Nutrition

Question

This piglix contains articles or sub-piglix about Nutrition

Answer 1

Animal nutritionist

An animal nutritionist is a person who specializes in animal nutrition, which is especially concerned with the dietary needs of animals in captivity: , pets, and animals in wildlife rehabilitation facilities.

The science of animal nutrition encompasses principles of chemistry (especially biochemistry), physics, mathematics, ethology (animal behavior). An animal nutrition in the food industry may also be concerned with economics and food processing.

A Bachelor of Science in agricultural, biological or related life sciences is usually required. A typical course would study metabolism of proteins, carbohydrates, lipids, minerals, vitamins and water, and the relationship of these nutrients and animal production. A Master’s degree in nutrition is often seen in animal nutrition and the field often requires a Ph.D. in the science of nutrition.

Those with an educational background can expect to be employed in the following areas:

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Answer 2

Atwater system

The Atwater system (after Wilbur Olin Atwater) or derivatives of this system are used for the calculation of the available energy of foods. The system was developed largely from the experimental studies of Atwater and his colleagues in the later part of the 19th century and the early years of the 20th at Wesleyan University in Middletown, Connecticut. Its use has frequently been the cause of dispute, but no real alternatives have been proposed. As with the calculation of protein from total nitrogen, the Atwater system is a convention and its limitations can be seen in its derivation.

Available energy (as used by Atwater) is equivalent to the modern usage of the term metabolisable energy (ME).

Metabolisable Energy=(Gross Energy in Food)−<!-- − -->(Energy lost in Faeces, Urine, Secretions and Gases).{\displaystyle {\text{Metabolisable Energy}}=\left({\text{Gross Energy in Food}}\right)-\left({\text{Energy lost in Faeces, Urine, Secretions and Gases}}\right).}

In most studies on humans, losses in secretions and gases are ignored. The gross energy (GE) of a food, as measured by bomb calorimetry is equal to the sum of the heats of combustion of the components – protein (GE_p), fat (GE_f) and carbohydrate (GE_cho) (by difference) in the proximate system.

GE=GEp+GEf+GEcho{\displaystyle {GE}={{GE}_{p}+{GE}_{f}+{GE}_{cho}}\,}

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Answer 3

Antinutrient

Antinutrients are natural or synthetic compounds that interfere with the absorption of nutrients. Nutrition studies focus on those antinutrients commonly found in food sources and beverages.

Protease inhibitors are substances that inhibit the actions of trypsin, pepsin and other proteases in the gut, preventing the digestion and subsequent absorption of protein. For example, Bowman-Birk trypsin inhibitor is found in soybeans.

Lipase inhibitors interfere with enzymes, such as human pancreatic lipase, that catalyze the hydrolysis of some lipids, including fats. For example, the anti-obesity drug orlistat causes a percentage of fat to pass through the digestive tract undigested.

Amylase inhibitors prevent the action of enzymes that break the glycosidic bonds of starches and other complex carbohydrates, preventing the release of simple sugars and absorption by the body. Amylase inhibitors, like lipase inhibitors, have been used as a diet aid and obesity treatment. Amylase inhibitors are present in many types of beans; commercially available amylase inhibitors are extracted from white kidney beans.

Phytic acid has a strong binding affinity to minerals such as calcium, magnesium, iron, copper, and zinc. This results in precipitation, making the minerals unavailable for absorption in the intestines. Phytic acids are common in the hulls of nuts, seeds and grains.

Oxalic acid and oxalates are present in many plants, particularly in members of the spinach family. Oxalates bind to calcium and prevent its absorption in the human body.

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Answer 4

Anthoxanthin

Anthoxanthins (flavones and flavonols) are a type of flavonoid pigments in plants. Anthoxanthins are water-soluble pigments which range in color from white or colorless to a creamy to yellow, often on petals of flowers. These pigments are generally whiter in an acid medium and yellowed in an alkaline medium. They are very susceptible to color changes with minerals and metal ions, similar to anthocyanins. As with all flavonoids, they exhibit antioxidant properties, and are important in nutrition, and are sometimes used as food additives. Darkening with iron is particularly prominent in food products. They are considered to have more variety than anthocyanins. Some examples are quercitin.

