This very sensitive renal response to calcium deprivation combines with the inverse relationship between calcium intake and absorption to stabilise the plasma ionised calcium concentration and to preserve the equilibrium between calcium entering and leaving the ECF over a wide range of calcium intakes. As the calcium allowances recommended for developed nations have been rising - and may still not have reached their peak - the gap between them and the actual calcium intakes in developing countries has widened. Studies in calcium and phosphorus metabolism. At zero calcium intake, all the faecal calcium is endogenous and represents the digestive juice calcium which has not been reabsorbed; net absorbed calcium at this intake is therefore negative to the extent of about mg 5 mmol 28, Acquired hypocuremia after gastric surgery.
Moizé and colleagues reported that, after five years, vitamin and mineral deficiencies with VSG corresponded with those seen five years after gastric bypass. VSG patients who take metformin also are at risk of vitamin B12 malabsorption. Despite universal supplementation, the prevalence of vitamin D deficiency was the most commonly observed deficiency five years postoperatively in VSG patients. Dumping Syndrome Dumping syndrome is more commonly seen with gastric bypass and caused by rapid emptying of simple carbohydrates into the jejunum-ileum, which leads patients to experience watery diarrhea, diaphoresis extreme sweating , episodic hypoglycemia, abdominal pain, bloating, stomach rumbling, tachycardia, flushing, and nausea.
The syndrome is categorized into early or late, depending on when symptoms begin and their severity. Typically, signs of early dumping syndrome include gastrointestinal upset, diarrhea, bloating, sweating, palpitations, and dizziness. Late dumping syndrome generally includes hypoglycemia, fainting, confusion, and excessive hunger.
However, Tzovaras and colleagues demonstrated that VSG patients, when given an oral glucose challenge, can experience clinical symptoms of early or late dumping syndrome characterized by hypoglycemia, nausea, diaphoresis, and fainting. Postoperative Nutritional Side Effects Interestingly, while VSG is dramatically different than gastric bypass and adjustable band surgery in terms of the procedure itself, patients who undergo VSG experience similar postoperative symptoms of nausea, vomiting, diarrhea, dehydration, gas, lactose intolerance, electrolyte imbalance, food aversions, and sensory enhancement.
Because VSG is considered a restrictive and food-limiting surgery, occasional nausea and vomiting can be experienced up to six months postoperatively or longer. The dietitian plays an integral role in identifying symptoms that may be related more to the surgical risks than to dietary consequences. For example, gastric leak, gastric ulcer, and gastric stricture are serious sleeve-associated risks that initially may present as dehydration, abdominal and back pain, fever, nausea, vomiting, and anemia.
The dietitian may be the first health care professional who recognizes these symptoms, which reinforces the importance of having an interdisciplinary health care team for the bariatric surgery patient.
However, there are several published bariatric nutrition practice guidelines available for RDs who counsel patients who have undergone bariatric surgery. In , Snyder-Marlowe and colleagues published micronutrient guidelines specific for VSG, and Table 2 summarizes these recommendations. The recommendations, which provide general information about early postoperative nutrition and micronutrients specifically for VSG, are summarized in Table 3.
The International Sleeve Gastrectomy Expert Panel Consensus Statement recommends patients wait to begin eating solid food until at least two weeks after surgery.
Patients should consume fluid 30 minutes after food consumption. General nutrition guidance and a proposed staged diet progression are outlined in Table 4. Puréed protein foods, incorporate puréed fruit, vegetables, and starch as recommended by dietitian.
Regular diet that incorporates a variety of nutrient-dense foods; focus on protein intake first to meet daily needs. Patients who have undergone VSG should be encouraged to participate in regular follow-up visits with their interdisciplinary bariatric team. For each patient, an RD should perform a comprehensive nutrition assessment to identify, prevent, or correct deficiencies.
Dietitians should be aware that patient compliance with a postoperative daily vitamin and mineral regimen is a challenge seen across all bariatric procedures.
Education and counseling should focus on supporting and teaching patients about meaningful lifestyle changes and correcting the misperception that bariatric surgery is a quick fix or magic bullet. Future Implications and Opportunities VSG is the fastest-growing bariatric surgical procedure worldwide.
