Disaccharide Carbohydrates

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Disaccharides are one of the four chemical groupings of carbohydrates (monosaccharides, disaccharides, oligosaccharides, and polysaccharides). A disaccharide (also called a double sugar) is the sugar formed when two monosaccharides (simple sugars; glucose, fructose, and galactose) are joined by glycosidic linkage. Like monosaccharides, disaccharides are soluble in water. Three common examples of disaccharides are sucrose (table sugar), lactose, and maltose.


Common sugar.

Disaccharides are one of the four chemical groupings of carbohydrates (monosaccharides, disaccharides, oligosaccharides, and polysaccharides). A disaccharide (also called a double sugar) is the sugar formed when two monosaccharides (simple sugars; glucose, fructose, and galactose) are joined by glycosidic linkage. Like monosaccharides, disaccharides are soluble in water. Three common examples of disaccharides are sucrose (table sugar), lactose, and maltose. The differences in these disaccharides are due to atomic arrangements within the molecule.

Disaccharides - Double sugars.

Refined table sugar is a disaccharide.

Lactose - Main sugar in milk.


Sucrose is a common, naturally occurring carbohydrate found in many plants. It is a disaccharide made from a combination of the monosaccharides glucose and fructose. Sucrose is often extracted and refined from either sugar cane or sugar beet for human consumption. This refined white, odorless, crystalline powder form of sucrose is commonly referred to as table sugar or just sugar. It also occurs naturally alongside fructose and glucose in other plants, in particular fruits and some roots such as carrots.

Lactose is a disaccharide sugar composed of galactose and glucose that is found in milk. The intestinal villi secrete the enzyme called lactase (β-D-galactosidase) to digest it. This enzyme cleaves the lactose molecule into its two subunits, the simple sugars glucose and galactose, which can then be absorbed. Children have this enzyme but some adults no longer form it and they are unable to digest lactose. Lactose makes up around 2–8% of milk (by weight), although the amount varies among species and individuals, and milk with a reduced amount of lactose also exists.

In people who are lactose intolerant, lactose is not broken down and provides food for gas-producing gut flora, which can lead to diarrhea, bloating, flatulence, and other gastrointestinal symptoms.

Sometimes, however, people confuse lactose intolerance with a milk allergy. While lactose intolerance is a digestive system disorder, a milk allergy is a reaction by the body’s immune system to one or more milk proteins. An allergic reaction to milk can be life threatening even if the person eats or drinks only a small amount of milk or milk product. A milk allergy most commonly occurs in the first year of life, while lactose intolerance occurs more often during adolescence or adulthood.

Maltose also known as malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond, formed from a condensation reaction. Maltose is the second member of an important biochemical series of glucose chains. Maltose is the disaccharide produced when amylase breaks down starch. It is found in germinating seeds as they break down their starch stores to use for food, which is why it was named after malt. It is also produced when glucose is caramelized.

Maltose is a sweet carbohydrate, but compared to the other common sweet carbohydrates, such as sucrose (table sugar) and fructose, it is a lot less sweet. Due to the lack of sweetness, maltose is hardly ever used as a sweetener. Instead, it does come into use in the malting process of barley, in order to make beer. The starches turn into maltose during the malting process, which adds a sweetness to beer to counteract the bitterness.

More importantly is the role maltose plays in digestion. Most plant starches are made up of repeating glucose units attached one after another, called amylose. Amylose can have hundreds of glucose units, and as such, it is too large for our small intestines to absorb in order to use the glucose for energy. Our body has an enzyme called amylase that can break the glucose-glucose bonds. The amylase can either break the starch into individual glucose units or into the disaccharide maltose. Our body can absorb maltose, which can later be broken into individual glucose molecules and then be used as energy.

Fuel for body's energy


Breaking apart a double sugar (disaccharide) into its two simple sugars is accomplished by hydrolysis with the help of a type of enzyme called a disaccharidase. As building the larger sugar ejects a water molecule, breaking it down consumes a water molecule. These reactions are vital in metabolism. Each disaccharide is broken down with the help of a corresponding disaccharidase (sucrase, lactase, and maltase). After digestion, disaccharides provide energy to muscles, fuel the central nervous system, metabolize fat and keep tissues from consuming protein for energy.

The disaccharide sucrose is an easily assimilated macronutrient that provides a quick source of energy, provoking a rapid rise in blood glucose upon ingestion. Sucrose, has an energy content of 3.94 kilocalories per gram (or 17 kilojoules per gram). The body breaks down sucrose into fructose and glucose during digestion. The resulting glucose and fructose molecules are then rapidly absorbed into the bloodstream. The fructose and glucose are then metabolized by the body to release energy to the cells. The energy produced during metabolism helps the body to carry out both physical and mental activities.

As a disaccharide, the main function of lactose is to provide energy to the body. When ingested, lactose is broken down into its two subunits glucose and galactose. Glucose is the primary source energy in the body and as such lactose acts as a source of this important energy molecule. Galactose on the other hand has to be converted to glucose in order to be useful as a source of energy in the body. This makes lactose’s primary function in the body to be as a source for glucose.

Milk is a good source for Lactose

Honey is a rich source for disaccharides.


The three sugars classed as disaccharides are sucrose, lactose, and maltose.

