How much sugar in a can of coke? The addictive power of sugar; would you give your child cocaine?

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So a can of coke contains about 9 teaspoons of sugar.  And we give it to our children as well as drink it ourselves. And there are about 6 teaspoons of sugar in a pot of fruit yoghurt. There are the 3 obvious problems: so much sugar will rot the teeth; cause a blood sugar surge which leads to mood swings, lack of concentration and irritability; and sugar had absolutely NO nutritional value; it contains no vitamins, no minerals, no protein, no fat.  It only contains a source of instant energy, which if not used up immediately in activity, will get turned into body fat.  Unfortunately, sugar has an additional problem and that is that it is highly addictive.  We want more and more of it.  The video is talking about the sugar in coke, but sugar is also in cakes, sweets, biscuits, bread, sauces, crisps – just look on the packets of food and see what it is added to.

There are quite a few studies done on sugar addiction.  I shall draw on 2, one by Professor Bart Hoebel of Princeton University who has studied the effects of sugar 1 for some years and the other by Magalie Lenoir2 of the University of Bordeaux.  Both these studies found that when sugar or saccharine came in liquid form – ie like a sugary drink, rats, the animals in the study, became addicted to it.  The Hoebel study focused on bingeing, the Lenoir on seeing which is most addictive, sweet water or cocaine. The Lenoir study used saccharine as a sweetener in the study, but when saccharine was replaced by sugar, the results were the same. Both studies used water sweetened to the same degree as fizzy drinks such as Coca Cola.  Since cocaine is the most addictive drug currently known, Lenoir’s finding that rats should prefer sugar to cocaine has significant implications.  The Lenoir study noted that in most mammals, including  primates and rodents, the taste for sweet things

evolved in ancestral environments poor in sugars and are thus not adapted to high concentrations of sweet tastants.  We speculate that the supranormal stimulation of the receptors by highly-sweetened diets generates a supranormal rewards, with the potential to override both homeostatic and self-control mechanisms and thus lead to addiction.

What both studies found was that drinking sugar water altered the brain.  When sugar water is drunk there is a rise in dopamine, the neurotransmitter of anticipation of good things to come.  As sugar water is continued to be drunk, some of the dopamine receptors die back because of the over stimulation and there is an increase in the opioid receptors.  The best known opioid drug is morphine.  This is what happens in the brains of people addicted to cocaine, morphine and nicotine – and this has also been found in the brains of obese people.

To focus on the Hoebel study, he found that sometimes these changes increase the inclination to take other substances of abuse, for example, alchohol.  Hoebel allowed his rats to binge on rat chow and sugar water.  When the rats were denied sugar water for a prolonged period, when it was reintroduced, they consumed more sugar than they ever had before, suggesting craving and relapse behaviour.  “In this case, abstinence makes the heart grow fonder” he said.  When sugar was withheld the rats went into withdrawal as their dopamine levels dropped.  Their teeth chattered and they stayed in the tunnels in their maze rather than venture into the open part – normally rats like to explore their surroundings.  However, they were too anxious to go out exploring.

The Lenoir study focused on a comparison of the addictive qualities of sugar v cocaine.  And essentially, the study found that sweet water was far more addictive than cocaine.  As said earlier, the study used saccharine water – but it was repeated with sucrose, and the results were the same.  The experiments were conducted on rats who had never experienced sugar water or cocaine and on rats who were already addicted to cocaine.  In every case, given a choice, the rats preferred the sweet water, even those addicted to cocaine.  They had access to the sugar or the cocaine by pressing the appropriate lever. In some of the experiments, only one lever worked and the other gave nothing. A couple of interesting points came out.  When rats new to sugar and cocaine were given access to cocaine only, on day 9 they preferred the cocaine lever to the one that gave nothing and by day 11 this had become statistically viable.  When given access to the sugar only, this became statistically viable by day 7.  The group that had access to either cocaine or sugar started choosing the sugar lever on day one and this had become statistically viable by day 2.  This clearly demonstrated the sugar water preference in its simplest form.

The researchers wondered why this should be so, so they found that cocaine takes an average of 6.2 seconds to hit the brain, peaking in effect in 4 – 20 seconds.  Sugar gives the full hit in under 2 seconds.  So to take this effect out, they delayed the delivery of the sugar water but not the cocaine.  Some rats did shift to the cocaine lever as a result, but overall the sugar lever was still preferred.  Bearing in mind what Sapolsky said about dopamine in the linked blog, when the researchers decided to make it harder for the rats to get the sugar water by making them have to press the lever 2 – 8 times, whilst they only had to press the cocaine lever once, this actually increased their preference for the sugar water.

Finally, the study did make note of a previous study which found that similar type experiments on monkeys using cocaine and saccharin pills did not show this preference for sweet things over cocaine – with the conclusion being that sugary drinks are particularly addictive.

Another study lead by Professor Hoebel3  found fat to be addictive too, but it does not have the same withdrawal symptoms as sugar.  Rats bingeing on sugar cut back on their rat chow, so did not gain weight.  However, rats allowed sugar and fat plus rat chow did gain weight, giving credence to the fact that doughnuts are particularly fattening because of the combination of fat and sugar.  So going to the gym then giving ourselves a treat of a cup of coffee and a biscuit will completely undo all weight loss efforts.  And, to return to the first paragraph, if children drink fizzy pop, since sugar is a source of instant energy, they will not have a proper appetite for proper food.  And, although fruit juices do have some vitamins, they are also very sweet, will be appetite suppressants and have addictive sweetness.  As Zoe Harcombe points out in her book Why do you overeat?, drinking an orange juice that boasts to  be made with the juice of 8 oranges is like eating 8 oranges one after the other – but without the fibre contained in an orange, so it is a huge sugar hit.  All sweet drinks, whether fruit juices, squashes, sweetened tea or coffee, fizzy drinks made with sugar or artificial sweeteners are more addictive than cocaine.  Since yoghurt is liquid, the same goes here too, unless the yoghurt is plain.  We can argue that the studies were done on rats and not on humans – but for obvious reasons, we can hardly study cocaine vs sugar addiction on humans.  Also if this argument is made, this is like an addict saying the substance makes their life more bearable; it is an excuse for continued addiction.  Yes, everybody does it.  Which makes coming off sugar hard.  But coming off sugar is an excellent step towards a brighter more motivated brain, steadier moods, a happier life – and weight loss.



  1. The linked article refers to a study published in Dec, 2008, and this is the report in the University press.  Prof Hoebel studies rats.  He feeds them rat chow – standard rat nosh – and sugar water, which is about 10% sugar, as the coke is above. []
  2. Lenoir M, Serre F, Gantin L, Ahmed S H.  Intense sweeteners surpasses cocaine reward.  PLoS ONE 2(8): e698 pub Aug 2007 []
  3. Avenon N, Rada P, Hoebel B.  Sugar and fat bingeing have notable differences in addictive-like behaviour.  J Nutr. Mar 2009 Vol 139 no 3 623-628 []

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