Which provide lipids

Shuttling of lipid constituents from the micelles across the unstirred water layer is a chain reaction that depends on low cellular concentration of lipids at the enterocyte [ 32 ]. Bile salts are efficiently recycled via absorption in the lower ileum and transported back to the liver for re-use in subsequent lipid digestion [ 34 ].

Once diffusion into the enterocyte has occurred, FA are re-esterified in the endoplasmic reticulum by the glycerolphosphate pathway or the monoacylglycerol pathway [ 35 ]. After re-esterification into a triacylglyceride, multiple triglycerides and cholesterol esters are packaged into a chylomicron [ 36 ]. The exterior of the chylomicron has a phospholipid bi-layer and apolipoproteins which increase solubility and enzymatic recognition [ 26 ]. Chylomicrons then enter the blood circulatory system via the lymphatic system at the thoracic duct [ 26 ].

Once chylomicrons enter the blood stream, they can be stored in adipocytes, or oxidized by myofibers and other cells [ 19 ]. If insulin and other anabolic hormones are elevated, chylomicrons will be directed to adipocytes for storage [ 37 ]. This process is regulated by the stimulation effect of insulin on adipocyte lipoprotein lipase, while the isoform of lipoprotein lipase in muscle cells is not stimulated by insulin [ 37 ]. Therefore, the multi-functional enzyme lipoprotein lipase will be expressed in the capillary lumen of adipocytes to process triglyceride-rich chylomicrons and other lipoproteins [ 37 ].

Fatty acids are passively diffused individually, and then re-esterified for storage as a triacylglyceride in adipocytes [ 19 ]. In contrast to long-chain triacylglycerols which contain FA with 16 to 20 carbons, medium-chain triacylglycerols predominantly contain saturated FA with 8 and 10 carbons.

Once these FA are rapidly cleaved by lipases, they have high water solubility and are readily absorbed into mucosal cells, even in the presence of low amounts of intraluminal bile salts and pancreatic lipases for chylomicron formation. These medium-chain FA are then bound to albumin and transported by the portal venous system to the liver, with a carnitine-independent transport into mitochondria for subsequent oxidation.

Supplemental fats and oils are commonly added to swine diets to increase energy density of the diet, but may also reduce dust, supply fat soluble vitamins and essential FA, and improve diet palatability [ 41 , 42 ].

Composition of lipids utilized in swine diets is highly variable. Approximate FA composition of several common, unblended, lipid sources used in swine diets is shown in Table 3. Fats and oils are considered to be highly digestible energy sources for pigs [ 43 — 50 ].

However, their source and dietary inclusion rate may affect nitrogen digestibility and retention, and amino acid absorption [ 45 , 46 , 48 , 51 — 54 ]. In general, the apparent total tract digestibility of lipids in nursery pigs increases with age [ 55 , 56 ] with digestibility of animal fats lard and tallow increasing to a greater extent with age compared with vegetable oils [ 44 — 47 ]. In addition to animal age, the other main factors affecting the digestibility of lipids, and its subsequent energy value to pigs, is carbon chain length, degree of saturation, and free fatty acid FFA content, especially in young pigs, Fig.

These responses are supported by others [ 54 , 59 — 61 ] who reported that digestibility of FFA is lower than that of triglycerides, which coincides with a lower digestible energy content of lipids with increasing concentrations of FFA [ 57 , 62 , 63 ]. In contrast, DeRouchey et al. Factors associated with the origin and processing of lipid products i.

These factors include the concentration and FA composition of mono- and di-glycerides, acid oils, soap stocks, presence of emulsifying agents, and degree of hydrogenation. Tullis and Whittemore [ 66 ] suggested that the poor digestibility of hydrogenated tallow in swine diets is likely due to the high concentration of stearic acid.

