In nutrition, diet is the sum of food consumed by a person or other organism. Dietary habits are the habitual decisions an individual or culture makes when choosing what foods to eat. The word diet often implies the use of specific intake of nutrition for health or weight-management reasons (with the two often being related). Although humans are omnivores, each culture and each person holds some food preferences or some food taboos. This may be due to personal tastes or ethical reasons. Individual dietary choices may be more or less healthy.
Proper nutrition requires ingestion and absorption of vitamins, minerals, and food energy in the form of carbohydrates, proteins, and fats. Dietary habits and choices play a significant role in the quality of life, health and longevity. It can define cultures and play a role in religion.
RELIGIOUS AND CULTURAL DIETARY CHOICES
Some cultures and religions have restrictions concerning what foods are acceptable in their diet. For example, only Kosher foods are permitted by Judaism, and Halal foods by Islam. Although Buddhists are generally vegetarians, the practice varies and meat-eating may be permitted depending on the sects. In Hinduism, vegetarianism is the ideal, Jain are strictly vegetarian and consumption of roots is not
permitted.
Many people choose to forgo food from animal sources to varying degrees (e. g. flexitarianism, vegetarianism, veganism, fruitarianism) for health reasons, issues surrounding morality, or to reduce their personal impact on the environment, although some of the public assumptions about which diets have lower impacts are known to be incorrect. Raw foodism is another contemporary trend. These diets may require tuning or supplementation such as vitamins to meet ordinary nutritional needs.
Weight management
A particular diet may be chosen to seek weight loss or weight gain. Changing a subject’s dietary intake, or “going on a diet”, can change the energy balance and increase or decrease the amount of fat stored by the body. Some foods are specifically recommended, or even altered, for conformity to the requirements of a particular diet. These diets are often recommended in conjunction with exercise. Specific weight loss programs can be harmful to health, while others may be beneficial (and can thus be coined as healthy diets). The terms “healthy diet” and “diet for weight management” are often related, as the two promote healthy weight management. Having a healthy diet is a way to prevent health problems, and will provide your body with the right balance of vitamins, minerals, and other nutrients.
Eating disorders
An eating disorder is a mental disorder that interferes with normal food consumption. It is defined by abnormal eating habits that may involve either insufficient or excessive diet.
Health
A healthy diet may improve or maintain optimal health. In developed countries, affluence enables unconstrained caloric intake and possibly inappropriate food choices.
It is recommended by many authorities that people maintain a normal weight by (limiting consumption of energy-dense foods and sugary drinks), eat plant-based food, limit red and
processed meat, and limit alcohol.
Sports drink
Sports drinks are beverages whose stated purpose is to help athletes replace water, electrolytes, and energy after training o competition, though their efficacy for that purpose has been questioned, particularly after exercise which is only moderate.
Categories of sport drinks
Sports drinks can be split into three major types:
- Isotonic sport drinks contain similar concentrations of salt and sugar as in the human body.
- Hypertonic sport drinks contain a higher concentration of salt and sugar than the human body.
- Hypotonic sport drinks contain a lower concentration of salt and sugar than the human body.
Most sports drinks are moderately isotonic, having between 4 and 5 heaped teaspoons of sugar per five ounce (13 and 19 grams per 250ml) serving.
PURPOSE AND EFFECTIVENESS
Athletes actively training and competing, lose water and electrolytes by sweating, and expending energy. However, Robert Robergs, an exercise physiologist at the University of New Mexico who studied Gatorade, said that unless someone is exercising or competing in a sporting event for longer than 90 minutes, there is no reason to drink something with excess sugar and electrolytes.
The Australian Institute of Sport states that excessive salt supplementation during exercise may lead to “gastrointestinal problems or cause further impairment of fluid balance” and may cause salt-induced cramps.
Sodium in drinks might help to avoid hyponatraemia (low sodium), but only after sustaining athletic activity for more than four hours; a sports drink containing sodium may be appropriate for recovery from intense and prolonged training
or competition.
A stated purpose of sports drinks, which provide many calories of energy from sugars, is to improve performance and endurance.
In an analysis by Matthew Thompson and colleagues from the Oxford Centre for Evidence Based Medicine, of 431 marketing claims of performance enhancement, most cited no evidence.
174 sources were cited for GlaxoSmithKline’s Lucozade; of them, Thompson found only three studies of high quality with a low risk of bias. The rigorous studies that did show improved endurance were “of limited relevance to most people because the tests were on elite athletes”.
Thompson said that, for the vast majority of people, drinking such products “could completely counteract exercising more, playing football more, going to the gym more”.
The drinks are marketed as soft drinks; in response to the Oxford analysis, a soft drinks industry spokesman claimed “By helping people participating in sport to perform better and to recover more quickly, sports drinks can encourage people to
exercise more”.
An effect of drinking sports drinks with carbohydrates without prolonged exercise is weight gain. A study presented at the Obesity Society’s Obesity 2012 scientific meeting found people in their teens gained 3. 5 pounds (1. 6flkg) over two years for every bottle of sports drink consumed per day. The leading author of the study, Alison Field of Harvard Medical School, said she was surprised to find that “Sports drinks have an even stronger relationship than sugared sodas with weight gain”.
