The most comprehensive, evidence based and balanced post on sugar

In this post I hope to give you a balanced, evidence based perspective on sugar. Is it really as bad as everyone says it is? Should you avoid it like the plague? In most cases where there is fear mongering, dogma, and hype around food, it is usually over exaggerated and the research on the topic is taken out of context. Taking the midline approach is usually the best option. Let me explain.

What is sugar?

Every cell in our body depends on sugar for energy. It is our brain’s primary energy source. Therefore, sugar is vital to our survival, hence it is no wonder we are genetically programmed to crave sweetness.

From an evolutionary perspective, this ensured our survival because before agriculture, our ancestors did not have much control over the sugars in their diet, which would have come from whatever plants were available in a given place and season. Therefore, when they got hold of foods that tasted sweet, they probably pigged out. Sweet food meant calorie density, low toxicity and because food was scarce at that time, it was important to load up on calories as much as possible when they could.

Sugar cultivation first started with sugar cane. Sugar was an expensive luxury until manufacturing became efficient enough to make “white gold” much more affordable.

Today, we add sugar in one form or another to the majority of processed foods we eat—everything from bread, cereals, crunchy snacks and desserts, to soft drinks, juices, salad dressings and sauces.

With our innate tendency to love sweet tasting foods (they ensured our survival as a species), and the availability of high calorie, sugar laden foods all around us, it can lead to overeating on these foods, which can be an issue, but as I will explain, it doesn’t make sugar intrinsically toxic.

Now before we start to dive into the crux of this post, it is important to sought out some terminology and technical information. In the Australian food industry, processed food, confectionery and soft drinks usually contain sucrose as a sweetener from sugar cane, which contains 50% fructose and 50% glucose. Sucrose is a glucose and fructose molecule bound together. Table sugar is sucrose.

Other processed foods use various other caloric sweeteners like dextrose, glucose syrup, high fructose corn syrup, honey, golden syrup, maltodextrose and trehalose. These sugars essentially contain varying ratios of fructose, glucose and sucrose, contained in various chemical structures.

Lastly, I would like to make a special mention about high fructose corn syrup (HFCS). HFCS was developed in the 1960s, where new technology allowed the U.S. corn industry to cheaply convert corn-derived glucose into fructose and produce high fructose corn syrup, which—despite its name—is almost equal parts free-floating fructose and glucose: 55 percent fructose, 42 percent glucose. Because fructose is about twice as sweet as glucose, an inexpensive syrup mixing the two was an appealing alternative to sucrose from sugarcane and beets. High fructose corn syrup is mainly used in the U.S food industry and has received a lot of hype as of late.

Virtually all plants have glucose, fructose and sucrose—not just one or another of these sugars. Although some fruits, such as apples and pears, have three times as much fructose as glucose (which is why they are sweeter), most of the fruits and veggies we eat are more balanced. Even foods like potato and sweet potato have mostly glucose in the form of starch but also contain small amounts of sucrose and fructose, just not as much, therefore they are not as sweet as fruit.

The difference between the sugars consumed in whole-foods like fruit and vegetables compared to processed food is that whole-food sugars exist within plant cell walls of fibre. Whereas sugar-sweetened beverages and food do not contain fibre and other nutrients that are found in fruits and vegetables. The presence of fibre in fruits and vegetables slows the digestion of sugar into the blood. Enzymes in our digestive system must first break down the plant cell walls to reach the sugars (glucose and fructose) within, as opposed to processed foods and drinks, where the sugars are absorbed straight away, in high amounts.

Sugar and overeating?

Dr. Lustig’s famous presentation called “Sugar: The bitter truth”, did a very good job of creating fear mongering and food dogma surrounding sugar, specifically fructose, in both processed foods and natural sources.

In his presentation he outlines how fructose is an evil toxin that causes weight gain and metabolic issues. He outlined that fructose is easy to over consume because unlike glucose, fructose does not trigger the release of insulin, which is a hormone that removes glucose from the blood and is involved in satiety. But is this really true? Let’s take a look.

