This document provides an overview of carbohydrates and lactose intolerance. It defines carbohydrates and describes the different types including sugars, starches, and fiber. It discusses the roles of carbohydrates in the body including energy supply, sparing protein, and glycogen storage. Symptoms, causes, and tests for diagnosing lactose intolerance are summarized. Management strategies like avoiding dairy and using alternative milks are also covered at a high level.

2. By
Zahraa Esmat Sayed Mahmoud
Under supervision of
Prof.Dr.Sonia Saleh Zaky
Professor of nutrition
Nutrition and Food Science Department.
Faculty of Home Economic.
Helwan University.
Prof.Dr.Ashraf Abd El-Aziz Abd El-Megeid
Professor of nutrition
Nutrition and Food Science Department.
Faculty of Home Economic.
Helwan University.

3. Introduction
Food affects almost everything we do. It affects how we look,
feel, and act. It even affects our abilities – how well we function
every day.
Food has an impact on life because it supplies nutrients,
which are substances in food that body needs to function
properly such as in growing, in repairing itself, and in having
supply of energy.
Nutrition is both a pure science and a social science. As a
pure science it looks at how the body uses nutrients. As a social
science it looks at the relationship between food and human
behavior and the environment, or how and why people eat.

4. Nutrition and Nutrients
There are six types of nutrients:
 Carbohydrates
 Fats
 Proteins
 Vitamins
 Minerals
 Water

6. General characteristics
The term carbohydrate is derived from the French:
hydrate de carbone.
compounds composed of C, H, and O
empirical formula: (CH2O)n

7. What are carbohydrates?
Carbohydrates, a group of molecules that
include sugars and starches, provide energy to
the body when the molecules are broken down.
All carbohydrates contain carbon, hydrogen,
and oxygen.

8. A carbohydrate with one unit of sugar such as
glucose, fructose, and galactose, are simple
sugars. Usually, the ratio of each of carbon to
hydrogen and oxygen is 1:2:1 such that there is
one carbon to two hydrogens to one oxygen.
Most of the sugars used in the body are six-
carbon sugars, so their formula is written as:
C6H12O6.

9. Two monosaccharides make a disaccharide.
There are three types of disaccharides:
Sucrose, which is made of glucose and fructose, is common
table sugar.
Lactose, made of glucose and galactose, is the sugar found in
dairy products.
Maltose, made of two glucose molecules, is found in anything
“malted” .Because disaccharides are too large to pass through
the cell membranes, they must be broken down into
monosaccharides first.

10. Polysaccharides
Polysaccharides are several monosaccharides linked in a
chain. There are two types of polysaccharides of importance
to the body: starches and glycogen.
Polysaccharides must be digested to their individual glucose
units for the body to be able to use the energy.
Cellulose, another type of polysaccharide, is a major
component of wood. It cannot be broken down into smaller
units, so it is not digestible. When we ingest cellulose, it is
considered roughage or fiber. Although we get no nutritional
value from cellulose, it binds cholesterol in the intestine and
helps us eliminate this chemical. Fiber also helps to regulate
the digestive tract and keep people “regular.”

11. How do we get carbohydrates from the diet?
The main sources of carbohydrates in our diet
are:
Foods made from cereal grains (e.g. bread,
flour, rice, pasta, and breakfast cereal). These
foods give us mainly complex or starchy
carbohydrate.
Fruit and vegetables especially potatoes, root
vegetables (e.g. carrots) and pulses (beans and
lentils) contain a mix of starches and sugars.

12. Lactose which is found in milk.
Table sugar, honey and soft drinks.
We break down most carbohydrates in the gut and
absorb them into our blood stream as individual sugar
units.
What is the function of carbohydrates?
Carbohydrates have five major functions within the body:
Energy supply, particularly for the brain in the form
of glucose

13. Avoiding the breakdown of amino acids for energy.
Avoiding ketosis from the breakdown of fatty acids.
Cellular , protein recognition, activation of growth factors and
modulation of the immune system.
Some carbohydrates are high in fiber, which helps prevent
constipation and lowers the risk for certain diseases such as cancer,
heart disease and diabetes.
What happens if we don't get enough carbohydrate?
Eating too little carbohydrate may lead to low blood sugar levels
(hypoglycaemia) .
Hypoglycaemia is a particular risk for some people with diabetes
who are on tablets or insulin. It can also affect very active sports
people, who may feel exhausted when their blood sugar and muscle
glycogen stores run low.

