Role of Carbohydrate in Health

and Diseases

Presented By: Uttara Singh L-2008.H.Sc.-46D

Introduction

Carbohydrates are polyhydroxy aldehydes, ketones, alcohols, acids, their simple derivatives and their polymers having linkages of the acetal type.

They may be classified according to their degree of polymerization and may be divided initially into three principal groups:

sugars oligosaccharides polysaccharides

Major Dietary Carbohydrates

Class (DP*) Sub-Group Components

Sugars (1-2)

Monosaccharides Glucose, galactose, fructose

Disaccharides Sucrose, lactose, trehalose

Polyols Sorbitol, mannitol

Oligosaccharides (3-9)

Malto-oligosaccharides Maltodextrins

Other oligosaccharides Raffinose, stachyose, fructo-oligosaccharides

Polisaccharides (>9)

Starch Amylose, amylopectin, modified starches

Non-starch polisaccharides Cellulose, hemicellulose, pectins, hydrocolloids

DP * = Degree of polymerization

Physiological Effect of Carbohydrate

Carbohydrates have a wide range of physiological effects : Provision of energy Effects on satiety Control of blood glucose and insulin metabolism Protein glycosylation Cholesterol and triglyceride metabolism Bile acid dehydroxylation Fermentation Hydrogen/methane production Short-chain fatty acids production Control of colonic epithelial cell function Bowel habit/laxation/motor activity Effects on large bowel microflora

Role of Carbohydrates in Maintenance of Health

Carbohydrates in the diet• 50 g/day carbohydrate required to avoid ketosis.• Carbohydrate provides the majority of energy in the diets of most

people. • Carbohydrate-containing foods are vehicles for important

micronutrients and phytochemicals. • Dietary carbohydrate is important to maintain glycemic

homeostasis and for gastrointestinal integrity and function.• Diets high in carbohydrate as compared to those high in fat,

reduce the obesity and its co-morbid conditions.• A diet should consist of at least 55% of total energy coming from

carbohydrate.

Physical Activity• Maintenance of energy balance is dependent both on energy intake and energy

expenditure. • The combination of a high carbohydrate diet and regular physical activity is the

optimal arrangement to avoid positive energy balance and obesity. • The increased energy needs of physical activity can be supplied by

carbohydrate .• The importance of carbohydrate in the diet becomes more critical as the

amount and intensity of physical activity increases.

Carbohydrate and Behaviour• It has been suggested that providing breakfast to children who do not typically

eat breakfast can increase cognitive performance. • It has been suggested that sugar consumption leads to hyperactivity in children.

Beneficial Effect of Carbohydrate in Disorders/Diseases

• Carbohydrates may directly influence human diseases by affecting physiological and metabolic processes.

• Carbohydrates may also have indirect effects on diseases, for example, by displacing other nutrients or facilitating increased intakes of a wide range of other substances frequently found in carbohydrate-containing foods.

Obesity

• The frequency of obesity has increased in many developed and developing countries.

• This is public health importance because of negative effect of obesity in relation to diabetes, coronary heart disease and other chronic diseases of lifestyle.

• Genetic ,environmental factors and lack of physical activity is believed to contribute to the increasing rates of obesity.

• As fat is stored more efficiently than excess carbohydrate, use of high carbohydrate foods is likely to reduce the risk of obesity in the long term.

• Excess energy in any form will promote body fat accumulation.

Non-insulin Dependent Diabetes Mellitus (NIDDM)• High rates of NIDDM in all population groups are associated with

rapid cultural changes in populations consuming traditional diets, and also with increasing obesity.

• Foods rich in non-starch polysaccharides and carbohydrate-containing foods with a low glycemic index appear to protect against diabetes.

• Some epidemiological evidence suggests particular benefit of appropriately processed cereal foods, while other epidemiological and clinical studies suggest benefits of non-starch polysaccharide from legumes and pectin-rich foods.

• Avoid obesity and increase intakes of foods rich in non-starch polysaccharide and carbohydrate-containing foods with a low glycemic index offers the best means of reducing the rapidly increasing rates of NIDDM.

Cardiovascular Disease• Genetics , lifestyle factors , dietary factors ,obesity and high intakes of

saturated fatty acids are involved in the etiology of coronary heart disease and influence both the atherosclerotic and thrombotic processes.

