Sugar. What you need to know.
If you believe the headlines sooner or later eating sugar is going to kill you. Is this really true ? Surely we have been eating sugar for generations……
What is sugar?
Sugars are the building blocks of all carbohydrates. Monosaccharide sugars are the simplest of all carbohydrates containing just six carbon atoms, twelve hydrogen atoms and six oxygen atoms arranged in a ring. Monosaccharides bond together to form oligosaccharides (containing 2-10 monosaccharide units ) and polysaccharides (>10 monosaccharides). Monosaccharides and some oligosaccharides taste sweet. Glucose and fructose are the most common monosaccharides and lactose (milk sugar), maltose (malt sugar) and sucrose (table sugar) are common disaccharides (oligosaccharides containing just 2 monosaccharides).
Sweetness
Although they all taste sweet, the intensity of that sweetness is different for different sugars. The table below gives the relative sweetness of the common mono- and di- saccharides. What it shows is that although all simple carbohydrates or sugars give 4calories of energy, fructose is by far the sweetest.
|
Name |
Sweetness Index |
Calories per Gram |
| Sucrose |
1 |
4 |
| Glucose / Dextrose |
0.75 |
4 |
| Fructose |
1.7 |
4 |
| Lactose |
0.15 |
4 |
| Maltose |
0.3 |
4 |
| Galactose |
0.3 |
4 |
All fruits and vegetables contain a mix of simple sugars, commonly sucrose, fructose and glucose. Regardless of its source, each gram of sugar supplies the body with the same amount of energy per gram (4 Calories per gram). It is the type of sugar as well as the quantity that contributes to sweetness. The chart below shows a comparison of different fruits and vegetables and their glucose, fructose, sucrose levels. The disaccharide sucrose contains one molecule of glucose and one of fructose.
Similarly natural sweeteners contain varying amounts of different mono- and di- saccharides. Although as I show in my piece on honey, no two natural sweeteners are really alike, the average table honey in the UK contains around 82g of sugar per 100g, made up of approximately 34g glucose and 43g fructose, 4g of maltose and a small amount of sucrose. Maple syrup is predominantly sucrose with a small amount of glucose and fructose.
Where the difference lies and where the problems start.
All sugars have the same energy value and although some are sweeter than others, they all taste sweet to the tongue. Until recently this is all you needed to know but research now shows that your body can tell the difference between glucose and fructose and treats them very differently.
The first difference is how they are digested. Your body metabolises glucose in the intestine and as it is absorbed, it causes blood sugar to rise. Complex carbohydrates (polysaccharides) such as starch and grain, or the glucose contained in fruit and vegetables is released slowly, in relatively small amounts at a time, allowing the body to process it efficiently. If blood glucose levels do rise to quickly, the pancreas releases insulin. The insulin binds to the glucose, carries it to the cells that need extra energy and then signals for remaining ‘energy’ to be stored in fat cells. The problems with glucose arise when levels are continuously high. Eating highly levels of processed carbohydrates like white flour, white rice and foods containing refined sugar, elevate blood glucose significantly. For a while, the pancreas can process these levels; however, over time this mechanism breaks down and insulin is either not released or doesn’t function efficiently. This can result in the chronically elevated blood glucose levels found in type 2 diabetes or in metabolic syndrome and because insulin is now inefficient, glucose is no longer delivered to the cells that need it.
Whereas glucose is processed in the gut, fructose is predominantly metabolised in the liver. When you consume large amounts of fructose particularly when it is in its concentrated form (agave, crystalline fructose, high-fructose corn syrup), it goes straight to your liver, avoiding the gastrointestinal tract altogether. This places a heavy toxic load on your liver, which must work very hard to process it and very high levels can result in scarring. Excess fructose is converted by the liver into glycerol, causing fatty liver and raised levels of triglycerides.
The second difference between glucose and fructose is how they interact with appetite. Research in people and animals has shown that excess glucose and insulin trigger both the feeling of being full and slight nausea (try eating an entire bag of jelly babies) but that high intake of fructose appears to increase appetite and ‘food-seeking’ behaviour.
Less research has been done on other sugars but research on maltose has suggested that although it is less sweet than glucose it may trigger an even greater insulin response and on lactose suggests that milk sugars are low risk.
Sugar – The bitter Truth
The first person to suggest that sugar was a problem was John Yudkin. In 1972 he wrote the book called Pure, White and Deadly in which he noted that modern methods of food manufacture allowed sweetness (the factor responsible for the palatability of fruit and grains) to be separated from the factors that give them their nutritional value (Vitamins, particularly vitamin C, fibre and minerals). He was the first to suggest that it was the consumption of ‘processed sugars’ that was the root caused coronary heart disease, obesity and diabetes. At the time his work was rubbished by the nutrition industry, which was focused on low fat and fibre.