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Answer 5

Auxology

Auxology, sometimes called auxanology (from Greek αὔξω, auxō, or αὐξάνω, auxanō, "grow"; and -λογία, -logia), is a meta-term covering the study of all aspects of human physical growth (though it is also a fundamental of biology, generally speaking). Auxology is a highly multi-disciplinary science involving health sciences/medicine (pediatrics, general practice, endocrinology, neuroendocrinology, physiology, epidemiology), and to a lesser extent: nutrition, genetics, anthropology, anthropometry, ergonomics, history, economic history, economics, socioeconomics, sociology, public health and psychology, among others.

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Answer 6

Biological value

Biological value (BV) is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism's body. It captures how readily the digested protein can be used in protein synthesis in the cells of the organism. Proteins are the major source of nitrogen in food. BV assumes protein is the only source of nitrogen and measures the proportion of this nitrogen absorbed by the body which is then excreted. The remainder must have been incorporated into the proteins of the organisms body. A ratio of nitrogen incorporated into the body over nitrogen absorbed gives a measure of protein "usability" – the BV.

Unlike some measures of protein usability, biological value does not take into account how readily the protein can be digested and absorbed (largely by the small intestine). This is reflected in the experimental methods used to determine BV.

BV uses two similar scales:

These two values will be similar but not identical.

The BV of a food varies greatly, and depends on a wide variety of factors. In particular the BV value of a food varies depending on its preparation and the recent diet of the organism. This makes reliable determination of BV difficult and of limited use — fasting prior to testing is universally required in order to ascertain reliable figures.

BV is commonly used in nutrition science in many mammalian organisms, and is a relevant measure in humans. It is a popular guideline in bodybuilding in protein choice.

For accurate determination of BV:

These conditions mean the tests are typically carried out over the course of over one week with strict diet control. Fasting prior to testing helps produce consistency between subjects (it removes recent diet as a variable).

There are two scales on which BV is measured; percentage utilization and relative utilization. By convention percentage BV has a percent sign (%) suffix and relative BV has no unit.

Biological value is determined based on this formula.

Where:

However direct measurement of N_r is essentially impossible. It will typically be measured indirectly from nitrogen excretion in urine.Faecal excretion of nitrogen must also be taken into account - this part of the ingested protein is not absorbed by the body and so not included in the calculation of BV. An estimate is used of the amount of the urinary and faecal nitrogen excretion not coming from ingested nitrogen. This may be done by substituting a protein-free diet and observing nitrogen excretion in urine or faeces, but the accuracy of this method of estimation of the amount of nitrogen excretion not coming from ingested nitrogen on a protein-containing diet has been questioned.

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Answer 7

Authority Nutrition

Authority Nutrition

Authority Nutrition is a website that provides articles about nutrition, health and weight loss.

The website was founded by Kris Gunnars in December, 2012, and now gets millions of visits each month. It currently holds the #1 Alexa rank for nutrition.

The website has several licensed nutritionists/dietitians writing articles. The website and its authors have been quoted and referred to in international media. Many of the articles have been republished in a variety of internet media sources.

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Answer 8

Blood lipids

Blood lipids (or blood fats) are lipids in the blood, either free or bound to other molecules. They are mostly transported in a protein capsule, and the density of the lipids and type of protein determines the fate of the particle and its influence on metabolism. The concentration of blood lipids depends on intake and excretion from the intestine, and uptake and secretion from cells. Blood lipids are mainly fatty acids and cholesterol. Hyperlipidemia is the presence of elevated or abnormal levels of lipids and/or lipoproteins in the blood, and is a major risk factor for cardiovascular disease.