More recently, Gatlin et al. Lecithin has been shown to have little impact on lipid and energy digestibility or growth performance in swine [ 68 — 72 ]. Lysolecithin hydrolyzed lecithin in which the sn-2 FA is removed has been shown to improve digestibility of soybean oil, lard, tallow and coconut oil, but had minimal effects on pig growth performance [ 49 ]. During a 28 d trial, Xing et al. On d, however, neither lipid nor energy digestibility was affected by lysolecithin supplementation, but there appeared to be a slight improvement in piglet weight gain [ 73 ].

Averette-Gatlin et al. Lipid digestibility also relates to the positioning of the FA on the triglyceride molecule [ 74 , 75 ]. However, determining the FA positioning on the glycerol molecule is difficult [ 76 ], and as a consequence, information on the effect of specific FA on the sn-1, sn-2, or sn-3 position of glycerol regarding lipid digestibility is sparse.

In general, it is believed that long-chain FA on the sn-1 and sn-3 positions are absorbed less efficiently than long-chain FA bound on the sn-2 position, due to their hydrophobic characteristics. This relationship is supported by Bracco [ 28 ] who suggested that the presence of a long-chain saturated FA SFA at the sn-1 and sn-2 positions of a triglyceride is partially responsible for the poor absorption of cocoa butter.

Furthermore, Smink et al. In swine, the effect of FA position is less clear. Scheeder et al. These results were supported by Innis et al. In contrast, Innis and Dyer [ 80 ] reported that the FA on the sn-2 position is conserved during digestion and absorption, and subsequently, it is reassembled to chylomicron triglycerides.

Fatty acid location on the glycerol molecule may also be important because long-chain non-esterified FA at the sn-1 and sn-3 positions may have reduced absorption due to their tendency to form insoluble soaps with divalent cations [ 81 , 82 ].

Even though research studies [ 54 , 85 — 87 ] have shown that the DE and ME content of various refined lipids in swine are similar to values reported in the NRC [ 88 ], the effect of fatty acid carbon chain length of less than 16 or greater than 18 as utilized by [ 57 , 63 , 83 , 84 ] , the specific location of the unsaturated or saturated fatty acids on the glycerol backbone [ 77 ], the effect of quality moisture, insoluble, and unsaponifiables- MIU , nonelutable material- NEM , and the extent of peroxidation on energy value among lipid sources has not been well established.

Beyond nursery pigs [ 44 — 47 , 55 , 56 ], there is little comparative data available to compare lipid digestibility or energy values of lipids between nursery, growing, finishing, and mature gestating or lactating sows , similar that which has been conducted for amino acids or fiber [ 89 , 90 ].

However, it is worthy to note that the NE of soybean oil or choice white grease was not found to be different between growing and finishing pigs [ 91 ] suggesting that digested lipids may be used at a relatively constant rate for incorporation into body lipids or for ATP synthesis. The net energy NE content of dietary lipids also needs to be more accurately determined. This approach was based on the NE of dietary lipid sources ranging from 6.

It is generally assumed that the efficiency of converting ME to NE for lipids is high [ 93 — 95 ]. This assumption is supported by Sauvant et al.

However, major discrepancies in the NE content of dietary lipids have been reported. Kil et al. It is interesting to note that in NRC [ 88 ], generalized equations based on constituents of the ingredient including ME, ash, and acid detergent fiber [ 98 , 99 ] were used for calculating NE content.

As a result, NE values for dietary lipid sources ranged from 4. In addition, the post-absorptive utilization efficiency of FA is determined whether it is used for a product body lipid deposition or a process ATP production. In their unaltered state, lipids are primarily comprised of saturated or unsaturated FA linked to a glycerol backbone. However, factors such as the degree of saturation, temperature, as well as exposure to oxygen, transition metals, undissociated salts, water, and other non-lipid compounds can affect the ultimate composition of a lipid over time [ — ].