• On the other hand, there is strong protective effect by a range of antioxidant nutrients found in fruits and vegetables,increasing carbohydrate intake can assist in the reduction of saturated fat.

• Among those who are overweight or obese it is more important to reduce total fat intake and to encourage the consumption of the carbohydrate-containing foods.

• Non-starch polysaccharides (NSP) have an appreciable effect in lowering serum cholesterol when consumed in naturally occurring foods and it may be used in the management hypercholesterolemia.

• Plant foods are good sources of potassium and reducing the sodium to potassium ratio may help to reduce the risk of hypertension as well as cerebrovascular disease.

Cancer• Gene defects in somatic cells is thought to be through DNA damage and failure of the DNA

repair system ( apoptosis).• Dietary carbohydrate is thought to be protective through mechanisms involving arrest of

cell growth, differentiation and selection of damaged cells for cell death (apoptosis). • Butyric acid which is formed in the colon from fermentation of carbohydrates fight against

the abnormalities.. • The process of fermentation may protect the colorectal area against the genetic damage

that leads to colorectal cancer through other mechanisms which include: the dilution of potential carcinogens; the reduction of products of protein fermentation through stimulation of bacterial growth; pH effects; maintenance of the gut mucosal barrier; and, effects on bile acid degradation. • Carbohydrate staple foods are a source of phytoestrogens which may be protective for

breast cancer.

Gastrointestinal Diseases • Intakes of non-starch polysaccharides(NSP) and

resistant starch (RS) are the most important contributors to stool weight.

• Increasing consumption of foods rich in NSP & RS carbohydrates like bran and cereals are very effective means of preventing and treating constipation, diverticular disease as well as haemorrhoids and anal fissures.

The Role of Carbohydrates in Exercise and Physical Performance

Some general dietary considerations • Health professionals argue that a healthy diet is one which

provides us with at least 50% of our daily energy intake in the form of carbohydrates, 35% or less from fats and the remainder from proteins.

• The common message is that we should move from high fat meat-based diets to those that are made up of more carbohydrates and fresh fruits and vegetables.

• Diet for athletes and active people should include more carbohydrate-containing foods.

• Their diets should be such that about 60% of their daily energy intake is obtained from carbohydrates,30% or less from fat and 10 to 15 % from proteins.

Carbohydrate Diets and Endurance Capacity :Studies

• A study exploring the link between diet and exercise capacity found that after a period on a high carbohydrate diet, endurance capacity on a cycle ergometer doubled in comparison with the exercise times achieved after consuming a normal mixed diet.

• In contrast, a fat and protein diet reduced exercise capacity to almost half that achieved after normal mixed diets.

• This clearly showed the benefits of eating a high-carbohydrate diet before prolonged exercise have been shown mainly during cycling and establish importance of the carbohydrate content in the diets of athletes preparing for competition.

• The importance of muscle glycogen during prolonged exercise was confirmed in studies which showed that fatigue occurs when muscle glycogen concentrations are reduced to low values.

Carbohydrate Diets and Endurance Capacity :Studies• One study examined the influence of different nutritional states

on the resynthesis of glycogen during recovery from prolonged exhaustive exercise.

• It found that a diet low in carbohydrate, and high in fat and protein for 2 to 3 days after prolonged submaximal exercise, produced a delayed muscle glycogen resynthesis, but when this was followed by a high carbohydrate diet for the same period of time, glycogen super compensation occurred ( Figure 1).

• This dietary manipulation not only increased the pre-exercise muscle glycogen concentration but also resulted in a significant improvement in endurance capacity (Figure 2).

• It was found that a carbohydrate-rich diet consumed for 3 days prior to competition, accompanied by a decrease in training intensity, resulted in increased muscle glycogen concentrations.

Carbohydrate Diets and Endurance Capacity :Studies• Studies on the influence of carbohydrate loading and

endurance capacity during running. • The runner’s normal mixed diets were modified by providing

either additional protein, complex carbohydrates or simple carbohydrates.

The 'complex' carbohydrate group supplemented their normal mixed diet with bread, potatoes, rice or pasta.

The 'simple' carbohydrate group ate their normal mixed diet but increased their carbohydrate intake with chocolates.

• The complex carbohydrate group improved their running times by 26%, and the simple carbohydrate group improved by 23%.

• There was no improvement in the performance times of the protein group.

Fig.1Muscle glycogen concentrations before and after constant load cycling to exhaustion, following three dietary conditions

Source: Adapted from Bergstrom, J.Hermansen,L., Hultman, E.,Saltin, B.

