Environmental Factors influence Human Biochemistry
Although our genetic makeup (and that of our microbiomes ) is an important factor that contributes to disease susceptibility and to other traits,factors in a person’s environment also are significant. What are these environmental factors? Perhaps the most obvious are chemicals that we eat or are exposed to in some other way. The adage “you are what you eat” has considerable validity; it applies both to substances that we ingest in significant quantities and to those that we ingest in only trace amounts.Throughout our study of biochemistry, we will encounter vitamins and trace elements and their derivatives that play crucial roles in many processes. In many cases, the roles of these chemicals were first revealed through investigation of deficiency disorders observed in people who do not take in a sufficient quantity of a particular vitamin or trace element.Despite the fact that the most important essential dietary factors have been known for some time, new roles for them continue to be discovered.A healthful diet requires a balance of major food groups. In addition to providing vitamins and trace elements, food provides calories in the form of substances that can be broken down to release energy that drives other biochemical processes. Proteins,fats, and carbohydrates provide the building blocks used to construct the molecules of life.Finally, it impossible to get too much of a good thing. Human beings evolved under circumstances in which food, particularly rich foods such as meat,was scarce. With the development of agriculture and modern economies, rich foods are now plentiful in parts of the world. Some of the most prevalent diseases in the so-called developed world, such as heart disease and diabetes, can be attributed to the large quantities of fats and carbohydrates present in modern diets. We are now developing a deeper understanding of the biochemical consequences of these diets and the interplay between diet and genetic factors.Chemicals are only one important class of environmental factors. Our behaviors also have biochemical consequences. Through physical activity, we consume the calories that we take in, ensuring an appropriate balance between food intake and energy expenditure. Activities ranging from exercise to emotional responses such as fear and love may activate specific biochemical pathways, leading to changes in levels of gene expression, the release of hormones, and other consequences. Furthermore,the interplay between biochemistry and behavior is bidirectional. Just as our biochemistry is affected by our behavior, so, too, our behavior is affected, although certainly not completely determined, by our genetic makeup and other aspects of our biochemistry. Genetic factors associated with a range of behavioral characteristics have been at least tentatively identified.Just as vitamin deficiencies and genetic diseases have revealed fundamental principles of biochemistry and biology, investigations of variations in behavior and their linkage to genetic and biochemical factors are potential sources of great insight into mechanisms within the brain. For example,studies of drug addiction have revealed neural circuits and biochemical pathways that greatly influence aspects of behavior. Unraveling the inter play between biology and behavior is one of the great challenges in modern science, and biochemistry is providing some of the most important concepts and tools for this endeavor.
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