Unlock the Secrets of Simple Carbohydrates: Why They Taste So Sweet!

Sugar, a term synonymous with sweetness, encompasses a vast array of soluble carbohydrates widely utilized in food. This article delves into the world of sugars, exploring their classification, sources, and impact on human health.

What are Sugars?

The generic name for sweet-tasting, soluble carbohydrates, many of which are used in food is Sugar. These carbohydrates are found in the tissues of most plants. From Sanskrit śarkarā, meaning "ground or candied sugar", came Persian shakar and Arabic sukkar. The Arabic word was borrowed in Medieval Latin as succarum, whence came the 12th century French sucre and the English sugar.

Simple vs. Compound Sugars

Sugars are broadly classified into simple and compound forms. Simple sugars, or monosaccharides, include glucose, fructose, and galactose. These are the most basic units of carbohydrates. Compound sugars, also known as disaccharides or double sugars, are formed when two monosaccharides bond together. Common examples include sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (two molecules of glucose).

Longer chains of saccharides are categorized as oligosaccharides or polysaccharides, and are not typically referred to as sugars. Starch, a glucose polymer abundant in plants, serves as a primary energy source in human food.

Sources of Sugars

Sugars are ubiquitous in nature. Honey and fruits are abundant natural sources of simple sugars. Sucrose is especially concentrated in sugarcane and sugar beet, making them efficient for commercial extraction to make refined sugar. Maltose may be produced by malting grain. Lactose is the only sugar that cannot be extracted from plants, as it occurs only in milk, including human breast milk, and in some dairy products.

In 2016, the combined world production of sugarcane and sugar beet was about two billion tonnes.

A Historical Perspective

Sugar was first produced from sugar cane in the Indian subcontinent. Diverse species of sugar cane seem to have originated from India (Saccharum barberi and S. edule) and New Guinea (S. Nearchus). In the mid-15th century, sugar was introduced into Madeira and the Canary Islands, where it was mass produced. Christopher Columbus introduced it to the New World leading to sugar industries in Cuba and Jamaica by the 1520s. The Portuguese took sugar cane to Brazil. By the 19th century, sugar had become a household item, and this evolution of taste and demand for sugar as an essential food ingredient resulted in major economic and social changes. Demand drove, in part, the colonisation and industrialisation of previously under-developed lands.

The Science Behind Sugars

Scientifically, sugar loosely refers to a number of compounds typically with the formula (CH2O)n. Some large classes of sugars, ranked in increasing order of molecular weight are monosaccharides, disaccharides, or oligosaccharides. Monosaccharides are also called "simple sugars", the most important being glucose. Most monosaccharides have a formula that conforms to CnH2nOn with n between 3 and 7 (deoxyribose being an exception). Glucose has the molecular formula C6H12O6.

The names of typical sugars end with -ose, as in "glucose" and "fructose". Such labels may also refer to any types of these compounds. Fructose, galactose, and glucose are all simple sugars, monosaccharides, with the general formula C6H12O6. They have five hydroxyl groups (−OH) and a carbonyl group (C=O) and are cyclic when dissolved in water.

Monosaccharides: The Building Blocks

Fructose: Also known as fruit sugar, fructose occurs naturally in fruits, some root vegetables, cane sugar and honey and is the sweetest of the sugars. It is one of the components of sucrose or table sugar.
Galactose: Galactose generally does not occur in the free state but is a constituent with glucose of the disaccharide lactose or milk sugar. It is less sweet than glucose.
Glucose: Glucose occurs naturally in fruits and plant juices and is the primary product of photosynthesis. Starch is converted into glucose during digestion, and glucose is the form of sugar that is transported around the bodies of animals in the bloodstream. Although in principle there are two enantiomers of glucose (mirror images one of the other), naturally occurring glucose is D-glucose.

The acyclic monosaccharides (and disaccharides) contain either aldehyde groups or ketone groups. These carbon-oxygen double bonds (C=O) are the reactive centers.

