(This is one of the better studies associating a vegetarian diet with chronic disease. It was a study of 34,192 California Seventh-day Adventists. This article includes excerpts from the study: “Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists” Gary E Fraser, From the Center for Health Research and the Department of Epidemiology and Biostatistics, Loma Linda University, CA.)
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
Summary of Subjects who ate Beef 3 times/wk Compared with Vegetarians
– and IHD (ischemic heart disease).
There were significant protective associations between nut consumption and fatal and nonfatal IHD (ischemic heart disease) in both sexes compared with those who ate nuts and reduced risk of IHD in subjects preferring whole-grain to white bread.
The lifetime risk of IHD was reduced by about 31% in those who consumed nuts frequently and by 37% in male vegetarians compared with non-vegetarians. Cancers of the colon and prostate were significantly more likely in non-vegetarians and frequent beef consumers also had higher risk of bladder cancer.
Intake of legumes was negatively associated with risk of colon cancer in non-vegetarians 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 non-vegetarians.
Thus, among Seventh-day Adventists, vegetarians are healthier than non-vegetarians but this cannot be ascribed only to the absence of meat.
Discussion
For over 40 years, it has been recognized that Seventh-day Adventists present a unique opportunity to study relations between diet and chronic disease. This is because of the wide variety of dietary habits of Seventh-day Adventists, whose diets are on average lower in saturated fat and higher in fiber than the diets of other Americans.
Of the Seventh-day Adventists we studied,
- About 20% were meat eaters who ate meat
- About 30% ate no meat products.
- Most ate dairy products and eggs and few ate vegan diets
- Of the meat-eating Seventh-day Adventists, about half ate meat as frequently as did other people.
This presents an opportunity to compare different dietary patterns within the Seventh-day Adventist group. The nutrient intake profile of Seventh-day Adventists is closer to that recommended by a number of professional bodies than is the diet of average Americans. Generally, Seventh-day Adventists had lower mortality from cancer, heart disease, and diabetes than did non-Adventists living in the same communities. We summarized findings associating the use of different foods to risk of cancer, ischemic heart disease (IHD), and other diseases within a Seventh-day Adventist population enrolled in a large cohort study (1-3).
The study was approved by the ethics review committee of Loma Linda University and has been described elsewhere (4).
3 Dietary Habits
Because there is some interest in comparing the risk for disease in vegetarian and nonvegetarian Seventh-day Adventists, 3 categories of dietary habits were defined.
1. Vegetarian, those who ate no fish, poultry, or meat (29.5%);
2. Semi-vegetarian, those who ate fish and poultry, but
3. Non-vegetarian, referring to the remaining subjects (49.2%).
(Only 2–3% of Seventh-day Adventists are vegans.)
A review of all medical records for evidence of a cancer or IHD diagnosis; pertinent portions of the records were microfilmed to allow confirmation of the diagnosis by senior medical personnel. All electrocardiograms were microfilmed and coded (5), and computerized record linkage (6) was also used to detect new cancer cases.
In addition, computerized matching with state death tapes and the National Death Index was used to identify fatal cases. A diagnosis of nonfatal myocardial infarction was confirmed if the international diagnostic criteria (7) were met.
Results
On average, the non-vegetarian Seventh-day Adventists consumed meat products ≈4.25 times/wk, and most of the meat was beef. The vegetarian Seventh-day Adventists consumed more tomatoes, legumes, nuts, and fruit, but much less coffee, donuts, and eggs. Non-vegetarian Seventh-day Adventists were much less likely to prefer whole-grain bread and also consumed alcoholic beverages 20 times more frequently than their vegetarian counterparts.
Thus, when comparing the health experiences of vegetarian and nonvegetarian Seventh-day Adventists, we cannot initially infer that any effects are due to differences in meat consumption.
The prevalence of obesity, hypertension, diabetes, and arthritis at baseline, confirmed by physicians’ diagnoses, were strikingly different among the 3 dietary subgroups of Seventh-day Adventists.
