Cohort Profile: The Adventist Health Study-2 (AHS-2)

The Adventist Health Study-2 (AHS-2) began in 2002 with the goal of investigating the role of selected foods to change the risk of cancer. AHS-2 is designed to provide more precise and comprehensive results than previous pioneering research among Seventh-day Adventists, a unique health oriented population with diverse dietary habits. The Adventist church, of 24 million adherents worldwide, promotes a healthy lifestyle. Church members are expected to be non-smokers and non-alcohol users, and are encouraged to eat a vegetarian diet. Many also avoid caffeine-containing beverages. However, adherence to these recommendations is quite variable. Adventists in North America are almost entirely a non-smoking population. The vast majority are nondrinkers and the small number who consume alcohol do so infrequently. But they have a wide diversity in dietary practices. Two previous longitudinal studies in California showed a small percentage are total vegetarians, many follow a lacto-ovo-vegetarian diet or eat meat less than once per week (semi-vegetarian) and about half have omnivorous diets similar to the general population. These studies in California, the Adventist Mortality Study (AMS) from 1960–66 and the first Adventist Health Study (AHS-1) from 1974–88 indicated that Adventists had lower risks for most cancers, cardiovascular disease and diabetes. Females lived 4.4 years and males 7.3 years longer when compared with the general California population. These studies also showed the advantage of a vegetarian diet among Adventists, found strong evidence that meat increased risk of colon cancer and coronary heart disease, and that nut consumption reduced risk of coronary heart disease. Other significant associations between cancers and other foods have also been reported. In the USA, it is estimated that there will be 1 444 920 new cases of cancer in 2007 (prostate 218 890, breast 180 510 and colon 112 340). It has been suggested that the lower incidence of prostate and breast cancer in the Far East may be due to the frequent consumption of soy. Adventists, in North America, with high levels and a wide range of soy consumption offer better opportunities than perhaps any other large group with a western diet to investigate the role of soy and other nutrients, such as calcium, in risk of cancers of the breast, prostate and colon. Thus, various characteristics of Adventists: the diversity in soy consumption and other foods, the virtual elimination of confounding from smoking and alcohol, the findings of previous studies and the potential to include a large group of AfricanAmericans resulted in the National Cancer Institute funding Loma Linda University to undertake AHS-2, with the goal to enroll 100 000 Adventists. Table 1 provides an overview and compares some characteristics of AHS-2 with the other Seventh-day Adventist cohort studies in California.