Disaccharides: Compound Sweetness

Lactose: Lactose is the naturally occurring sugar found in milk. A molecule of lactose is formed by the combination of a molecule of galactose with a molecule of glucose. It is broken down when consumed into its constituent parts by the enzyme lactase during digestion.
Maltose: Maltose is formed during the germination of certain grains, the most notable being barley, which is converted into malt, the source of the sugar's name. A molecule of maltose is formed by the combination of two molecules of glucose.
Sucrose: Sucrose is found in the stems of sugarcane and roots of sugar beet. It also occurs naturally alongside fructose and glucose in other plants, in particular fruits and some roots such as carrots. The different proportions of sugars found in these foods determines the range of sweetness experienced when eating them. A molecule of sucrose is formed by the combination of a molecule of glucose with a molecule of fructose.

Longer than disaccharides are oligosaccharides and polysaccharides. Cellulose and chitin are polymers, often crystalline, found in diverse plants and insects, respectively. Cellulose cannot be digested directly by animals.

Production and Types of Sugar

Sugarcane accounted for around 21% of the global crop production over the 2000-2021 period. Sugar cane requires a frost-free climate with sufficient rainfall during the growing season to make full use of the plant's substantial growth potential. The crop is harvested mechanically or by hand, chopped into lengths and conveyed rapidly to the processing plant (commonly known as a sugar mill) where it is either milled and the juice extracted with water or extracted by diffusion. The juice is clarified with lime and heated to destroy enzymes. The resulting thin syrup is concentrated in a series of evaporators, after which further water is removed. The resulting supersaturated solution is seeded with sugar crystals, facilitating crystal formation and drying. Molasses is a by-product of the process and the fiber from the stems, known as bagasse, is burned to provide energy for the sugar extraction process.

Sugar beet became a major source of sugar in the 19th century when methods for extracting the sugar became available. It is a biennial plant, a cultivated variety of Beta vulgaris in the family Amaranthaceae, the tuberous root of which contains a high proportion of sucrose. It is cultivated as a root crop in temperate regions with adequate rainfall and requires a fertile soil. The crop is harvested mechanically in the autumn and the crown of leaves and excess soil removed. The roots do not deteriorate rapidly and may be left in the field for some weeks before being transported to the processing plant where the crop is washed and sliced, and the sugar extracted by diffusion. Milk of lime is added to the raw juice with calcium carbonate. After water is evaporated by boiling the syrup under a vacuum, the syrup is cooled and seeded with sugar crystals.

Refined Sugar and its Varieties

Refined sugar is made from raw sugar that has undergone a refining process to remove the molasses. Raw sugar is sucrose which is extracted from sugarcane or sugar beet. The sugar may be transported in bulk to the country where it will be used and the refining process often takes place there. The first stage is known as affination and involves immersing the sugar crystals in a concentrated syrup that softens and removes the sticky brown coating without dissolving them. The crystals are then separated from the liquor and dissolved in water. The resulting syrup is treated either by a carbonatation or by a phosphatation process. Both involve the precipitation of a fine solid in the syrup and when this is filtered out, many of the impurities are removed at the same time. Removal of color is achieved by using either a granular activated carbon or an ion-exchange resin. The sugar syrup is concentrated by boiling and then cooled and seeded with sugar crystals, causing the sugar to crystallize out. The liquor is spun off in a centrifuge and the white crystals are dried in hot air and ready to be packaged or used. Refined sugar is widely used for industrial needs for higher quality.

