Carbohydrates and Sugar

Sugar is the generic name given for sweet tasting soluble carbohydrates found in many foods. Sugar is found in differing quantities, combinations, natural, artificial and labelled under many different guises making it almost impossible to avoid completely.  

Table sugar, also known as sucrose, is a hydrocarbon found in plants. It is a disaccharide (two sugars joined) of the monosaccharide’s glucose and fructose.

Around ten thousand years ago sugar cane was first domesticated in New Guinea. Seven thousand years later it was spread by travellers to the Middle East, where it was sold to the Venetians, who around 800 years ago sold it to the rest of Europe. It was then more valuable than gold and only the very wealthy could afford it. Sugar was used to make sculptures and used to show how wealthy a person was. Before we were introduced to sugar we would sweeten our food using honey and fruit.

In the seventies there was a huge increase in obesity, heart disease and diabetes in the western world. The experts began to research and perform studies to find out what might be causing this epidemic. They concluded that the common denominator was an increase in blood lipids. If there was an increase in blood lipids this must be coming from a high fat diet. This is what led to the low-fat craze we are still seeing today. For the past fifty years there have been thousands of low fat products produced and we can still see them on supermarket shelves. Yet why is it that we have higher obesity, diabetes, heart problems than ever before? The short answer is sugar. Fifty years ago, there was an increase in the use and consumption of sugar in the western diet, plus a lot of low-fat foods are often high in sugar.

So how is sugar making us fat?

Once our body’s fuel stores are full, over consumption of any macronutrient will subsequently be converted and stored as fat, this process is called lipogenesis. Five hundred years ago, before mass production and trade in sugar, we had very little sugar of any form in our diet. The sugar we did eat was found in nuts, fruit, vegetables and grains in their natural whole food form. The food industry increased its production of processed, quick, easy, convenient foods in the 1970’s massively increasing the usage of the cheap sugar known as fructose, from sources such as corn. Between 1970 and 2000 fructose consumption increased a huge amount.

A survey performed in the 1990’s in America showed that an average person consumed 19 teaspoons (80 grams) of added sugar per day and fifty percent was from fructose. 

Fructose is found in many processed foods such as soft drinks and sweets in the form of HFCS (high fructose corn syrup) and as already mentioned sucrose (table sugar).

The reason fructose is relevant is in the way it is metabolised. Glucose is the body’s preferred source of fuel. After eating, food is broken down into its primary states (protein = amino acids, fat = triglycerides, carbohydrates = glucose). Glucose is easily transported into the blood stream and used for energy or stored as glycogen. However fructose needs to firstly be transported to the liver to be converted into glucose, and either used for energy or stored as glycogen. The liver has a finite glycogen storage capacity, once the capacity is reached through a complex series of reactions, the remainder will be converted to and stored as fat. A large amount of fructose consumed at one time (a soft drink for example), will inevitably increase fat production, usually around the abdomen.

Fat around the middle is prominent in individuals with high blood lipids and associated with conditions such as type 2 diabetes, insulin resistance and heart disease (there is more information about these below). Another interesting point is that production of the hormone leptin (which increases after eating to signal satiety) is decreased with chronic fructose consumption, disrupting our inbuilt regulatory systems. In short, chronic fructose intake turns off hunger signals, subsequently keeping you eating above and beyond your recommended calorie intake. It also decreases LDL cholesterol, increases HDL cholesterol and increases fat production.

Carbohydrates are often misunderstood as they can be broken down into many different categories. Firstly, there are simple sugars known as monosaccharide’s (1 sugar), which join to create disaccharide’s (2 sugars), oligosaccharide’s (3-9 sugars) and more complex sugars known as polysaccharide’s (10 plus). These are found in all carbohydrate containing foods, in varying lengths and sweetness’s.


Glucose (dextrose), galactose and fructose are all simple sugars. As these are single sugars they don’t need to be broken down, which means they can enter the blood stream quickly, creating an increase in blood sugar and providing quick energy. This is “generally” not a good scenario, however there are circumstances when sugars are required quickly (post training, long distance events, for diabetics suffering from hypoglycaemia).

Glucose - the body’s main fuel source. It releases quickly into the blood stream and is found in fruit, pasta, vegetables, whole grains and legumes.

