Carbohydrates as Macronutrients and its Importance to Health and Wellness

What are Macronutrients?

Macronutrients are the nutrients we need in larger quantities that provide us with energy. They are nutrients that provide calories or energy and are required in large amounts to maintain body functions and carry out the activities of daily life. There are three broad classes of macronutrient namely, proteins, carbohydrates and fats.

Carbohydrates as Macronutrients

One of the three primary types of food and a source of energy is carbohydrates. Carbohydrates are primarily sugars and starches that are broken into glucose by the body (a simple sugar that the body can use to feed its cells). In a wide variety of healthy and unhealthy foods, carbohydrates are included, including bread, beans, milk, popcorn, potatoes, cookies, pasta, soft drinks, maize, and cherry pie. They come in a number of ways as well. Sugars, fibers, and starch are the most common and abundant types. A significant part of a balanced diet is foods that are high in carbohydrates. Carbohydrates supply glucose to the body, which is converted into energy that is used to sustain body functions and physical activity.

Classification of Carbohydrates

Carbohydrates are sometimes referred to by nutritionists as either simple or complex. The exact difference between these groups may, however, be unclear.

Simple Carbohydrates

Simple carbohydrates are the basic type of carbohydrates. Simple carbohydrates are found in soft drinks, candy, cookies and other sweet snacks. These foods are often made with white sugar, a type of sugar that has been processed. Natural sugars are often found with simple carbohydrates. Fruit, milk and vegetables contains natural sugars. Honey is a natural sugar as well. People eat natural sugar in its original form. It’s easier to handle simple carbohydrates because they’re less complicated (or simpler). They come from sources like fruit and sugar, as well as just about everything else that’s sweet. The human body will break these things down easily, and that is where some of the issues lie.

Complex Carbohydrates

A major energy source for the body is complex carbohydrates. They provide the sustained fuel for exercise, everyday living activities and even rest that the body requires. Single units (monosaccharides), which are bound together, are also complex carbohydrates. There are two to ten basic units of sugar in the oligosaccharides. Hundreds and thousands of associated monosaccharides include polysaccharides. Complex carbohydrates have energy that is very long-lasting.

Various forms of carbohydrates are distinguished on the basis of their hydrolysis actions. Mainly, they are divided into three groups:

• Monosaccharides
• Disaccharides
• Polysaccharides

Monosaccharides

Carbohydrates referred to as monosaccharide are those carbohydrates that cannot be further hydrolyzed to give simpler polyhydroxy aldehyde or ketone units. If an aldehyde group is present in a monosaccharide, it is called an aldose and, on the other hand, if it contains a keto group, it is called a ketose.

Disaccharides

Disaccharides yield two molecules of either the same or different monosaccharides on hydrolysis. The two units of monosaccharides are joined by an oxide bond that is formed by water molecule loss, and this bond is called a glycosidic bond. Sucrose is one of the most prevalent disaccharides that give glucose and fructose on hydrolysis. The other two essential disaccharids are maltose and lactose (also known as milk sugar). There are two α-D-glucose in maltose and two β-D-glucose in lactose that are linked by an oxide bond.

Polysaccharides

Polysaccharides contain long monosaccharide units joined together by glycosidic linkage. Most of them serve as storage for food, e.g. From Starch. The primary storage polysaccharide for plants is starch. It is an α glucose polymer and is made up of two components: amylose and amylopectin. Also, cellulose is one of the polysaccharides found mainly in plants. It consists of β-D-glucose units connected by a glycosidic bond between one glucose unit’s C1 and the next glucose unit’s C4.

Functions of Carbohydrates in the Body

Carbohydrates have six major functions within the body:

• Provision of energy and regulating blood glucose
• Breakdown of fatty acids and preventing ketosis
• Sparing the release of Protein as Energy
• Acting as flavor and sweeteners
• Production of dietary fiber
• Biological recognition processes

Provision of Energy and Regulating Blood Glucose

The only sugar the body uses to provide nutrition for its tissues is glucose. Therefore, all digestible polysaccharides, disaccharides and monosaccharides must ultimately be transformed by different liver enzymes into glucose or a glucose metabolite. The level of blood glucose must be kept relatively constant because of its associated  importance for proper cellular function.

It also includes regulating the level of blood glucose, among the enormous metabolic activities that the liver performs. Pancreatic beta cells sense the increase in blood glucose during periods of food intake and start to secrete the hormone insulin. Insulin binds to several cells that have sufficient peptide hormone receptors in the body and induces a general absorption of cellular glucose. Insulin induces the uptake of glucose in the liver as well as the synthesis of glycogen, a polymer for glucose storage. In this way, by the action of insulin, the liver is able to remove high blood glucose levels.

