Fructose Sugar

Obesity is becoming almost an epidemic in many western countries and it is starting at a younger and younger age. The answer to why is becoming increasingly clear. It is sugar, too much of it and the wrong kind of sugar that we are getting in processed foods and when we dine out especially at fast food restaurants.

The name sugar is used to describe a whole class of compounds, most of them sweet but we usually think of sugar as the granular white table sugar, sucrose, we spoon into coffee and tea make them sweet.  It has been around for a couple of centuries and it comes mostly from cane sugar that’s grown best in the tropics. It’s a disaccharide, that is it is two sugars linked together with a structure as shown on the right.  When we eat it, it’s broken down by an enzyme into two separate simple sugars, glucose and fructose.  You will probably recognize ‘glucose’ as the blood sugar molecule that the body can use to give us quick energy but the fructose is another story.

One of my earlier blogs was about ‘chirality’ and in it I talked about molecules often being left or right handed and the problems the left handed molecules can cause. The reason is that our cells are full of protein molecules that are called enzymes that are vital catalysts  in making our complicated body chemistry work quickly at body temperatures. The way an enzyme works is shown in a simple animation.  It turns out that our body has no enzyme to handle the left handed fructose molecule that is released as sugar is broken down and so it is treated like a foreign body or toxin and is sent directly to the liver. From there, most of it ends up as body fat. Another problem is that since the fructose goes to the liver, it doesn’t increase blood sugar levels and doesn’t signal the brain when you’ve eaten enough so you tend to eat much more than you need.

To make matters worse, food scientists have found a substitute for cane sugar that is even worse for us. Fructose happens to be a lot sweeter than glucose and they have produced a High Fructose Corn Syrup [HFCS] that is generally 55% fructose to 45% glucose and has the advantage of being cheaper and much easier to handle than white granulated sugar.  HFCS is apparently now being put into everything from baby formula to bread and checking the label doesn’t help much because it can be classified as a carbohydrate.  In some drinks the HFCS is as high as 65% and there are no regulations that prevent the use of HFCS’s as high as 90%. 

The best advice is to stay away from processed foods and sugar. So for desert, it sounds like eating nice fresh fruit would be the best solution.  Wrong – in fruits the sweetness comes from fructose! So even though fresh fruit is very nutritious, be aware of the fructose you’re ingesting – click on the link to check out amounts in the different kinds of fruit.

Honey has a lot of good stuff in it but have a look at the amount of fructose in it. Maple Syrup is mostly sucrose so if you have a ‘sweet tooth’, the only answer I can come up with is to use other kinds if sweeteners.  I like to grow the stevia plant because it’s natural. You can now obtain it in dried form at a health food store. It's about 300 times as sweet as sugar so take care. Barley malt extract is another alternative. 

If you want to know all the science and have time - you could listen to Dr. Lustig's video.  Rie 

Chirality revisited

As a break from our harsh Canadian winters we ‘went south’ to the Caribbean islands for many years. I love beach combing and as a result, I have baskets full of sea shells at the cottage that I have picked up and enjoy handling.

When I read that spiral shells were a good example of the invisible chirality [left or right handedness] that many molecules in living systems possess, I lined up some of my spiral shells with their earliest growing tips down and took the picture on the left. When you look at the picture, you can’t help but see that the open ‘mouth’ of the shell is always on the left.

Try it out yourself the next time you have any spiral shells at hand, and you may be lucky enough to find a shell that breaks the rule and opens on the right. They are rare, but exceptions do exist, and therefore the shell's outward chirality must be for another reason, because our body’s chiral molecules are always only one-handed without exception! For snails, the reason for the shell coiling happens to be sex. Snails make coiled shells because their sexual organs are usually twisted, and it is difficult with snails of opposite handedness to mate. Picture on the right is the Nautilus shell.

The fact that our body’s DNA, enzyme and sugar molecules, etc., are chiral was not generally known until a widespread medical tragedy occurred. In the late 1950’s, a drug called ‘thalidomide’was developed by a pharmaceutical company as a sedative and a treatment for morning sickness in early pregnancy. When tested on animals it had few or no side effects, and so was used in many countries, including the UK and Canada starting in 1958. It was not until 1961 that doctors fully realized the drug was the cause of severe birth defects – many children developing flippers instead of arms.  It was withdrawn but too late for kids shown on the left .

When thalidomide was investigated, the results knocked organic chemists for a loop. It was discovered that the molecule was chiral, and when synthesized in the lab, equal amounts of two isomers, one left-handed and the other right-handed, were produced. Because molecules involved in our body chemistry are also chiral, the two isomers reacted differently, with one isomer causing the birth defects. Fortunately, under normal circumstances, if we ingest a molecule with the wrong handedness, our bodies recognize it and - unlike the unfortunate thalidomide case where a fetus was in an early stage of development - it is sent to the liver where most toxins are dealt with.

The development of one-handedness in our body chemistry probably happened just by chance when life first formed on our planet. Should we ever travel to another planet many light years away, it is possible that life started there with its molecules having the opposite handedness, and we could eat as much of their food as we wanted, but we would starve to death! Rie