Fructose - fructose doesn’t have such an impact on blood sugar. However due to its metabolism which takes place via the liver, in high quantities it increases the production of triglycerides. It is found in fruit sugar, which is in fruits, honey, some vegetables and soft drinks. Fructose elicits a low glycaemic response when consumed from whole fruits.

Galactose - found in legumes, dried figs and dairy products.


Two simple sugars joined together are known as disaccharide’s. Examples are lactose, sucrose and maltose.                                                                 

Lactose - milk sugar, which is a combination of galactose and glucose. It's mainly found in dairy products, but can also be found in bread, baked foods, cereals and processed snacks.

Sucrose - table sugar, which is a combination of fructose and glucose. It's found in sugar cane, some fruits, vegetables and sweetened products (cereals, ice cream, desserts and yoghurts).

Maltose - malt sugar, which is a combination of two glucose molecules and is released fast into the blood stream. Found in barley, cereals containing barley, malt products like malted milkshakes and beer.


Three to nine sugars combined create a sugar known as an oligosaccharide. Found in small amounts in many plants. Humans don’t have enzymes to break down oligosaccharides, which means they are indigestible in the small intestine. They then move through to the large intestine where beneficial colonic bacteria break them down (ferment) into absorbable nutrients. Short chain fatty acids are a beneficial breakdown product for the large intestine lining. Also known as soluble fibre, oligosaccharide can help with constipation. Eaten in large quantities they can cause bloating, flatulence and stomach pain.

There are many different forms of oligosaccharides:

FOS (Fructo-oligosaccharide) - found in Jerusalem artichoke and onions. It is a prebiotic (non-digestible nutrient), which increases the beneficial intestinal bacteria and subsequently promotes intestinal lining health. Oligofructose and trans-galactooligosccharide’s are also prebiotics.

Arabinoxylan (oligosaccharide) - found in cereal grains.

GOS (Galacto- oligosaccharide) - Raffinose, Stachyose and Verbascose found in beans, peas, pulses, cabbage and whole grains.

Gluco- oligosaccharide - produced from sucrose.

Human milk oligosaccharide - found in breast milk.

Lactosucrose - produced from lactose and sucrose.

There are many more.


Polysaccharides can be broken down into many categories. There are three main types of polysaccharide - starch, non-starch polysaccharide and glycogen.

Starch - found in plants, it can be either digestible or non-digestible. Starch consists of a large number of glucose units joined together. Most green plants produce starch for energy. Starch can be broken down into amylose (linear chain) and amylopectin (branch chained). Starch contains 20-25% amylose and 75-80% amylopectin depending on the specific plant. Starch begins its digestion in the mouth where the chewing action initiates the release of saliva secreted from salivary glands. The saliva contains the enzyme known as salivary amylase. The digestion continues in the small intestine and eventually glucose is released into the blood stream. Each molecule of glucose yields four calories. The breakdown also yields carbon atoms that are needed for fat and protein synthesis

Non-starch polysaccharide - (fibre) changes the nature of the contents in the gastrointestinal tract and changes how other nutrients and chemicals are absorbed. This can again be broken down into two categories, soluble and insoluble fibre. Soluble fibre absorbs water to become a gelatinous, viscous substance and is fermented by bacteria in the digestive tract. Insoluble fibre has a bulking action and is not fermented. Chemically, dietary fibre consists of non-starch polysaccharides such as arabinoxylans, cellulose, and many other plant components such as resistant dextrins, inulin, lignin, waxes, chitins, pectins, beta-glucans, and oligosaccharides.

Food sources of dietary fibre are often divided according to whether they provide (predominantly) soluble or insoluble fibre. Plant foods contain both types of fibre in varying degrees, according to the plant's characteristics.

Soluble fibre helps to remove hardened faecal matter from the lining of the colon wall. Soluble fibre binds to bile acids in the small intestine, making them less likely to enter the body, this in turn lowers cholesterol levels in the blood as bile acids are involved in fat metabolism. Soluble fibre also attenuates the absorption of sugar, reducing the blood sugar response after eating, normalises blood lipid levels and, once fermented in the colon, produces short-chain fatty acids as byproducts with a wide range of physiological activities. Short chain fatty acids are a major energy source for colonocytes (cells of the colon) and they produce an acid environment preventing growth of harmful bacteria and yeasts. It may also be beneficial in lowering overall blood cholesterol and bad LDL cholesterol. It also slows the rate at which glucose enters the blood so helps diabetes and blood sugar control.

