Epidemiology is a broad field that encompasses more than just anatomy or physiology or disease. Moreover, a fundamental understanding of biochemistry and molecular/cellular biology is integral to the study of biomedicine.
From the CDC website:
http://www.cdc.gov/excite/epidemiology.html
Epidemiology can include clinical and molecular epidemiology, which consider microorganisms and biochemical processes. Epidemiology can include looking at regional or global health outcomes for any of a number of things, including (but not limited to) specific diseases and pathogens, obesity, nutrition, mental health, occupational injuries, pollution, environmental hazards, or natural disasters. Consequently, you can study any of a number of things–molecular biology, biochemistry, kinesiology, applied physiology, nursing, psychology, anthropology, environmental science, to name a few–and go on to the field of epidemiology and public health. Most important, perhaps, is math/statistics, as most modern epidemiological study involves using statistics and quantitative methods to examine these things.
Regardless of what you major in, if you want to study epidemiology/public health, it would serve you well to take courses in math/statistics/bioinformatics/biostatistics.