Lipid peroxidation is a complex and dynamic process that degrades and produces numerous peroxidation compounds over time [ ]. The lipid peroxidation process has been classically described in three phases: 1 the initiation phase involves the formation of free lipid radicals and hydroperoxides as primary reaction products, 2 the propagation phase where the hydroperoxides formed are decomposed into secondary peroxidation products, and 3 the termination phase which involves the formation of tertiary peroxidation products [ , — ]; Figs.

With advances in understanding and measuring oxidation reactions with more sophisticated chromatography and spectroscopy methods, a more integrated paradigm has emerged to recognize the complexity of lipid oxidation Fig. Generalized lipid peroxidation process. Generalized lipid peroxidation process [ ]. Integrated scheme for lipid oxidation [ ]. Peroxidation of lipids is caused primarily by the attack of an oxygen molecule on unsaturated fatty acids. The rate of oxygen uptake by a fatty acid increases with the degree of unsaturation, but the mechanisms of peroxidation for the various types of FA are different [ ].

Although saturated and monounsaturated FA MUFA are essentially resistant to peroxidation, saturated FA can undergo peroxidation, but at a much slower rate. In addition, the degree of unsaturation of a FA on the sn-1, sn-2, or sn-3 positions may also affect the susceptibility of a lipid to peroxidation. A triglyceride with an unsaturated FA located on the sn-2 position, and SFA located on the sn-1 and sn-3 positions, would have a lower ability to be peroxidized compared to having a triglyceride with PUFA located on the sn-1 and sn-3 positions, and a SFA on the sn-2 position [ — ].

However, this may be dependent upon the method of randomization [ ]. Peroxidation susceptibility among fatty acids can be very different. For example, DHA, which contains 6 double bonds, is 8-times more prone to peroxidation than linoleic acid, which has only 2 double bonds, and times more susceptible to peroxidation than oleic acid which has only 1 double bond.

Thus, the total PI for a particular lipid can range from 5 or less for coconut oil and tallow low potential for peroxidation to greater than for menhaden fish oil or algae oil high potential for peroxidation; Table 4. Belitz et al. The accuracy of these PI estimates relative to their impact on animal performance has not been evaluated.

Relative susceptibility of double bonds to peroxidation [ ]. The PI developed by Holman [ ] is based solely on oxygen uptake by fatty acids and provides no specific details on which lipid peroxidation products are produced or the impact that these compounds have on energy and feeding value to pigs.

Lipid hydroperoxides initially formed during the lipid peroxidation process not only have the potential to reduce its caloric value and subsequent animal health and growth performance of animals, but also result in the formation of secondary and tertiary peroxidation products aldehydes, ketones, alcohols, hydrocarbons, volatile organic acids, and epoxy compounds which may also negatively affect feeding value and animal productivity [ 18 ].

Consequently, the increase and subsequent decrease in the amount of various lipid peroxidation products over time during the phases of the peroxidation process increases the difficulty of accurately measuring and assessing the extent of lipid peroxidation.

Because lipid peroxidation is a dynamic process, where compounds are continually produced and degraded over time, many theoretical schematics representing the production and degradation of peroxidation products have been proposed Lubuza, ; [ 11 ]. Figure 7 provides a theoretical illustration of this dynamic process and further subdivides the process into the initiation, propagation, and termination phases [ ]. Chemical and physical changes of oil due to heating adapted from [ ].

Some of the most common chemical assays used to indicate the extent of lipid peroxidation are described in Table 5. Of these tests, peroxide value PV , anisidine value AnV , and thiobarbituric acid reactive substances TBARS are the most common indicative tests used in the feed industry. Peroxide value measures peroxidation products produced during the initiation phase, while AnV and TBARS are measures of peroxidation products produced during the propagation phase of peroxidation.

These measures, however, do not measure compounds that remain unchanged during the peroxidation process, and hydroperoxides and aldehydes are subsequently degraded as peroxidation progresses Fig. In addition, these assays are not necessarily specific for the compounds which they were originally designed to measure [ , ]. Consequently, new and more reliable methods utilizing HPLC or GC-MS are warranted, especially for aldehydes that are considered to be highly cytotoxic.