The hormone glucagons, on the other hand, are secreted into the bloodstream by pancreatic alpha cells after detecting falling blood glucose levels. Glucagon acts to decrease the amount of glucose in the bloodstream after binding to targeted cells such as skeletal muscle and brain cells. In order to release glucose into the blood, this hormone prevents the uptake of glucose by muscle and other cells and facilitates the breakdown of glycogen in the liver. Glucagon also facilitates gluconeogenesis, a mechanism involving the synthesis of glucose from amino acid precursors. Via the effects of both glucagon and insulin, blood glucose can typically be controlled in concentrations between 70 and 115mg/100 ml of blood.

Epinephrine and cortisol are other hormones of interest in glucose control. Both hormones are secreted from the adrenal glands, but although cortisol mobilizes glucose during times of emotional stress or exercise, epinephrine mimics the effects of glucagon.

Breakdown of Fatty Acids and Preventing Ketosis

Given the unique capacity of the liver to regulate homeostatic blood glucose levels, it only stores enough for fasting for twenty-four hours. The tissues in the body that preferentially depend on glucose, especially the brain and skeletal muscles, must search for an alternative source of energy after twenty-four hours. Adipose tissue starts to release fatty acids into the bloodstream during fasting cycles when the insulin to glucagon ratio is low. Long hydrocarbon chains consisting of a single group of carboxylic acids are fatty acids and are not very soluble in water. During resting conditions, the skeletal muscle continues to use fatty acids for energy; the brain, however, does not afford the same luxury.

In order to cross the blood-brain barrier, fatty acids are too long and dense. Proteins from different body tissues are then broken down into amino acids and used by the liver to make the brain and muscle glucose. This process is known as gluconeogenesis or “the production of new glucose.” The body enters a state called ketosis if fasting is prolonged for more than a day. Ketosis is derived from the root word ketones, implying a carbon atom with two lateral groups connected to an oxygen atom. When there is no longer enough oxaloacetate in the mitochondria of cells to condense with fatty acid-formed acetyl CoA, ketones are released. Oxaloacetate is a four-carbon compound that starts the first Krebs Cycle reaction, a cycle that involves a series of reactions that generate high-energy species that are ultimately used to generate energy for the cell. Since oxaloacetate is made from pyruvate (a glucose metabolite), in order to burn fat, a certain amount of carbohydrate is needed. Otherwise, it would not be possible to fully break down the fatty acids and create ketones.

Sparing the release of Protein as Energy

So why are carbohydrates necessary if other carbon compounds, including fatty acids and ketones, can be used as energy by the body? Maintaining a daily intake of carbohydrates can, first of all, prevent protein from being used as a source of energy. In order to biosynthesize enzymes, antibodies, receptors and other essential proteins, gluconeogenesis will slow down and amino acids will be released. In addition, the weakening of skeletal muscle and other tissues such as the heart, liver, and kidneys would be avoided by a sufficient amount of carbohydrates. Ketosis can, most importantly, be avoided. Although the brain can adapt to the use of ketones as a fuel, carbohydrates are preferentially used and a minimum amount of glucose circulating in the blood is required to work properly. Lower blood glucose levels may cause headaches in some people before the adaptation process occurs. It is recommended that the average individual eats at least 50 to 100g of carbohydrates a day to avoid these ketotic symptoms.

Although the protein degradation and ketosis processes can create problems of their own during extended fasting, during glucose shortages, they are adaptive mechanisms. In short, in order to conserve proteins for other cellular functions, the first goal of metabolism during a prolonged fast is to provide adequate glucose for the brain and other organs that rely on it for energy. Changing the use of fuel from glucose to fatty acids and ketone bodies is the next priority for the body. Ketones will become increasingly important as a source of fuel from then on, while fatty acids and glucose will become less important.

Acting as Flavor and Sweeteners

A less significant feature of carbohydrates is to provide foods with sweetness. Receptors at the tip of the tongue bind to small bits of carbohydrates and transmit to the brain what human beings experience as a “sweet” signal. Different sugars vary in sweetness, however. Fructose, for instance, is about twice as sweet as sucrose, and sucrose is about 30 percent sweeter than glucose.

It is possible to identify sweeteners as either nutritional or alternative. Sucrose, glucose, fructose, high fructose corn syrup, and lactose have all been listed before and include nutritious sweeteners. Not only do these kinds of sweeteners add flavor to the food, they can also be metabolized for energy.

Alternative sweeteners, on the other hand, have no energy for food and include saccharin, cyclamate, aspartame, and acesulfame. There is still debate about saccharin and cyclamate as artificial sweeteners, but aspartame and acesulfame are commonly used in many foods. Both aspartame and acesulfame are hundreds of times sweeter than sucrose, but as it is much more stable than aspartame when heated, only acesulfame can be used in baked goods.

