Letteratura scientifica selezionata sul tema "Carbohydrates in human nutrition physiological eff"

AbstractThe purpose of the present review is to describe how human physiology at very low carbohydrate intakes relates to the criteria for nutritional essentiality. Although we did not limit ourselves to one particular type or function of carbohydrates, we did primarily focus on glucose utilisation as that function was used to determine the recommended daily allowance. In the general population, the human body is able to endogenously synthesise carbohydrates, and does not show signs of deficiency in the absence of dietary carbohydrates. However, in certain genetic defects, such as glycogen storage disease type I, absence of dietary carbohydrates causes abnormalities that are resolved with dietary supplementation of carbohydrates. Therefore, dietary carbohydrates may be defined as conditionally essential nutrients because they are nutrients that are not required in the diet for the general population but are required for specific subpopulations. Ketosis may be considered a physiological normal state due to its occurrence in infants in addition to at very low carbohydrate intakes. Although sources of dietary carbohydrates can provide beneficial micronutrients, no signs of micronutrient deficiencies have been reported in clinical trials of low-carbohydrate ketogenic diets. Nonetheless, more research is needed on how micronutrient requirements can change depending on the dietary and metabolic context. More research is also needed on the role of dietary fibre during a low-carbohydrate ketogenic diet as the beneficial effects of dietary fibre were determined on a standard diet and several studies have shown beneficial effects of decreasing non-digestible carbohydrates.

The defining effect of prebiotics is to stimulate selectively the growth of bifidobacteria and lactobacilli in the gut and, thereby, increase the body's natural resistance to invading pathogens. Prebiotic carbohydrates may also have additional, less specific, benefits because they are fermented in the large intestine. The prebiotic carbohydrates that have been evaluated in humans at the present time largely consist of fructans or galactans. There is consistent evidence from in vitro and in vivo studies that these are not digested by normal human enzymes, but are readily fermented by anaerobic bacteria in the large intestine. There are no reports of faecal recovery of measurable quantities of prebiotic carbohydrates. Through fermentation in the large intestine, prebiotic carbohydrates yield short-chain fatty acids, stimulate the growth of many bacterial species in addition to the selective effects on lactobacilli and bifidobacteria, they can also produce gas. Along with other fermented carbohydrates, prebiotics have mild laxative effects, although this has proved difficult to demonstrate in human studies because the magnitude of laxation is small. Potentially, the most important effect of prebiotic carbohydrates is to strengthen the body's resistance to invading pathogens and, thereby, prevent episodes of diarrhoea. At the present time, this effect has not been convincingly demonstrated in either adults or children, although there have been attempts to ameliorate the diarrhoea associated with antibiotics and travel, but without success. However, prebiotic carbohydrates clearly have significant and distinctive physiological effects in the human large intestine, and on the basis of this it is likely that they will ultimately be shown to be beneficial to health.

The human oro-gastrointestinal (GI) tract is a complex system, consisting of oral cavity, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus, which all together with the accessory digestive organs constitute the digestive system. The function of the digestive system is to break down dietary constituents into small molecules and then absorb these for subsequent distribution throughout the body. Besides digestion and carbohydrate metabolism, the indigenous microbiota has an important influence on host physiological, nutritional and immunological processes, and commensal bacteria are able to modulate the expression of host genes that regulate diverse and fundamental physiological functions. The main external factors that can affect the composition of the microbial community in generally healthy adults include major dietary changes and antibiotic therapy. Changes in some selected bacterial groups have been observed due to controlled changes to the normal diet e.g. high-protein diet, high-fat diet, prebiotics, probiotics and polyphenols. More specifically, changes in the type and quantity of non-digestible carbohydrates in the human diet influence both the metabolic products formed in the lower regions of the GI tract and the bacterial populations detected in faeces. The interactions between dietary factors, gut microbiota and host metabolism are increasingly demonstrated to be important for maintaining homeostasis and health. Therefore the aim of this review is to summarise the effect of diet, and especially dietary interventions, on the human gut microbiota. Furthermore, the most important confounding factors (methodologies used and intrinsic human factors) in relation to gut microbiota analyses are elucidated.