- Obesity increased as meat consumption increased such that a 5’ 10” male non-vegetarian weighed 14 lb more on average than did his vegetarian counterpart. A 5’4” female revealed a weight difference of 12 lb. These results were for subjects aged 45–60 yrs, but similar results were seen for the other ages.
- Hypertension and diabetes were both 2-fold greater in the non-vegetarians than the vegetarians.
- Rheumatoid arthritis and rheumatism was 50% greater. (These results were statistically significant, consistent for both sexes, and adjusted for age.)
- Beef consumption of 3 times/wk had a 2.31-fold greater risk than did the vegetarian men. However, no associations were found between beef consumption and fatal IHD inwomen.
Nuts and Whole-Grain Bread
The food that was most consistently associated with reduced risk of both fatal and nonfatal IHD was nuts. Those who ate nuts 4–5 times/wk had only 50% of the risk of those who ate nuts ≤ 1 time/wk.
We found this association to be consistent across many different subgroups of the population (9). The association could not be explained by confounding with vegetarian status because it was found equally within both vegetarian and non-
vegetarian segments of the Seventh-day Adventist population.
The other food that predicted risk of IHD was a preference for whole-grain bread. Those who preferred whole-grain bread had relative risks of 0.89 for fatal IHD and 0.56 for nonfatal IHD in comparison to subjects who preferred white bread, after adjusting for all non-dietary risk factors and consumption of 7 other foods (9).
We also noted that the effects of traditional risk factors for IHD, such as diabetes, hypertension, past smoking, obesity, and physical inactivity, were seen in this Seventh-day Adventist cohort (11), just as in other study populations.
Associations of cancer risk with vegetarian status (adjusted for age, sex, and smoking habits where appropriate) were shown for the more common cancers. Both colon and prostate cancer were significantly more common among the non-vegetarian Seventh-day Adventists.
Despite careful searching, no clear dietary associations with breast cancer could be found in this population. However, the risk of prostate cancer was 54% greater in the non-vegetarians. The lower risk in vegetarians appeared to be associated with higher consumption of dried fruits and perhaps tomatoes and lower consumption of fish (14).
The data indicates that both red meat and white meat consumption increase the risk of colon cancer. It was also noted that legume consumption appeared to have a protective effect against colon cancer.
A strong inverse association was found between fruit consumption and risk of lung cancer in this largely nonsmoking population. (17) This association was found after cigarette smoking history, age, and sex were adjusted for, and occurred for both of the main histologic subtypes. (18)
Associations between fruit consumption and all incident lung cancers in California Seventh-day Adventists adjusted for age, sex, and cigarette-smoking history. Using a multivariate, multiple-decrement-lifetable approach (19), we showed that vegetarian Seventh-day Adventist women live 2.52 yrs longer than non-vegetarians.
Discussion
Our findings strongly suggest that dietary factors have an important influence on longevity and the risk of a number of chronic diseases. In general, we found that:
1. Vegetarians had lower risks of obesity, hypertension, diabetes, arthritis, colon cancer, prostate cancer, fatal IHD in males, and death from all causes.
2. The consumption of nuts and whole-grain bread were protective against both fatal and nonfatal IHD, whereas beef consumption was hazardous for males.
3. The consumption of fruit and legumes appeared to be protective against a number of cancers, whereas meats probably increase the risk for cancers of the colon and bladder.
It is important to note that vegetarians may have lower disease risk because of their lack of meat consumption, but it is equally possible that this protection could be due to increased consumption of fruits, vegetables, or nuts. Upon multivariate analysis, the latter often appeared to be the case.
It is now well-known that vegetables, fruit, grains, and nuts contain phytosterols and unsaturated fats that lower blood cholesterol concentrations. These same foods contain dietary fiber, which also lowers blood cholesterol and may protect against colon cancer (20).
