Journal of Nutrition and Metabolism

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Dose is one of the major determinants. Retrieved 19 March Its primary use is as feed for high-producing dairy cows, because of its high protein content and highly digestible fiber, and secondarily for beef cattle, horses, sheep, and goats. The dictionary is also downloadable at Archive. Though supplementation with fermentable carbohydrates has been consistently associated with increased colonic proglucagon mRNA expression [ — ], only few studies detected increased plasma GLP-1 circulating levels in parallel [ — , — ]. Retrieved June 13, These products are readily accepted by consumers.

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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, [70] 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, [70] 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. This is made possible by the fact that largely inert atmospheric nitrogen is changed in a nitrogen fixation process to biologically usable forms in the soil by bacteria.

Plant nutrition is a difficult subject to understand completely, partially because of the variation between different plants and even between different species or individuals of a given clone. Elements present at low levels may cause deficiency symptoms, and toxicity is possible at levels that are too high.

Reversible peripheral neuropathy induced by vitamin B12 deficiency [in French] [published online ahead of print January 25, ]. Iverson D, McKenzie M.

Neurologic complications of gastric bypass surgery for morbid obesity [letter]. Nutritional and metabolic complications of bariatric surgery [review]. Am J Med Sci. Oh R, Brown DL. Vitamin B12 deficiency [review]. Dietary intake pattern relates to plasma folate and homocysteine concentrations in the Framingham Heart Study. Accessed September 9, Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies.

Diagnostic value of the mean corpuscular volume in the detection of vitamin B12 deficiency [review]. Scand J Clin Lab Invest. Folate intake and food sources in the US population. Am J Clin Nutr. Role of folic acid in atherosclerosis after kidney transplant: Folic acid antagonists during pregnancy and the risk of birth defects. N Engl J Med. Conversion and retention of pteroylmonoglutamate by jejunum.

Folate status following gastric bypass surgery the great folate mystery. Intestinal transport of zinc and folic acid: Drugs affecting homocysteine metabolism: An iron-regulated ferric reductase associated with the absorption of dietary iron [published online February 1, ].

Iron deficiency anemia [review]. Institute of Medicine Food and Nutrition Board. The National Academies Press; Copper deficiency in humans [review]. Copper absorption and bioavailability [review]. Osteomalacia with bone marrow fibrosis due to severe vitamin D depletion following gastrointestinal bypass surgery for severe obesity [published online ahead of print].

Bone metabolism and risk of secondary hyperparathyroidism 12 months after gastric banding in obese pre-menopausal women. Gastric bypass surgery for morbid obesity leads to an increase in bone turnover and a decrease in bone mass.

J Clin Endocrinol Metab. Effect of gastric bypass surgery on vitamin D nutritional status. Angstadt J, Whipple O. Developing a new bariatric surgery program. Despite the clear association between soluble fibers and weight loss, their effects on subjective measures of satiety are not conclusive. For example, the addition of 2. The soluble resistant dextrins promoted, in a dose-dependent manner, increased satiety when added to desserts and to carbohydrate-based meals [ — ].

Moreover, a nutrition bar containing guar gum 5. Subjects described to be significantly less hungry before lunch after consuming barley—but not wheat—and rice-containing foods [ ]. Barley-based foods enhanced as well satiety when compared to a high-glycemic index food or a food with no dietary fiber [ — ]. Similarly, a preload of 5. This was also associated with a significant reduction of energy intake at the subsequent lunch [ ]. In contrast, a meal replacement bar containing 1. Dose is one of the major determinants.

Solid foods are known to increase satiety and decrease hunger more effectively than liquid ones [ ]. Moreover, another concern to be addressed in future studies is the type of control to use.

No dietary fiber that may function as a control for satiety studies has been actually identified. It should be noted that the body weight was not the primary concern of these studies as they focused on changes in blood sugar or blood lipids. The satiating properties of soluble dietary fibers have been explained by various mechanisms, all of which are related to several stages in the process of appetite regulation such as taste, gastric emptying, absorption, and fermentation [ ].

Firstly, the viscosity of soluble fibers plays an important role in their ability to induce satiety [ , , ]. A higher viscosity meal delays gastric emptying [ , , ] and slows the digestion and absorption of nutrients, more precisely glucose, due to reduced enzymatic activity and mucosal absorption [ 31 , ], leading to early satiety sensations. The overall gastric emptying rate of healthy volunteers, as assessed by the paracetamol absorption test, was slower after the high viscosity oat bran-enriched beverage as compared to the low viscosity drink [ ].

