Sweet enough?

When is sweet not sweet?

Poor old Mars PLC, their range of Dolmio sources have been the focus of attention since they warned their customers that they were for occasional consumption only. On their website all the ingredients are clearly presented and they are not dissimilar to rival products in this large sector of the food industry.

They were criticised for the fat, salt and sugar content of their range but to be honest these figures would not be any different from a home ‘prepared from scratch’ version. For example the average sugar content was 4.2g per 100g of sauce. That’s only a teaspoon in a very large dollop of sauce (fresh tomatoes would match that)... there was 5g of fat and 0.8g of salt or  other words less than a teaspoon of olive oil and a pinch of salt. So why the warning?  

There is however something common to nearly all mass produced,  thickened, sweetish liquid products from yoghurt drinks to soups and sauces.

The story goes way back to the late 1950’s when the food industry in the US was converting its excess cereals to new products which were proving very popular with the prepared food industry. These were the product of breaking down starch into smaller molecules by a process called hydrolysis. These products are called hydrolysates and in descending order of complexity and thickening power are: partially hydrolysed starch/modified starch; glucose syrups; oligosaccharides/maltodextrins. All are made from glucose molecules and the products get sweeter as they get simpler and more like glucose. They are used extensively to thicken and sweeten food products.

Clearly these products are sugar-like and the challenge was and is to say how glucose-like they are if only for the purposes of labelling but more importantly for concerns on the effects of  excess consumption of sugar.

Work carried out in the early 1960’s1 showed clearly that the real-life absorption of glucose in the intestine derived from these products was very rapid indeed, often exceeding that of pure glucose and greater than that of sugar (sucrose). Moreover the products which were first broken down to maltose (glucose-glucose) was  itself used as a fuel by the intestines’ cellsl to power the process of absorption. This was a very important finding and one which is well understood by the food industry and overlooked by its lablling.

GI ( glycemic index) v the modern food label.

One classification of the rate of uptake of glucose from foods is the glycemic index(GI). This index measures how much and how quickly glucose enters the bloodstream after eating a particular food. The reference point is glucose itself and other foods are rated against this. It is therefore not surprising to find that maltodextrins which are small molecules having 3 to 20 glucose molecules in them have high GI indices and the sugars in a complex food like sweet dates have a relatively low GI. Unfortunately the GI rating is full of counterintuitive anomalies; fructose, a simple sugar, has a low GI and potatoes (quite clearly ‘complex’) can have very high GI’s. GI is actually useful for measuring glucose availability but is steadily dropping from labelling for the confusing reasons above.  Instead we have standardised and now familiar analyses which read  ‘carbohydrates of which sugars’.

Here ‘sugars’ are glucose, maltose, lactose and sucrose. What we call ‘sugar’ is sucrose alone. Carbohydrates would include partially hydrolysed starch, corn syrups and maltodextrins as well as the whole starches from flours.

The point I am making is that in terms of the sugar-equivalent effects the label under estimates the bio-available  ‘sugariness’. This means a thick soup or drinking yogurt may have a lot more sugar-equivalents in it via maltodextrins and the like than is obvious from looking at the ‘sugars’ content.

To go full circle to the first paragraph you don’t have to be sweet to be sugary! This may be why manufacturers are getting twitchy about the healthiness of their soups and sauces. It also explains why ‘home made’ may have the same labeled amounts of sugars as the manufactured stuff but be nowhere near as potentially taxing on your insulin response to sugar uptake.

1. THE ABSORPTION OF SUCROSE, MALTOSE AND HIGHER OLIGOSACCHARIDES FROM THE ISOLATED RAT SMALL INTESTINE BY E. B. CHAIN, K. R. L. MANSFORD AND F. POCCHIARI.

J. Physiol. (1960), 154, pp. 39-51 Printed in Great Britain

Why Sugar is more fattening than Fat

The problem with sugar.

The current consumption of sugar in such huge quantities is truly a dietary phenomenon. ‘Sugar’ is most often taken dissolved in a drink. In this form sugars such as sucrose ( a combination of glucose and fructose), lactose ( a combination of glucose and galactose) or simple glucose and fructose are gulped down in unprecedented amounts as fruit juices, ‘smoothies’, energy drinks or skinny-lattes. And they are drunk in volumes that would have astonished those accustomed to a tea cup.

Few sedentary workers care or know that a regular* ‘skinny latte’ contains as much sugar as a macho ‘five teaspoons luv’ mug of ‘builder's’ tea’ or that healthy pot of fruit yogurt for lunch can match that amount of sugar with ease...just don’t wash it all down with a smoothie (34g = 7 teaspoons of sugar in 250ml). No question about it, sugar consumption around the world is a phenomenon worthy of our attention. Sugar-sweet has gone from being a luxury borne of honey (glucose and fructose) to mega-tonne cheap and cheerful cereal-syrup ( also glucose and fructose).