14.  If we eat too little carbohydrate, over time our body will begin
to use up some stored fat but quickly moves on to burning its
own protein tissue such as in the heart and muscles. A low intake
of wholegrain cereals, fruit and vegetables rich in indigestible
carbohydrate can also lead to bowel problems such as
constipation.
What does the Glycaemic Index of carbohydrates
mean?
 Different carbohydrate-containing foods are digested and
absorbed at different rates.
 The Glycaemic Index (GI) is the classification used to identify
which carbohydrates are quickly broken down to glucose (high
GI) and which are slowly broken down(low GI).

15.  Glyceamic index is defined
as the area under the blood
glucose curves seen after
ingestion of a meal with
carbohydrate-rich food,
compared with the area
under the blood glucose
curve observed after a meal
consisting of the same
amount of carbohydrate in
the form of glucose or
white bread.
Glyceamic index

16. Examples of medium and low GI carbohydrate foods
include:
Wholegrain and seeded bread
 Pasta, basmati rice
 Oats and muesli
Beans and pulses
 Most fruit and vegetables including sweet
potatoes and new boiled potatoes in their
skins
 Milk and yogurt.

17. Preview of
Carbohydrate
Metabolism

18. Storing glucose as glycogen
• 1/3rd of total glycogen is stored in liver and
2/3rd in muscle.
• When blood glucose falls liver cells break
down glycogen into single molecules of
glucose, which becomes available to supply
energy to central nervous system and other
organs .
• During exercise the muscle cell themselves use
up the glycogen they store.

19. Using glucose as energy
Glycolysis (“glucose-splitting”)
Glucose (6C) is split into two pyruvate/pyruvic acid
(3C) molecules.
– It does not require oxygen (gas O2).
– Amount of energy harvested from 1 glucose:
2 ATP
2 NADH (actively transported into mitochondria
of eukaryotic cells)

20. Making glucose from proteins
Glycogen stores only last for some hours , if a
person does not replenish the depleted
glycogen stores, body protein are broken
down to make glucose by a process called
“gluconeogenesis”
Taking adequate amount of carbohydrate
prevents the use of protein for energy, this
role of carbohydrate is called protein sparing
action.

21. Making ketone bodies from fat fragments
Inadequate supply of carbohydrates causes
break down of body fat reserves. This not only
supplies energy but also produces ketone
bodies.
Some ketone bodies are used by muscle and
other tissues for energy, but when produced
in excess they accumulate in blood and cause
ketosis (disturbance of bodies normal acis-
base balance)

22. Converting glucose to fats
Excess carbohydrates can be converted to fats
when glycogen stores are filled to capacity.
However storing carbohydrates as fats is an
energetically expensive process. So, body fats
mainly come from dietary fats.

23. Maintaining glucose homeostasis
• Blood glucose homeostasis is regulated mainly
by two hormones:
(i)Insulin- secreted when blood glucose is high.
Controls transport of glucose from blood to
muscle and fat cells
(ii) Glugagon- secreted when blood glucose is
low. Helps in release of glucose from storage.

24. Overview of Carbohydrate Metabolism

25. Requirements for carbohydrate
 Carbohydrates are not essential nutrients, because the
carbon skeletons of amino acids can be converted into
glucose .
 However, the absence of dietary carbohydrate leads to
ketone body production ,and degradation of body protein
whose constituent amino acids provide carbon skeletons
for gluconeogenesis .
 The RDA for carbohydrate is set at 130 g/day for adults
and children, based on the amount of glucose used by
carbohydrate-dependent tissues, such as the brain and
erythrocytes.
 Adults should consume 45–65 percent of their total
calories from carbohydrates.