Soluble fibre is mainly found in legumes, vegetables, fruits, oats, barley, rye and seeds.

Insoluble fibre helps keep the bowels regular. Consuming insoluble fibre also produces healthful compounds during its fermentation. This type of fibre has the ability via its passive hygroscopic properties (the ability of a substance to attract and hold water molecules from the surrounding environment through either absorption or adsorption with the absorbing or adsorbing material becoming physically changed, by an increase in volume, stickiness, or other physical characteristics) to increase bulk, soften stools, and shorten transit time through the intestinal tract.

Disadvantages of a diet high in fibre are the potential for significant intestinal gas production and bloating and elimination of important nutrients. Constipation can occur if insufficient fluid is consumed with a high-fibre diet. Constipation also results in the re-absorption of toxins. 

Insoluble fibre is mainly found in wheat bran, other whole grains and some vegetable and fruit skins. The recommended daily amounts are 25g for a woman and 38g for a man. This can be achieved by eating more plant-based foods (vegetables, beans, fruits, nuts, wholegrains).  

Functions of fibre in the body

  • Improves transit time and assists the movement of waste products through the gut. Fibre acts like a broom and sweeps waste material along the digestive tract, thus preventing the build-up of stale faeces in the colon, which can lead to toxins being released which irritate the digestive tract.

  • Balances the levels of glucose by binding to the sugar molecules and slowing down their absorption into the blood.

  • Stabilises blood cholesterol and therefore reduces the risk of heart disease, by binding to bile salts and preventing them entering the blood stream.

  • Protects against haemorrhoids, varicose veins, diverticular disease, gallstones, kidney disease and constipation.

  • Reduces the build up of toxins, yeasts and unfriendly bacteria.

  • Binds to and deactivates carcinogens therefore helping reduce the risk of colon cancer.

Glycogen - is the body's stored sugar, a multi-branched polysaccharide of many glucose units joined together. Glycogen is the form in which humans and animals store energy (1400-2000 calories or 350-500grams). It is stored primarily in muscle tissue and the liver. Approximately one teaspoon (four grams) of sugar is found in the blood stream at any time. When blood sugar is low in a fasted state glycogen is released from the liver to keep blood sugar at a healthy level. Glycogen is highly branched, similar in structure to the starch amylopectin.  

Sugar and health                                                          

Simple sugars do not contain fibre, vitamins and minerals, which means they are empty calories. There is plenty of evidence to show the detrimental effects sugar has on the body. There are millions of pounds spent in the health system on conditions caused by an unhealthy high sugar diet. Sugar is addictive, a study using mice showed that sugar is eight times more addictive than cocaine!

Teeth - over-consumption of sugar has been shown to cause dental issues. The only sugar that isn't bad for your teeth is lactose from dairy, as that isn't broken down in the mouth like other sugars, but actually further down the digestive system.

Obesity - the body has a finite capacity to process and store sugar. Too much sugar entering the blood rapidly will lead to panic response, pushing large amounts of sugar into the cells. It can be used for energy, however, if you're not being active it can be stored as glycogen. If your glycogen stores are already replenished (as we can only store between 1400-2000 calories worth) the remainder will be stored as fat. If a person consumes sugar on a chronic basis this will inevitably lead to an increase in fat storage. It’s a lot easier than you may think to reach your daily recommended sugar limit (6 teaspoons for women and 9 teaspoons for men).

Tiredness, memory loss, and headaches - general symptoms around lethargy are related to blood sugar imbalance. Glucose and maltose (glucose-glucose) are the two sugars that have the largest effect on blood sugar. Blood sugar is the amount of sugar in our blood at any one time. Blood sugar imbalance is a condition in which your body does not handle glucose effectively, through either eating the wrong carbohydrates at the wrong time or from a condition known as insulin resistance (for more information on blood sugar see our separate blood sugar article).  