Insulin causes the release of leptin, which is a hormone that suppresses hunger. In rats, fructose also supposedly appears to raise ghrelin, which increases hunger, therefore this could lead to overeating of fructose and other calories as satiety signals are supposedly not working. However, these rats were fed isolated fructose.

Studies show that when humans are given fructose, glucose or sucrose, there is no difference to appetite hormones. Furthermore, fructose within our diet is never ingested without glucose. Foods/drinks that contain fructose, even processed ones, will also contain glucose.

Therefore, the claim that sugar (mainly fructose) in processed foods and plants can lead to overeating because it disrupts hormonal signals that are responsible for hunger and satiety, are not supported by research.

What is supported by research is that if refined sugar products are making up a lot of your caloric intake in your diet (especially sugar filled drinks), it is unlikely that you will be compensating for these additional calories in other parts of your diet, therefore leading to an overall increased caloric intake, which can cause weight gain and increased blood lipids. This is because these foods lack nutrient density and caloric density is not associated with satiety.

However, in the backdrop of a nutrient dense diet from mostly whole-foods, it is less likely that you will overeat on processed foods. Also, when people consume sugars in fruit, since whole fruit contains fiber and other nutrients, it’s difficult to eat a lot of fruit without simultaneously reducing the intake of other foods, therefore decreasing overall caloric intake.

The proposed mechanism of this may be due to the fact that sugar filled, processed foods are high in calories but low in nutrients, which means that we are less likely to feel satiated from these foods, even if we are consuming a lot of calories. Whereas if we are consuming many of our calories from nutrient dense foods, we are more likely to feel full and therefore decrease our overall caloric intake, even if we are eating some amounts of refined sugar. This supports the notion that in the backdrop of a nutrient dense diet, a small amount of sugar from processed foods is unlikely to cause issues, because it doesn’t magically cause you to want to eat more. Nutrient density is associated with satiety.

Sugar and a fatty liver?

When we ingest sugar such as sucrose, the body breaks sucrose into its free parts, which are made up of glucose and fructose. The body only uses glucose in energy production; therefore the fructose must first go to the liver so it can be converted into glucose. It was then proposed that eating large amounts of fructose taxes the liver because it spends so much energy turning fructose into other molecules that it may not have much energy left for all its other functions. A consequence of this energy depletion is the production of uric acid, which research has linked to gout, kidney stones, high blood pressure and insulin resistance (feature of type 2 diabetes).

Furthermore, because the liver plays an important role in fat metabolism, if it is overworked in converting fructose to glucose, then fat metabolism is put on the back burner and fats can’t be transported out of the liver, leading to a fat accumulation in the liver (fatty liver disease). A fatty liver can also be caused by excess alcohol consumption and is implicated in heart disease and diabetes. It was also thought that fructose is the most efficient substrate for de novo lipogenesis (DNL), which is the process by which the liver converts carbohydrates to fat.

High fructose consumption was shown to cause a fatty liver in mice, however, the issue with these studies is that mice have a very different carbohydrate metabolism to humans. When mice are on a high fructose diet that doesn’t provide excess calories, it’s common to see 50 percent of the fructose turned into fat, even when they’re not overeating.

However, in humans, 50 percent ends up as glucose, 25 percent goes to lactate and greater than 15 percent goes to glycogen. The remainder is converted to energy and 2-3% is converted to fat via de novo lipogenesis.

The mice in these studies were also being fed isolated fructose in amounts that humans don’t even come close to consuming on a daily basis, even if a person has a diet high in processed food. This is why fructose in these mice were treated as a “toxin” by their bodies. Too much of anything can be a toxin, as the dose makes the poison.

Lastly, human studies have not found any positive associations between fructose consumption and a fatty liver, levels of triglycerides, cholesterol or uric acid, nor any significant link to waist circumference or body mass index (BMI).