26. Requirements for carbohydrate
 It is recommended that added sugar represent no more than
25% of total energy because of concerns that sugar may
displace nutrient-rich foods from the diet, potentially leading
to deficiencies of certain micronutrients.

27. Factors affecting requirements of carbohydrate
 The minimal amount of carbohydrate required,
either from endogenous or exogenous sources,
is determined by the brain’s requirement for
glucose .
 The requirement for glucose has been reported
to be approximately 110 to 140 g/day in adults.
When glucose production or availability
decreases below that required for the complete
energy requirements of the brain, there is a rise
in ketoacid production in the

28. liver in order to provide the brain with an alternative fuel This
has been referred to as a ketosis .Generally this occurs in a
starving person only after glycogen stores in the liver are
reduced to a low concentration and the contribution of hepatic
glycogenolysis is greatly reduced or absent .
 The available evidence based on the majority of studies on
the relationship dietary fiber to gastrointestinal health,
several chronic diseases (colon cancer, breast cancer),
glucose tolerance, insulin response as well as weight
control and maintenance, indicated that the beneficial
effects of fiber in humans are most likely related to the
amount of food consumed but not the individual’s age or
body weight .

29. Health effects of starch and fiber
Weight control: Food rich in complex
carbohydrates provides less energy per bite and
also provides satiety.
Heart disease: diets high in soluble fibers and
low in animal fats and cholesterol is associated
with lower risk of heart disease.
Cancer: high carbohydrate diet protects
against some types of cancer (eg. Colon
cancer).

30. Diabetes: High carbohydrate low fat diet helps
in weight control , and this is the most
effective way to prevent diabetes type 2.
GI health: dietary fibers enhance health of GI
tract and hence blocks absorption of unwanted
constituents of food. Insoluble fibers
(cellulose) enlarge stool and prevents
constipation.

31. Glucose and the nervous system
Glucose is the only fuel normally used by brain
cells. Because neurons cannot store glucose,
they depend on the bloodstream to deliver a
constant supply of this precious fuel.

32. Lactose intolerance

33. Lactose intolerance It also called lactasdeficiency and hypolactasia.

34. classified as one of three types:
Primary lactase deficiency
is genetic, only affects adults and is caused by the absence of
a lactase persistence allele. It is the most common cause of lactose
intolerance as a majority of the world's population lacks these alleles.
Secondary acquired or transient lactase deficiency
is caused by an injury to the small intestine, usually during infancy
fromacute gastroenteritis, diarrhea, chemotherapy, intestinal
parasites or other environmental causes.

35. Congenital lactase deficiency
is a very rare, autosomal recessive genetic disorder that prevents
lactase expression from birth. It is particularly common
in Finland. People with congenital lactase deficiency are thus
unable to digest lactose from birth, and they are unable to digest
breast milk .
Symptoms
The principal symptom of lactose intolerance is an adverse reaction
to products containing lactose (primarily milk), including:
•Abdominal bloating .
• Cramps.
• flatulence
•Diarrhea.
•Nausea.
•Borborygmi (rumbling stomach) .
•Vomiting (particularly in adolescents).

36. Diagnosis
Four tests are available:
Hydrogen breath test
In a hydrogen breath test, after an overnight fast, 25 grams of
lactose (in a solution with water) is swallowed.
 If the lactose cannot be digested, enteric bacteria metabolize it
and produce hydrogen, which, along with methane, if produced,
can be detected on the patient's breath by a clinical gas
chromatograph or compact solid-state detector.
The test takes about 2 to 3 hours to complete.

37. Blood test
In conjunction, measuring blood glucose level every 10 to 15
minutes after ingestion will show a "flat curve" in individuals with
lactose malabsorption, while the lactase persistent will have a
significant "top", with a typical elevation of 50% to 100%, within
one to two hours. However, due to the need for frequent blood
sampling, this approach has been largely replaced by breath testing.
Lactose tolerance test:
In a lactose tolerance test, you will be given a drink of lactose
solution, and then a sample of blood will be taken from your arm
using a needle. The blood will be tested to see how much glucose
(blood sugar) it contains.