Human milk represents a cornerstone for growth and development of infants, with extensive array of benefits. In addition to exceptionally nutritive and bioactive components, human milk encompasses a complex community of signature bacteria that helps establish infant gut microbiota, contributes to maturation of infant immune system, and competitively interferes with pathogens. Among bioactive constituents of milk, human milk oligosaccharides (HMOs) are particularly significant. These are non-digestible carbohydrates forming the third largest solid component in human milk. Valuable effects of HMOs include shaping intestinal microbiota, imparting antimicrobial effects, developing intestinal barrier, and modulating immune response. Moreover, recent investigations suggest correlations between HMOs and milk microbiota, with complex links possibly existing with environmental factors, genetics, geographical location, and other factors. In this review, and from a physiological and health implications perspective, milk benefits for newborns and mothers are highlighted. From a microbiological perspective, a focused insight into milk microbiota, including origins, diversity, benefits, and effect of maternal diet is presented. From a metabolic perspective, biochemical, physiological, and genetic significance of HMOs, and their probable relations to milk microbiota, are addressed. Ongoing research into mechanistic processes through which the rich biological assets of milk promote development, shaping of microbiota, and immunity is tackled.

White lupin seeds have been used in human nutrition and treatment for several thousand years. Nowadays the use of white lupin seeds is limited by a small scale of their production. However, in the last 20 years quite new properties of white lupin have been discovered for the application in the production of different kinds of functional food. Unique traits of protein, fatty acids with a desirable ratio of omega-6 to omega-3 acids, and fibre as well as other specific components, for example oligosaccharides and antioxidants or non-starch carbohydrates, make white lupin an excellent component in many healthy diets. The effects of white lupin components concern the physiological condition of the human body, including diabetes, hypertension, obesity, cardiovascular diseases, lipid concentration, glycaemia, appetite, insulin resistance, and colorectal cancer. Seeds are used among others for the production of gluten-free flour, bacterial and fungal fermented products, noodle and pasta products, as substitutes of meat, egg protein and sausages, also are cooked, roasted and ground and mixed with cereal flour in the production of bread, crisps and pasta, crisps and dietary dishes.

Due to factors such as cultivar, fertilization, maturation or climate conditions, as well as the date of their harvest, chokeberries (Aronia melanocarpa) differ in their content of minerals, vitamins, carbohydrates, amino acids, organic acids, fats, aroma compounds and especially polyphenols, substances exerting a beneficial impact on health. The total content of the most important ingredients, polyphenolic compounds, influence many proven chokeberry activities like antioxidative, anti-inflammatory, hypotensive, antiviral, anticancer, antiplatelet, antidiabetic and antiatherosclerotic, respectively. Polyphenolic compounds such as anthocyanins, flavonoids, procyanidins and phenolic acids in different rates and amounts are responsible for all mentioned activities. In the human body, they undergo different biotransformative processes strengthening their bioactivity inside and outside cells. The popularity of chokeberry has been significant lately because of its effects on human health and not just because of its nutritional value. The main interest in this review has been refocused on the chokeberry benefits to human health, nutritional contribution of its components, particularly polyphenolic compounds, and its physiological effects.

Abstract Living organisms are in close dependence with the environment. There is also a permanent exchange of substance, energy and information between the human body and the environment, an exchange that underlies the development of all biological processes. In the normal biological processes, the essential environmental factors compete, among which we mention the air, water and food. The importance of food (lat. alimentum - aliment)consists of the intake of nutrients necessary for all life processes. The substances from food are generically described by the term “nutrient principles” or “food principles”, often being used the term “nutrients”. Among nutrients, depending on their amount in the food products and the physiological and biochemical role, there are the macronutrients (carbohydrates, lipids and protides), micronutrients (mineral compounds of biological interest and vitamins) as well as other nutrients (water, fibres, biologically-active substances).