Production of Dietary Fiber

For many purposes, dietary fibers, such as cellulose, hemicellulose, pectin, gum and mucilage, are essential carbohydrates. Soluble dietary fibers such as pectin, gum and mucilage move into the small intestine without digestion and are degraded by the large intestine through fatty acids and gases. The fatty acids formed in this way can either be used or ingested into the bloodstream as a fuel for the large intestine. Therefore, for proper intestinal health, dietary fiber is necessary.

The use of soluble and insoluble fiber in general makes it much easier to remove waste. Since dietary fiber is both indigestible and a water attractant, stools become broad and fluffy. As a consequence, with less pressure, feces can be expelled. However, inadequate intake of fiber will alter the stool’s composition and increase the amount of force needed during defecation. During the removal of waste, excessive pressure can cause places in the large intestinal wall to create small pouches called diverticula from between bands of smooth muscle. During defecation, haemorrhoids can also result from excessive pressure.

Diverticulosis is regarded as the illness of having multiple diverticula in the large intestine. While diverticula are often asymptomatic, food particles are stuck in their folds and the particles are metabolized into acids and gases by bacteria. Eventually, the diverticula, a condition known as diverticulitis, can become inflamed. In order to cure the disease, the patient is given antibiotics to kill the bacteria while the dietary intake of fiber is limited before the infection has subsided. If the inflammation has been reduced, a high fiber diet is started to prevent a relapse.

In addition to intestinal disease prevention, diets rich in fiber have other health benefits. By rising the bulk of a meal without yielding much energy, high fiber intake decreases the risk of developing obesity. Despite the fact that calorie consumption has declined, an enlarged stomach contributes to happiness.

Diabetics may also benefit from eating a daily amount of dietary fiber outside of dieters. When in the intestine, to avoid a sudden rise in blood glucose levels, it slows the absorption of glucose. The absorption of cholesterol, a compound which is thought to lead to atherosclerosis or scarring of the arteries, may also be decreased by a relatively high fiber intake. A decrease in the release of insulin after meals can further reduce serum cholesterol. Since insulin is known to promote the production of cholesterol in the liver, a reduction in the absorption of glucose after meals via fiber intake can help regulate the levels of serum cholesterol. In addition, dietary fiber intake can help prevent colon cancer by diluting possible carcinogens by enhancing water retention, binding carcinogens to the fiber itself, and accelerating food passage through the intestinal tract so that there is less time for cancer-causing agents to function.

Biological Recognition Processes

Not only do carbohydrates perform dietary purposes, they are also thought to play important roles in processes of cellular recognition. For example, glycoprotein sequences are found in many immunoglobulins (antibodies) and peptide hormones. These sequences are composed of carbohydrate-linked amino acids. The carbohydrate polymer attached to the rest of the protein can be broken by circulating enzymes or spontaneously degraded over the course of several hours or days. In order to begin its own degradation, the liver may identify variations in length and can internalize the protein. Carbohydrates can, in this way, mark the passage of time for proteins.

Source of Carbohydrates for the Body

All five food groups include carbohydrates: grains, fruits, vegetables, meats, and beans (in some processed meats and beans only), and dairy products. In fruits, fruit juices, and dairy products, fast-releasing carbohydrates are more prevalent, while in starchy vegetables, beans, and whole grains, slow-releasing carbohydrates are more abundant. In processed foods, soft drinks, and candy, fast-releasing carbohydrates are also present in large quantities. On average, 15 grams of carbohydrates are found in a serving of fruit, whole grains or starches. There are about 12 grams of carbohydrates in a serving of milk and about 5 grams of carbohydrates in a serving of vegetables. Specific amounts of carbohydrates, fiber, and added sugar from different foods are given in the table below:

Sources: US Department of Agriculture. National Nutrient Database for Standard Reference.

Carbohydrates are found in a wide array of both healthy and unhealthy foods—bread, beans, milk, popcorn, potatoes, cookies, spaghetti, soft drinks, corn, and cherry pie. They come in a number of ways as well. Sugars, fibers, and starch are the most common and abundant types. An significant part of a balanced diet is foods that are high in carbohydrates. But the quality of carbohydrates is significant; some forms of foods rich in carbohydrates are better than others:

• Healthy Carbohydrates: Unprocessed or minimally processed whole grains, herbs, fruits and beans are the healthiest sources of carbohydrates, encouraging good health by supplying vitamins, minerals, fiber and a host of essential phytonutrients.
• Unhealthy Carbohydrates: White bread, pastries, sodas, and other heavily processed or refined foods contain unhealthier sources of carbohydrates. These products contain carbohydrates that are readily digested and may lead to weight gain, interfere with weight loss, and facilitate diabetes and heart disease.

