March 5, 2014

expert reaction to how addictive sugar is, following news reports of comments by Dame Sally Davies

Chief medical officer for England Dame Sally Davies told a committee of MPs she believed research will find sugar is addictive.

Dr Dominic M Dwyer, School of Psychology, Cardiff University, said:

“Addiction is a broad term, but its key component is that of “dependence” – which can be indicated by excessive and unwanted consumption, interference with other valued activities, and a persistent desire for the object of dependence.  For drug addiction, these things are also associated with increased tolerance (e.g.  a decrease in a drug’s effects) and withdrawal (e.g. adverse effects when the drug is not taken, and the taking of the drug to alleviate withdrawal symptoms).  The overlap between the brain systems related to natural rewards like sugar and other foods and those affected by drugs of abuse are well documented:  indeed, addiction has been likened to the hijacking of these natural reward systems by drugs of abuse.  There is also good evidence from animal models that excessive consumption of high-sugar (and high-fat) diets can produce abnormal function in natural brain reward systems similar to those produced by exposure to drugs of abuse.  However, there is also evidence to suggest that the processing of sugar and drugs of abuse can be separated within these brain reward systems.  Human-based research on the effects of obesity and overconsumption of sugar rich foods on these reward systems and the overlap with drug abuse is in its infancy.  Direct application of clinical criterion for drug dependence does suggest that some people’s consumption of food would meet these criterion (approximately 5% of the population) but that key differences are also present (in particular with respect to tolerance and withdrawal).  Moreover, even though such food “addiction” is over-represented in obese individuals, most people meeting clinical standards of obesity do not show addiction-like responses to foods (at least 90% of obese individuals do not show this “addiction-like” profile), and addiction-like behaviours might be more closely tied to binge eating disorders.  That said, other research has shown that sugars are powerful reinforcers in supporting food-preference learning.  These acquired preferences can drive the choice for, and overconsumption of, foods that are inconsistent with a balanced and healthy diet.  Thus, even outside their addiction-like potential, sugars can have a significant effect on obesogenic eating patterns.

“In summary, the idea of sugar (and other food) addiction is valid in principle, but there are important differences between addiction-like responses to foods and those to drugs of abuse.  Researchers are using both humans and animal models to investigate the similarities and differences between foods and drugs of abuse.  Although certainly present in some people, addiction-like behaviours towards sugar and other foods are present only in a minority of obese individuals.  However, it should be remembered that sugar can drive the overconsumption of foods alongside its addiction-like potential.”

Prof David Nutt, Chair of the Independent Scientific Committee on Drugs (ISCD) and Head of the Department of Neuropsychopharmacology and Molecular Imaging at Imperial College London, said:

“There is not currently scientific evidence that sugar is addictive, though it is well known that sugar has psychological effects, including producing pleasure, and these are almost certainly mediated via brain reward systems. Refined sugar gets into the brain faster than sugar from starch and we know from drugs that the faster substances get into the brain, the bigger the hit.

“The other big issue is fructose (corn sugar) which is less good at suppressing appetite than glucose. This means that more fructose gets eaten before satiety sets in.”

Prof Suzanne Dickson, Professor of Physiology, The Sahlgrenska Academy at the University of Gothenburg, said:

“I coordinate the EC project NeuroFAST, which is looking, amongst other things, at the question of food addiction. Indeed, we have formed a consensus opinion on the matter (see http://www.neurofast.eu/consensus/). The bottom line is that we find very little evidence that any food, ingredient, combination or additive (with the exception of caffeine) has addictive properties.  In other words, unlike addictive drugs, there is very little evidence that any food acts on our brain to make us addicted to it. 

“Moving away from the food to the person – it seems unquestionable that some individuals display behaviours towards food that are consistent with addiction, especially those with binge eating disorder.  If food itself is not the culprit, how can we explain this addictive-like behaviour towards it? To answer this question we need to explore additional avenues – are certain people genetically susceptible? Are there environmental factors such as our stressful lifestyle, for which over-eating palatable foods rich in sugar and/or fat help us to cope with stress?  Maybe early life experience even in the womb programme our susceptibility to over-eating disorders.”

Prof Barry Everitt, Professor of Behavioural Neuroscience, University of Cambridge, said:

“The issue of whether or not sugar is addictive is complex as it is obvious that sugar (and fats) are reinforcing and that they do indeed result in activation of the dopamine system in the reward system in the brain. However, drugs like cocaine activate dopamine release far more than food reinforcers do. It is also the case that some, but not all, of the physiological adaptations to repeated addictive drug exposure are similar to those following repeated sugar or fat exposure.  But the suggestion that food is addictive sends out a misleading and unhelpful message, even though we could all do with cutting down on or eliminating sugar intake.

“The important issue is that some individuals lose control over their food, especially sugar (and junk or fat-rich) food. This small sub-group might, then be viewed as ‘addicted’, but it may also be discovered that the loss of control in this sub-group might have a predisposing metabolic/neuroendocrine condition.

“The message that ‘we’d better watch out for this sugar stuff is misleading’, as far as I am concerned, because it suggests if you eat it you risk becoming addicted and the evidence does not support that.”