In Depth

Diabetes awareness month: the science behind sugar addiction

November is a very important month, as we acknowledge both National Diabetes Awareness Month and World Diabetes Day, on November 14th.

National Diabetes Awareness Month was launched back in 1991 as a way of drawing attention to the disease and its impact on so many lives. World Diabetes Day was chosen in commemoration of Dr. Frederick Banting who helped to discover insulin back in 1921.

In support of this, we thought it would interesting to discuss the science behind sugar addiction.

The science behind sugar addiction

It is safe to say that in today’s society sugar is hard to avoid. Often we don’t even realise we are eating it. Have you ever wondered why you crave sugary foods and why they make you feel better initially?

Well research has shown that there is a valid explanation. Sugar induces a drug-like effect, altering the chemistry in our blood, thus imposing neurological changes. These findings have led to the belief that sugar can in fact be addictive.

What is addiction?

The definition of addiction can vary. It has been described in the literature as the compulsion to consume a substance driven by . From this a tolerance to the substance occurs over a period of time. This results in the need for an increased dosage, to achieve the same effect. Consequently, the individual becomes dependent, meaning withdrawal symptoms are presented, should the substance not be consumed.

Some argue that there is a difference between physical addiction and psychological addiction. Physical addiction is thought to involve the characteristic withdrawal symptoms, as witnessed in drug and alcohol addictio, whilst psychological dependence involves uncontrolled, compulsive use. Psychological dependence is thought to include things such as shopping, exercise, gambling and the consumption of highly palatable foods, for example sugar (1).

Alternatively, some believe the term addiction describes both psychological and physical dependence. This includes both the classic cases of addictio, such as drug abuse, and non-drug entities, for example gambling and food (2). Therefore, we must consider sugar addiction as not only a physical problem, but also a cognitive impairment. As explained by Avena et al. to be classed as a sugar addictio, individuals will display signs of bingeing, withdrawal and cravings (2).

Why is sugar addictive?

The brain is composed of many different areas that are involved in the reinforcement of both drug and food intake. Inside these areas there are neurotransmitters (chemical messengers that transmit signals from one cell to another). It is understood that due to overlaps in the brain’s circuitry, drugs and sugar activate the same neural systems (2).

There are several different theories behind why sugar can be an addictive substance. These include the effects it enforces on dopamine, endorphins, a genetic predisposition, serotonin and environmental cues.

Dopamine:

Dopamine is one of the many neurotransmitters (chemical messengers) in the brain and is responsible for the regulation of pleasure. Addictive substances such as cocaine and heroine are understood to activate dopamine receptors, elevating extracellular dopamine levels in the nucleus accumbens.

The nucleus accumbens is an area of the brain involved in reward and reinforcement behaviours. Our brains are designed in such a way that makes us repeat particular actions that provide us with reward or pleasure, regardless of their outcome. Hence why certain substances or activities become addictive.

Interestingly similar effects have been observed following the consumption of sugary foods.  This can explain why highly palatable, sugary foods give us both a sense of pleasure and keep us going back for more even though we know they aren’t good for us.

Endorphins (opioid):

The effects of sugar on the brain’s activity have also been observed in the endorphin system. Endorphins are naturally occurring opioids (a type of neurotransmitter) produced by the body. They act on opioid receptors in the nervous system, stimulating the release of dopamine.

Endorphins are involved in motivational processes related to pain, for example pain sensation and tolerance. They also provide a sense of calmness and impose anti-depressant effects. The release of endorphins exerts similar effects to that of opioid drugs (morphine), including pain relief and a sense of euphoria.

You might have heard some individuals describe exercise as addictive. This is due to the release of endorphins following physical activity. As discussed previously, our brains are designed to make us repeat pleasurable actions, explaining why exercise can become addictive.

Research has also shown that in the case of sugar addictio, following periods of intermittent access to sugar, withdrawal symptoms are displayed when the sugar or food has been removed. As in the case of opiate withdrawal, food deprivation has been found to result in the same two neurochemical manifestations. Firstly, reductions in dopamine in the nucleus accumbens and secondly, increased release of acetylcholine (a neurotransmitter) from the nucleus accumbens (3).

These observations therefore suggest that consuming sugar not only provides a sense of euphoria, but also leads to dependency, as food deprivation can cause withdrawal symptoms similar to that of opiates. As with other addictions, individuals will build a tolerance, requiring higher dosages in order to satisfy their cravings. This is also known as ‘decreased sensitivity of the dopamine reward system’ (4).

Genetic predisposition:

There is also evidence supporting the concept that genetics play an important role in our preference for sugary tasting foods. As with alcoholics and drug addicts, cravings are satisfied through self-medication, activating the dopamine and endorphin reward pathways.

