Ninety-six thousand Seventh-day Adventists, ages 30 to 112, from all 50 U.S. states and Canada were enrolled in the second Adventist Health Study (AHS-2) from 2002 to 2007, including 25 percent African American participants and smaller proportions of other racial and ethnic minorities. Although the study has now resulted in more than 200 reports in the medical literature from AHS-2, you may reasonably say, “What does that mean for me?”
We already know that Adventists are particularly long-lived on average—part of a so-called Blue Zone. We also know that red meat consumption increases risk of several disorders, and that nut consumption protects against heart disease and possibly some other problems. More recently we found that meat protein is associated with higher risk and nut protein with lower risk of heart disease. Thus, it may not only be fats that are relevant to disease risk.
Vegetarianism
In AHS-2 we have focused mainly on Adventists who eat differently from each other. These include nonvegetarians (about 50 percent of our study Adventists) who nevertheless are generally more health-conscious than the average American. They eat meats only about three times per week, at least half of these being chicken or fish. Then there are pesco-vegetarians (about 8 percent of AHS-2) who eat only fish as a flesh food; lacto-ovo-vegetarians (about 32 percent of AHS-2), who consume no flesh foods, but as with the pesco-vegetarians may eat dairy foods and eggs; and finally total vegetarian Adventists (about 8-9 percent of AHS-2), who eat no animal products at all.
Many common afflictions of middle and later life are caused by inflammation at the cellular level. These include heart disease, diabetes, many cancers, autoimmune disorders (such as rheumatoid arthritis and systemic lupus erythematosus [SLE]). All categories of vegetarians have lower levels of C-reactive protein (CRP), a marker of inflammation, especially the total vegetarians as compared to nonvegetarian Adventists. Further, all vegetarians have markedly lower body weights (adjusting for height) as compared to nonvegetarians. This is important, as excess fatty tissue produces chemicals that enhance inflammation. Vegetarians have markedly lower rates of diabetes, an inflammation-mediated disorder in which, in adult-onset diabetes, insulin does not work as well as it should. Our data show that eating mainly plant foods is associated with better sensitivity to insulin, and that an omega-3 fatty acid from plant foods, alpha-linolenic acid (ALA, found especially in soy, flaxseed, chia, and walnuts), appears to be responsible for this. We have seen that many of these seem to be at highest levels in the blood and adipose tissues of our total vegetarians.
We also analyzed the apparent effects of meats and dairy. We have not documented any adverse effects of fish or poultry, except to say, for poultry at least, that it can matter greatly what one may choose to replace it with after it is eliminated. We have evidence that vegetable sources of protein that may replace poultry, such as whole grains, legumes, or nuts, will often have protective properties not possessed by the poultry. Fish may have some protective properties. Red meats, their dense calories, their lack of dietary fiber, their saturated fats, and probably some of their proteins increase the risk of overweight, diabetes mellitus, heart disease, and colorectal (and perhaps some other) cancers. They have little to recommend them.
We would note that Black church members should understand that our findings show that they have approximately the same trends with diet and health reported here. There is strong evidence that healthy dietary patterns are important in reducing or addressing health disparities among Black Americans as well.
Cancers
Three cancers are particularly common in Western societies: colorectal cancer, breast cancer in women, and prostate cancers in men. While the lifestyle recommended by Adventists may not protect from all chronic diseases, it protects from many of these, sufficient to make it clearly beneficial.
There is good evidence from many sources that red meat, particularly processed red meat, increases risk of colorectal cancer. Results from AHS-2 are consistent with this. It is also worth noting that the pesco-vegetarians had a particularly lower risk of colorectal cancer, and that was unlikely to be a result of chance. Further study is needed to determine if it was the fish or some other characteristic of the pesco-vegetarians that led to a lower risk.
Many studies, including AHS-2, find that dairy consumers have lower risk of colorectal cancers, so total vegetarians who consume no dairy, get a little less protection here than other vegetarians. But our data, drilling a little deeper, suggest that this dairy effect on colorectal cancer is likely due to dairy’s calcium content, and calcium is also easily found in a wide variety of vegetable products.
In AHS-2 we noted that two hormone-responsive cancers, breast cancer in women and prostate cancer in men, were 25-35 percent less common in total vegetarians, but not at all less frequent in lacto-ovo- or pesco-vegetarians, when compared to nonvegetarians. We have now analyzed and reported apparently clear trends of increased risk of these two cancers with some dairy products, in particular, dairy milk. We found little or no discernible effect for cheese and yogurt. The dairy milk association seemed almost pharmacologic, starting to accumulate at quite small amounts of regular, long-term consumption. The maximum effects (at least a 50 percent increase in risk) were achieved at only ¾ cup per day. We speculate that this may be related either to sex hormones from the cows, which are found in small quantities in milk particularly, or to effects of milk protein on a hormone called IGF-1, which is thought to increase risk of both of these cancers. Low-fat and regular fat milks had almost identical effects, suggesting that it is not the milk fat that may be causing the problem.