In 2009 Robert Lustig, a pediatric endocrinologist at University of California posted the lecture ‘Sugar the bitter truth’ onto YouTube. The video went viral and has had over 4million views to date. Where John Yudkin had failed, Robert Lustig had succeeded and his work on the toxic effects of sugar have had huge world wide coverage in the press. I was lucky enough to listen to Professor Lustig speak when he was in London last year and he has published a book about his work, Fat Chance – The Hidden Truth about Sugar, Obesity and Disease, which is very readable. His arguments are convincing and research is increasingly backing his theories. He has linked high sugar consumption and particularly consumption of fructose with world increases in obesity, cancer, mental illness, diabetes and heart disease. His and other research has shown that you don’t need to be obese to have an increased health risk from eating sugar. The YouTube film below is his latest, updating his research and giving physiological reasons behind his advice to cut down on sugar. It is long but the first five minutes can be skipped as there is a long introduction.
The food industry
The food industry loves sugar because if you add sugar to anything we will eat more of it. Throughout evolution sweetness has signalled that something is good to eat and nutritious and we are hard-wired to enjoy sweet foods. The food industry also loves sugar because not only does it improve taste but it also acts as a preservative and can modify texture.
The food industry likes processed sugars more than traditional sugars because they are cheaper to produce and by using a number of different sweeteners it is possible to adapt both texture and taste. Also by splitting out the sugars they can distort the ingredients list with no one type of sugar hitting the top spot.
The food industry loves fructose because it is very very sweet meaning you need less raw material. It is also cheap to produce.
The slimming industry loves fructose because it is very very sweet meaning you need less of it. As all sugars have the same energy value, fructose is a lower calorie sugar gram for gram than sucrose or glucose. It also has a very low glycemic index, 19 ± 2, compared with 100 for glucose and 68 ± 5 for sucrose. This is purely because it does not raise blood sugar or stimulate insulin production, so is really a red herring.
What should you do ?
Although there is good evidence that eating excessive sugar can increase your risk of cancer, heart disease, diabetes, liver disease and obesity, as well as fogging your brain and effecting your memory, there is actually little evidence that eating sugar as part of whole foods within a balanced diet is damaging. Much of the research points to the speed at which sugar is ingested being the damaging factor and suggests that eating sugar as part of a meal or within whole food slows its absorption and allows the body to process it efficiently. This fits with Robert Lustigs research which suggests sugar is a toxin and John Yudkins work which highlighted the problems of eating sugars without their natural nets. It also fits in with most healthy eating advice where a foods value depends on its nutritional value and with good dental practise.
There is some research that suggests that sugar consumption is far more damaging in the absence of omega-3 fats. Although more conclusive in animal studies, what the research shows is that high fructose diets in the absence on adequate omega-3 oils results in high triglyceride, glucose and insulin levels and a decrease in brain synaptic activity, weakening an individuals ability to learn or memorise. This has been shown to be reversible with supplementation.
Most countries do not have recommended intakes of sugar. The world health organisation recommends that less than 10% of total energy consumed should be simple sugars, though this recommendation is based as much on reducing the risk of tooth decay as it is for improving long term health. For an adult eating 2000calories a day, this would be about 50 grams, or the equivalent of 4 tablespoons of granulated sugar.
Advice
- Be aware of what you are eating. There are now literally hundreds of different sweeteners on the market and many processed foods will contain more than one.
- Eat a well balanced diet containing adequate fruit and vegetables and omega-3 oils. The Harvard Healthy Eating Plate is a good basis for a balanced diet.
- Avoid adding sugar.
- Avoid wasted calories. A 330ml can of fizzy pop contains around 140calories and 39g of sugar. It has little other nutritional value and with nothing to digest, the sugar will hit the blood stream quickly causing blood sugar to spike.
- Watch for sugar in drinks, not only are they often wasted calories but as it ‘blends’ better with liquids, it is often high fructose syrup. AND there has been research showing that children are less likely to eat healthily if they have a sweet drink as it makes the food taste bitter.
Types of Sugar found in processed food.
Agave: Although hailed as a natural product and in many sports foods and drinks, agave is actually highly processed. Agave is high in fructose, different brands range from 56-92% fructose. It is about 33 percent sweeter than table sugar. Light agave syrup resembles maple syrup or honey in flavour, though the taste is more delicate, which is why agave is increasingly popular for energy drinks, teas, nutrition bars etc. Amber and dark agave nectar taste similar to caramel, and can be used like maple syrup on pancakes and waffles. Agave has about 60 calories per tablespoon, compared to 40 calories for the same amount of table sugar but agave is about 1 1/2 times sweeter than sugar so recipes need less of it. It has a glycemic index of between 10 & 20.
Coconut sugar: Has been championed by the health food industry as coconut sugar is thought to contain small amounts of Iron, Zinc, Calcium and Potassium, chain fatty acids, polyphenols and antioxidants. It also contains a fibre called Inulin, which may slow glucose absorption and explain its lower glycemic index (35) than regular table sugar. There is very little research to back these claims.