Short- and medium chain fatty acids are absorbed directly into the blood via intestine capillaries and travel through the portal vein. Long-chain fatty acids, on the other hand, are too large to be directly released into the tiny intestine capillaries. Instead they are coated with cholesterol and protein (protein coat of lipoproteins) into a compound called a chylomicron. The chylomicron enters a lymphatic capillary and enters into the bloodstream first at the left subclavian vein (having bypassed the liver).

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Answer 9

Blood sugar regulation

Blood sugar regulation is the process by which the levels of blood sugar, primarily glucose, are maintained by the body within a narrow range. This phenomenon of tight regulation is commonly referred to as glucose homeostasis. Insulin and glucagon are the most well known of the hormones involved, but more recent discoveries of other glucoregulatory hormones have expanded our understanding of this process.

Blood sugar levels are regulated by negative feedback in order to keep the body in homeostasis. The levels of glucose in the blood are monitored by many tissues, but the cells in the pancreas's Islets of Langerhans are among the most well understood and important.

If the blood glucose level falls to dangerous levels (as in very heavy exercise or lack of food for extended periods), the Alpha cells of the pancreas release glucagon, a hormone whose effects on liver cells act to increase blood glucose levels. They convert glycogen into glucose (this process is called glycogenolysis). The glucose is released into the bloodstream, increasing blood sugar. Hypoglycemia, the state of having low blood sugar, is treated by restoring the blood glucose level to normal by the ingestion or administration of dextrose or carbohydrate foods. It is often self-diagnosed and self-medicated orally by the ingestion of balanced meals. In more severe circumstances, it is treated by injection or infusion of glucagon.

When levels of blood sugar rise, whether as a result of glycogen conversion, or from digestion of a meal, a different hormone is released from beta cells found in the Islets of Langerhans in the pancreas. This hormone, insulin, causes the liver to convert more glucose into glycogen (this process is called glycogenesis), and to force about 2/3 of body cells (primarily muscle and fat tissue cells) to take up glucose from the blood through the GLUT4 transporter, thus decreasing blood sugar. When insulin binds to the receptors on the cell surface, vesicles containing the GLUT4 transporters come to the plasma membrane and fuse together by the process of endocytosis, thus enabling a facilitated diffusion of glucose into the cell. As soon as the glucose enters the cell, it is phosphorylated into Glucose-6-Phosphate in order to preserve the concentration gradient so glucose will continue to enter the cell. Insulin also provides signals to several other body systems, and is the chief regulator of metabolic control in humans.

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Answer 10

Body fat percentage

The body fat percentage (BFP) of a human or other living being is the total mass of fat divided by total body mass; body fat includes essential body fat and storage body fat. Essential body fat is necessary to maintain life and reproductive functions. The percentage of essential body fat for women is greater than that for men, due to the demands of childbearing and other hormonal functions. The percentage of essential fat is 2–5% in men, and 10–13% in women (referenced through NASM). Storage body fat consists of fat accumulation in adipose tissue, part of which protects internal organs in the chest and abdomen. The minimum recommended total body fat percentage exceeds the essential fat percentage value reported above. A number of methods are available for determining body fat percentage, such as measurement with calipers or through the use of bioelectrical impedance analysis.

The body fat percentage is a measure of fitness level, since it is the only body measurement which directly calculates a person's relative body composition without regard to height or weight. The widely used body mass index (BMI) provides a measure that allows the comparison of the adiposity of individuals of different heights and weights. While BMI largely increases as adiposity increases, due to differences in body composition, other indicators of body fat give more accurate results; for example, individuals with greater muscle mass or larger bones will have higher BMIs. As such, BMI is a useful indicator of overall fitness for a large group of people, but a poor tool for determining the health of an individual.

Epidemiologically, the percentage of body fat in an individual varies according to sex and age. Various theoretical approaches exist on the relationships between body fat percentage, health, athletic capacity, etc. Different authorities have consequently developed different recommendations for ideal body fat percentages.

This graph from the National Health and Nutrition Examination Survey in the United States charts the average body fat percentages of Americans from samples from 1999–2004:

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