Overall vegetarian Adventists have about 10 percent lower risk of all cancers combined, when compared to nonvegetarian Adventists. Turning to the specific types of vegetarians, total vegetarians have about a 20 percent lower risk of all cancers combined, lacto-ovo-vegetarians about 10 percent lower risk, pesco-vegetarians about 15 percent lower risk, each when compared to nonvegetarian Adventists. But when we compare all Adventists to non-Adventists, there is at least a 30 percent lower risk. This tells us that even the relatively health-conscious nonvegetarian
Adventists are gaining some benefit and have less cancer risk than non-Adventist Americans.
Other Disorders
Although our focus was mostly on cancer, we have taken the opportunity to explore possible effects of lifestyle on a small number of other disorders. There is little doubt that Adventist vegetarians do much better than Adventist nonvegetarians with respect to risk of diabetes, high blood pressures, and blood cholesterol levels. In all of these, the total vegetarians do best of all, followed by lacto-ovo-vegetarians and pesco-vegetarians. We have found, however, that total vegetarians tend to have a higher risk of bone fractures (and thus presumably osteoporosis), but for them, this can be largely mitigated by adequate calcium and vitamin D supplements. For everyone, regular vigorous physical activity and adequate (but not excessive) animal or vegetable dietary protein is usually adequate to promote good bone health.
Recent AHS-2 publications also indicate that the autoimmune disorder SLE is less prevalent in vegetarians, perhaps partially related to higher intake of the ALA omega-3 fatty acid. This is preliminary work that needs more study to further support causal connections.
One of our reports that got much attention in the press was that we found Adventists who spaced their meals such that there was a long (perhaps 16-hour) “fast” overnight had less weight gain over several decades of adult life. We also found that those preferring to make breakfast their main meal did well in this regard. It is noteworthy that the recently promoted “16/8” diet to lose weight has become popular and for many works well without great feelings of hunger. To have perhaps a little later breakfast and a little earlier supper about eight hours later is one option, although other plans with similar spacings are possible.
Total Mortality
The final focus of AHS-2 results is how diet relates to total mortality—the risk of dying during a particular age. Often as doctors we encounter elderly keenly health-conscious Adventists who are discouraged, and sometimes angry, that they now suffer from a chronic disease. While we can and do sympathize with their distress, it is worth pointing out that protection afforded by a healthy lifestyle is that of a lower risk, not the absence of risk. Second, Adventists do finally suffer from essentially the same disorders as others. The benefit is that they usually come at later ages. That is how we live longer on average, and with better quality of life.
At younger years (about 65 years of age), lower risk of dying from any cause is found in male vegetarians (about 16 percent lower, especially in total vegetarian males), and in women about 8 percent lower, compared to Adventist nonvegetarians. In later years, however (say, 75 years of age and above) we do not find clear evidence of a total mortality benefit for the vegetarians as a group. Comparing the various dietary patterns, pesco- and lacto-ovo-vegetarians seem to do the best for overall total mortality. So it seems that vegetarian diets, as we currently practice them, are especially tending to prevent premature deaths at younger ages, allowing more of us to achieve older ages. In those who have survived that long, however, the advantage in total vegetarians and lacto-ovo-vegetarians for total mortality then becomes harder to detect. Some advantage seems to persist at older ages for pesco-vegetarians.
One area of potential concern is a signal of increased deaths in vegetarians related to neurological diseases (such as stroke, dementia, and Parkinson’s disease), but only in old age. More research is under way to give more clarity, especially in regard to potential nutrients that could explain this difference and may be targets for supplementation if there is evidence of deficiency. Nonetheless, when compared to a U.S. Census population, total deaths in vegetarian and nonvegetarian Adventists combined are estimated at 33 percent and 22 percent lower at younger and older ages, respectively.
Our bodies, their physiology and chemistry, are marvelously complex, but as we age, many bodily functions tend to become less efficient. Vitamin B12 is absorbed less well by the stomach, for instance, and the skin does less well when using sunlight to form vitamin D. Total vegetarians, and many lacto-ovo-vegetarians, should supplement B12 as they grow older.
Summary
In summary, it is clearly true that Adventists as a group are doing better than others, and this includes the nonvegetarians! The vegetarian Adventists are doing better yet. This is especially so for the pesco- and lacto-ovo-vegetarians, and male total vegetarians, when looking at total mortality. More of us are living to older ages. In our latest, more comprehensive data, however, we do not find any clear overall mortality (longevity) advantage for total vegetarian women, though male total vegetarians are especially protected from deaths at earlier ages, as compared to nonvegetarians.
As compared to nonvegetarians, total vegetarians especially and also other vegetarians are doing particularly well as far as less heart disease, kidney disease, diabetes, and high blood pressure, thus “delivering” more of us to those older years. Despite this, it appears that for some in their later years the vegetarian advantage may then be offset by not doing quite so well from neurological diseases, when compared to low meat-and-fish-consuming elderly nonvegetarian Adventists.
Clearly, diet is very complex. Medical and dietary research results in a constantly changing picture. What we will write in 10 years is likely to have some differences from what we write today, but hopefully these differences will be relatively minor, mainly filling gaps in our present understanding. What we can say with confidence is that the Adventist “health message” has resulted in many hundreds of thousands of extra good quality years of life among church members, this over five to six generations.