38. Milk tolerance test:
In a milk tolerance test, you will be given a glass of milk (about
500ml) and your blood sugar levels will be tested. If your blood
sugar levels do not rise after drinking the milk, you may be
lactose intolerant.
After an overnight fast, blood is drawn and then 50 grams of
lactose (in aqueous solution) is swallowed. Blood is then drawn
again at the 30 minute, 1-hour, 2-hour, and 3-hour mark. If the
lactose cannot be digested, blood glucose levels will rise by less
than 20 mg/dL .

39. Stool acidity test
This test can be used to diagnose lactose intolerance in infants,
for whom other forms of testing are risky or impractical.
The infant is given lactose to drink. If the individual is tolerant,
the lactose is digested and absorbed in the small intestine;
otherwise it is not digested and absorbed and it reaches the colon.
The bacteria in the colon, mixed with the lactose, cause acidity
in stools. Stools passed after the ingestion of the lactose are tested
for level of acidity.
If the stools are acidic, the infant is intolerant to lactose.
Stool pH in lactose intolerance < 5.5.

40. Management
Lactose intolerance is not usually an absolute condition:
The reduction in lactase production, and the amount of lactose
that can therefore be tolerated, varies from person to person.
Since lactose intolerance poses no further threat to a person's
health, the condition is managed by minimizing the occurrence
and severity of symptoms.
Avoiding lactose-containing products:
Dietary control of lactose intolerance depends on people learning
through trial and error how much lactose they can handle. Label
reading is essential, as commercial terminology varies according
to language and region.

41. Alternative products
Soy milk
 It has about the same amount of protein as cow's milk, though
the amino acid profile differs.
Natural soy milk contains little digestible calcium as it is
bound to the bean's pulp, which is insoluble in humans.
To counter this, many manufacturers enrich their products
with calcium carbonate available to human digestion.
 Unlike cow's milk, it has little saturated fat and
no cholesterol.

42.  The American Academy of Pediatrics considers soy milk a
suitable alternative for children who cannot tolerate human or
cow's milk, or whose parents opt for a vegan diet. They find no
medical benefit to using soy milk instead of human or cow's
milk.
Rice milk
Compared to cow's milk, rice milk contains more carbohydrates,
but does not contain significant amounts of calcium or protein,
and no cholesterolor lactose.
Commercial brands of rice milk, however, are often fortified
with vitamins and minerals, including calcium, vitamin
B12, vitamin B3, and iron.

43. Almond milk
 Unlike animal milk, almond milk contains
no cholesterol or lactose. As it does not contain any animal
products, it is suitable for vegans and vegetarians who
abstain from dairy products.
 Commercial almond milk products often come in
plain, vanilla or chocolate flavors and are sometimes
enriched with vitamins. Almond milk can also be made at
home by combining ground almonds with water in a blender.
Vanilla flavoring and sweeteners are often added.
 Almond milk is not a suitable replacement for breast milk,
cow's milk or hydrolyzed formulas in children under two
years of age due to the low protein content.

44. Coconut milk
 Coconut milk contains a large proportion of lauric acid, a saturated fat
that raises blood cholesterol levels by increasing the amount of high-
density lipoprotein cholesterol that is also found in significant amounts
in breast milk and sebaceous gland secretions.
 This may create a more favourable blood cholesterol profile, though it is
unclear if coconut oil may promote atherosclerosis through other
pathways.
 Because much of the saturated fat of coconut oil is in the form of lauric
acid, coconut oil may be a better alternative to partially hydrogenated
vegetable oil when solid fats are required.In addition, virgin coconut oil is
composed mainly of medium-chain triglycerides,which may not carry the
same risks as other saturated fats.
 Early studies on the health effects of coconut oil used partially
hydrogenated coconut oil, which creates trans fats, and not virgin coconut
oil, which has a different health risk profile.