Risk Factors and Disease
Vegans avoid all animal products in their diet, even eggs and dairy products. The reason for these choices is often animal rights rather than the expectation of better health. One might, however, predict that certain risk factors would have even more favorable values for vegans than for lactoovo vegetarians since the intake of saturated fats, cholesterol, and sodium is lower still in vegans, and their consumption of dietary fiber and potassium is greater. If a lacto-ovo vegetarian diet is beneficial, do vegans gain even further benefits? Evidence that addresses this question is presented in this chapter.
My intention is not to establish the nutritional adequacy of the vegan diet in terms of recommended daily allowances for nutrients and vitamins, but, in keeping with the rest of this book, to focus on the risk for common chronic diseases. However, a vegan diet is nutritionally adequate if certain precautions are taken (see Chapter 15), and these have been succinctly reviewed by the American Dietetic Association (ADA Reports, 1997).
In comparison with lacto-ovo vegetarians, vegans, in some settings at least, consume less total energy and generally obtain a greater percentage of calories from carbohydrates, and less from fats (particularly saturated fats), and show a higher ratio of dietary polyunsaturated fats to saturated fatty acids (Famodu et al., 1999; Li et al., 1999; Toohey et al., 1998). In addition, vegan diets contain very little vitamin B12 without supplements (Rauma et al., 1995a), but the level of fiber and folate consumption is often high, especially if expressed as a percentage of calories (Famodu et al., 1999; Roshanai and Sanders, 1984; Toohey et al., 1998). Intake of antioxidant vitamins, and their serum levels, may be much higher in vegans than in omnivores (Rauma et al., 1995b), but it is not certain whether there are consistent differences between vegans and lacto-ovo vegetarians (Toohey et al., 1998).