Among many environmental factors nutrition is paramount, permanently and exclusively affecting in multidisciplinary mode on the biological and social essence of the human body. Therefore, this article describes the results of the actual supply of people aged of 60-89 years taking into account their eating habits associated with age-related changes in the gastrointestinal tract and metabolism. The study involved 611 respondents aged of 60-89 years, including men (23.9%) and women - 76.1%, living in Astana, the average age accounts of 73 ± 0.41years. The actual food was studied by frequency and a 24-hour simulation, recommended by the WHO for epidemiological studies. In assessing the adequacy of the supply of the reference values there were taken norms of physiological requirements in energy and nutrients for the population of gerontological groups of the Republic of Kazakhstan, as well as the norms of consumption of micronutrients on a scale of FAO / WHO. The study of the actual nutrition of the category of persons of Astana showed the diet of elderly people to be consisted of foods containing mostly protein and animal fats and digestible carbohydrates, while two latters were characterized by an excess of saturated fatty acids, the lack of polyunsaturated fatty acids, a high level of simple consumption carbohydrates from refined foods such as sugar, refined cereals, flour and poly- micronutrient failure of the nutrition on vitamins (deficiency of vitamin D, a, B1, E, C, biotin, folic and pantothenic acid) and minerals (calcium deficiency, potassium).

Development of the preimplantation embryo is reliant on nutrients present in the milieu of the reproductive tract. While carbohydrates, amino acids, lipids, and micronutrients are often considered when discussing preimplantation embryo nutrition, environmental oxygen is frequently overlooked. Although oxygen is not classically considered a nutrient, it is an important component of the in vitro culture environment and a critical regulator of cellular physiology. Oxygen is required to sustain an oxidative metabolism but when oxygen becomes limited, cells mount a physiological response driven by a family of transcription factors termed ‘hypoxia inducible factors’ which promote expression of a multitude of oxygen sensitive genes. It is this hypoxic response that is responsible not only for the switch to a glycolytic metabolism but also for a plethora of other cellular responses. There has been much debate in recent years over which environmental oxygen tension is preferential for the culture of preimplantation embryos. The review will evaluate this question and highlights how research using human embryonic stem cells can inform our understanding of why culturing under physiological oxygen tensions may be beneficial for the development of embryos generated through clinical in vitro fertilisation.

Polyphenols are dietary constituents of plants associated with health-promoting effects. In the human diet, polyphenols are generally consumed in foods along with macronutrients. Because the health benefits of polyphenols are critically determined by their bioavailability, the effect of interactions between plant phenols and food macronutrients is a very important topic. In the present review, we summarise current knowledge, with a special focus on the in vitro and in vivo effects of food macronutrients on the bioavailability and bioactivity of polyphenols. The mechanisms of interactions between polyphenols and food macronutrients are also discussed. The evidence collected in the present review suggests that when plant phenols are consumed along with food macronutrients, the bioavailability and bioactivity of polyphenols can be significantly affected. The protein–polyphenol complexes can significantly change the plasma kinetics profile but do not affect the absorption of polyphenols. Carbohydrates can enhance the absorption and extend the time needed to reach a maximal plasma concentration of polyphenols, and fats can enhance the absorption and change the absorption kinetics of polyphenols. Moreover, as highlighted in the present review, not only a nutrient alone but also certain synergisms between food macronutrients have a significant effect on the bioavailability and biological activity of polyphenols. The review emphasises the need for formulations that optimise the bioavailability and in vivo activities of polyphenols.

