Carbohydrates

Carbohydrates are the sugars, starches and fibers; one of the basic food groups.

1. Sugar is the generalized name for sweet, short-chain, soluble carbohydrates, many of which are used in food. They are composed of carbon, hydrogen, and oxygen. Simple sugars are called monosaccharides and include glucose (or dextrose), fructose, and galactose. The table sugar most customarily used as food is sucrose - hydrolyses into fructose and glucose in the body. Other disaccharides include maltose and lactose. Longer chains of sugars are called oligosaccharides. 
2. Starch is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants as an energy store. It is the most common carbohydrate in human diets and is contained in large amounts in staple foods such as potatoes, wheat, maize (corn), rice. Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol. 
3. Fiber is consists of non-starch polysaccharides such as arabinoxylans, cellulose, and many other plant components such as resistant starch, resistant dextrins, inulin, lignin, chitins, pectins, beta-glucans, and oligosaccharides, and are derived from plants. 
   1. Dietary fibers are not digested by gastrointestinal enzymes. 
   2. Soluble fiber dissolves in water, changes as it goes through the digestive tract, where it is fermented by bacteria, partially into physiologically active byproducts - healthful compounds. 
   3. Insoluble fiber does not dissolve in water and stays intact as it moves through your digestive system, can be prebiotic and metabolically ferment in the large intestine. Dietary fibers can change absorption of other nutrients and chemicals. Some soluble plant fibers can modulate intestinal inflammation and are contrabiotic. Many types of so-called dietary fiber are not actually fibrous.

Food energy is chemical energy that animals derive from their food and molecular oxygen through the process of cellular respiration to sustain their metabolism and to drive their muscles.

 Organisms derive food energy from carbohydrates, fats and proteins as well as from organic acids, polyols, and ethanol present in the diet.

Energy is measured in joules (J). The kilojoule (kJ) is most often used for food-related quantities.

The "food calorie" or kilocalorie (kcal or Cal), equal to 4.184 kilojoules. "Small calorie" (cal), equal to 1/1000 of a food calorie, that is often used in chemistry.

Fats and ethanol have the greatest amount of food energy per mass, 37 and 29 kJ/g (8.8 and 6.9 kcal/g), respectively. Proteins and most carbohydrates have about half of that: 17 kJ/g (4.1 kcal/g).

Amount of Food Energy per Mass:

1. Fats: 37 kJ/g (8.8 kcal/g);
2. Ethanol: 29 kJ/g ( and 6.9 kcal/g).
3. Proteins and most carbohydrates: ~ 17 kJ/g (4.1 kcal/g);
4. Organic acids: 13 kJ/g (3.1 kcal/g);
5. Polyols, including sugar alcohols: 10 kJ/g (2.4 kcal/g);
6. Fiber: 8 kJ/g (2 kcal/g).

Conventional food energy is based on heats of combustion in a bomb calorimeter and corrections that take into consideration the efficiency of digestion and absorption and the production of urine.

The amount of water, fat, and fiber in food determines its energy density.

About 20% of the energy is used by brain. Much of the rest is used for the basal metabolic requirements of other organs and tissues.

Fats are one of the three main macronutrient groups in human diet.

Foods containing dietary fat have a mix of specific types of fats. Fats are made up of saturated and unsaturated fatty acids and called saturated or unsaturated depending on how much of each type of fatty acid they contain.

Fats are compounds of fatty acids.

• Unsaturated fats, liquid at room temperature - predominantly found in nuts and seeds.
  Evidence clearly shows that unsaturated fat remains the healthiest type of fat. The American Heart Association suggests that 8-10 percent of daily calories should come from polyunsaturated fats. Monounsaturated fats can lower blood pressure, improve blood cholesterol levels, ease inflammation, stabilize heart rhythm, and reduce the cardiovascular risk.
  • Monounsaturated - found in high concentrations in peanuts, avocados, olives, almonds, hazelnuts, pecans, pumpkin and sesame seeds.
  • Polyunsaturated fats - in sunflower seeds, soybeans, flaxseeds, walnuts.
• Trans fats, or trans-unsaturated fatty acids, are made by heating liquid vegetable oils in the presence of hydrogen gas and a catalyst, a process called hydrogenation, and naturally found in beef fat and dairy in small amounts. Trans fats are the worst type of fat for the body.
• Saturated fat is mainly found in animal foods, but also in a few plant foods: coconut and palm oil.
• The American Heart Association recommends limiting saturated fat to no more than 7 percent of calories.

Proteins are organic polymers composed of many amino acids joined together to form long chain.

Examples of proteins include antibodies, enzymes, and some types of hormones (insulin).

There are about 20 different amino acids that occur naturally in proteins.

Plants can synthesize all of the amino acids essential for life. 

Water is an essential nutrient - it is required in amounts that exceed the body's ability to produce it. Water is a transparent and nearly colorless chemical substance. Its chemical formula is H2O, meaning that its molecule contains one oxygen and two hydrogen atoms. All biochemical reactions occur in water. It fills the spaces in and between cells and helps form structures of large molecules such as protein and glycogen. 

Most foods contain water. The body can usually get 20% of its total water requirements from solid foods alone. The human body can last weeks without food, but only days without water. The digestion process also produces water as a byproduct and can provide around 10% of the body’s water requirements.  

Safe drinking water is essential to humans and other lifeforms even though it provides no calories or organic nutrients.

Water covers 71% of the Earth's surface. It is vital for all known forms of life.

• 97% of the planet's crust water is found in seas and oceans,
• 1.7% in groundwater,
• 1.7% in glaciers and the ice caps.

Only 2.5% of this water is freshwater, and 98.8% of that water is in ice (except in clouds) and groundwater. Less than 0.3% of all freshwater is in rivers, lakes.

Abut one billion people lack access to safe water. It was estimated that by 2025 more than half of the world population will be facing water-based vulnerability, and by 2030 water demand in some developing regions of the world will exceed supply by 50%.

Approximately 70% of the freshwater used by humans goes to agriculture.

Safe drinking water is essential to humans and other lifeforms even though it provides no calories or organic nutrients. ~One billion people still lack access to safe water. It was estimated that by 2025 more than half of the world population will be facing water-based vulnerability, and by 2030 water demand in some developing regions of the world will exceed supply by 50%.

Agriculture accounts for 92% of the freshwater footprint of humanity; almost one third relates to animal products.

https://doi.org/10.1016/j.wri.2013.03.001