The RD, as an integral member of an interdisciplinary bariatric health team, plays an important role in identifying, preventing, and correcting nutritional challenges before and after VSG. While long-term research is needed to elucidate the evidence-based practice most appropriate for dietary counseling with VSG patients, dietitians should consider participating in research that reports findings and validates nutrition recommendations.
RDs should encourage patients who have undergone any type of bariatric surgery to obtain postoperative follow-up care with their interdisciplinary bariatric teams. As the number of VSG surgeries increases each year, and coupled with the lack of long-term evidence on the efficacy of the procedure, providing proper nutrition advice to patients becomes even more critical.
Learning Objectives After completing this continuing education course, nutrition professionals should be better able to:. Describe the history of vertical sleeve gastrectomy VSG as a stand-alone bariatric procedure and distinguish its mechanism of action and efficacy. Vertical sleeve gastrectomy VSG as a stand-alone bariatric procedure first began as which of the following? It was the second step in a Roux-en-Y gastric bypass for patients who were super morbidly obese.
VSG always was considered a stand-alone bariatric procedure. It was the first step in a two-step bariatric procedure called biliopancreatic diversion with duodenal switch. It was the first step in a two-step bariatric procedure called vertical banded gastroplasty. Which appetite-stimulating hormone decreases following VSG? Which of the following is the key aspect of the mechanism of action by which VSG induces weight loss? It is a restrictive procedure that reduces stomach capacity to approximately 90 to mL and decreases the amount of food intake.
It causes calorie and vitamin malabsorption by disrupting how food flows from the stomach to the intestines. It reduces gastric emptying. It causes an increase in hunger by increasing ghrelin production. Wernicke-Korsakoff syndrome has been reported in VSG patients. This syndrome is caused by a deficiency of which vitamin? Those with inflammatory bowel disease b.
Those eligible for or awaiting a liver transplant c. Those with mild gastroesophageal reflux disease GERD.
When and for what purpose is the liver-shrinking diet recommended? Postoperatively to reduce the incidence of gallstones b. Preoperatively to reduce the size of the liver to assist with laparoscopic view c. Postoperatively to enhance weight-loss success d.
Preoperatively to begin teaching patients about portion control. Chemical fermenters added to the feed have been used to predict digestibility. The method is also used to study rumen function and the metabolism of certain compounds, e.
The advantage of the two methods is that the analysis is not expensive if laboratory facilities are available and that it can be performed fairly quickly.
The methods can also be used to assess the digestibility of grab samples of grass or of cut samples of stover and straws taken after crop harvesting.
These are inserted into the rumen of test animals and removed after a prescribed period. The loss of material from the bag as a result of fermentation is then calculated. The method is more applicable to on-station research, but it can be used together with the rumen cannula method to determine intake.
Nutritive value of feed This part of the module focuses on the methods and techniques used in estimating the supply of different nutrients to animals in particular situations or systems, in relation to their need for these nutrients.
It starts with a general section on estimating the main feed components. It then goes straight to fibre analysis because of the difficulties involved in estimating feed values in very fibrous diets. Finally, it looks at some of the techniques in use for the physical sampling, from stands of different kinds of feed, for laboratory analysis.
Methods to estimate feed components The feed value of a source of feed can be assessed on the basis of its energy value, crude protein content and mineral content, using methods specifically designed to estimate these components of feed. The energy yield of a source of feed such as natural pasture can be estimated from its dry-matter weight per unit area. Module 6 discusses the various methods used to estimate biomass or dry-matter weight under rangeland conditions.
Many of these methods rely on the use of predictive equations based on the relationship between biomass and the vegetation characteristics e. Samples can be taken to establish similar predictive relationships for the estimation of dry-matter weight of crop residues.
Powell , for instance, used grain yield to predict total stover dry-matter weight and stalk and leaf dry-matter weights for millet and sorghum. The relationships, which were based on data obtained from randomly chosen sites in Kaduna State, Nigeria, were highly significant Figure 5. Van Raay and de Leeuw adopted a similar procedure to determine the DM weight of crop residues in Katsina, Nigeria.
They established predictive relationships on the basis of stalk and stand density, plant height and plant edibility subjectively estimated. Relationships between sorghum and millet grain yields and stover dry-matter DM yields. Having obtained an estimate of dry-matter yield, an estimate of digestibility is then required before the desired approximation of the energy yield can be calculated.