Another aldehyde derived from the peroxidation of linoleic acid is 2, 4-decadienal DDE , and although it is less well known and studied compared to HNE [ ], it also represents a terminal lipid peroxidation compound which can be analyzed by some commercial laboratories, while HNE cannot. Polymeric compounds are also formed during the later phases of peroxidation Fig.

Like many of the compounds previously described, measurement of polymers is not a common analytical procedure used for evaluating lipid quality in the animal feeds and feed ingredients, but may have important implications for assessing the safety and feeding value of lipids.

Due to the high variability in composition of lipids and the phases involved in lipid peroxidation, there appears to be no single method that adequately describes or predicts lipid peroxidation [ ]. Therefore, to accurately analyze the amount of lipid damage caused by peroxidation, it is necessary to determine the degree of lipid peroxidation by using more than one assay and determine peroxidation at several time intervals related to each phase of peroxidation.

However, despite its practical advantages, Shahidi and Wanasundra [ ] indicated that TOTOX does not have a sound scientific basis because it combines variables with different dimensions. In addition, this measure fails to incorporate any compounds associated with the termination phase of peroxidation such as DDE or HNE, a measure of polymeric compounds, or a measure of remaining peroxidative potential which can be determined by active oxygen method AOM or oil stability index OSI.

Furthermore, no research studies have been published that have examined the potential synergistic or interactive effects between initiation, propagation, or termination phase lipid peroxidation products on the overall feeding value and quality of a lipid. Recently, Liu et al. They also conducted an extensive analysis of peroxidation compounds and reported numerous correlations among various composition and peroxidation indicator and predictive measures.

However, due to the potential confounding effect of lipid source composition and individual peroxidation methods, they indicated that caution should be used when interpreting their data. Because of the confounding effect of lipid source and predictive peroxidation tests, we recently conducted a time series peroxidation analysis of corn oil. Tables 6 and 7 provide a detailed description of the composition and peroxidation measures of heated corn oil at each time point, while Fig.

The changes in the various lipid peroxidation measures over time clearly show that peroxidation occurred when the corn oil was heated at either temperature, but depending upon temperature, the rate of production and concentrations of peroxidation compounds was dramatically different.

These data confirm the complexity of the peroxidation process and the challenges of interpreting results from various peroxidation measures as described by others. Nutritionists and feed manufacturers use a variety of qualitative and quantitative methods to assess the quality of feed ingredients including physical, chemical, and biological tests.

Physical evaluation of feed ingredients often includes color, smell, and taste characteristics that are qualitative criteria, but are used to identify characteristics that are thought to potentially lead to suboptimal animal performance when used in animal feeds. Chemical tests are quantitative and allow accurate estimation of energy and nutrient content as well as possible contaminants and toxic compounds.

Biological evaluation of feed ingredients is the most definitive measure of the feeding value of an ingredient, but it is time consuming, expensive, involves controlled experimental procedures and the use of animals, and as a result, cannot be used routinely as part of a feed manufacturing quality control program.

As reported by van Kempen and McComas [ ] and Shurson et al. The indices reported in these reports are general descriptors used to define lipid quality or ensure that the lipid products meet trading specifications, but provide limited information regarding their feeding value. Furthermore, these quality measures provide no information regarding the degree of lipid peroxidation of a lipid source. Therefore, additional measurements are required to assess lipid peroxidation. A recent examination of lipid samples obtained from a local feed manufacturer showed a wide range 0.

Peroxidation also occurs in feed ingredients and complete feeds during storage and can be affected by feed processing conditions. Presence of oxygen, transition metals e. Therefore, animals fed these peroxidized lipids can develop metabolic oxidative stress [ — ].