Coarse-grain sugar: Also known as sanding sugar, composed of reflective crystals with grain size of about 1 to 3 mm, similar to kitchen salt.
Granulated sugar: Also known as table sugar or regular sugar, is used at the table, to sprinkle on foods and to sweeten hot drinks (coffee and tea), and in home baking to add sweetness and texture to baked products (cookies and cakes) and desserts (pudding and ice cream). Granulated sugar has about 0.6 mm crystals.
Milled sugars: Such as powdered sugar (icing sugar) are ground to a fine powder.
Screened sugars: Such as caster sugar are crystalline products separated according to the size of the grains.
Cube sugar: Sometimes called sugar lumps, are white or brown granulated sugars lightly steamed and pressed together in block shape.
Brown sugars: Are granulated sugars, either containing residual molasses, or with the grains deliberately coated with molasses to produce a light- or dark-colored sugar such as muscovado and turbinado. They are used in baked goods, confectionery, and toffees. Their darkness is due to the amount of molasses they contain.

Glucose syrup and corn syrup are widely used in the manufacture of foodstuffs. Inverted sugar syrup, commonly known as invert syrup or invert sugar, is a mixture of two simple sugars-glucose and fructose-that is made by heating granulated sugar in water. Molasses and treacle are obtained by removing sugar from sugarcane or sugar beet juice, as a byproduct of sugar production. In winemaking, fruit sugars are converted into alcohol by a fermentation process. If the must formed by pressing the fruit has a low sugar content, additional sugar may be added to raise the alcohol content of the wine in a process called chaptalization. Heating sugar to near 200 °C for several minutes yields a product called burnt sugar. Often additives are used to modify the resulting caramels, e.g. alkali or sulfites. Low-calorie sweeteners are often made of maltodextrin with added sweeteners.

Sugar Consumption and Health Implications

Globally on average a person consumes about 24 kilograms (53 pounds) of sugar each year. Worldwide sugar provides 10% of the daily calories (based on a 2000 kcal diet). In 1750, the average Briton got 72 calories a day from sugar. In 1913, this had risen to 395. There is a popular misconception that cancer can be treated by reducing sugar and carbohydrate intake to supposedly "starve" tumours.

The Food and Drug Administration announced changes to the Nutrition Facts panel displayed on all foods, to be effective by July 2018. New to the panel is a requirement to list "added sugars" by weight and as a percent of Daily Value (DV). For vitamins and minerals, the intent of DVs is to indicate how much should be consumed. For added sugars, the guidance is that 100% DV should not be exceeded. 100% DV is defined as 50 grams. For a person consuming 2000 calories a day, 50 grams is equal to 200 calories and thus 10% of total calories-the same guidance as the WHO. To put this in context, most 12-US-fluid-ounce (355 ml) cans of soda contain 39 grams of sugar.

The Allure and Impact of Added Sugars

Added sugars are sugars that are added to packaged foods to boost flavor or allow food to be more shelf-stable. Added sugars are not chemically different from naturally occurring sugars. The typical American diet includes a substantial amount of processed food, and 74% of processed foods contain added sugar. On average, that adds up to 22 teaspoons (88 grams) of added sugar-an extra 350 calories-every day. Consuming large amounts of added sugars, particularly from sugar-sweetened beverages, increases the risk of developing obesity, Type 2 diabetes, or cardiovascular disease.

Navigating Hidden Sugars

Added sugars can be tricky to spot on food labels. A common trick manufacturers use is to add sugar from multiple sources, keeping sugars farther down on the ingredient list.

The Role of Carbohydrates in the Body

Carbohydrates are one of the three macronutrients in the human diet, along with protein and fat. Carbohydrates play an important role in the human body. They act as an energy source, help control blood glucose and insulin metabolism, participate in cholesterol and triglyceride metabolism, and help with fermentation. The digestive tract begins to break down carbohydrates into glucose, which is used for energy upon consumption. Any extra glucose in the bloodstream is stored in the liver and muscle tissue until further energy is needed. Carbohydrates is an umbrella term that encompasses sugar, fruits, vegetables, fibers, and legumes.

Complex vs Simple Carbohydrates

Simple Carbohydrates: One or two sugars (monosaccharides or disaccharides) combined in a simple chemical structure.
Complex Carbohydrates: Three or more sugars (oligosaccharides or polysaccharides) bonded together in a more complex chemical structure.