The fibrous portions of a feed must, therefore, be considered before more accurate estimates of nutritive value can be made. Feeds with a high biomass per unit area are often low in energy since they also contain a high proportion of indigestible fibrous matter.
Methods of fibre analysis have been devised to separate those portions of fibre which can be utilised by the ruminant from those which are essentially indigestible. Fibre analysis is thus particularly important in the assessment of the nutritive value of these feeds. For the purposes of illustration, however, the following average relationships can be used: Let us calculate the feed energy requirements of a kg liveweight ox for maintenance, foraging and production, and compare these with the availability of energy to that animal from its feed supply.
The maintenance fasting metabolism requirement is determined as follows: Km tends to lie in the range 0. We can call this 'foraging'. The energy requirement for foraging Ef are given by the formula: To gain weight, an animal needs between 12 and 27 MJ of ME per kg liveweight, depending on the percentage that fat constitutes in the meat accumulated.
We can now compare supply and requirements of feed energy per ox for the 90 days of the dry season as follows: The standard laboratory method for the estimation of crude protein is the Kjeldahl method which is described in most texts on animal nutrition e. McDonald et al, ; Church and Pond, The analysis is used to determine the crude protein content of a sample of grass or stover, and the results can then be used to establish predictive regression equations similar to those illustrated in Figure 5.
When estimating the crude protein content of browse plants and crop residues, it should be borne in mind that the presence of certain phenolics tannins in these feeds can affect the availability of nitrogen to the ruminant. This is particularly true of feeds high in insoluble polyphenolics, for which the calculated crude protein content may overestimate the amount of nitrogen which can actually be synthesised into protein e. Woodward and Reed, Analysis should only be attempted if mineral deficiencies are clearly evident.
Even then, if other nutrients such as energy or crude protein are more limiting as is likely to be the case on African rangelands , the mineral constraint should be dealt with only after the primary deficiencies have been rectified Little, The methods used by ILCA researchers to diagnose the more common deficiencies involve blood, bone, liver, milk and faecal samples and are discussed in general terms below.
All the methods outlined rely on adequate laboratory facilities. For a more detailed account of symptoms of mineral deficiency and the role of minerals in animal nutrition, the user is referred to basic nutrition texts, e. Cullison and Church and Pond Whole blood, blood serum and blood plasma samples have been used to diagnose mineral deficiencies particularly phosphorous and magnesium in livestock.
Values significantly below 'normal' concentrations or ranges indicate the nutritional status of an animal with respect to a particular mineral, but the evidence is not always conclusive McDowell et al, Precautions must, for instance, be taken when samples are taken in less than optimum conditions since exercise, stress, temperature and other factors can alter mineral concentrations.
Such factors are often difficult to control in African conditions Mtimuni, and have resulted in high concentrations of phosphorous in serum when the concentration in forages consumed was, in fact, extremely low. Little et al described a method for obtaining accurate estimates of blood inorganic P concentrations, but the difficulties of interpretation of such data were noted by Gartner et al Basically, only low blood inorganic P values have any diagnostic value.
Because of the problems just described, tests using bone samples have been developed to test for phosphorus deficiency in livestock. Samples of rib bone can be obtained by simple surgery. For FSR diagnostic work, simple measurements that can be made on certain long bones at slaughter can provide results which are generally more reliable than those obtained from blood samples.
These methods have been described by Little Liver samples have been used to diagnose for copper, cobalt and vitamin A deficiencies in African livestock Tartour, ; van Niekerk, ILCA has used samples of milk to diagnose mineral deficiencies in cattle in Ethiopia.
However, since milk composition is influenced by such factors as cow age, stage of lactation and genetic potential, milk sampling tends to be unreliable. The 'let-down' problem associated with zebu cattle Module 5 also means that it is cliff cut to obtain representative samples in field studies. Large variations in butterfat content between successive milkings of the same cow reflect this problem Lambourne et al, However, milk samples are very useful in the diagnosis of iodine deficiency Committee on Mineral Nutrition, Apart from their use in digestibility and intake studies, faecal samples have been used to diagnose for phosphorus and sodium deficiencies Little, Sodium problems are diagnosed more accurately, but with more difficulty, from saliva samples.