1 = Mixed diet for 3 days2 = Low carbohydrate diet for 3 days3 = High carbohydrate diet for 3 days

Fig.2Cycling time to exhaustion at constant load under three dietary conditions

1 = Mixed diet for 3 days2 = Low carbohydrate diet for 3 days3 = High carbohydrate for 3 days

Carbohydrate Diets and High Intensity Exercise

• Multiple-sprint sports involve a mixture of brief periods of exercise of maximum intensity followed by recovery periods of rest or light activity, and last up to 90 minutes.

• There is rapid utilization of muscle glycogen during several brief periods of maximal exercise, the rate of glycogenolysis decreases as exercise continues.

• Sports which demand that their participants perform a combination of submaximal running and brief periods of sprinting, such as soccer, reduces muscle glycogen values.

• Performance is impaired when glycogen value lowered, so carbohydrate loading would be necessary for participants in multiple-sprint sports.

Composition of Pre-exercise Meals

• Low glycemic index carbohydrate improve endurance capacity.

• Eating a high fat meal before exercise is not recommended as a nutritional preparation for endurance competitions because these meals take a longer time to digest.

• From animal studies to suggest that increased fat intake will result in a lower oxidation of carbohydrate during exercise.

• The pre-exercise meals contained approximately 280g of carbohydrate in the high carbohydrate meal and 84g in the high fat meal.

Recovery from Exercise

• Carbohydrate replacement is one of the most important events during recovery.

• Several days participation in sport need a normal mixed diet containing about 4 to 5 g/kg body weight (BW) of carbohydrate to replace muscle glycogen stores.

• Increasing the carbohydrate intake to 8 g/kg BW per day may not be enough to prevent a significant reduction in muscle glycogen concentrations after 5 successive days of hard training.

• A high carbohydrate diet and adequate fluid intake to avoid dehydration are the two most important elements in the formula for successful participation in sport.

Disorder of Carbohydrate Metabolism in Health Dental Caries

• Foods containing sugars may be easily broken down by α-amylase and bacteria in the mouth and can produce acid which increases the risk of caries.

• Starches with a high glycemic index produce pronounced changes in plaque.

• The impact of these carbohydrates on caries is dependent on the type of food, frequency of consumption, degree of oral hygiene performed, availability of fluoride, salivary function, and genetic factors.

• Dental caries should be prevented by fluoridation and adequate oral hygiene, and don’t take sucrose intake alone.

Glycogen Storage Diseases• Glycogen storage diseases are caused by lack of enzymes

glucose-6-phosphatase,maltase,glycogen phosphorylase needed to change glucose into glycogen.

• Symptoms include weakness, sweating, confusion, kidney stones, and stunted growth.

• The diagnosis is made by examining a piece of tissue under a microscope (biopsy).

• Treatment depends on the type of glycogen storage disease and usually involves regulating the intake of carbohydrates.

• Give uncooked corn starch every 4 to 6 hours around the clock.• Give carbohydrate solutions through a stomach tube all night to

prevent low blood sugar levels from occurring at night.

Types and Characteristics of Glycogen Storage DiseasesName Affected Organ,Tissues or

CellsSymptoms

Type O Liver or muscle Episodes of low blood sugar levels (hypoglycemia) during fasting if the liver is affected

Von Gierke's disease (type IA) Liver and kidney Enlarged liver and kidney, slowed growth, very low blood sugar levels, and abnormally high levels of acid, fats, and uric acid in blood

Type IB Liver and white blood cells Low white blood cell count, recurring infections, and inflammatory bowel disease

Pompe's disease (type II) All organs Enlarged liver and heart and muscle weakness

Forbes' disease (type III) Liver, muscle, and heart Enlarged liver or cirrhosis, low blood sugar levels, muscle damage, heart damage, and weak bones .

Andersen's disease (type IV) Liver, muscle, and most tissues Cirrhosis, muscle damage, and delayed growth and development

McArdle disease (type V) Muscle Muscle cramps or weakness during physical activity

Hers' disease (type VI) Liver Enlarged liver-Episodes of low blood sugar during fasting-Often no symptoms

Tarui's disease (type VII) Skeletal muscle and red blood cells

Muscle cramps during physical activity and red blood cell destruction (hemolysis)

Galactosemia

• Galactosemia is caused by lack the enzyme galactose-1-phosphate uridyl transferase needed to metabolize the galactose sugar in milk.