Healthy adult diets should include 45% to 65% carbohydrates as part of the daily intake, equaling about 200 g to 300 g per day. Carbohydrates contain about 4 kcal/ gram (17 kJ/g).

Fiber: An Essential Carbohydrate

Fiber is an important carbohydrate as well. Healthy adults should consume about 30 g per day of fiber, as it is found to reduce the risk of coronary heart disease, strokes, and digestive issues.

Types of Fiber:

Insoluble: Remains in the intestines, thereby softening and bulking the stool. Benefits include regularity of bowel movements and a decreased risk of diverticulosis. Examples: brans, seeds, vegetables, brown rice, and potato skins.
Soluble: Helps decrease blood cholesterol and LDL levels, reduces straining with defecation, and blunts postprandial blood glucose levels. Examples are fleshy fruit, oats, broccoli, and dried beans.

Glycemic Index

A glycemic index is a tool used to track carbohydrates and their individual effects on blood sugar. This scale ranks carbohydrates from 0 to 100 based on how rapidly the rise in blood glucose occurs upon consumption. Low glycemic foods (55 or less) produce a gradual increase in blood sugar. Medium glycemic foods (56 to 69) include quick oats, brown rice, and whole-wheat bread. High glycemic foods (70 to 100) increase the risk of type 2 diabetes, heart disease, obesity, and ovulatory infertility.

Clinical Significance of Carbohydrate Intake

An increase in simple carbohydrates may contribute to obesity, a disease that puts individuals at an even greater risk for further disorders such as cardiovascular disease. Carbohydrate intake also contributes to non-insulin-dependent diabetes (type 2 diabetes), a growing epidemic. However, foods rich in non-starch polysaccharides and low-glycemic foods protect against diabetes. Increased sugar consumption also contributes to the development of dental caries.

Carbohydrate malabsorption can present with symptoms of constipation, diarrhea, flatulence, and abdominal pain. It may occur as a result of congenital or acquired defects in enzyme metabolism or intestinal mucosa. Celiac and Crohn's disease are examples of secondary malabsorption. Small intestinal bacterial overgrowth (SIBO) can occur as a result of gastric bypass or gastric dysmotility disorders (chronic diabetes, scleroderma), resulting in a compromise of the absorptive interface and severe malabsorption. On the other hand, lactose intolerance is a primary lactase deficiency. Lactase is the enzyme that breaks down lactose, a disaccharide, into monosaccharides glucose and galactose in the brush border of enterocytes. Lactase deficiency is the most common enzyme deficiency in the world. The most frequently used method for diagnosing carbohydrate malabsorption is the hydrogen exhalation test. Treatment of most carbohydrate malabsorption disorders includes avoidance of the associated mono- or disaccharide.

Glucose vs. Fructose

Glucose travels through the bloodstream to all of our tissues, and every cell in the body readily burns it for energy. In contrast, fructose is almost exclusively taken up and metabolized by the liver. Excess glucose and fructose are both converted to fat and stored. However, the fat made from glucose is more likely to end up in fat tissue, whereas fat made from fructose is more likely to accumulate in the liver.

The Body's Sugar Regulation System

The amount of glucose circulating in the blood of an average healthy adult is equal to only one or two packets' worth (about 5 grams). To keep blood glucose steady, the body alternates between storing excess glucose after meals and supplying glucose to the blood between meals. Some glucose is stored in liver and muscle cells as glycogen, and some is converted to fat for storage in adipose tissue. Glycogen and glycerol (a component of fat) are easily converted back to glucose. However, we cannot make glucose from fatty acids. When the body’s supply of glycogen is depleted, muscle proteins are broken down and used by the liver to regenerate blood glucose.

Cultural and Historical Significance

Originally, no sugar was white; anthropologist Sidney Mintz writes that white likely became understood as the ideal after groups who associated the color white with purity transferred their value to sugar. In India, sugar frequently appears in religious observances.

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