However, the analysis of mineral deficiencies is probably best done by feed analysis at the diagnostic phase of farming systems research. The methods described above are more applicable to specific problems requiring more sensitive analysis Little, A knowledge of the symptoms involved will provide further confirmatory evidence e.
The opinions of traditional herders will also be useful in identifying mineral deficiencies particularly the need for salt , as will be the movement of stock over large distances to natural sources of minerals. Fibre analysis The crude-fibre Weende method is described in most texts on animal nutrition. The method has been widely used to determine the fibre content of feed, but it has two serious shortcomings, particularly with respect to highly fibrous feeds such as crop residues, straws etc.
Ruminants can, however, utilise some cellulose and hemicelluose though lignin is essentially indigestible. The digestibility of a feed therefore tends to be underestimated.
As a result, a portion of these components is included in the nitrogen-tree extract sugars and starches and is, therefore, assumed to be highly digestible. The digestibility of a feed therefore tends to be overestimated. Because of these shortcomings, Van Soest devised a method which separates feed dry matter into two fractions - one of high or uniform digestibility and the other of low or non-uniform digestibility. Feed samples are boiled in a neutral-detergent solution and components are separated as follows: This fraction more closely corresponds to the true fibre fraction than the estimate of the Weende crude-fibre analysis.
However, NDF is not a uniform chemical entity, its overall nutritive value is considerably influenced by the amount of lignin present. To determine this amount, the feed is treated by acid detergent, and the procedure is known as the acid-detergent fibre ADF analysis. By heating the NDF in acid detergent, the presence of tannins can also be detected.
The detergent analysis and its different procedures are discussed in greater detail by Van Soest and Reed and Van Soest Because of the high costs of reagents and apparatus used in detergent analysis, developing countries have been slow to adopt the method. ILCA's Animal Nutrition Section has recently developed a low-cost micro-fibre apparatus which uses one tenth of the amount of reagent used in conventional detergent analysis experiments.
Feed sampling for laboratory analysis The types of feed usually sampled for laboratory analysis are crop residues and hays, grains and fresh forage or silage. Crop residues and hays. Most African farmers store crop residues and hays in stacks, and the nutritive value of the feed tends to be highly variable both within and between stacks.
This increases sampling requirements and complicates the procedures involved. Because of the variability in the nutritive value of crop residues and hay commonly encountered, it is useful to make a visual estimate of the variation in a selected stack before sampling begins, and to interview the farmer about the time of harvesting, the methods of stacking used and the composition of the stack i.
Sampling may be done with a coring device or by hand. Samples should always be taken from a cross-section of each chosen stack. When large stacks are encountered, dismantling may be necessary to ensure that samples from the less accessible parts are obtained.
When the coring device is used, at least 10 samples should be taken per stack. The material gathered should be properly mixed, weighed and stored in a dry place before dispatching it to the laboratory. The combined dry weight of corings taken per stack should not be less than 2 kg. The samples should be clean and stored in a porous paper or a piece of cloth to avoid moisture contamination.
Relevant information date, feed type, sample weight, identification should be recorded in duplicate. When samples are taken by hand, several visits are normally required to ensure that the nutritive value of the stack is properly assessed.
At each visit, grab samples should be taken from the face of the stack and mixed. They should be taken at every an, as the farmer makes use of the stack. If the farmer finishes one stack and starts another, or alternates between different stacks, new samples should be taken following the same procedure.
Although hand-sampling is tedious, changes in feed quality over time e. With coring, several return trips would be required if specific information on quality change over time was needed. Grain samples are usually taken with a grain probe. Between cores should be taken at random from the storage bin.
The samples should then be mixed and separated into subsamples of about g. Each sub-sample should be placed in a porous paper or cloth sack and properly labelled before dispatch or storage. These are usually fresh forage or silage. If it is not possible to weigh the sample when it is taken, one half should be placed in a sealed plastic bag to retain moisture and then weighed after returning from the field.
This fresh weight is needed to calculate dry-matter content after drying. The other half of the sample should be kept in a porous paper or cloth sack for other analyses than dry-matter content. In the event that samples cannot be transported to the laboratory the same day, they should be dried either by hanging under cover or by spreading them out on paper in a dry and protected place.