• Symptoms include vomiting, jaundice, diarrhoea, and abnormal growth.

• The diagnosis is based on a blood test. • Treatment involves completely eliminating milk and milk products

from the diet.• Most common and the most severe form is referred to as classic

galactosemia.

Hereditary Fructose Intolerance• Hereditary fructose intolerance is caused by lack of the enzyme

fructose-1 phosphate aldolase needed to metabolize fructose. • A by-product of fructose accumulates in the body, blocking the

formation of glycogen and its conversion to glucose.• Symptoms includes sweating, confusion, seizures and coma. • Children who continue to eat foods containing fructose develop

kidney and liver damage, resulting in jaundice, vomiting, mental deterioration, seizures, and death.

• Diagnosis is based on the chemical examination of liver tissue determines that the enzyme is missing.

• Treatment involves excluding fructose ,sucrose, and sorbitol from the diet.

Mucopolysaccharidoses• Mucopolysaccharidoses are a group of hereditary disorders caused by

the absence or malfunctioning of lysosomal enzymes like N-acetylglucosaminidase,Galactose-6-sulfate sulfatase,Beta-galactosidase needed to break down molecules called glycosaminoglycans.

• They show characteristics like rough facial appearance and abnormalities of the bones, eyes, liver, and spleen, accompanied by intellectual disability.

• Symptoms include short stature, hairiness, stiff finger joints, and coarseness of the face.

• The diagnosis is based on symptoms and a physical examination. • A bone marrow transplant may help.• Excess mucopolysaccharides enter in the blood and are deposited in

abnormal locations throughout the body.

Disorders of Pyruvate Metabolism• Pyruvate metabolism disorders are caused by lack of the enzymes

pyruvate carboxilase and dehydrogenase which are involved in pyruvate metabolism.

• These disorders cause a buildup of lactic acid and a variety of neurologic abnormalities.

• Symptoms include seizures, intellectual disability, muscle weakness, and coordination problems.

• Some children are helped by diets that are either high in fat and low in carbohydrates or high in carbohydrates and low in protein.

• Problems with pyruvate metabolism can limit a cell's ability to produce energy and allow a buildup of lactic acid.

• These disorders are diagnosed by measuring enzyme activity in cells from the liver or skin.

Protein glycosylation

• Proteins glycation is dependent on the concentration of glucose and fructose in blood and the half-life of the protein.

• The reaction is between the monosaccharide and the amino group of an amino acid, usually lysine, to form a Shiff’s base which undergoes rearrangement and formation of Amadori products.

• As the reaction progresses, increasingly complex Maillard products are formed with the eventual production of Advanced Glycation End-products or AGEs which are associated with irreversible loss of protein function.

• The extent of glycation of specific proteins, such as Haemoglobin in diabetics serves as an indication of medium term control of blood glucose.

Fermentation • Fermentation is the colonic phase of the digestive process and breakdown of

carbohydrates in the large intestine.• This process involves gut microflora and is unique to the colon of humans because it

occurs without the availability of oxygen.• It results in the formation of the gases hydrogen, methane and carbon dioxide, as well

as short chain fatty acids (SCFA) (acetate, propionate and butyrate), and stimulates bacterial growth (biomass).

• The gases are either absorbed and excreted in breath, or passed out via the rectum.• SCFA which are rapidly absorbed and metabolized by the body.• Acetate passes primarily into the blood and is taken up by liver, muscle and other

tissues.• Propionate is a major glucose precursor in ruminant animals such as the cow and

sheep, but this is not an important pathway in humans. • Butyrate is metabolized primarily by colonocytes and regulate cell growth,

and to induce differentiation .

Bowel habit • Non-starch polysaccharides are the principal dietary component affecting laxation

through increases in bowel content bulk and a speeding up of intestinal transit time.

• The extent of the effect depends on the chemical and physical nature of the polysaccharides and the extent to which they are fermented in the colon.

• Fermentable polysaccharides stimulate increases in microbial biomass in the colon, resulting in some increase in fecal weight.

• More transit time ,less feacal weight and vice-versa.

Microflora• Carbohydrate which is fermented stimulates the growth of bacteria in the large gut.• The efficiency of conversion of carbohydrate to biomass is determined by: the type of substrate, the rate of breakdown and the transit time through the large intestine .