Extensive studies of coronary heart disease have been conducted among Adventists, both in the United States and abroad. However, the Adventist Health Study has gone an important step further in collecting data on both fatal and non-fatal cases of coronary heart disease.
For fatal cases of coronary heart disease, the older Adventist Mortality Study found that the mortality rates for Adventist men in particular were only 66 percent as compared to their non-Adventist counterparts. When compared only to non-smoking non-Adventists, the figure rose to 76 percent. Differences for women were less impressive.
Studies of risk factors associated with coronary heart disease in Adventists have also been done since the early 1950s. Typically, serum cholesterol levels have been shown to be significantly lower for Adventists when compared to non-Adventists. Actual levels have generally been at least 10 to 30 milligrams per deciliter lower.
More recently, Dr. Fraser and his colleagues looked at 160 randomly selected Adventist middle-aged men and a similarly-aged non-Adventist group of neighbors in Southern California. This study was one of only a few studies to look at lipoprotein subfractions in Adventists. They found the HDL cholesterols to be 42.3 in Adventists as compared to 46 in non Adventists. The LDL cholesterols were 125.1 in Adventists and 134.0 in non-Adventists. Though the ratio between the HDL and LDL levels was similar, the differences in levels of the component lipoproteins were highly statistically significant. It is noted that lower levels of HDL cholesterol are characteristic of populations with lower fat intakes. The risk meaning of this lower level in vegetarians is unknown. Some controversy surrounds the risk factor of high blood pressure in vegetarians. However, both Adventist and non-Adventist vegetarians probably experience a reduction of 4 to 5 millimeters systolic and 2 to 3 millimeters diastolic, considered to be a relatively minor difference.
The risk factor of little or no exercise has not been studied to any great extent in Adventists. However, in the study of 160 middle-aged Southern California Adventists and their neighbors, the question was asked, "How many times each week do you exercise enough to provoke a sweat?" In Adventists, the responses were 2.38 times per week and the non-Adventists said 1.5 times per week, or one third less. In this case, the difference in exercise habits was highly statistically significant. The risk factor of obesity has also received very little attention in Adventists. However, in the previously mentioned study, the Quetelet index of obesity in Adventists showed very little difference from their non-Adventist neighbors.
It has been argued that Adventist populations are so unique in their lifestyles that none of the findings can be accurately applied to general non-Adventist populations. To counter that argument, Dr. Fraser and his colleagues investigated the associations between the factors of age, sex, diabetes mellitus, hypertension, cigarette smoking, physical activity, and obesity and the incidence of both fatal and non-fatal heart disease in the Adventist Health Study population. They also used several statistical models to analyze their data. It was found that these risk factors seemed to have the same role in predicting heart disease among Adventists as had been repeatedly shown in non-Adventist populations. Also, the various statistical models were consistent with each other in their results.
Within the Adventist population there was a doubling of risk for definite myocardial infarction when comparing diabetics to non-diabetics, a nearly three-fold elevation in risk when comparing hypertensive Adventists to normal Adventists, and an elevation in risk of heart attack for current and past smokers, as compared to those who had never smoked. In the analysis of obesity, using the Quetelet index, the relationship between moderate to high body mass and increased risk of heart attack was more than two-fold. Comparing the sexes, the risk of myocardial infarction in men was 2.87 times higher than women, and the risk of definite fatal coronary heart attack in men was 1.90 times higher than women. The investigators could safely conclude that their results were very similar to non-Adventist populations, implying that associations between dietary factors and heart disease found in Adventists would also probably apply to the population at large.
A series of nutritional questions, included in the questionnaire and based on 55 food items, provided the basis for some new findings. For example, a dietary question would read "Mark the box that comes the closest to how frequently you use each food when following your usual routine. Responses ranged from "never consume" to "more than once a day." For bread, the question read "What one type of bread do you use most of the time?" with options being "white," "100% whole wheat or whole grain," "sprouted wheat or wheat berry," and "other"--meaning rye, cracked wheat, pumpernickel, or soy. Responses for the various fruit and beef questions were summed to form indices for each. The researchers went a step further and validated the adequacy of the dietary questionnaire, using a dietary substudy conducted on 147 randomly-selected local study subjects. These individuals answered a questionnaire with the same questions on it and also completed five random 24-hour recalls during a three-month period.
Diet and Heart Disease
The effects of diet on the risk of coronary heart disease (CHD) are of increasing interest in heart disease research. The dietary questions included in the questionnaire showed that 21 percent of the Adventists said that they consumed beef more than twice a week, 10 percent ate fish as often as once a week, 35 percent admitted to coffee use, 77 percent consumed primarily whole wheat bread, 66 percent ate nuts at least once a week with 24 percent eating nuts more than four times a week, and 81 percent ate fruit at least once a day with 49 percent eating fruit at least three times a day.
The research team found 134 new cases of definite non-fatal CHD and 260 new cases of fatal CHD during the six-year follow-up period. In each of these new cases, no history of heart disease existed at the beginning of the study. The most striking findings of this nutritional analysis suggested that both nuts and whole wheat bread significantly reduced the risk of CHD, and this will be discussed in more detail in the next section. Evidence was also found showing a relationship between eating beef and fatal heart attacks in males. Adventist men who ate beef more than two times a week experienced a significant increase in fatal CHD.
Worldwide attention to certain findings of The Adventist Health Study should not detract from other significant findings relating to the consumption of whole wheat bread and beef. The researchers found that individuals in the study who consumed mainly whole wheat bread had a relative risk of 59 percent for non-fatal coronary heart disease, and 89 percent for fatal heart disease, compared to those who mainly ate white bread. This suggests that eating whole wheat bread does indeed protect against heart disease.
In contrast, consuming beef seemed to increase the risk of fatal coronary heart disease for men. Those who ate beef up to three times a week had a risk nearly two times greater than those who said they never ate beef. And men who consumed beef at least three times a week showed more than twice the relative risk compared to those who never ate beef. On the other hand, beef consumption did not clearly change the risk of heart disease in women.