Alternatively, samples can be hung in sacks above the coil of a kerosene refrigerator. If drying is delayed, samples should be kept in plastic bags out of direct sunlight to avoid spoilage, or they should be stored frozen. Cored samples should be taken from the pit using the procedure outlined above for stacked hay and crop residues. If sampling is done by hand, about 20 grab samples should be taken from the freshly cut face and mixed thoroughly.
A subsample of 2 kg is required for analysis. The procedure should be repeated every third or fourth face cut to account for within-pit variability. If oven-drying is not possible, one of the drying methods given for fresh forage will suffice.
References Abel N O J. Cattle-keeping, ecological change and communal management in Ngwaketse. Goat management research at the University of Ife. Proceedings of the workshop on small ruminant production systems in the humid zone of West Africa, held in Ibadan, Nigeria, January The nutrient requirements of farm livestock No.
Technical reviews and summaries. Considerations on data collection and evaluation. Kearl S ed , Livestock in mired farming systems: Research methodologies and priorities. Utilization of fodder banks. Bayer W and Otchere E O. Effect of livestock-crop integration on grazing time of cattle in a subhumid African savanna. Australian Academy of Science, Canberra, Australia. Measuring the benefits of subsistence versus commercial livestock production in Africa. Flora CB ed , Animals in the farming system.
Farming Systems Research Paper Series 6. Beef cattle nutrition and tropical pastures. Influence of sward characteristics on grazing behaviour and growth of Hereford steers grazing tropical grass pastures. Australian Journal of Agricultural Research 29 1: Basic animal nutrition and feeding. John Wiley and Sons Inc. Committee on mineral nutrition. Tracing and treating mineral disorders in dairy cattle. Feeds and feeding Third edition.
Dahl G and Sandford S. Which way to go? Livestock and land use in the T. Measuring the secondary production of pasture: An applied example in the study of an extensive production system in Mali. The current state of knowledge. Grazing behaviour of cattle during continuous and rotational grazing of the Matopos sandveld of Zimbabwe. Zimbabwe Journal of Agricultural Research 18 1: Gartner R J W. Little D A and Winks L. Minerals limiting production of ruminants grazing tropical pastures.
Units of metabolic body size for comparisons amongst adult sheep and cattle. Ramsay, Ware Publishing Pty Ltd. Nitrogen fertility in Oxisols and Ultisols of the humid tropics. Cornell International Agriculture Bulletin Kassam A and Andrews D. Effects of sowing date on growth, development and yield of photosensitive sorghum at Samaru, northern Nigeria Experimental Agriculture 11 2: Livestock water needs in pastoral Africa in relation to climate and forage.
Semenye P and Butterworth M. Pastoral systems research in sub-Saharan Africa. The utilization of dietary energy by steers during periods of restricted food intake and subsequent re-alimentation. The effect of time on the maintenance requirements of steers held at constant five weights. Journal of Agricultural Science 88 1: Studies on cattle with oesophageal fistulae: The relation of the chemical composition of feed to that of the extruded bolus.
Comparison of concentrations of mineral nutrients in feeds and associated boluses. In , Hart discovered that trace amounts of copper are necessary for iron absorption.
In , Albert Szent-Györgyi isolated ascorbic acid , and in proved that it is vitamin C by preventing scurvy. In , he synthesized it, and in , he won a Nobel Prize for his efforts. Szent-Györgyi concurrently elucidated much of the citric acid cycle. In the s, William Cumming Rose identified essential amino acids , necessary protein components that the body cannot synthesize.
In , Underwood and Marston independently discovered the necessity of cobalt. In , Eugene Floyd DuBois showed that work and school performance are related to caloric intake. In , Erhard Fernholz discovered the chemical structure of vitamin E and then he tragically disappeared. In , rationing in the United Kingdom during and after World War II took place according to nutritional principles drawn up by Elsie Widdowson and others.
In , The U. Department of Agriculture introduced the Food Guide Pyramid. The list of nutrients that people are known to require is, in the words of Marion Nestle , "almost certainly incomplete". Some nutrients can be stored - the fat-soluble vitamins - while others are required more or less continuously. Poor health can be caused by a lack of required nutrients, or for some vitamins and minerals, too much of a required nutrient. The macronutrients are carbohydrates , fiber , fats , protein , and water.
