Sugar, the Sweet and the Sour

In recent conversations I have had it seems like an area that continues to catch people out in their efforts to switch over to a better diet is the area of sugars and other foods that help to add sweetness. The most common query tends to be, ‘What ‘healthy’ options can I use to sweeten my food?’ Firstly let me point out that this is not going to be a blog about artificial sweeteners such as aspartame, sucralose and saccharin. To put it bluntly, they are not a healthy alternative to sugar. They have their own set of concerns and I certainly do not advise their intake, but that is an entirely different blog for another day. This blog is going to focus on sugar, syrups and other foods used to add a sweet taste to our diet and to investigate whether there is a healthy sugar.

I would like to get straight to the heart of the issue here. Just last week I had someone point out to me that fruit contained ‘healthy’ sugar. This illustrates one of the great points of confusion around the human diet. If something is natural and especially if it is plant based there is an underlying assumption that it is therefore healthy and good for us. The majority of the world’s sugar supply is drawn from 2 naturally occurring plants, sugar cane and sugar beets. Agreed the sugars are drawn out of the plants through industrial processing, but that does not change the compounds that existed in these plants already. In fact, there are many plants that actually have naturally higher levels of sugar and are much sweeter to taste than cane and beets. Most popular fruits are a classic example of this. In fact many popular fruits today have been selectively bred to increase their sweetness (sweeter foods sell better) and as a result contain more sucrose than the same fruits did just 30 years ago. Besides why would the sugar in fruit be any healthier than the sugar in cane or beets? Is it a different compound? Simply put, no! Yes, whole fruit will have some vitamins and minerals contained within, but does this somehow negate the potentially damaging effects of the sugar component? Certainly, this should at least be questioned in the naturally higher sugar fruits like mangoes, dates, raisins, apples, bananas, pears, oranges and grapes. It is no coincidence, by the way, that these same fruits are the best-selling varieties in the country either! More sugar, more sales. Simple formula, but it works.


Typical white sugar is more correctly called ‘sucrose’ which is a combination of the basic units glucose and fructose in an approximately 50:50 ratio. Regardless of the source of the sugar, white table sugar, golden syrup, honey, fruit concentrate or whole fruit, the chemistry of the sugar is very much the same; it is still a blend of glucose and fructose in varying amounts. Glucose and fructose are composed of the same molecular elements as well. They both have 6 carbons, 12 hydrogen and 6 oxygen atoms. However, they do look a little different. Glucose is a 6 carbon hexagonal ring and fructose a 5 carbon pentagonal ring. These different shapes mean that the body has to metabolize them differently. We will get into that in a moment.

Over the years these 2 molecules have developed different reputations in relation to health. Glucose has taken the brunt of abuse for disrupting our blood glucose levels, driving up insulin and playing a primary role in the causation of obesity and diabetes. Fructose on the other hand seems in large part to have been branded as healthy because it is known as the fruit sugar. These half-truths have created several pervasive myths around the impact of certain foods on our health.

Glucose is the compound that serves as the basis of comparison for every other food listed on the glycaemic index. Glucose is traditionally given a value of 100 and then other foods are tested and have their rate of absorption compared to glucose and given a respective value. Years ago when glycaemic index was becoming mainstream it was pointed out that fructose had a very low glycaemic index and therefore must be helpful in maintaining lower blood glucose levels. It was promoted for some time as being diabetic ‘friendly’ as well. That tag has quickly faded away as research has shown that fructose actually makes the insulin resistance that underlies the condition even worse!


When the intestine absorbs glucose it is able to draw it directly through the tissues into the blood stream to be shipped around for use in body cells, especially the brain and nervous system. The overwhelming majority of glucose that may reach the liver is converted to the perfectly safe storage form of glycogen. Fructose is not delivered direct into the blood stream. It is passed up a direct blood supply between the intestine and the liver call the hepatic portal vein. Fructose is then managed by the liver and often goes through different metabolic processes prior to being released into the blood again. It is this transport via the liver that gives fructose its low glycaemic index because it takes longer to impact on the blood.

Whilst glucose has a very effective system for ensuring it enters the cells quickly without too many negative effects (it is controlled by insulin), fructose is a more complicated beast. There are several key concerns with the way fructose is managed within the body.

·       Significant amounts of fructose delivered to the liver cannot be metabolized by the cells and get converted to triglycerides (fats)

·       Fructose alters liver enzyme function increasing liver insulin resistance (diabetic tendencies) leading to higher blood insulin and greater visceral fat storage

·       Fructose undergoes the Maillard (browning) reaction 7 times faster than glucose suggesting it may increase cellular glycation, aging processes and cancer formation

·       Fructose has, in many ways, similar effects on the liver as alcohol

Dr. Robert Lustig refers to fructose as the ‘…same poison as alcohol but without the buzz!’ Unlike alcohol, fructose is not metabolized in the brain and as such does not have the same deleterious effects on behaviour. However, fructose causes the liver to take the brunt of the damage under the radar potentially leading to a condition called non-alcoholic fatty liver disease. This is basically the same set of problems that destroys the liver of an alcoholic, but as the name suggests it is not caused by alcohol. It is caused by fructose excess!

So what about these so called ‘healthy’ sweeteners used by the side of the food industry that cares? Well you decide. Agave syrup (or ‘nectar’ as it is often called to make it sound better), even the organic variety, is normally between 70-95% fructose. Bearing in mind that the health damaging reputation of industrial high fructose corn syrup (the sweetener of choice for the soft drinks industry) has been built on a 55% fructose blend, it doesn’t really bode too well for Agave. All the negative effects listed above will clearly be enhanced with richer doses of fructose being sent to the liver down the portal vein. Another option often used in health food bars and in supposedly better tinned fruit is ‘fruit concentrate’ or fruit juice. This is exactly what the name suggests, the juice of a given fruit with the water boiled off so as to concentrate the sugars within. This will damage most of the vitamin content leaving primarily a concentrated source of sugar behind. In fact it is not uncommon to find the most used juice concentrates are from apples, grapes and pears as these have some of the highest naturally occurring fructose content and taste even sweeter as fructose has 70% more sweetness than typical sucrose.


Simple squeezed fruit juice may not be concentrated, but it still allows for an increased intake of sugar compared to eating a whole piece of fruit. For example, a single apple has a glycaemic index of 40 and a glycaemic load of 6, whereas a glass of pure apple juice has a GI of 44 and a GL of 13 – more than double the volume of sugar within a comparative ‘portion’ of fruit. A similar story is found with most fruit juices. Therefore, on this basis it becomes difficult to see how pure fruit juice can be as beneficial to health as eating whole fruit. Twice the sugar in one portion will only increase the negative impact on the body and if it is apple or grape juice you will get a hard liver-hitting dose of fructose to boot!

So what does it all boil down to? Sugar from any source is still sugar. Eaten in excess amounts it can still upset blood chemistry, poison the liver and lead to ill health. However, science is steadily showing that processing foods to increase the fructose content has and is leading us down the road of dysfunction and disease. Fruit juice doubles our sugar intake compared to fruit alone. Even modern breeding of sweeter fruits with higher glucose and fructose contents may yet prove to be another means of ingesting larger amounts of health disrupting sugar! So can whole fruit still be part of a ‘good’ diet? Well certainly it can, but perhaps it would be best eaten in moderation and only when in season. 1 or 2 whole fruit portions a day at most. It would be best that we place greater focus on a broad and plentiful supply of seasonal vegetables to draw in our needed vitamins, minerals and fibre. It may not be quite as convenient as fruit, but it will support greater health in the long term. 

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