Food energy
Food energy is potential energy that animals (including humans) derive from their food through the process of cellular respiration. (Cellular respiration involves either the process of joining oxygen with the molecules of food (aerobic respiration) or the process of reorganizing the atoms within the molecules (anaerobic respiration). )
Humans and other animals need a minimum intake of food energy to sustain their metabolism and to drive their muscles. Foods are composed chiefly of carbohydrates, fats, proteins,water, vitamins, and minerals.
Carbohydrates, fats, proteins, and water represent virtually all the weight of food, with vitamins and minerals making up only a small percentage of the weight. (Carbohydrates, fats, and proteins comprise ninety percent of the dry weight of foods. ) Organisms derive food energy from carbohydrates, fats and proteins as well as from organic acids, polyols, and ethanol present in the diet.
Some diet components that provide little or no food energy, such as water, minerals, vitamins, cholesterol, and fibre, may still be necessary to health and survival for other reasons. Water, minerals, vitamins, and cholesterol are not broken down (they are used by the body in the form in which they are absorbed) and so cannot be used for energy.
Fiber, a type of carbohydrate, cannot be completely digested by the human body. Ruminants can extract food energy from the respiration of cellulose thanks to bacteria in their rumens.
Using the International System of Units, researchers measure energy in joules (J) or in its multiples; the kilojoule (kJ) is most often used for food-related quantities.
An older metric system unit of energy, still widely used in food-related contexts, is the calorie; more precisely, the “food calorie”, “large calorie” or kilocalorie (kcal or Cal), equal to 4. 184 kilojoules. (Contrast the “small calorie” (cal), equal to 1/1000 of a food calorie, that is often used in chemistry and in physics.) Within the European Union, both the kilocalorie (“kcal”) and kilojoule (“kJ”) appear on nutrition labels. In many countries, only one of the units is displayed; in the US and Canada labels spell out the unit as “calorie” or as “Calorie”.
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 17flkJ/g (4.1flkcal/ g).
The differing energy density of foods (fat, alcohols, carbohydrates and proteins) lies mainly in their varying proportions of carbon, hydrogen, and oxygen atoms. Carbohydrates that are not easily absorbed, such as fiber, or lactose in lactose-intolerant individuals, contribute less food energy. Polyols (including sugar alcohols) and organic acids contribute 10flkJ/g (2. 4flkcal/g) and 13flkJ/g (3. 1flkcal/g)respectively. The amount of water, fat, and fiber in foods determines those foods’ energy density.
Theoretically, one could measure food energy in different ways, using (say) the Gibbs free energy of combustion, or the amount of ATP generated by metabolizing the food. However, the convention is to use the heat of the oxidation reaction, with the water substance produced being in the liquid phase.
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 urea and other substances in the urine. The American chemist Wilbur Atwater worked these out in the late 19th century.
Each food item has a specific metabolizable energy intake (MEI). This value can be approximated by multiplying the total amount of energy associated with a food item by 85%, which is the typical amount of energy actually obtained by a human after respiration has been completed.
In animal nutrition, where energy is a critical element of the economics of meat production, researchers may determine a specific metabolizable energy for each component (protein, fat, etc.) of each ingredient of the feed.
Nutrition labels
Many governments require food manufacturers to label the energy content of their products, to help consumers control their energy intake. In the European Union, manufacturers of packaged food must label the nutritional energy of their products in both kilocalories and kilojoules, when required.
In the United States, the equivalent mandatory labels display only “Calories”, often as a substitute for the name of the quantity being measured, food energy; an additional kilojoules figure is optional and is rarely used. The energy available from the respiration of food is usually given on labels for 100flg, for a typical serving size (according to the manufacturer), and/or for the entire pack contents.
The amount of food energy associated with a particular food could be measured by completely burning the dried food in a bomb calorimeter, a method known as direct calorimetry. However, the values given on food labels are not determined burns the dietary fiber, and so does not allow for fecal losses; in this way.
The reason for this is that direct calorimetry also thus direct calorimetry would give systematic overestimates of the amount of fuel that actually enters the blood through digestion.
What are used instead are standardized chemical tests or an analysis of the recipe using reference tables for common (protein, carbohydrate, fat, etc.). These results are then converted ingredients to estimate the product’s digestible constituents into an equivalent energy value based on the following standardized table of energy densities.
However “energy density” is a misleading term for it once again assumes that energy is IN the particular food, whereas it simply means that “high density” food needs more oxygen during respiration, leading to greater transfer of energy.
RECOMMENDED DAILY INTAKE
Increased mental activity has been linked with moderately increased brain energy consumption. Older people and those with sedentary lifestyles require less energy; children and physically active people require more.
Recommendations in the United States are 2, 700 and 2, 100flkcal (11, 300 and 8, 800flkJ) for men and women (respectively) between 31 and 50, at a physical activity level equivalent to walking about 2 to 5flkm (1fl1D2 to 3flmi) per day at 5 to 6flkm/h (3 to 4flmph) in addition to the light physical activity associated with typical day-to-day life, with French guidance suggesting roughly the same levels.
Recognizing that people of different age and gender groups have varying daily activity levels, Australia’s National Health and Medical Research Council recommends no single daily energy intake, but instead prescribes an appropriate recommendation for each age and gender group. Notwithstanding, nutrition labels on Australian food products typically recommend the average daily energy intake of 2, 100flkcal (8,800flkJ).