Is sugar addictive?

Sugar is contained in highly palatable foods, but it is not addictive.

The human brain is hard-wired to be motivated by certain key goals that supported the survival and reproduction of our ancestors. One of these key goals is of course food intake.

When our brains accomplish a key goal that is hard wired in us because it is essential to our survival (e.g. food intake), a powerful brain chemical called dopamine is released. Dopamine is a “reward” chemical in the brain and after its release, it causes you to become more likely to execute specific behaviours that are essential to your survival, the next time you find yourself in a situation with sensory cues associated with carrying out that specific survival behaviour. These cues include sounds, smell, taste and location. This is a reason as to why you may crave certain foods just at the smell of them or if you are in a location where you usually consume a particular type of food.

Dopamine causes you to become more likely to execute specific behaviours that cause its release, when environmental cues are provided. In this case, it could be the sight and smell of certain foods.

The larger the surge of dopamine, the more motivated you will be the next time you encounter those cues. This is well illustrated by highly addictive drugs like crack cocaine and methamphetamine, which cause an immense release of dopamine that motivates drug-seeking behaviours. Addiction, at its core, is a very strong craving. The dopamine release in response to sugar is not even close to the magnitude of dopamine release in response to drugs, which is why it is wrong to proclaim that sugar is as addictive as drugs. Drug withdrawal is nothing like processed food/sugar withdrawal.

When we consume food, sensors in the mouth and small intestine detect the glucose, fructose, fatty acids, and amino acids in starch, sugar, fat, and protein and send a signal to the brain that releases dopamine. And the more concentrated those nutrients are in a food source, the greater the surge in dopamine.

From an evolutionary perspective, the release of dopamine in response to high calorie, highly palatable, sweet and fatty foods makes sense. As mentioned above, when we were hunter gatherers, food was scarce and when we came across calorie dense foods like sugary fruits and honey, the dopamine surge was crucial to our survival as it made us splurge on these foods because we didn’t know where our next meal was going to come from. Now in the modern world, where high calorie food is so accessible, this evolutionary response leads to weight gain.

Highly processed, high calorie foods such as foods like chips, fries, bacon, cookies, cake, ice cream, and chocolate deliver exactly what our brains are instinctively looking for, concentrated starch, sugar, fat, salt, and protein, which is why we crave these foods when we see them, hear them, smell them and find ourselves in locations/situations where we are used to consuming them. This is not a coincidence that these foods are manufactured in this way. Food companies hire scientists to manufacture foods that stimulate reward centres in our brains.

Interestingly, chocolate is the most frequently craved food among women, and it’s also a common craving for men. From the brain’s perspective, this isn’t hard to understand. Chocolate is not only a highly concentrated source of fat and sugar, it also contains a chemical called theobromine. Like its cousin caffeine, theobromine is a mild stimulant that acts on the same brain pathway as dopamine.

As you can see, ultimately, our brain and its reward pathways are what drive weight gain. Everyone talks about insulin, leptin and other hormones, however the malfunctioning of these hormones are usually a downstream effect of consuming too many processed foods, which is driven by our brain.

Sugar and the immune system?

Refined sugar in processed food has also been implicated in reduced immune system efficiency. The studies that have shown this are done with immune cells in a petri dish and they demonstrated a reduced capacity to kill pathogens (e.g. viruses, bacteria) following sugar exposure (from sucrose, glucose and fructose) however, cells in a petri dish work very differently to cells in the body, therefore these studies are unreliable.

Sugar and cancer?

It is true that cancer cells use glucose in the blood to replicate. However, for as long as a person lives, they will have glucose in their bloodstream to supply the brain, nervous system and other organs. Therefore, it is unavoidable to remove glucose from your blood completely, however the goal in cancer treatment would be to minimize huge amounts of glucose in your blood from eating excessive amounts of carbohydrates, beyond your energy needs.

