CHD incidence of 0.84 (95% CI: 0.71, 1.00; P = 0.17) and 1.23 (1.04, 1.45; P = 0.07), respectively, and the relative risks for subjects in the highest intake quintiles for the various carotenoids varied from 0.90 to 0.99. Subjects with higher supplemental vitamin C intake had a lower CHD incidence. Compared with subjects who did not take supplemental vitamin C, those who took >700 mg supplemental vitamin C/d had a relative risk of CHD incidence of 0.75 (0.60, 0.93; P for trend < 0.001). Supplemental vitamin E intake was not significantly related to reduced CHD risk. Conclusions: The results suggest a reduced incidence of major CHD events at high supplemental vitamin C intakes. The risk reductions at high vitamin E or carotenoid intakes appear small. KEY WORDS Antioxidant, carotenoids, cohort, coronary heart disease, diet, Pooling Project of Cohort Studies on Diet and Coronary Disease, vitamin C, vitamin E

Background: Since meat products represent a major source of protein in the Western diet, findings on whether meat intake significantly contributes to the burden of fatal disease have important clinical and public health implications. Objective: The objective was to examine whether a very low meat intake (less than weekly) contributes to greater longevity. Design: We reviewed data from 6 prospective cohort studies and report new findings on the life expectancy of long-term vegetarians from the Adventist Health Study. Results: Our review of the 6 studies found the following trends: 1) a very low meat intake was associated with a significant decrease in risk of death in 4 studies, a nonsignificant decrease in risk of death in the fifth study, and virtually no association in the sixth study; 2) 2 of the studies in which a low meat intake significantly decreased mortality risk also indicated that a longer duration ( [is greater than or equal to] 2 decades) of adherence to this diet contributed to a significant decrease in mortality risk and a significant 3.6-y (95% CI: 1.4, 5.8 y) increase in life expectancy; and 3) the protective effect of a very low meat intake seems to attenuate after the ninth decade. Some of the variation in the survival advantage in vegetarians may have been due to marked differences between studies in adjustment for confounders, the definition of vegetarian, measurement error, age distribution, the healthy volunteer effect, and intake of specific plant foods by the vegetarians. Conclusion: Current prospective cohort data from adults in North America and Europe raise the possibility that a lifestyle pattern that includes a very low meat intake is associated with greater longevity. KEY WORDS Vegetarians, aging, epidemiology

Although results from epidemiologic studies of diet have taught us a great deal, much of the evidence remains mired in controversy because of the inconsistency of results among apparently good studies. I conclude that this can be largely explained by the combination of 2 problems: confounding and measurement error. This recognition allows some judgment as to which studies may be less prone to these difficulties and a search for new analytic methods that can produce less biased and more consistent results. The potential correlations between many nutrients, and to a lesser extent foods, make it difficult to know whether the nominated variable is actually the active principle or whether there is some other dietary risk factor that is closely associated. It is not generally recognized that all traditional analyses of this sort are based on a powerful but incorrect assumption: that there are no errors in dietary assessment. If the incorrect assumption is not satisfied, relative risk estimates become distorted--reduced by one-half or more in some cases. Regression calibration is a newer technique that uses a calibration substudy to provide information about errors and to correct results from the main study. There are a number of variants of this technique, all requiring assumptions about the data. Regression calibration methods that use carefully selected biological surrogates (correlates) of the dietary factor of interest in the calibration study seem to use more realistic assumptions. KEY WORDS Measurement error, bias, confounding, dietary patterns, regression calibration

Cancer incidence was monitored in a population of 34 000 Seventh-day Adventists in California. By religious belief, Adventists do not consume tobacco, alcohol, or pork and approximately one-half adhere to a lactoovovegetarian lifestyle. Only a small percentage are pure vegetarians. Comparisons of cancer-incidence rates in this population with an external reference population were completed by calculating standardized morbidity ratios (SMRs) for all cancer sites. Also, within the population, relative risks were calculated by using date obtained from a detailed lifestyle questionaire that members of the study population completed. For all cancer sites combined in males, the SMR was lower in the Adventists (SMR = 0.73). The SMR was also lower in males for most individual cancer sites. However, prostate cancer risk was higher. For females, the all-cancer SMR was lower but not significantly so (SMR = 92). Most site-specific SMRs were lower, although not as much as the male SMRs. The SMR for endometrial cancer was significantly higher in female Adventists.