Some of the structural material can be used to generate energy internally, and in either case it is measured in Joules or kilocalories often called "Calories" and written with a capital C to distinguish them from little 'c' calories. Vitamins, minerals, fiber, and water do not provide energy, but are required for other reasons.
Molecules of carbohydrates and fats consist of carbon, hydrogen, and oxygen atoms. Carbohydrates range from simple monosaccharides glucose, fructose and galactose to complex polysaccharides starch. Fats are triglycerides , made of assorted fatty acid monomers bound to a glycerol backbone.
Some fatty acids, but not all, are essential in the diet: Protein molecules contain nitrogen atoms in addition to carbon, oxygen, and hydrogen. The fundamental components of protein are nitrogen-containing amino acids , some of which are essential in the sense that humans cannot make them internally.
Some of the amino acids are convertible with the expenditure of energy to glucose and can be used for energy production, just as ordinary glucose, in a process known as gluconeogenesis.
By breaking down existing protein, the carbon skeleton of the various amino acids can be metabolized to intermediates in cellular respiration; the remaining ammonia is discarded primarily as urea in urine. Carbohydrates may be classified as monosaccharides , disaccharides , or polysaccharides depending on the number of monomer sugar units they contain.
They constitute a large part of foods such as rice , noodles , bread , and other grain -based products, also potatoes , yams, beans, fruits, fruit juices and vegetables. Monosaccharides, disaccharides, and polysaccharides contain one, two, and three or more sugar units, respectively.
Polysaccharides are often referred to as complex carbohydrates because they are typically long, multiple branched chains of sugar units. Traditionally, simple carbohydrates are believed to be absorbed quickly, and therefore to raise blood-glucose levels more rapidly than complex carbohydrates. This, however, is not accurate.
Dietary fiber is a carbohydrate that is incompletely absorbed in humans and in some animals. Like all carbohydrates, when it is metabolized it can produce four Calories kilocalories of energy per gram. However, in most circumstances it accounts for less than that because of its limited absorption and digestibility. Dietary fiber consists mainly of cellulose, a large carbohydrate polymer which is indigestible as humans do not have the required enzymes to disassemble it.
There are two subcategories: Whole grains, fruits especially plums , prunes , and figs , and vegetables are good sources of dietary fiber. There are many health benefits of a high-fiber diet.
Dietary fiber helps reduce the chance of gastrointestinal problems such as constipation and diarrhea by increasing the weight and size of stool and softening it.
Insoluble fiber, found in whole wheat flour , nuts and vegetables, especially stimulates peristalsis ;— the rhythmic muscular contractions of the intestines, which move digest along the digestive tract.
Soluble fiber, found in oats, peas, beans, and many fruits, dissolves in water in the intestinal tract to produce a gel that slows the movement of food through the intestines. This may help lower blood glucose levels because it can slow the absorption of sugar. Additionally, fiber, perhaps especially that from whole grains, is thought to possibly help lessen insulin spikes, and therefore reduce the risk of type 2 diabetes. The link between increased fiber consumption and a decreased risk of colorectal cancer is still uncertain.
A molecule of dietary fat typically consists of several fatty acids containing long chains of carbon and hydrogen atoms , bonded to a glycerol.
They are typically found as triglycerides three fatty acids attached to one glycerol backbone. Fats may be classified as saturated or unsaturated depending on the detailed structure of the fatty acids involved. Saturated fats have all of the carbon atoms in their fatty acid chains bonded to hydrogen atoms, whereas unsaturated fats have some of these carbon atoms double-bonded , so their molecules have relatively fewer hydrogen atoms than a saturated fatty acid of the same length.
Unsaturated fats may be further classified as monounsaturated one double-bond or polyunsaturated many double-bonds. Furthermore, depending on the location of the double-bond in the fatty acid chain, unsaturated fatty acids are classified as omega-3 or omega-6 fatty acids.
Trans fats are a type of unsaturated fat with trans -isomer bonds; these are rare in nature and in foods from natural sources; they are typically created in an industrial process called partial hydrogenation. There are nine kilocalories in each gram of fat. Fatty acids such as conjugated linoleic acid , catalpic acid, eleostearic acid and punicic acid , in addition to providing energy, represent potent immune modulatory molecules.