Natural sweeteners:

 Due to the fear mongering around processed and refined sugar, natural sweeteners like honey, stevia, maple syrup and coconut sugar have grown in popularity. The word “natural” has started to become synonymous with “harmless” or “healthy,” however just because something is natural, doesn’t mean it is harmless or healthy. Take snake venom for example, extremely natural yet extremely dangerous.

Natural sweeteners, similar to refined sugar, contain sucrose, glucose and fructose in varying amounts. However, natural sweeteners, due the fact they are extracted from plants) often contain other compounds that may be good for our health.

For example, honey contains phytochemicals that have been shown in animal studies to confer potential health benefits. 3-5 teaspoons of honey has been shown to increase vitamin C and glutathione levels. It also may have anti-cancer, anti-inflammatory (in the gut), antiviral and antibacterial properties. Lastly, in obese individuals it has been shown to decrease LDL cholesterol, triglycerides, inflammatory markers, homocystiene and blood glucose. Another example is molasses, which seems to contain antioxidant phytonutrients, as well as relatively high amounts of potassium, calcium, B6, iron and magnesium.

Lastly, although the stevia plant does not contain any calories, it is commonly used as a natural sweetener, which can be traced back to glycoside (bound to sugar) compounds of steviol that contain the active rebaudioside A and steviosides. Unlike artificial sweeteners, stevia confers pharmacological actions and may have anti-cancer, blood pressure lowering, satiety, anti-oxidant (in the liver, kidneys, pancreas, brain), anti-inflammatory, anti-bacterial and glucose lowering properties. It must be noted that high doses may cause infertility and potentially cancer based on animal studies, therefore it is probably best not to over consume stevia, with the upper limit sitting at 8mg/kg.

Natural sweeteners still contain sugar, but may confer other health benefits.

When can sugar be a real issue?

Refined sugar from processed foods becomes an issue when it starts to displace other more nutrient dense foods in the diet that are beneficial to health and it becomes the foundation of a person’s diet. We need certain nutrients for our body to function and they do not come from processed foods. Therefore, if processed foods become a large part of a person’s diet, it can lead to increased caloric intake and poor health due to nutrient deficiencies.

Sugar can also be an issue when people have diabetes or insulin resistance, because these people’s bodies cannot effectively shuttle the sugar they ingest into their cells, therefore it lingers in the blood causing all sorts of issues that can lead to kidney damage, nerve damage, eye damage, increased infection risk, high blood pressure and cardiovascular disease risk.

Fructose may also be an issue in those who have gut issues like IBS (irritable bowel syndrome). People with digestive issues sometimes find it difficult to absorb fructose within fruits and vegetables that contain high amounts, relative glucose. This leads to fructose being excessively fermented in the gut causing uncomfortable gut symptoms.

Wrap up

In conclusion, excess sugar can be harmful to health however there is actually no evidence that small amounts of refined sugar in the context of a nutrient-dense, whole food diet (and active lifestyle) is harmful.

When people decide to “avoid” sugar, such as in Feb fast, or as part of a detox, they generally feel better because they end up making more conscious food decisions, eating less nutrient void foods and eating more nutrient dense foods. It’s not magic, it is the basic principles of eating well, which is trying to eat more whole-foods and less processed and refined foods.

Avoiding all refined sugar from the diet is rarely necessary as refined sugar is not harmful to health in moderate amounts, and most people would be better off avoiding the stress that comes from being unnecessarily fearful of any food that has even a trace amount of refined sugar in it. The stress that comes along with excessive food restrictions and the guilt when you stray from your food restrictive diet, can be much more harmful than having a bit of refined sugar here and there.

As long as the foundation of your diet is made up of mostly unprocessed, nutrient dense, whole-foods, then there is no problem with the occasional sugar treat, especially on special occasions. Sometimes the context in which we consume food is more important than the actual food we are consuming. Consuming processed food with good company in a joyful environment once in a while, is very different to consuming it alone at home after a stressful day at work, when you couldn’t be bothered cooking yourself a wholesome meal.