Secondly, the lower palatability of fiber-rich meals may affect food intake in a negative manner [ — ]. A strong inverse relationship is described between palatability and satiation [ ]. A significant inverse relationship is reported between satiety and glucose and insulin responses to carbohydrate-rich breakfast cereals [ , ] and to beverages with different glycemic effects [ ].

However, other studies did not report any association of glucose and insulin postprandial levels with satiety [ , ]. They suggested that the release of putative satiety peptides is a more crucial component of mechanisms initiating and maintaining satiety.

Such statement leads to the fourth suggested mechanism that delineates the role of short-chain fatty acids in appetite control. Short-chain fatty acids regulate the release of various gut hormones, which play an important role in satiety signaling.

The role of short-chain fatty acids in appetite regulation and the potential underlying mechanisms will be elucidated in the following sections. The fermentability of soluble fibers by colonic microbiota is greater than that of insoluble fibers.

Pectin, resistant starches, gums, and polyfructans such as inulin are the most highly fermented substrates. On the other hand, acetate passes more freely into the peripheral circulation [ ]. Several functions are attributed to short-chain fatty acids, being recently proposed as key energy homeostasis signaling molecules [ ]. Accumulating evidence has attributed the satiating effects of fermentable carbohydrates to short-chain fatty acids, their major fermentation products [ ].

Short-chain fatty acids regulate appetite through several mechanisms. First, short-chain fatty acids have a role in slowing gastrointestinal motility, thus controlling digestion and nutrient absorption and eliciting an anorexigenic effect.

The majority of the studies linking short-chain fatty acids to gastrointestinal motility stems from ruminant animal studies [ ], where the production of short-chain fatty acids is greater than that in humans due to differences in gut physiology [ ].

However, there are some studies on nonruminants showing that short-chain fatty acids may regulate the overall transit time of the digesta through the large intestine [ , ]. Such responses were hypothesized to occur via three possible pathways: In addition, short-chain fatty acids were suggested to regulate gastrointestinal motility by affecting the release of the gastrointestinal 5-hydroxytryptamine 5-HT via the activation of the free fatty acid receptor 2 FFA2 , the major receptor for short-chain fatty acids.

The activation of various 5-HT receptor subtypes stimulates vagal nodose neurons and consequently prolongs colonic transit time [ , ]. Short-chain fatty acids also regulate appetite by modulating the release of various appetite-related hormones throughout the gastrointestinal tract [ ]. Peptide YY Peptide YY is a amino acid peptide, first isolated from porcine upper small intestine [ ]. PYY is secreted throughout the entire length of the gastrointestinal tract, with the highest concentrations found in the colon and rectum [ ].

Circulating PYY levels are the lowest in the fasting state and increase following the consumption of a meal, peaking at hours and remaining elevated for several hours. Peripheral PYY administration decreased food intake and body weight gain in rats [ ]. Similarly, it decreased appetite and food intake both in lean and obese humans [ , ]. An increased PYY response was consistently described following the consumption of various soluble dietary fibers. Postprandial PYY clearly increased after the consumption of psyllium-enriched test meals in healthy volunteers [ ].

The consumption of PolyGlycopleX, a novel functional fiber complex manufactured from three dietary fibers to form a highly viscous polysaccharide with high water-holding and gel-forming properties, for 3 weeks resulted in significantly increased fasting PYY levels as compared to the control product in healthy adults [ ].

The direct infusion of short-chain fatty acids into rabbit and rat colons significantly increased PYY secretions [ , ]. The stimulatory effects of short-chain fatty acids on PYY secretions are mainly attributed to a direct interaction between short-chain fatty acids and PYY cells.

In fact, FFA2 also known as GPR43 , the major receptor for short-chain fatty acids, is colocalized with PYY immunoreactive enteroendocrine L cells both in rat ileum and human colon [ , ].

Glucagon-Like Peptide 1 Glucagon-like peptide 1 is cosecreted with PYY from the intestinal L cells, encoded by the proglucagon gene [ ]. It is described with a potent incretin effect, stimulating insulin secretion in a glucose-dependent manner. Circulating GLP-1 levels rise following nutrient ingestion, in proportion to the energetic content of the meal [ ]. An acute intracerebroventricular administration of GLP-1 to rodents induced a decline in short-term energy intake [ ], and was associated with a reduced body weight following repeated administration [ ].