Traditionally, the effects of diet on coronary heart disease have been attributed to the effects of medium-chain fatty acids, soluble fiber, and dietary cholesterol on serum low-density-lipoprotein (LDL) cholesterol concentrations. We review evidence here that may other dietary substances may affect risk, often via mechanisms not involving LDL-cholesterol concentrations directly. Such substances include phytosterol, tocotrienols, arginine, and antioxidant vitamins. The effects of diet on high-density-lipoprotein-cholesterol concentrations, triglycerides (fasting and postprandia), oxidized LDL particles, prostaglandins, and endothelium-derived relaxing factor are described. Finally, an illustration of some epidemiologic associations between diet and coronary disease events is made from the Adventist Health Study data.

Adventists are encouraged to adopt vegetarian eating habits. However, this admonition is followed to a variable extent. The Adventist Health Study cohort was defined at baseline in 1976. Dietary data were collected by using a food-frequency questionnaire containing 55 questions on foods and food groups, along with 10 other qualitative questions. We divided the 34198 subjects, mainly Seventh-day Adventist, into vegetarians (no meat products), partial vegetarians (meat [is less than] weekly), and nonvegetarians. A cross-sectional analysis using baseline data found trends across these 3 dietary patterns showing that vegetarian Adventists eat fruit, tomatoes, legumes, and nuts more frequently than do non- or partial vegetarians, but consume a similar frequency of salads. Vegetarians eat fewer eggs and doughnuts, and prefer whole-grain breads. Trends were consistent, and differences ranged from 10% to 70% across dietary categories. Nonvegetarian Adventists drink much more coffee (a 17-fold difference) and are much more likely to use alcohol (a 22-fold difference), than vegetarians. The meat they consume is largely beef. Consequently, the generally lower risk status of vegetarian Adventists involves much more than the absence of meat.

In the context of a validation study for a food-frequency questionnaire (FFQ) as part of the Adventist Health Study in 1994-1996, we explored the food pattern of 158 California Seventh-day Adventists aged 23-88 y. Forty-two percent were vegetarians (their combined consumption of any meat products was less than once per week) and the remainder consumed meat products 1-11 times/wk. Educational attainment was high in both groups (91.1% of vegetarians and 86.8% of omnivores were college graduates). Sex and marital status distributions were similar in both groups. The average age of the vegetarians and omnivores was 56.4 y and 50.5, respectively; body mass index (in kg/[m.sup.2]) was 25.1 and 26.9, respectively. The diet was assessed using a FFQ with 200 food items listed, each with a specified portion size. Marked increases in the mean frequency of consumption were observed in vegetarians for fresh fruit, canned fruit, dried fruit, all fruit combined, fruit juices, legumes, and nuts. Vegetarians seemed to eat less cooked vegetables, soups, bread, cereals, pasta, pizza, sweets, desserts, snacks, seasonings, and additives than omnivores. Significant differences in the mean of frequencies between vegetarians and omnivores persisted after adjustment for age and sex for the following food groups: dried fruit (8.3 servings/mo), all fruit combined (40.3), eggs and dairy products (-17.3), oils and margarines (-12.4), fish (-5.4), meat products (-13.2), dressings (-9.7), and salads and raw vegetables (-10.8). The results suggest that in a free living population exclusive of vegetables, vegetarians seems to eat more whole plant foods and less processed and diary products than omnivores.

In a 6-y prospective cohort study, we examined the relation between diet and incident colon cancer among 32051 non-Hispanic, white cohort members of the Adventist Health Study. This population was characterized by a low prevalence ([is less than] 4%) of current smoking or alcohol use, and 30% ate no meat. The risk of colon cancer by intake levels of specific foods was determined from proportional hazard regression. In the total population, a positive association with meat intake for nonvegetarians compared with strict vegetarians (RR: 1.84; 95% CI: 1.20, 2.81; P for trend = 0.01), and a negative association with legume intake for [is greater than] 2 servings/wk compared with [is less than] 1 serving/wk (RR: 0.52; 95% CI: 0. 32, 0.85; P for trend = 0.02) was observed. Among subjects favoring specific types of meat, significant positive associations for red meat and white meat (fish and poultry) were also observed. An effect of the relative intake of meat and legumes was shown whereby the increase in risk due to meat intake was most evident among those in the low intake category of legumes for nonvegetarians compared with strict vegetarians (RR: 2.58; 95% CI: 1.21, 5.501; P for trend = 0.009) and the decrease in risk due to legume intake was most evident among those in the high intake category of meat for [is greater than] 2 servings/wk compared with [is less than] 1 servings/wk (RR: 0.34; 95% CI: 0.14, 0.867; P for trend = 0.004). The findings from this population identify both red and white meat intake as important dietary risk factors for colon cancer and raise the possibility that the risk from meat intake can be modified by consumption of legumes.

