Food energy

Dr.P.NithiyaAssistant Professor

DSCAS(W)Perambalur

Food

• Food is any substance consumed to provide nutritional support for the body.

• It is usually of plant or animal origin, and contains essential nutrients, such as fats, proteins, vitamins, or minerals.

• The substance is ingested by an organism and assimilated by the organism's cells to provide energy, maintain life, or stimulate growth.

Food Energy

• Food energy is energy that animals (including humans) derive from their food, through the process of cellular respiration, the process of joining oxygen with the molecules of food (aerobic respiration) or of reorganizing the atoms within the molecules for anaerobic respiration.

Units of energy

• Calorie• Respiratory quotient• SDA•

Calorie

• The calorie equals the amount of thermal energy necessary to raise the temperature of one gram of water by 1 Celsius degree, at a pressure of 1 atm.

• For thermochemistry a calorie of 4.184 J is used, but other calories have also been defined, such as the International Steam Table calorie of 4.1868 J.

• Food energy is measured in large calories or kilocalories, often simply written capitalized as "Calories" (= 103 calories).

Respiratory quotient (RQ)

• The respiratory quotient (or RQ or respiratory coefficient), is a dimensionless number used in calculations of basal metabolic rate (BMR) when estimated from carbon dioxide production.

• Such measurements, like measurements of oxygen uptake, are forms of indirect calorimetry.

• It is measured using Ganong's Respirometer.• It can be used in the alveolar gas equation.

Respiratory quotient (RQ)

• The respiratory quotient (RQ) is the ratio:• RQ = CO2 eliminated / O2 consumed

• where the term "eliminated" refers to carbon dioxide (CO2) removed ("eliminated") from the body.

• In this calculation, the CO2 and O2 must be given in the same units, and in quantities proportional to the number of molecules. Acceptable inputs would be either moles, or else volumes of gas at standard temperature and pressure.

Specific Dynamic Action (SDA)

• Thermic effect of food (abbreviated as TEF), also known as specific dynamic action (SDA) of a food or dietary induced thermogenesis (DIT), is the amount of energy expenditure above the resting metabolic rate due to the cost of processing food for use and storage.

SDA

• Simply, it's the energy used in digestion, absorption and distribution of nutrients.

• It is one of the components of metabolism along with resting metabolic rate and the exercise component.

• A commonly used estimate of the thermic effect of food is about 10% of one's caloric intake, though the effect varies substantially for different food components.

• For example, dietary fat is very easy to process and has very little thermic effect, while protein is hard to process and has a much larger thermic effect.

Net protein utilization

• The net protein utilization, or NPU, is the ratio of amino acid converted to proteins to the ratio of amino acids supplied.

• This figure is somewhat affected by the salvage of essential amino acids within the body, but is profoundly affected by the level of limiting amino acids within a foodstuff.

Net protein utilization

• Experimentally, this value can be determined by determining dietary protein intake and then measuring nitrogen excretion.

• One formula for NPU is:NPU = ((0.16 × (24 hour protein intake in grams) - (24 hour urinary urea nitrogen) + 2) - (0.1 × (ideal body weight in kilograms) / (0.16 × (24 hour protein intake in grams))

As a value, NPU can range from 1 to 0, with a value of 1 indicating 100% utilization of dietary nitrogen as protein and a value of 0 an indication that none of the nitrogen supplied was converted to protein

Basal metabolism Rate

• Basal metabolic rate (BMR) is the minimal rate of energy expenditure by warm-blooded animals at rest.

• It may be reported in units ranging from watts/hour to ml O2/min or kJ per hour per kg body mass.

Basal metabolism Rate

• Proper measurement requires a strict set of criteria be met.

• These criteria include being in a physically and psychologically undisturbed state, in a thermally neutral environment, while in the post-absorptive state (i.e., not actively digesting food).

Body Mass Index

• The body mass index (BMI), or Quetelet index, is a measure of relative size based on the mass and height of an individual.

• The index was devised by Adolphe Quetelet during the course of developing what he called "social physics", between 1830 and 1850.

• The BMI for a person is defined as their body mass divided by the square of their height—with the value universally being given in units of kg/m2. So if the weight is in kilograms and the height in metres, the result is immediate, if pounds and inches are used, a conversion factor of 703 (kg/m2)/(lb/in2) must be applied.

• Body Mass Index = or