Peroxidation can also occur in the gastrointestinal tract, tissues, and cells resulting in damage which can negatively impact animal health and metabolism. Reactive oxygen species are produced endogenously by aerobic metabolism and the immune system, but reactive oxygen species can also be provided exogenously from the diet or produced in the gastrointestinal tract during digestion. At the cellular level, oxidative stress results in a cascade of events, beginning with damage or modification of cellular and subcellular membranes containing lipids, as well as damage to proteins, nucleic acids, and carbohydrates [ , ].

Furthermore, some aldehydes e. Peroxidative damage at the cellular level may increase cell rigidity and permeability, cause cell necrosis, impair cell function and integrity, contribute to structural damage of tissues, and increase demand for metabolic antioxidants [ , ]. Exogenous e. Metabolic oxidative stress occurs when pro-oxidants overwhelm the antioxidant capacity of an animal [ ].

Therefore, animals with inadequate supplies of endogenous antioxidants relative to metabolic demand may develop metabolic oxidative stress. Although the number of studies are limited, feeding diets containing peroxidized lipids has been shown to result in negative effects on health and growth performance of swine and poultry [ , ]. Diets containing peroxidized lipids cause reduced gain efficiency [ — ], growth rate [ , ], increased metabolic oxidative status [ , ], reduced energy digestibility [ , ], increased mortality [ , ], impaired immune function [ ], and reduced meat quality [ , , ].

Therefore, feeding diets containing peroxidized lipids can negatively affect overall animal health, growth performance, and meat quality. Biological samples can be used to measure reactive compounds, indicators of biological damage, or antioxidants to determine metabolic oxidative status. Free radicals can be measured with electron spin resonance, but due to their short half-life, they are difficult to quantify and measurement requires specialized equipment.

Unfortunately, this assay may detect relatively stable free radicals generated from antioxidants, and as a result, it is not specific to reactive oxygen species [ ]. Furthermore, free radicals associated with peroxidation may be present at undetectable concentrations because of they are rapidly catabolized [ ]. Some alternative assays to electronic spin resonance have been developed that are specific for hydroxy free radicals, but they are not utilized routinely [ ].

Measurement of the amount of various peroxidation products in a biological sample may also provide information about metabolic oxidation status of an animal. Hydrogen peroxide [ ], conjugated dienes [ ], and TBARS have been measured as indicators of metabolic oxidation status, but the use of TBARS and conjugated dienes has been criticized because they lack specificity. Specific aldehydes, such as MDA and HNE, can also be measured in biological samples along with compounds indicative of peroxidative damage such as protein carbonyls, 8-hydroxy-deoxyguanosine, and isoprostanes [ ].

However, the concentrations of these compounds in various tissues at which they are of concern have not been determined. However, Esterbauer et al. Esterbauer et al. Liver damage resulting from feeding peroxidized diets can be measured indirectly using transaminase enzymes. Serum concentrations of hepatic transaminase enzymes have been used to assess hepatocytic damage or necrosis [ ], and elevated levels of glutamate-oxalacetate transaminase and glutamate-pyruvate transaminase [ ] or aspartate transaminase [ ] in serum have been reported when pigs were fed diets containing inadequate concentrations of vitamin E, indicating that metabolic oxidative stress contributed to hepatocytic damage.

In addition to measurements of oxidative damage, specific endogenous antioxidants can be measured and used to assess metabolic oxidative status of an animal. Vitamin A and E can be measured in serum or liver, where relatively low concentrations may indicate metabolic oxidative stress. Negative correlations between vitamin E and TBARS concentrations in biological samples [ — ] indicate that vitamin E is catabolized during metabolic oxidative stress. Additional measures of endogenous antioxidants, such as glutathione and vitamin C, or the activity of enzymes such as glutathione peroxidase, catalase, and superoxide dismutase can be used as indicators of the ability of the animal to counteract metabolic peroxidative damage.

Besides measuring specific antioxidants, other assays can be used to characterize overall metabolic antioxidative status. Measurement of the total radical-trapping antioxidant, ferric-oxide reducing antioxidant, and the trolox a water soluble analog of vitamin E with antioxidant properties equivalent antioxidant capacity have been used to determine the combined antioxidants activity of a sample [ ].