Digestion and Absorption (Metabolism) of Carbohydrates

Carbohydrates are hydrophilic and require a series of reactions to digest them to monosaccharides which are absorbed in the small intestine.

Digestion:

The purpose of the digestion of carbohydrates is to break down both disaccharides and complex carbohydrates for absorption into monosaccharides, but not all are completely absorbed throughout the small intestine (e.g.,fiber). In the mouth, digestion starts with salivary amylase released during the chewing process. In people eating diets rich in carbohydrates, there is a positive feedback loop resulting in increased oral amylase secretion. In the serous cells of the salivary glands, amylase is synthesized. Amylase splits maltose and polysaccharides into starches. Amylase is pH sensitive and is therefore inhibited in the stomach’s acidic environment. Due to insufficient exposure, just 5 per cent of starch is broken down by salivary amylase. In two classes, salivary amylase has increased in significance; infants with reduced development of pancreatic amylase in the first 9 months and children with cystic fibrosis or other etiologies with pancreatic insufficiency.

Absorption:

Products must be absorbed and transported to the portal circulation once carbohydrates are digested. Usually, digestion and absorption are combined, with the enzymes closely located to the suitable transporters. In the small intestine, glucose absorption occurs through the SGLT-1 transporter (sodium glucose co-transporter). Via the GLUT5 transporter, fructose absorption is completed by facilitated diffusion. Glucose and galactose are actively transferred by the sodium glucose transporter (SGLT-1) located in the brush border of the small intestine from the small intestine lumen.

Recommended Dietary Allowance (RDA) for Carbohydrates

The Recommended Dietary Allowance (RDA) of 130 grams per day of carbohydrates for children and adults. This is the minimum average amount taken by the brain to function properly. For carbohydrates, the Acceptable Macronutrient Distribution Range (AMDR) is between 45 and 65 percent. This implies that a person should eat between 225 and 325 grams of carbohydrate per day on a 2,000 kilocalorie diet. Added sugars can provide 25 percent of the total calories consumed. A much smaller intake of added sugar is recommended by the World Health Organization – 10% or less of the total calories consumed. The dietary fiber recommendations are focused on consumption levels proven to prevent heart disease from occurring.

Effects of Carbohydrates Deficiencies on Health

The major source of energy for the body is carbohydrates. They enable the brain, kidneys, muscles of the heart, and central nervous system to fuel. Fiber, for example, is a carbohydrate that improves digestion, helps to feel full and holds levels of blood cholesterol in check. When a person does not get enough carbohydrates in his/her diet, the body will store extra carbohydrates in the muscles and liver for use. Headaches, exhaustion, weakness, trouble concentrating, nausea, constipation, bad breath and vitamin and mineral deficiency can be caused by a carbohydrate-deficient diet.

When people adopt a diet that is low-carbohydrates. Whatever is not immediately used for energy after eating carbohydrates is processed as glycogen in the muscles or converted into fat in the liver. During physical activity, the body first uses glycogen for energy, but if insufficient carbohydrates have been consumed, glycogen stores are exhausted. As a result, because the body does not get the glycogen it needs for food, it continues to break down protein for use as energy in muscles.

The effects become dangerous after a few months on a low-carbohydrate diet, particularly for individuals with an active lifestyle. Metabolism slows down, fat accumulation builds and there is an increase in the risk of fatigue, dehydration and muscle aches. Individuals who exercise frequently do not adopt a diet that significantly limits carbohydrates for this purpose. They won’t have the stamina to do their workouts if they don’t eat enough of these things.

The ketogenic diet, otherwise called the keto diet, is the ultimate low-carbohydrate diet. It includes significantly decreasing the consumption of carbohydrates to 5 to 10 percent of the daily intake of calories and receiving much of the calories from fat and some protein.

The liver converts fat into acids called ketones in carbohydrate deprivation, which are used by the body for food. This process, known as ketosis, usually starts after three or four days of carbohydrate restriction.

The loss of water weight associated with glycogen depletion is attributed to early weight loss on the keto diet. People can experience unpleasant short-term effects after a few days, such as nausea, fatigue, and dizziness, which are a cluster of symptoms known as keto flu.

Over time, dehydration, altered chemical balance in the blood and dangerously low blood sugar levels can result from ketosis. Other long-term effects are uncertain, but lack of fiber intake can cause constipation and low consumption of fruits, vegetables and whole grains can result in nutritional deficiencies.

Some individuals should not try the diet because of health issues that could result from the keto diet. This include those that have liver disease, pancreatitis and fat metabolism disorders.