Phosphorated carbohydrate
Properties are same as carbohydrates. So see below at carbohydrates record for details.
CARBOHYDRATES
ENERGY REQUIREMENTS
The largest component of energy expenditure is attributed
to the lean body mass and is known as the basal metabolic
rate (BMR). The lean body mass (related to weight and
height) declines with age and is lower in women than men.
Extra energy is required for growth, for pregnancy and
lactation, for muscular activity and when febrile. There is
considerable variation in energy expended between indivi-
duals of the same size, age, sex and activity. Adaptation
occurs to an inadequate energy intake and to a lesser degree
to superfluous energy intake. The largest variable in
determining energy requirements is the energy attributed to
exercise and movement. There are two units in use for
energy: kilocalories and kilojoules (I kcal = 4.184kJ).
Though both are metric, joules are SI units and are
preferred in Europe for scientific usage. Approximate daily
energy requirements are listed below. Adult
requirements for essential nutrients are given below also.
ENERGY-YIELDING NUTRIENTS
Three nutrients can act as energy substrates: carbohydrate,
fat and protein. Protein has a profoundly negative effect on
appetite and its use as an energy substrate should not be
contemplated for this and other biochemical reasons.
Carbohydrate and fat are the most important energy sub-
strates and have an additional functional role.
Daily energy requirement :
Healthy female At rest-1600 kcal, Light work-2000 kcal, heavy work- 2250 kcal
Healthy Male - At rest- 2000 kcal, Light work- 2700 kcal, Heavy work- 3500 kcal
Carbohydrates :
Carbohydrates found in foods may be classified
according to their degree of polymerisation into
three main groups, namely sugars, oligosaccharides,
and polysaccharides: all of these are made up only
of carbon, hydrogen, and oxygen. Sugars can be fur-
ther subdivided into monosaccharides (single-mole-
cule sugars), such as fructose and glucose.
disaccharides (whose molecules consist of two
monosaccharides joined together), such as lactose
and sucrose. and sugar alcohols (polyols) such as
sorbitol and mannitol. Oligosaccharides typically
consist of 3 to 9 monosaccharides joined together
and include malto-oligosaccharides such as malto-
dextrins; Polysaccharides consist of many monosac-
charides joined together and include starches and
non-starch polysaccharides such as cellulose. Non-
starch polysaccharides are the major fraction of diet-
ary fibre, and many authorities now consider this
term is preferable to dietary fibre.
The 'available' carbohydrate
(starches and sugars) supplies a major part of the energy in
a normal diet (4kcal/g). No individual carbohydrate is an
essential nutrient as the body can make it for itself from
protein. However, if the available carbohydrate intake is
less than 100 g per day, ketosis is likely to occur. Sugars are
found in fruits, milk (lactose) and some vegetables.
Starches are mostly found in cereals, root vegetables and
legumes. The major carbohydrates in food are listed below :
SOURCES OF CARBOHYDRATES IN FOOD
Available sugars
β’ Monosaccharides-ribose, glucose, fructose
β’ Disaccharides-sucrose, lactose, maltose
Available polysaccharides
β’ Starch, glycogen, synthetic glucose polymers
Unavailable polysaccharides
β’ Most forms of dietary fibre
Sugars
Sugars are classified by the UK. Department of Health as
intrinsic (naturally incorporated in the cellular structure of
fruits, milk etc.) or extrinsic (extracted, refined, concentrated,
e.g. beet or cane sucrose). Intrinsic sugars and the foods
that contain them are thought to be more acceptable
nutritionally than extrinsic sugars because they are associ-
ated with other nutrients naturally present in the food.
Extrinsic sugars are one of the factors that can contribute to
the development of dental caries if eaten/sucked frequently.
Starches
Starches in cereal foods (wheat, rice), root foods (potatoes,
cassava) and legumes are the nutrients which provide the
largest proportion of calories in most diets around the
world unless these diets are unusually high in fat or sugars.
Although all starches are polymers of glucose, linked by
the same 1-4 glycosidic linkages, they do not all behave in
the same way when they are eaten.
Some starches are digested promptly by salivary and
then pancreatic amylase and produce a steep rise in blood
glucose. Other starches are more slowly digested, because
they are protected in the structure of the food, because of
the crystal structure or because the molecule is unbranched
(amylose). After ingestion, the blood glucose rise is flatter
and lower. The glycaemic index (see the information box)
quantifies the effect of different carbohydrates on the blood
glucose after a test meal. A small percentage of dietary
starch may completely escape digestion in the small
intestine and pass unchanged into the large intestine, where
it is fermented by the resident bacteria. This resistant .starch
thus behaves in much the same way as dietary fibre and is
thought to confer a beneficial effect on the intestinal
mucosa.
GLYCAEMIC INDEX
β’ The glycaemic index is the incremental area under the 2-hour
plasma glucose curve after eating the amount of a food
containing 50 g carbohydrate - the corresponding area after
50 g of glucose in water
β’ The glycaemic index is high for bread, potatoes and glucose,
and lower for pasta, legumes and whole-grain cereals. The
index may be useful in constructing therapeutic diets for
diabetes.
Dietary fibre
Dietary fibre, or non-starch polysaccharides, is the natural
packing of plant foods. It can be defined as those parts of
food which are not digested by human enzymes. The
principal classes of dietary fibre are cellulose, hemicellulo.ses,
lignins, pectins and gums. These are all polysaccharides
(i.e. carbohydrates) except lignin, which occurs with
cellulose in the structure of plants. Pectins and gums are
viscous, not fibrous.
Some types of dietary fibre, notably the hemicellulose of
wheat, increase the water-holding capacity of colonic
contents and the bulk of faeces. They relieve simple
constipation, appear to prevent diverticulosis and may
reduce the risk of cancer of the colon. Other, viscous,
indigestible polysaccharides like pectin and guar gum have
greater effect in the upper gastrointestinal tract. They tend
to slow gastric emptying, contribute to satiety, and may
flatten the glucose tolerance curve and reduce plasma
cholesterol concentration.
Dietary fibre (and resistant starch) is partly fermented in
the large intestine by resident bacterial flora, yielding a
small quantity of volatile fatty acids which are absorbed
through the colonic mucosa. Flatus formation is common.
There are as yet no official recommended intakes for
dietary fibre, but the present average intakes of about
15-20 g/day in affluent countries are thought to be too low.