Similarly, an intravenous infusion of GLP-1 both in normal weight and in obese subjects resulted in a dose-dependent reduction in food intake [ ]. Variable GLP-1 responses to soluble dietary fiber intake were described, whether elevated, inhibited, or unaffected.

On the other hand, the ingestion of pasta enriched with a small amount of psyllium fiber 1. Such discrepancies in findings could be attributed to differences in the structures and food sources of ingested soluble fibers and their administered doses. Colonic fermentation appears to be essential in explaining GLP-1 release in response to soluble dietary fibers, despite inconsistent findings.

Though supplementation with fermentable carbohydrates has been consistently associated with increased colonic proglucagon mRNA expression [ — ], only few studies detected increased plasma GLP-1 circulating levels in parallel [ — , — ]. A strong association between postprandial hydrogen production and plasma GLP-1 concentrations was also reported. On the contrary, others have shown no effect of fermentable carbohydrates on circulating GLP-1 levels, whether acutely [ ] or over a short duration of 6 days [ ].

Based on these findings, the duration of supplementation is an important factor to consider when suggesting fermentation as a basis for soluble fibers-induced GLP-1 release. A sufficient time of weeks must be given in order to allow adaptation of the gut microbiota to the additional fermentable carbohydrate within the diet for maximal fermentation to take place [ ] and for GLP-1 levels in circulation to be subsequently affected.

Cholecystokinin Cholecystokinin was among the first hormones shown to modulate food intake [ ]. It is secreted from the I cells of the small intestine in response to food ingestion [ ]. Cholecystokinin circulating levels rise rapidly after a meal, reaching a peak within 15 minutes.

It was found to reduce food intake when infused both in rodents and humans [ , ]. In fact, plasma CCK levels are strongly associated with subjective measurements of satiety in women [ ]. Limited studies described the interaction between soluble dietary fibers and CCK release.

The role of fermentation and more specifically short-chain fatty acids in regulating CCK release is still poorly understood. In pigs, ileal infusion of short-chain fatty acids did not affect CCK circulating levels [ ]. Ghrelin Ghrelin is the only known orexigenic hormone in the gut. It was initially identified as an endogenous ligand for growth hormone secretagogue receptor GH-SR in rat stomach [ ]. Circulating ghrelin levels increase before meals and fall rapidly after eating [ ].

Both central and peripheral administration of ghrelin increased food intake and body weight in rodents [ , ]. Discrepancies in findings could be explained by variations in the physical and chemical properties of ingested soluble fibers, their different administered doses, and the forms of ghrelin being measured in circulation.

Several mechanisms were suggested to explain fiber-induced ghrelin suppression, most importantly fermentation. Such colonic fermentation may reduce ghrelin via increasing circulating PYY levels. Administration of PYY to humans reduced serum ghrelin levels [ ].

In addition to colonic fermentation, other mechanisms were also hypothesized. A possible inner-gastric pathway may operate through gastric somatostatin, which is released following the consumption of beet fiber in diabetic individuals [ ]. Somatostatin administration decreased ghrelin secretion in rats [ ] and lowered circulating ghrelin levels in humans [ ]. In addition, GLP-1 release in response to soluble fibers is another potential mechanism.

Infusion of GLP-1 into isolated rat stomach suppressed ghrelin secretions [ ]. Such satiating capacity appears to be comparable to that of other soluble viscous and fermentable fibers. Short-chain fatty acids affect satiety by primarily modulating the release of various appetite-regulating hormones, including PYY, GLP-1, and ghrelin. Since research in this area is still limited, such mechanisms necessitate further investigation.

Insufficient intake of dietary fiber has been reported worldwide. However, the estimates of fiber intake are highly variable. Based on the results of the Nationwide Food Consumption Survey, a mean dietary fiber intake of Similarly, a mean daily fiber intake of In contrast, Hallfrisch et al.

In Canada, low daily dietary fiber intakes have been also noted. According to Nova Scotia Department of Health [ ], the mean dietary fiber intake was estimated to be Similarly, in a more recent study on healthy Canadian adolescent males, a median dietary fiber intake of In Europe, the estimated national values for dietary fiber intake were found to fall within a narrower range: Thus, fiber intakes worldwide are well below the recommended levels despite the recommendations of several health organizations to increase the consumption of foods with high fiber content.

The introduction of fiber into traditional and processed foods provides one method by which to increase fiber intake [ 81 ]. The best-known examples of functional foods are fermented milks and yoghurts.

Several fiber-fortified dairy products are now appearing in market, with inulin being a popular fiber source for such products due to its combined nutritional and technological characteristics [ — ].

Protective Factors