Additional analyses of the Adventist Health Study findings showed a remarkable relationship between eating nuts and whole wheat bread, and experiencing a reduced risk for coronary heart disease (CHD). These findings were the subject of a research article submitted by Dr. Fraser and his colleagues to the Archives of Internal Medicine, and published in its July 1992 issue. Substantial newspaper and television coverage resulted.
The most outstanding findings of this part of the overall study show that nut consumption reduces the risk of both fatal and nonfatal coronary heart disease. Again, the researchers looked for a variety of ways to disprove the finding, adjusting the data for differences in age, sex, smoking habits, exercise, relative weight, and hypertension. The protective qualities of nuts remained statistically significant and essentially unchanged in magnitude.
Those individuals who ate nuts one to four times a week had 74 percent the risk of suffering from definite nonfatal myocardial infarction and 73 percent the risk of definite fatal coronary heart disease as compared to those who ate nuts less than once a week. However, those individuals who ate nuts five or more times a week had only 52 percent the risk of definite nonfatal MI and a 62 percent risk of definite fatal CHD as compared to the group who ate nuts less than once a week.
Age- and sex-adjusted analyses of the associations between nut consumption and definite CHD were calculated for various subgroups within the Adventist Health Study. Results were examined to see if the association between nut consumption and CHD held up in different segments of the population. The consistency was quite remarkable and adds to the researchers' confidence in the importance of these findings.
In the following statistics, the percentages mentioned represent the groups eating nuts five or more times a week, as compared to those who ate nuts less than once a week. In the first example, the two sexes were evaluated separately and results compared. Men who ate nuts more than five times a week enjoyed a 40 percent risk and women a 52 percent risk, as compared to those who ate nuts less than once a week. Those less than 80 years old who ate nuts more than five times a week showed 47 percent the risk, and those more than 80 years old who ate nuts frequently had a relative risk of 45 percent compared to those individuals who ate nuts infrequently.
Both "ever-smokers" and "never-smokers" showed 54 percent the risk of coronary heart disease when they ate nuts five or more times a week. Study participants with normal blood pressure showed that eating nuts more than five times a week reduced their risk of coronary heart disease to 40 percent, and hypertensive individuals had a relative risk of 70 percent, compared to similar subjects who ate few nuts.
When eating nuts five or more times a week, vegetarians showed a risk of 44 percent as compared to low nut-eating vegetarians, and non-vegetarians a risk of 51 percent as compared to low nut-eating non-vegetarians. For exercise habits, those individuals classified as the "low exercise group" who ate nuts five or more times a week had a relative risk of 62 percent and those in the "high exercise group" had a relative risk of 39 percent.
Using the body-mass index, or BMI, as an index of obesity, those eating nuts more than five times a week with a BMI greater than or equal to 23.9 (that is, above average obesity), had 46 percent the risk of coronary heart disease and those with a BMI of less than 24 had a risk of 53 percent, when compared respectively to low nut consumers of a similar obesity status.
Thus, these associations are consistent and of sizeable magnitude, implying a probable causal relationship. Several mechanisms for this finding have been suggested, including the relationship between the high poly- and mono-unsaturated fat content of nuts and the lowering of blood cholesterol, the anti-oxidant properties of the high Vitamin E content of nuts, or the high arginine content in nuts (an amino acid precursor of nitric oxide), which leads to relaxation of the arterial walls. All three of these would tend to reduce atherosclerosis.
The study's strengths lie in the large size of the cohort group, the extensive data gathered on each subject, the inclusion of both men and women from a wide range of ages, and, perhaps most important, the wide range of nut consumption among Adventists.