In addition, the content of a number of antioxidant substances (eg, tocopherols, ascorbate, carotenoids, saponins, and flavonoids) may reduce the risk of heart disease by preventing the oxidation of LDL cholesterol. They may also reduce the risk of cancer by preventing oxidative damage to nucleic acids and other cellular components (21). A variety of indoles and isothiocyanates that are present in or formed from cruciferous vegetables activate phase II enzymes that can help detoxify carcinogenic substances and may also inhibit phase I enzymes that convert procarcinogens to carcinogens (22).
In contrast, meat products contain no dietary fiber and often contain substantial quantities of cholesterol and saturated fats that raise LDL-cholesterol concentrations. Meats do not contain significant amounts of phytochemicals, although small quantities may be found in meats as a consequence of the animals having eaten plants. Moreover, there is some evidence that the process of heating and cooking meats, particularly if there is any burning, may form compounds such as polycyclic aromatic hydrocarbons and heterocyclic amines that are carcinogenic (23, 24). Consumption of meat has also been shown to increase fecal content of potentially carcinogenic N-nitroso compounds (25). Thus, our results are largely in keeping with findings from basic research.
Although there is wide variation, it should be noted that the average Seventh-day Adventist vegetarian does not consume a low-fat diet. Estimates from our 1976 studies of Seventh-day Adventists showed that the average fat consumption was 100.5 g/d in vegetarians and 102.2 g/d in non-vegetarians. The difference between these groups was in the type of fat consumed; the ratio of polyunsaturated to saturated fats was 0.83 in the vegetarians and 0.63 in the non-vegetarians. Thus, the improved health experience of Seventh-day Adventists as a whole and particularly vegetarian Seventh-day Adventists has not required a low-fat diet, but rather the relative avoidance of saturated, primarily animal fats in favor of diets emphasizing vegetables, fruit, nuts, and grains.
Preliminary data suggest that very-low-fat diets such as those consumed by vegans do not clearly reduce total or cause-specific mortality (26) below the rates seen in the more liberal vegetarians, although more evidence is needed.
Our findings that vegetarian dietary habits were associated with reduced prevalence of diabetes, hypertension, and arthritis invite further exploration but may be partially explained by the lower prevalence of obesity among vegetarians. Previously published data suggest that mortality associated with diabetes mellitus is considerably lower in California Seventh-day Adventists compared with non-Adventists, as well as for vegetarian compared with nonvegetarian Seventh-day Adventist men (27).
The apparent marked difference between men and women in the effect of beef consumption on risk of fatal IHD is of interest, but may be due in part to chance. Note that for women consuming beef ≥3 times/wk, our result allows for the possibility of a relative risk of 1.56 within the 95% CI, despite the best estimate of 0.76. Relevant to this is the recent pooled analysis of vegetarian cohort studies (26) that included this study and did show a significant hazardous effect for nonvegetarian women, although it was not as strong as that seen in men.
It has been argued that risk of IHD in women is at least as responsive to lower blood HDL cholesterol concentrations as in men, but less responsive to LDL cholesterol concentrations (28,29) than in men, and that HDL concentrations drop further in women than men on a low-fat diet (30–32). HDL concentrations are a little lower in Seventh-day Adventists than non-Adventists (33–36), probably because of the trend toward vegetarian, modestly lower-fat diets. However, the decrement in HDL cholesterol concentrations for Seventh-day Adventist women is small and the large sex difference in HDL concentrations is maintained in Seventh-day Adventists.
In Summary
It is clear that for cancers of the colon and prostate, and fatal heart disease in men, vegetarian Seventh-day Adventists have an advantage over their nonvegetarian counterparts. This is probably also true for risks of diabetes mellitus, hypertension, and arthritis. Moreover, these effects are related to both the reduced consumption of meat and the increased intake of fruit, vegetables, grains, and nuts by the vegetarians. Making comparisons within this special population reduces the likelihood of confounding by other non-dietary factors. The absence of tobacco and the limited use of alcohol in this population also reduce the likelihood of confounding.
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