Insulin resistance - after we eat the food is digested and broken down into its smallest forms. Glucose is the simple form of sugar that passes through into the blood. This increase in blood sugar initiates the release of Insulin. Insulin is a hormone produced by the beta cells from the islets of Langerhans located in the pancreas. Insulin then binds to the sugar, transporting it to the cells to be either used for energy, stored as glycogen or fat. Insulin is required for cell regulation including their growth. It is also essential in the metabolism of sugar (carbohydrates), lipids (fat), and amino acids (protein). Insulin resistance is a condition in which the body's cells have become resistant to effects of insulin, creating a need to release more insulin to remove the toxic levels of sugar from the blood. The more insulin produced the more resistant the cells become. Eventually the pancreas cannot produce enough insulin to cope with the body's demands. This is caused by a chronic high sugar (or high glycaemic) diet, were large amounts of insulin are constantly being produced. Insulin resistance is related to a condition known as metabolic syndrome, which increases the risk of developing heart disease and diabetes. Insulin resistance can be due to both generic and/or lifestyle factors. Medical conditions such as fatty liver, arteriosclerosis, skin tags, female reproductive problems and acanthosis Nigerians are all associated with insulin resistance. Although not exclusively, people with insulin resistance are more likely to be obese. Genetic factors can be the cause however a majority of insulin resistance cases can be managed through nutrition, exercise and, in extreme cases, medication. High resting blood glucose and insulin levels are a predictor that you may be insulin resistant.

Diabetes - type 2 diabetes is a growing problem, often known as late onset diabetes since it tends to affect people aged over thirty-five. However it is becoming increasingly common in younger people due to increased sugar consumption in their diet. There are two types of diabetes, type-1 (insulin dependent) and type 2. Type 2 is the most common form of diabetes affecting 90-95% of sufferers and is largely due to lifestyle. Insulin is secreted by the pancreas and is the hormone in the body responsible for reducing blood sugar when it gets too high. When we eat food that is high in fast releasing sugar, the level of glucose in the blood will rise rapidly above normal levels. As high blood sugar levels are toxic, the body panics and releases insulin quickly, which then reduces the blood sugar levels too far, causing symptoms of hypoglycaemia or low blood sugar (causing hunger, dizziness, irritability, lack of concentration, brain fogginess, palpitations, and numbness or tingling of the lips). The adrenal glands now release adrenalin to correct the drop. This cascade of hormonal responses to correct a high sugar meal/snack, over time, puts pressure on both the pancreas and adrenal glands impairing their function and exhausting them, reducing their output and effectiveness. This leads to some type 2 sufferers not secreting sufficient amounts of insulin, requiring insulin injections to correct the imbalance. However, generally sufferers do have sufficient amounts of insulin, but the body’s insulin receptors do not react correctly to insulin (insulin resistance). It can be controlled by diet and lifestyle modifications. There are a number of factors affecting the likelihood of contracting type 2 diabetes (diet, weight, race, age, lack of exercise, and heredity). Ninety percent of overweight people have got diabetes. In many cases, the condition can be controlled without the need for insulin or other drugs, instead purely by making dietary changes. Additionally, people eating a diet high in sugar, refined carbohydrates (white bread and pasta, pre-packaged convenience meals, sweets, confectionary), high in stimulants (tea, coffee, alcohol, chocolate), too much meat and dairy and with a low fibre intake are more susceptible. Sometimes there are no symptoms, it may only be noticed by a routine urine test (glucose present) or blood test. Other problems associated with diabetes are extreme thirst, increased hunger, and increased urination. Dehydration due to large amounts of water being drawn from the body to help dilute the high amounts of sugar in the blood and help the kidneys remove it. This causes a large amount of water loss, which increases dehydration. Chronic high glucose levels will lead to damage to cells, nerves (damaging eyes and extremities), kidney damage, and predispose a person to atherosclerosis (narrowing) of arteries, which can cause heart attacks and strokes.

Cancer - high sugar consumption will inevitably lead to an increase in insulin. Insulin is an anabolic hormone, meaning it promotes growth. A high sugar diet can increase the proliferation of cancerous cells.   

Other related health issues - studies have shown that high levels of sugar in the blood can damage collagen in the skin leading to wrinkles. Acne and inflammation is also associated with high blood sugar levels.