*a ‘cup of tea’ is approx 150ml a regular latte is 300ml

Other modern diet-related phenomena include: global epidemics of Type 2 diabetes and obesity boasting staggering statistics such as nearly 1 in 10 of the world being diabetic and over 50% overweight. By any standards that’s impressive.

Is there a link between sugar, diabetes and obesity? Yes of course there is, obviously. Do we have a cause and effect relationship or a just a correlation? The biochemistry of sugar metabolism is well known, it’s standard undergraduate fare. So below is just that, in an easy to swallow soluble form.

The problem with being well fed

Let’s start with a few basic rules. Firstly assume we are animals in what is known as ‘the well fed state’. That is to say that at most times of the day we have had sufficient food to make sure that our ‘ready to access’ stores of food are full or nearly so. By this we actually mean our stores of glycogen in the muscles and liver are full. Glycogen in turn is a polymer (multiple) of glucose molecules and is readily converted to back to simple glucose when we need it in a hurry when exercising for example.  We can store upto 2kg of this stuff even so it’s fair to say a typical modern worker qualifies as well fed with full or nearly full stores.

Secondly let’s get our sugars straight. Glucose is our ‘main man’ its alter egos (isomers) fructose and galactose (respectively from fruit and milk) are, once digested and absorbed, very rapidly converted into glucose. So when we have ‘various sugars’ on a label these are sucrose, lactose, maltodextrin (oligosaccharides), glucose, galactose and fructose but thanks to our speedy biochemistry for all practical purposes we are talking glucose. In this respect food labelling is not misleading or being too vague when it says ‘carbohydrates of which sugars’. ‘Sugars’ is sugar is pretty much actually glucose.

Thirdly, glucose levels in the blood are tightly regulated by the hormone Insulin. Glucose’s Goldilocks zone is 4-7 mmol/litre of blood, or in simple terms 1 teaspoon of sugar for all the blood in the body…. too much and glucose is rushed out of the blood urged on by a surge of Insulin-mediated action into a safe haven. This haven are the aforementioned glycogen stores … unless of course they are full because we are well fed and currently inactive. So here our story begins.

The sugar stores are full:

Sugars shunted out of the bloodstream enter cells, be they liver cells, muscle cells or adipose (fat) cells. Here they are broken down by an ancient biochemical process called Glycolysis. It forms the basis of anaerobic respiration, otherwise called fermentation. Glycolysis ( literally the splitting of sugars)is fast, requires no oxygen and it makes enough energy to keep a simple cell alive and even reproducing.

However by an accident of history the waste product of glycolysis just happened to be the food of choice for a bacterium-like creature which came to live within all of our cells and that was what is now the mitochondrion, complete with its own biochemistry and the ability to turn the end products of glycolysis into carbon dioxide and water with the use of oxygen.  

The modern cell thus has the ability to metabolise sugars completely into carbon dioxide and water so long as has a good supply of oxygen. This process we call oxidative respiration and it supplies enough energy for cells not only to live and divide but to specialise into nerves, brains and muscles.  

The key point here is to appreciate that energy production in the modern cell required the fusion of two biochemistries, that of the host cell ( glycolysis) and that of its mitochondrial guests. Together they made enough energy to make us.

We have enough energy already:

Mitochondria are great accountants. When a cell has enough energy for its needs they back off production and vice versa. Mitochondria are not immortal they age inside the cell, their capacity to produce more energy on demand drops with age and they are inclined to tick over producing just the required energy to keep a cell going and little more, even when demanded. It’s like being sedentary all the time when you are older. They won't be rushed or forced into action by  the supply side and only by demand on only then if they are up to it.

Imagine then that you have stopped growing and started to age ( c 25 yrs old), have a sedentary lifestyle ( ie you are inactive for most of the day..say typing at a computer as I am now), are well fed ( ie not in a starved or semi-starved state) and you drink that skinny-latte or that smoothie right now. The sugar races into your blood stream, quick as a flash insulin responds to keep the glucose under control, the glycogen stores are full, quick...push the sugar into the cells, whoosh glycolysis swings into action...uh oh the mitochondria are on a go slow. There is enough energy in the cell already, no real demand for more, what now?

The ‘what now’ is really simple. The end products of glycolysis cannot be allowed to accumulate in a cells they will poison it. Fortunately this problem has a work around. The products can be made safe by joining them together to form a large molecule and stored in the form we know as fat. Storage depots include fatty muscles, fatty livers and of course the specialized fat cells themselves.

Oops. This means that pick your food right ( dissolved sugar is best), pick a good time of day ( a few more hours at the desk or in front of the TV beckons) make sure you have had breakfast lunch or supper so that you are not semi-starved and almost every sugar molecule you take in should convert straight to fat having of course just given your tired old insulin response system a fright and a good work out.

That’s why you get fat and have diabetes.

PS Don’t bother to go to the gym later on, you’ve missed your chance, that fat molecule is snugly tucked away.