High Fructose Corn Syrup (HFCS): Also called glucose-fructose syrup. A combination of fructose and glucose made by processing corn syrup. Enzymatic processing converts some of the corn syrup’s glucose into fructose to produce a desired sweetness. The resulting syrup is sweeter and more soluble than most other sugars. HFCS 55 (mostly used in soft drinks) is approximately 55% fructose and 42% glucose. A recent University of Southern California analysis of popular sodas (all sweetened with HFCS) found that the percent of fructose can be as high as 65 percent. Lots of research on HFCS has found that they can be linked to obesity, cancer, heart disease and mental health problems.
Invert Sugar: Used as a food additive to preserve freshness and create smoothness. It is made from sucrose broken down into its respective parts – fructose and glucose. Although the starting place is different the result is much the same thing as an HFCS. The fact that fructose is free and no longer joined to glucose makes inverted sugar sweeter than sucrose or glucose.
Maltodextrin: A highly processed powdered sweetener enzymatically derived from starch and resulting in a mixture of Glucose, Maltose, Oligosaccharides and Polysaccharides. In the US, the starch is usually corn, rice or potato; in Europe, it is commonly wheat. Foods that have maltodextrin often say “Low Sugar” or “Complex Carbohydrate”, but maltodextrin is very easily digested, has a glycemic index of 150 and is not good.
Molasses: The thick, dark syrup that’s leftover when sugar beets or sugar cane are processed into granulated sugar. Black strap is loaded with vitamins, minerals and trace elements naturally present in the sugar cane plant and is a good source of iron, vitamin B6, potassium, calcium and magnesium.
Rice Syrup (Brown Rice Syrup): Derived by cooking down rice or rice flour with enzymes. The final product is 45% maltose, 3% glucose, and 52% maltotriose. The syrup breaks down rather slowly, providing more of a time-release energy flow than sugar. About 13 calories per teaspoon and is less sweet than sugar. Tastes like butterscotch or caramel. Though it is said to have a low glycemic index (25), it is not recommended for diabetics, since its sweetness comes from maltose, which can cause spikes in blood sugar.
Stevia: Also known as sweet leaf or sugarleaf. Stevia plants are dried and subjected to a water extraction process. 300 times sweeter than sugar with zero calories and a GI of <1. Too good to be true ? Im afraid so. There are real health risks associated with eating something sweet without calories. Watch out for my piece on artificial sweeteners coming soon.
Sugar Alcohols: Also know as polyols and derived from a plant sugar which is extracted by differing means, then reduced and then hydrogenated, then recrystallized. Part of their structure resembles sugar and part is similar to alcohol, yet they are neither sugar nor alcohol, they just resemble their molecular structure. Contain about 2.6 calories per gram. Occur naturally in plant products such as fruits, berries, starches, seaweeds. Products which use sugar alcohols can be called “sugar free”. Sugar alcohols all behave differently in the body.
Erythritol: has very small molecules and so passes directly through the system without metabolizing. Since it never makes it to the large intestine, this sugar alcohol does not cause the bloating and gas that are often associated with other sugar alcohols. 70% as sweet as sucrose. Heat-stable. People mix it with Stevia. (Organic Zero is a brand name).
Isomalt: Is made from sucrose. It is a mixture of gluco-mannitol and gluco-sorbitol. Isomalt is only partially digested in the intestines and behaves much like fiber in the digestive tract. Is 45 – 65 percent as sweet as sugar and does not tend to lose its sweetness or break down during the heating process. Isomalt absorbs little water, so it is often used in hard candies, toffee, cough drops and lollipops.
Lactitol: Made from milk sugar (lactose). Lactitol is partially absorbed as glucose by the body and the remaining amount is fermented in the large intestine. Therefore may cause distress in the large colon. 30-40 percent as sweet as sugar, but its taste and solubility profile resembles sugar so it is often found in sugar-free ice cream, chocolate, candy, baked goods, preserves and chewing gums.
Maltitol: Made by hydrogenation of maltose obtained from starch. 75-90% percent as sweet as sugar. It gives a creamy texture to foods. Maltitol is slowly absorbed in the intestine and excessive consumption can have a laxative effect and produce intestinal gas, bloating, and diarrhea.
Mannitol: Is mainly extracted from seaweed for use in food manufacturing. Has 50-70 percent of the relative sweetness of sugar. Mannitol lingers in the intestines for a long time and therefore often causes bloating and diarrhea. Mannitol is found in a wide variety of natural products, including almost all plants. Mannitol does not absorb moisture and is used to dust chewing gum to prevent it from sticking.
Sorbitol: Is manufactured from corn syrup. 50 percent as sweet as sugar. It is often an ingredient in sugar-free gums and candies. Is found naturally in fruits and vegetables. It has less of a tendency to cause diarrhea compared to mannitol but can also aggravate irritable bowel syndrome.
Xylitol: Is also called “wood sugar” and can be extracted from corncobs, birch wood, raspberries, plums, vegetables, mushrooms and some cereals. Xylitol has the same relative sweetness as sugar. It is found in chewing gums. Xylitol is produced by hydrogenation of the raw material, which converts the sugar into an alcohol. Tooth friendly.
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