Results associating diet with chronic disease in a cohort of 34 192 California Seventh-day Adventists are summarized. Most Seventh-day Adventists do not smoke cigarettes or drink alcohol, and there is a wide range of dietary exposures within the population. About 50% of those studied ate meat products [is less than] 1 time/wk or not at all, and vegetarians consumed more tomatoes, legumes, nuts, and fruit, but less coffee, doughnuts, and eggs than did nonvegetarians. Multivariate analyses showed significant associations between beef consumption and fatal ischemic heart disease (IHD) in men [relative risk (RR) = 2.31 for subjects who ate beef [is greater than or equal to] 3 times/wk compared with vegetarians], significant protective associations between nut consumption and fatal and nonfatal IHD in both sexes (RR [approximately equals] 0.5 for subjects who ate nuts [is greater than or equal to] 5 times/wk compared with those who ate nuts [is less than] 1 time/wk), and reduced risk of IHD in subjects preferring whole-grain to white bread. The lifetime risk of IHD was reduced by [nearly equal to] 31% in those who consumed nuts frequently and by 37% in male vegetarians compared with nonvegetarians. Cancers of the colon and prostate were significantly more likely in nonvegetarians (RR of 1.88 and 1.54, respectively), and frequent beef consumers also had higher risk of bladder cancer. Intake of legumes was negatively associated with risk of colon cancer in nonvegetarians and risk of pancreatic cancer. Higher consumption of all fruit or dried fruit was associated with lower risks of lung, prostate, and pancreatic cancers. Cross-sectional data suggest vegetarian Seventh-day Adventists have lower risks of diabetes mellitus, hypertension, and arthritis than nonvegetarians. Thus, among Seventh-day Adventists, vegetarians are healthier than nonvegetarians but this cannot be ascribed only to the absence of meat. Am J Clin Nutr 1999;70(suppl):532S-8S. KEY WORDS Seventh-day Adventists, vegetarians, diet, ischemic heart disease, cancer, longevity, mortality, cardiovascular disease, coronary artery disease, diabetes, arthritis, lung cancer, prostate cancer, colon cancer, pancreatic cancer, cancer prevention, nuts, beef, meat

We combined data from 5 prospective studies to compare the death rates from common diseases of vegetarians with those of nonvegetarians with similar lifestyles. A summary of these results was reported previously; we report here more details of the findings. Data for 76 172 men and women were available. Vegetarians were those who did not eat any meat or fish (n = 27808). Death rate ratios at ages 16-89 y were calculated by Poisson regression and all results were adjusted for age, sex, and smoking status. A random-effects model was used to calculate pooled estimates of effect for all studies combined. There were 8330 deaths after a mean of 10.6 y of follow-up. Mortality from ischemic heart disease was 24% lower in vegetarians than in nonvegetarians (death rate ratio: 0.76; 95% CI: 0.62, 0.94; P [is less than] 0.01). The lower mortality from ischemic heart disease among vegetarians was greater at younger ages and was restricted to those who had followed their current diet for [is greater than] 5 y. Further categorization of diets showed that, in comparison with regular meat eaters, mortality from ischemic heart disease was 20% lower in occasional meat eaters, 34% lower in people who ate fish but not meat, 34% lower in lactoovovegetarians, and 26% lower in vegans. There were no significant differences between vegetarians and nonvegetarians in mortality from cerebrovascular disease, stomach cancer, colorectal cancer, lung cancer, breast cancer, prostate cancer, or all other causes combined. Am J Clin Nutr 1999;70(suppl):516S-24S. KEY WORDS Vegetarians, vegans, mortality, ischemic heart disease, colorectal cancer, breast cancer, prostate cancer