Generally, these assays induce oxidative conditions and measure the oxidation of marker molecules added to the assay. However, the application of these assays on biological samples is often criticized because the accelerated pro-oxidant conditions of the assays do not reflect conditions in vivo [ ]. Numerous assays can be used to partially assess the extent of metabolic oxidative stress in an animal, but no single measure can be used as a definitive indicator because of the complexity of the various physiological effects.

Therefore, multiple measurements must be used to evaluate metabolic oxidative status, but the relative importance of specific measures relative to animal health and growth performance is not well understood. Unfortunately, there is also limited information about the use of various peroxidation measures to predict the ability of an animal to utilize a lipid source for energy. Antioxidants are chemical compounds that reduce lipid peroxidation, and are commonly added to feed ingredients and complete feeds for this purpose.

However, antioxidants do not reverse peroxidation once it occurs [ ]. There are many natural e. In addition, several herbs e. Each antioxidant compound varies in effectiveness in the prevention of peroxidation and mode of action.

However, exogenous antioxidants are generally classified as primary or secondary antioxidants based ontheir mode of action, but some antioxidants have several modes of action and act synergistically with other antioxidant compounds [ ]. Primary antioxidants generally exist as mono- or polyhydroxy phenolic compounds with various ring substitutions, and quench free radicals, reactive intermediates of peroxidation, or reactive oxygen species to disrupt the chain reaction of peroxidation. As a result, antioxidant radicals are produced and stabilized by the delocalization of the unpaired electron around the phenolic ring [ ].

Primary antioxidant radicals are deactivated by binding with other antioxidant free radicals to create dimers of antioxidant molecules, or they can be regenerated via reduction reactions with other antioxidants [ ].

Carotenoids, flavonoids, phenolic acids, tocopherols, tocotrienols, lignans, butylated hydroxytoluene, butylated hydroxyanisole, ethoxyquin, propyl gallate, tertiary-butylhydroquinone, and other phenolic compounds act as primary antioxidants [ ]. Secondary antioxidants reduce peroxidation by chelating pro-oxidant metal ions, reducing primary antioxidants, decomposing hydroperoxides, deactivating singlet oxygen, or acting as oxygen scavengers [ ].

These types of antioxidants generally require the presence of other compounds to utilize their antioxidant effects, such as prolonging the effectiveness of phenolics and chelators that inhibit pro-oxidant effects of metals [ ]. Carboxylic acid compounds such as phosphoric acid derivatives e. The oxidative stability of soybean oil declined with the addition of 0. Therefore, chelators such as citric acid are effective in reducing peroxidation in the presence of metals. Other secondary antioxidants work as reducing agents and oxygen scavengers.

Vitamin C, carotenoids, some amino acids e. Clements et al. Some antioxidants act synergistically when two or more antioxidants are combined resulting in total antioxidant activity exceeding the sum of individual activity of the antioxidants [ ]. Other secondary antioxidants act synergistically by regeneration of primary antioxidants to extend the functionality of primary antioxidants. Cort [ ] showed that ascorbic acid reduces tocopheroxyl radicals to allow regeneration of functional tocopherol.

Dietary addition of antioxidants, such as butylated hydroxyanisole, butylated hydroxytoluene, tocopherol, and ethoxyquin has been evaluated in humans, rodents, and livestock, but their impact on animal physiological and growth performance parameters has been inconsistent [ ]. Dibner et al. Likewise, supplementation of additional antioxidants improved growth performance in pigs fed diets containing dried distillers grains with solubles, peroxidized corn oil, or peroxidized soybean oil [ , , ].

In contrast, others have shown that supplementation of antioxidants have no effect on growth performance in animals under dietary oxidative stress conditions [ — ]. Relative to foods containing antioxidant capacity in human nutrition, a database for the Oxygen Radical Absorbance Capacity for selected foods [ ] is available. When energy needs are high, the body welcomes the high-caloric density of fats.