Fruit has been given a bad name by some over the past few years due to its fructose content. It is true that fructose in high quantities, and in a more processed state, can increase fat storage. However, fruit is packed full of essential nutrients (vitamin C, potassium), antioxidants, and fibre, which has the effect of slowing the disaccharide entering the blood and liver. Like any food there are healthier options. Those that have a higher ratio of glucose to fructose are recommended (pears, apples, berries, clementine, cantaloupe melon) rather than the higher fructose fruit (bananas, grapes, mangos, dates, raisins, figs). It's ok to eat fruit in moderation like any other food, two pieces a day is recommended. Eating fruit and vegetables can help prevent chronic disease, including cancer.      

Helpful food terminology

What is the difference between, whole, refined and processed? We see these terms all the time but what do they mean?

Whole foods - refers to a food that has not had any nutrients removed or been altered from its natural state (barley, buckwheat, amaranth, quinoa, brown rice).

Processed foods - this is where a foods structure has been changed. Forms of processing include cooking, pureeing, crushing, freezing, grinding, mincing, emulsification, pickling, pasteurisation and many more. Although processed foods have been structurally changed, they haven’t had any nutrients removed. However they more often than not have things added (some cereals, some breads, tinned fruit, bacon).

Refined foods - these are foods that have had nutrients removed, making them empty calories and lacking the all-important fibre. This is done generally to extend shelf life (white bread, white rice and pasta).

Hidden sugar - dextrose, dextran, multi-dextrose, fructose, barley, malt, butter syrup, corn sugar, caramel, corn syrup, date sugar, fruit juice, carab syrup, diatase, glucose, castor sugar, lactose, icing sugar, treacle, cane juice to name a few.

What about artificial sweeteners?

Artificial sweeteners were created to satisfy sugar cravings without using calories from sugar and the associated weight gain. Sweeteners can be six hundred times sweeter than sugar and, like sugar, come in many guises (saccharin, sucralose, acesulfame, aspartame). They have been linked to many health problems.

Sugar metabolism begins on the tongue, preparing the digestive system for food. An artificial sweetener causes the body to prepare itself for a huge amount of sugar, releasing insulin to deal with the huge amount it thinks it is about to receive, but the sugar doesn’t make it to the blood stream. One theory is that the anticipation of the sugar that doesn’t actually arrive actually increases sugar cravings. Studies have shown that regardless of whether the food uses natural or artificial sweeteners, it creates an increased sugar craving. It is worth remembering that foods sweetened with artificial sweeteners, such as baked items and sweets still contain calories in the form of carbohydrates, fats and protein, which will initiate an insulin release (the effects of which is already mentioned). There is a theory that when people eat foods containing artificial sweeteners they tend to consume more. The reasons for this may be psychological, thinking that as there is less sugar we can eat more, or physiological, as we are not getting the same satiety signals we would with natural sugar. Interestingly studies have shown that calorific consumption of foods sweetened with artificial sweeteners are similar to the calories consumed with sugar sweetened version. 

There are significant health risks associated with artificial sweeteners. Thirty-seven studies using as many as 400,000 people over ten years showed that artificial sweetener intake was associated with an increased risk of diabetes, heart disease, syndrome x and weight gain. Different studies also showed that artificial sweetener users are more likely to be overweight than those who don’t consume soft drinks at all. The soft drinks industry will often say that these sweeteners are deemed safe by the appropriate regulators, however the fact is that millions of people consume these sweeteners and relatively little has been done to assure their long-term safety. In 1977 a study in rats showed that artificial sweeteners caused cancerous tumours in the urinary tract, reproductive systems, lungs and stomach. However, due to both the food industry lobbying and public outcry that the sweeteners may be taken off the market, American congress concluded that the sweetener saccharin must carry a label saying that the product may be hazardous to health and has been determined to cause cancer in laboratory animals.   

In conclusion, it is clear that we need to reduce sugar intake. The world health organisation recommends that only ten percent of calories should come from sugar. The government recommends no more than 6 teaspoons for women and 9 teaspoons for men. The sugar industry is huge and extremely powerful, with considerable economic influence that is sadly to the detriment of our health and well-being. Both sugar and artificial sweeteners will perpetuate the sugar craving. The best way to reduce sugar is simply to stop eating processed foods and eat a diet high in natural whole foods.

This article has
been written by
Terry Fairclough