Any food that has added sugar, such as desserts, soda and bread, contains sucrose. Homemade and prepackaged quick breads, muffins, pancakes and waffles also contain sucrose. Fruit-flavored juices, salad dressing, ketchup, some frozen fruit, flavored yogurts, candy, cookies, ice cream and ready-to-eat cereals are other foods that contain sucrose.

Lactose is found in dairy foods such as milk, cheese, yogurt, butter and ice cream. Foods made with milk, such as whipping cream, pudding, custard and cream soups, also contain lactose. Milk chocolate, nougat, instant potatoes, salad dressing, pancake mix, bread and some baked goods may also contain small amounts of lactose.

Maltose is present in malt products such as malted milkshakes and malted candies. Maltose also appears in foods in which starch is fermented by yeast or enzymes, such as in bread or brewed beverages. Some breakfast cereals contain maltose, as do cooked sweet potatoes.

Malt drinks as a source for maltose

Deficiency results in low energy.


When your blood sugar (glucose) levels fall below the normal range, it’s called hypoglycemia, or insulin shock. Low blood sugar can happen when you skip a meal or are malnutrition. It can also happen if your pancreas releases more insulin than it should after you’ve eaten.

Another possible cause of low blood sugar is drinking too much alcohol, especially on an empty stomach. This can interfere with the liver’s ability to release stored glucose into your bloodstream. Hepatitis and other problems with your liver can also lead to low blood sugar. Other causes include kidney disorders, anorexia nervosa, a pancreatic tumor, or adrenal gland disorders.

Insufficient blood sugar levels can cause a rapid heartbeat and heart palpitations. However, even if you have diabetes, you may not always have obvious symptoms of low blood sugar. It’s a condition called “hypoglycemia unawareness.” This happens when you experience low blood sugar so often that it changes your body’s response to it. Normally, low blood sugar causes your body to release stress hormones, such as epinephrine. Epinephrine is responsible for those early warning signs, like hunger and shakiness. When low blood sugar happens too frequently, your body may stop releasing stress hormones (hypoglycemia-associated autonomic failure, or HAAF). That’s why it’s so important to check your blood sugar levels often.

Every cell in your body needs sugar to work properly. It’s your body’s main source of energy. Low blood sugar levels can cause a variety of problems within your central nervous system. Early symptoms include weakness, lightheadedness, and dizziness. You may feel nervous, anxious, or irritable, and you’ll probably be hungry. Lack of coordination, chills, clammy skin, and sweating are common. Tingling or numbness of the mouth may be a sign of low blood sugar. Other symptoms include blurred vision, headache, and confusion. You may have difficulty performing simple tasks. When blood sugar levels drop during the night, you may have nightmares, cry out during sleep, or other unusual behaviors.

Severe low blood sugar is sometimes called insulin shock. Untreated, it can be very dangerous, resulting in seizures, loss of consciousness, or death.

Can lead to weight gain.

Can cause heart problems due to potential of increasing cholesterol.


Over consumption of sugar can cause a barrage of health problems.

It overloads and damages your liver. The effects of too much sugar or fructose can be likened to the effects of alcohol. All the fructose you eat gets shuttled to the only organ that has the transporter for it and that is your liver. This severely taxes and overloads the organ, leading to potential liver damage.

Potential liver damage

It causes your body into gain weight and affects your insulin and leptin signaling. Fructose fools your metabolism by turning off your body's appetite-control system. It fails to stimulate insulin, which in turn fails to suppress ghrelin, or "the hunger hormone," which then fails to stimulate leptin or "the satiety hormone." This causes you to eat more and develop insulin resistance

It causes metabolic dysfunction. Eating too much sugar causes a barrage of symptoms known as classic metabolic syndrome. These include weight gain, abdominal obesity, decreased HDL and increased LDL, elevated blood sugar, elevated triglycerides, and high blood pressure.

It increases your uric acid levels. High uric acid levels are a risk factor for heart and kidney disease. In fact, the connection between fructose, metabolic syndrome, and your uric acid is now so clear that your uric acid level can now be used as a marker for fructose toxicity.

Homopolysaccharides of glucose are broken down by maltase and Isomaltase to produce glucose. The lack of the Sucrase-Isomaltase enzyme, one of the four integral glycoproteins, causes sucrose and maltose intolerance and is called Congenital Sucrase-Isomaltase Deficiency. This congenital disorder is most prominent in infancy but can develop later in life. It is caused by a recessive autosomal mutation (mostly SI and SII). Nonetheless, depending on the type of mutation there are certain degrees of intolerance. According to this degree, physicians may decide the amount of starch the patient may have to remain healthy. This intolerance begins when infants begin to eat nutrients that contain starch, mainly containing maltose. One can notice that a patient suffers from this pathology when they have “stomach cramps, bloating, excess gas production, nausea, vomiting and diarrhea. Upper respiratory tract and viral infections are common. These digestive problems can lead to lower than normal weight gain and growth. Possible associations are kidney stones and copper malabsorption.” Further studies have shown that certain patients with different degrees of mutation can actually improve throughout the years, reaching a maximum improvement at ages 3 years and 6 months.

Reduce the intake of free sugars to less than 10% of total energy intake.


The World Health Organization recommends that both adults and children reduce the intake of free sugars to less than 10% of total energy intake. A reduction to below 5% of total energy intake brings additional health benefits, especially in what regards dental caries (cavities in the teeth).

Sugar found naturally in milk, fruit and vegetables doesn't count as free sugars. We don't need to cut down on these sugars, but remember that they are included in the "total sugar" count.

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