For instance, infants and growing children require proper amounts of fat to support normal growth and development. If an infant or child is given a low-fat diet for an extended period, growth and development will not progress normally. Other individuals with high-energy needs are athletes, people who have physically demanding jobs, and those recuperating from illness. When the body has used all of its calories from carbohydrates this can occur after just twenty minutes of exercise , it initiates fat usage.

A professional swimmer must consume large amounts of food energy to meet the demands of swimming long distances, so eating fat-rich foods makes sense. In contrast, if a person who leads a sedentary lifestyle eats the same high-density fat foods, they will intake more fat calories than their body requires within just a few bites. Use caution—consumption of calories over and beyond energy requirements is a contributing factor to obesity.

Fat contains dissolved compounds that contribute to mouth-watering aromas and flavors and increase palatability of food.

Fat also adds texture to food. Baked foods are supple and moist. Frying foods locks in flavor and lessens cooking time. How long does it take you to recall the smell of your favorite food cooking? What would a meal be without that savory aroma to delight your senses and heighten your preparedness for eating a meal?

Fat plays another valuable role in nutrition. Fat contributes to satiety, or the sensation of fullness. When fatty foods are swallowed the body responds by enabling the processes controlling digestion to retard the movement of food along the digestive tract, thus promoting an overall sense of fullness.

Oftentimes before the feeling of fullness arrives, people overindulge in fat-rich foods, finding the delectable taste irresistible. Indeed, the very things that make fat-rich foods attractive also make them a hindrance to maintaining a healthful diet. While fats provide delicious smells, tastes, and textures to our foods, they also provide numerous calories. To allow your body to experience the satiety effect of the fat before you overindulge, try savoring rich foods. Eating slowly will allow you to both fully enjoy the experience and be sated with a smaller portion.

Remember to take your time. Drink water in between bites or eat a lower fat food before and after a higher fat food. The lower-fat foods will provide bulk, but fewer calories. Skills to Develop Explain the role of lipids in overall health. Functions of Lipids in the Body: Storing Energy The excess energy from the food we eat is digested and incorporated into adipose tissue, or fatty tissue.

Functions of Lipids in the Body: Insulating and Protecting Did you know that up to 30 percent of body weight is comprised of fat tissue? Functions of Lipids in the Body: Aiding Digestion and Increasing Bioavailability The dietary fats in the foods we eat break down in our digestive systems and begin the transport of precious micronutrients. If people consume more carbohydrates than they need at the time, the body stores some of these carbohydrates within cells as glycogen and converts the rest to fat.

Glycogen is a complex carbohydrate that the body can easily and rapidly convert to energy. Glycogen is stored in the liver and the muscles. Muscles use glycogen for energy during periods of intense exercise. A few other body tissues store carbohydrates as complex carbohydrates that cannot be used to provide energy.

Added sugars are syrups and other caloric sweeteners used in other food products. Added sugars are listed as an ingredient in food labels. They include brown sugar, corn sweetener, corn syrup, dextrose, fructose, glucose, high-fructose corn syrup, honey, invert sugar, lactose, malt syrup, maltose, molasses, raw sugar, sucrose, trehalose, and turbinado sugar. Naturally occurring sugars, such as those in fruit or milk, are not added sugars.

The glycemic index of a carbohydrate represents how quickly its consumption increases blood sugar levels. Values range from 1 the slowest to the fastest, the index of pure glucose. However, how quickly the level actually increases also depends on what other foods are ingested at the same time and other factors. The glycemic index tends to be lower for complex carbohydrates than for simple carbohydrates, but there are exceptions.

For example, fructose the sugar in fruits has little effect on blood sugar. Processing: Processed, refined, or finely ground foods tend to have a higher glycemic index. Type of starch: Different types of starch are absorbed differently. For example, potato starch is digested and absorbed into the bloodstream relatively quickly. Barley is digested and absorbed much more slowly.