There exist a wide variety of metabolic responses to different types of carbohydrates and their influence on metabolism during endurance training. Recent studies revealed that the physiological responses to food are far more complex than was previously appreciated. The rapid release of insulin and the decline in blood sugar levels during the first stages of endurance training are linked to the Glycemic Index of foods. Researchers cannot still make use of the old distinction between starchy and sugary food or simple and complex carbohydrates. These distinctions are based on the chemical analysis of the food, which does not totally reflect the effects of these foods on the body. The Glycemic Index is a more reliable guideline to apply in nutritional management for endurance athletes. The major object of the study was to indicate the importance of utilizing the Glycemic Index (GI) as part of the nutritional preparation for endurance events. The study investigated the advantages of ingesting a Low Glycemic Index meal prior to exercise and compared it with the ingestion of a High Glycemic Index meal. A pretest-posttest design was used. Twelve healthy, male and female cyclists participated in the study. Subjects were selected according to their level of training. The total test period consisted of 14 days, which included two different dietary interventions of 7 days each. Diet -and training analysis were done on the subjects prior to the commencement of the study. Each subject completed three exercise trials. The first exercise trial consisted of a V02max test until exhaustion. Two submaximal trials (65 - 70 % of V02max) followed and were preceded by two dietary interventions. The dietary interventions (7 days each) had the same amount of CHO, fat and protein but differed in the Glycemic Index of the pre-exercise meals. The first pre-exercise meal was a High Glycemic Index (HGI) meal. The second pre-exercise meal was a Low Glycemic Index (LGI) meal. The results of the study indicated the advantages of ingesting a Low Glycemic Index meal prior to endurance exercise. The drop in blood glucose levels significantly differed (p<0.05) with an average of 0.68 mmol/L between the two tests after 10 minutes of cycling. It took 20 minutes for the blood sugar level of the first testto reach the same level of the blood sugar level of the second test. After the ingestion of the High Glycemic Index meal in Test 1, the blood lactate levels were significantly higher (p<0.05) during the first 15 minutes. The total distance covered by the subjects was 22.86 km after the first dietary intervention (High glycemic Index food) and 27.43 km after the second dietary intervention (Low glycemic Index food) although it is not statistically significant due to the small sample size. The difference in the distance covered of the two tests is 4.57 km in a period of 50 minutes. Subjects indicated that they experienced more physical strain (higher RPE values) in Test 1 (High Glycemic Index food) than in Test 2 (Low Glycemic Index food) (p<0.05). The study results support the fact that Low glycemic index food may confer an advantage when eaten prior to prolonged strenuous exercise by providing a slow¬releasing source of glucose to the blood without causing extensive hypoglycemia. Proper preparation and the correct choice of the pre-exercise meal can exclude the occurrence of sudden drops in the blood sugar levels. The Glycemic Index can also be successfully applied during and after events to improve performance.
Dissertation (MA (MHS))--University of Pretoria, 2007.
Arts, Languages and Human Movement Studies Education
unrestricted

Adolescent athletes of this era are more pressurized than adolescents of previous generations to perform at an optimum level (Micheli & Jenkins 2001, p49). The importance of winning can result in adolescent athletes developing inappropriate nutritional practices such as neglecting hydration and consuming insufficient carbohydrate (Micheli & Jenkins 2001, p57). Consuming insufficient fluid leads to dehydration which reduces a soccer player’s ability to continue training. Consuming inadequate carbohydrate reduces performance and blood glucose levels during training. This study aimed to determine the hydration status, fluid and carbohydrate intake of male, adolescent soccer players during training. A cross-sectional study was conducted among 122 amateur male, adolescent soccer players (mean age = 15.8 ± 0.8 years; mean BMI = 20.4 ± 2.0 kg/m2). The players’ hydration status before and after training, was measured using urine specific gravity and percent loss of body weight. Their carbohydrate intake, as well as the type and amount of fluid consumed, were assessed before, during and after training. A questionnaire was administered to determine the players’ knowledge regarding the importance of fluid and carbohydrate for soccer training. The study had an 87.1% response rate. The mean environmental conditions did not predispose players to heat illness. However, the players were at risk of developing heat illness during six of the 14 training sessions. Although the mean urine specific gravity indicated that players were slightly dehydrated before and after training, 43.8% of players were very or extremely dehydrated before training and 53.6% after training. A few (3.3%) were extremely hyperhydrated before training and after training (7.0%). On average players lost less than 1% of body weight during training and less than 3% of players dehydrated more than 2%. Players consumed mainly water before (289.17 ± 206.37 ml), during (183.20 ± 158.35 ml) and after (259.09 ± 192.29 ml) training. More than 90% stated that water was the most important fluid to consume before, during and after training. Very few (4.7%) correctly stated that carbohydrate should be consumed before, during and after training. Players were found to be slightly dehydrated before and after training and therefore were not consuming enough fluids during training. Players consumed inadequate amounts and types of fluid and carbohydrate. This not only compromises their performance but also health. Players were not aware of the importance of fluid and carbohydrate for soccer training. This study is unique in that it focused on the carbohydrate and hydration practices of socioeconomically disadvantaged adolescent soccer players during training. The study sample therefore represents a high risk group about which there is limited published data both locally and internationally. This study generated important baseline information which was lacking before on the hydration status, fluid and carbohydrate intake of adolescent soccer players in South Africa.
Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.