Mechanical digestion begins the process of digestion. Otherwise known as chewing, it "involves mixing, grinding, or crushing large pieces of food into small pieces" (Lab: Mechanical and chemical digestion, n.d, Chapter 38). In contrast, the process of chemical digestion occurs inside of the body within the digestive organs, "when digestive enzymes break down complex molecules, such as carbohydrates, into simple molecules, such as glucose" (Lab: Mechanical and chemical digestion, n.d, Chapter 38). When digesting a ham and cheese sandwich, first the teeth grind the sandwich mechanically. Then this is followed by the process of breaking down the food chemically within the body. While mechanical digestion is a willed activity in the sense we select the foods we eat and how much we chew, chemical digestion is not.
During the process of chemical digestion, "the parietal cells of the stomach produce HCl and secrete it primarily in response to ingested protein or fat" (in the cheese and the ham) and protect the stomach against harmful bacteria that might have entered the body during food preparation or consumption (Haas 2012). After the food leaves the stomach, "the small intestine carries out most of the digestive process, absorbing almost all of the nutrients you get from foods into your bloodstream. The walls of the small intestine make digestive juices, or enzymes, that work together with enzymes from the liver and pancreas to do this" (Organs: Large and small intestines, 2013, Children's Hospital of Pittsburgh). By the time the food reaches the large intestine, it consists mainly of dead cells and fiber. 'Helpful' bacteria in the large intestine "feed on this mixture. These helpful bacteria produce valuable vitamins that are absorbed into your blood, and they also help digest fiber" (Organs: Large and small intestines, 2013, Children's Hospital of Pittsburgh).
Q2. Food Safety & Technology
Technology such as refrigeration and preserving has vastly improved the ability of human beings to eat a wider variety of foods safely, year 'round. "Yeasts, moulds and bacteria" are the primary causes of food spoilage (Causes of the spoilage of food, n.d., Food Preservation). As well as being unpleasant to look at and taste in most forms, spoilage and contamination can cause illness in humans. The core principles of food safety include proper hygiene (hand-washing, wearing protective gloves, not working while ill); keeping food at the proper temperature through heating or refrigeration; by cooking food until done (keeping food out of the danger zone of bacterial growth of 140-41F); and avoiding cross-contamination (such as not using the same knife to cut raw poultry and vegetables for example) (The basic principles of food safety, 2006, NH Department of Health & Human Services).
Eating organic food does not mean that one automatically is eating food that is safe. However, according to the USDA, "organic produce and other ingredients are grown without the use of pesticides, synthetic fertilizers, sewage sludge, genetically modified organisms, or ionizing radiation. Animals that produce meat, poultry, eggs, and dairy products do not take antibiotics or growth hormones… Organic-certified operations must have an organic system plan and records that verify compliance with that plan" (Organic FAQ, 2013, Organic.org). Organic food can still be contaminated with pathogens, but there are other health risks many consumers want to avoid association with the consumption of pesticides and antibiotics.
Carbohydrates are the body's most easily available energy source, and are critically necessary to engage in short bursts of activity. "The carbohydrate in foods is broken down to glucose (blood sugar). Glucose can be used immediately for energy or converted to glycogen and stored in the liver and muscle tissue. Muscle glycogen provides immediate fuel for exercising muscles" (Barke 2005). Carbohydrates are also necessary for endurance, given that the body cannot break down fat for fuel in the absence of adequate carbohydrate intake. And "a high carbohydrate eating plan helps preserve lean body mass (since more protein is broken down when inadequate carbohydrate is available for energy)" (Barke 2005).
Not eating enough carbohydrates can actually be dangerous, given that the brain, heart, and kidney rely upon carbohydrates to function. "If your diet does not include enough carbohydrates your body will take extreme measures to get the energy it needs; it will feed on carbohydrates stored in muscles and attempt to chemically break down the proteins you eat until those proteins…