Fiber content: The more fiber a food has, the harder it is to digest. As a result, sugar is absorbed more slowly into the bloodstream. Ripeness of fruit: The riper the fruit, the more sugar it contains, and the higher its glycemic index.

Fat or acid content: The more fat or acid a food contains, the more slowly it is digested and the more slowly its sugars are absorbed into the bloodstream.

Preparation: How a food is prepared can influence how quickly it is absorbed into the bloodstream. Generally, cooking or grinding a food increases its glycemic index because these processes make food easier to digest and absorb. Other factors: The way the body processes food varies from person to person, affecting how quickly carbohydrates are converted to sugar and absorbed.

How well a food is chewed and how quickly it is swallowed also have an effect. The glycemic index is thought to be important because carbohydrates that increase blood sugar levels quickly those with a high glycemic index also quickly increase insulin levels. The increase in insulin may result in low blood sugar levels hypoglycemia Hypoglycemia Hypoglycemia is abnormally low levels of sugar glucose in the blood.

Hypoglycemia is most often caused by drugs taken to control diabetes. Much less common causes of hypoglycemia include other Carbohydrates with a low glycemic index do not increase insulin levels so much. As a result, people feel satiated longer after eating. Consuming carbohydrates with a low glycemic index also tends to result in more healthful cholesterol levels and reduces the risk of obesity Obesity Obesity is excess body weight.

See also Diabetes Mellitus In spite of the association between foods with a low glycemic index and improved health, using the index to choose foods does not automatically lead to a healthy diet. For example, the glycemic index of potato chips and some candy bars—not healthful choices—is lower than that of some healthful foods, such as brown rice. A fat gram is densely concentrated with energy, containing more than double the amount of energy as a gram of carbohydrate.

Hunger remains a problem for people worldwide, and being able to store energy when times are good can help them endure a period of food insecurity. In other cases, the energy stored in adipose tissue might allow a person to weather a long illness. Unlike other body cells that can store fat in limited supplies, fat cells are specialized for fat storage and can expand almost indefinitely in size.

An overabundance of adipose tissue can be detrimental to your health, from mechanical stress on the body due to excess weight and hormonal and metabolic changes. Obesity can increase the risk for many diseases, including type 2 diabetes, heart disease, stroke, kidney disease, and certain types of cancer. It can also interfere with reproduction, cognitive function, and mood. Thus, while some body fat is critical to our survival and good health, it can be a deterrent to maintaining good health in large quantities.

Lipids also help the body produce and regulate hormones for everything from appetite to the reproductive system to blood clotting. Lipids are key to brain structure and function; the lipids form nerve cell membranes, insulate neurons the cables that send messages throughout the body , and help send signals within the brain.

The average body fat for a man is 18 to 24 percent and for a woman is 25 to 31 percent 1. Still, adipose tissue can comprise a much larger percentage of bodyweight depending on the degree of obesity of the individual.

Some of this fat is stored within the abdominal cavity, called visceral fat, and some are stored just underneath the skin, called subcutaneous fat. Visceral fat protects vital organs—such as the heart, kidneys, and liver. The blanket layer of subcutaneous fat insulates the body from extreme temperatures and helps keep the internal climate under control.

It pads our hands and buttocks and prevents friction, as these areas frequently come in contact with hard surfaces. It also gives the body the extra padding required when engaging in physically demanding activities such as ice skating, horseback riding, or snowboarding.

There are two types of fat stored as adipose tissue: subcutaneous fat and visceral fat. The combination of the fat and the nutrients allows the nutrients to be digested more easily and absorbed into the body.

This improved absorption is called increased bioavailability. Dietary fats can also increase the bioavailability of compounds known as phytochemicals —non-essential plant compounds considered beneficial to human health. Many phytochemicals are fat-soluble, such as lycopene found in tomatoes and beta-carotene found in carrots, so dietary fat improves the absorption of these molecules in the digestive tract.