Saturated fats typically from animal sources have been a staple in many world cultures for millennia. Saturated and some trans fats are typically solid at room temperature such as butter or lard , while unsaturated fats are typically liquids such as olive oil or flaxseed oil. Trans fats are very rare in nature, and have been shown to be highly detrimental to human health, but have properties useful in the food processing industry, such as rancidity resistance.
Most fatty acids are non-essential, meaning the body can produce them as needed, generally from other fatty acids and always by expending energy to do so. However, in humans, at least two fatty acids are essential and must be included in the diet.
An appropriate balance of essential fatty acids— omega-3 and omega-6 fatty acids —seems also important for health, although definitive experimental demonstration has been elusive. Both of these "omega" long-chain polyunsaturated fatty acids are substrates for a class of eicosanoids known as prostaglandins , which have roles throughout the human body.
They are hormones , in some respects. The omega-3 eicosapentaenoic acid EPA , which can be made in the human body from the omega-3 essential fatty acid alpha-linolenic acid ALA , or taken in through marine food sources, serves as a building block for series 3 prostaglandins e.
The omega-6 dihomo-gamma-linolenic acid DGLA serves as a building block for series 1 prostaglandins e. An appropriately balanced intake of omega-3 and omega-6 partly determines the relative production of different prostaglandins, which is one reason why a balance between omega-3 and omega-6 is believed important for cardiovascular health.
In industrialized societies, people typically consume large amounts of processed vegetable oils, which have reduced amounts of the essential fatty acids along with too much of omega-6 fatty acids relative to omega-3 fatty acids. Moreover, the conversion desaturation of DGLA to AA is controlled by the enzyme deltadesaturase , which in turn is controlled by hormones such as insulin up-regulation and glucagon down-regulation.
The amount and type of carbohydrates consumed, along with some types of amino acid, can influence processes involving insulin, glucagon, and other hormones; therefore, the ratio of omega-3 versus omega-6 has wide effects on general health, and specific effects on immune function and inflammation , and mitosis i.
Proteins are structural materials in much of the animal body e. They also form the enzymes that control chemical reactions throughout the body. Each protein molecule is composed of amino acids , which are characterized by inclusion of nitrogen and sometimes sulphur these components are responsible for the distinctive smell of burning protein, such as the keratin in hair.
The body requires amino acids to produce new proteins protein retention and to replace damaged proteins maintenance. As there is no protein or amino acid storage provision, amino acids must be present in the diet. Excess amino acids are discarded, typically in the urine.
For all animals, some amino acids are essential an animal cannot produce them internally and some are non-essential the animal can produce them from other nitrogen-containing compounds. About twenty amino acids are found in the human body, and about ten of these are essential and, therefore, must be included in the diet.
A diet that contains adequate amounts of amino acids especially those that are essential is particularly important in some situations: A complete protein source contains all the essential amino acids; an incomplete protein source lacks one or more of the essential amino acids.
It is possible with protein combinations of two incomplete protein sources e. However, complementary sources of protein do not need to be eaten at the same meal to be used together by the body. Water is excreted from the body in multiple forms; including urine and feces , sweating , and by water vapour in the exhaled breath. Therefore, it is necessary to adequately rehydrate to replace lost fluids. Early recommendations for the quantity of water required for maintenance of good health suggested that 6—8 glasses of water daily is the minimum to maintain proper hydration.
Most of this quantity is contained in prepared foods. For healthful hydration, the current EFSA guidelines recommend total water intakes of 2. These reference values include water from drinking water, other beverages, and from food. The EFSA panel also determined intakes for different populations. Recommended intake volumes in the elderly are the same as for adults as despite lower energy consumption, the water requirement of this group is increased due to a reduction in renal concentrating capacity.
Dehydration and over-hydration - too little and too much water, respectively - can have harmful consequences. Drinking too much water is one of the possible causes of hyponatremia , i.
Pure ethanol provides 7 calories per gram. For distilled spirits , a standard serving in the United States is 1. A 5 ounce serving of wine contains to calories. A 12 ounce serving of beer contains 95 to calories. Alcoholic beverages are considered empty calorie foods because other than calories, these contribute no essential nutrients. The micronutrients are minerals , vitamins , and others. Dietary minerals are inorganic chemical elements required by living organisms,  other than the four elements carbon , hydrogen , nitrogen , and oxygen that are present in nearly all organic molecules.
The term "mineral" is archaic, since the intent is to describe simply the less common elements in the diet. Some are heavier than the four just mentioned, including several metals , which often occur as ions in the body. Some dietitians recommend that these be supplied from foods in which they occur naturally, or at least as complex compounds, or sometimes even from natural inorganic sources such as calcium carbonate from ground oyster shells.
Some minerals are absorbed much more readily in the ionic forms found in such sources. On the other hand, minerals are often artificially added to the diet as supplements; the most famous is likely iodine in iodized salt which prevents goiter. Many elements are essential in relative quantity; they are usually called "bulk minerals". Some are structural, but many play a role as electrolytes. Many elements are required in trace amounts, usually because they play a catalytic role in enzymes.
Vitamins are essential nutrients,  necessary in the diet for good health. Vitamin D is an exception, as it can be synthesized in the skin in the presence of UVB radiation , and many animal species can synthesize vitamin C. Vitamin deficiencies may result in disease conditions, including goitre , scurvy , osteoporosis , impaired immune system, disorders of cell metabolism, certain forms of cancer, symptoms of premature aging, and poor psychological health , among many others.
Phytochemicals such as polyphenols are compounds produced naturally in plants phyto means "plant" in Greek. In general, the term is used to refer to compounds which do not appear to be nutritionally essential and yet may have positive impacts on health. To date, there is no conclusive evidence in humans that polyphenols or other non-nutrient compounds from plants have health benefit effects. While initial studies sought to reveal if nutrient antioxidant supplements might promote health, one meta-analysis concluded that supplementation with vitamins A and E and beta-carotene did not convey any benefits and may in fact increase risk of death.
Vitamin C and selenium supplements did not impact mortality rate. Health effects of non-nutrient phytochemicals such as polyphenols were not assessed in this review.
Animal intestines contain a large population of gut flora. In humans, the four dominant phyla are Firmicutes , Bacteroidetes , Actinobacteria , and Proteobacteria. Bacteria in the large intestine perform many important functions for humans, including breaking down and aiding in the absorption of fermentable fiber, stimulating cell growth, repressing the growth of harmful bacteria, training the immune system to respond only to pathogens, producing vitamin B 12 , and defending against some infectious diseases.
There is not yet a scientific consensus as to health benefits accruing from probiotics or prebiotics. Carnivore and herbivore diets are contrasting, with basic nitrogen and carbon proportions vary for their particular foods. Many herbivores rely on bacterial fermentation to create digestible nutrients from indigestible plant cellulose, while obligate carnivores must eat animal meats to obtain certain vitamins or nutrients their bodies cannot otherwise synthesize.
Plant nutrition is the study of the chemical elements that are necessary for plant growth. Some elements are directly involved in plant metabolism. However, this principle does not account for the so-called beneficial elements, whose presence, while not required, has clear positive effects on plant growth. A nutrient that is able to limit plant growth according to Liebig's law of the minimum is considered an essential plant nutrient if the plant cannot complete its full life cycle without it.
There are 16 essential plant soil nutrients, besides the three major elemental nutrients carbon and oxygen that are obtained by photosynthetic plants from carbon dioxide in air, and hydrogen , which is obtained from water.
Plants uptake essential elements from the soil through their roots and from the air consisting of mainly nitrogen and oxygen through their leaves. Green plants obtain their carbohydrate supply from the carbon dioxide in the air by the process of photosynthesis. Carbon and oxygen are absorbed from the air, while other nutrients are absorbed from the soil. These hydrogen ions displace cations attached to negatively charged soil particles so that the cations are available for uptake by the root.
In the leaves, stomata open to take in carbon dioxide and expel oxygen. The carbon dioxide molecules are used as the carbon source in photosynthesis. Although nitrogen is plentiful in the Earth's atmosphere, very few plants can use this directly. Most plants, therefore, require nitrogen compounds to be present in the soil in which they grow.