It is understood that one’s ability to experience pleasurable activities, such as watching the tv or enjoying time with friends and family, is influenced greatly by the presence of the ‘dopamine 2 receptor’ (a protein encoded by a specific gene). For this reason, the ‘dopamine 2 receptor’ is also known as the ‘pleasure receptor’. Consequently, those with deficiencies in these receptors can have a greater tendency look to substance abuse for pleasure. For example, drugs, alcohol or sugar.

The ‘dopamine 2 receptor’ contains different forms of genes (alleles), one important one being the ‘A1 allele’, which has been linked to depressionand a number of addictive disorders. Research has shown an inverse relationship between the existence of the ‘A1 allele’ and impaired ‘dopamine 2 receptor’ density.

This implies that individuals with the ‘A1 allele’ have a greater tendency to turn to substance abuse, including sugar, as a result of deficiencies in ‘dopamine 2 receptors’. The presence of this gene and subsequent deficiency in the ‘dopamine 2 receptor’ has also been linked to an increased risk in alcoholism, obesity, bulimia and binge eating disorder. In addition, its presence has been observed amongst those suffering from anorexia and a desire to be thin (5). Such findings suggest that the presence of the ‘A1 allele’ might in fact influence the development of many other psychological disorders (6).

The importance of genetics is supported by research showing strong links between sugar addiction and individuals with a paternal history of alcohol and drug addiction. Interestingly associations have also been made between many addictive behaviours including bulimia, binge eating, certain forms of obesity and alcohol dependence, with the thought that such disorders are linked to issues with the endorphin system (3).

Serotonin & tryptophan:

Research has also shown that sugar or carbohydrate cravings might in fact be caused by low levels of the neurotransmitter serotonin or its substrate tryptophan (an amino acid). Serotonin is involved in the regulation of happiness, well-being and pain modulation. It also helps to regulate the circadian rhythm and sleep patterns.

Foods high in carbohydrates and sugar increase serotonin production, which as a result elevates one’s mood, helps to manage pain and can induce sleepiness. Therefore, individuals that crave sugary foods, might actually be experiencing low levels of serotonin. This might elucidate why many individuals crave sugary comfort foods in the evening or when they are feeling low or stressed. Serotonin levels also tend to be reduced around the time of female menstruation, explaining why many women feel low and crave comfort foods at this time (3).

Alternatively, it has been documented that sugar or carbohydrate craving might be due to low levels of tryptopha, which is an amino acid and the precursor for serotonin. It is understood that following the consumption of food, tryptophan and six other amino acids compete for entry to the brain. Out of the seven amino acids, the amino acid most prevalent in the blood will gain access into the brain (3).

As tryptophan is not present in many foods, it can be challenging for tryptophan to dominate and gain entry to the brain. High carbohydrate meals have however been found to aid the dominance of tryptopha, therefore gaining entry into the brain. This is enabled by the carbohydrate rich meal causing increased blood glucose levels, therefore stimulating the release of insulin from the pancreas. Interestingly the remaining six amino acids that compete with tryptophan are sensitised to insulin, therefore causing them to leave the blood, allowing tryptophan to dominate. Individuals can experience a feeling of sleepiness following increases in both tryptophan and serotonin (7).

Due to serotonin’s positive effects on mood and pain-modulatio, it might not be surprising that chronic carbohydrate cravings such as this have been found to be prevalent amongst certain groups. These include individuals with obesity, bulimia, binge eating disorders, smokers, alcoholics, those with drug dependence and those suffering from chronic pain, such as diabetic neuropathy (3).

Ways to naturally increase serotonin include a healthy diet, with a focus on improving gut bacteria, avoiding sugar and an increased consumption of micronutrients. It is also helpful to ensure you are getting enough sleep, as this is a time where serotonin is replenished.  Managing your stresslevels and taking part in regular exercise can also be beneficial.

Other areas of the brain:

In addition to the nucleus accumbens, other areas of the brain have also been found to be involved in sugar addiction. These include the orbito-frontal cortex, caudate nucleus, hippocampus and insula.

The orbito-frontal cortex is another area of the brain involved in reward processes. Interestingly, research analysing the brain activity of individuals following sugar consumption showed stimulation of this specific area.  It also showed that simply being presented with food stimulated this area amongst those who are food-deprived or just simply hungry (1).

The caudate nucleus, hippocampus and insula are all areas of the brain that have been found to be stimulated during periods of food cravings. Such findings support the understanding that sensory memory plays an important part in one’s food cravings, as individuals have a vision of what needs to be consumed, in order to satisfy their cravings. The same areas of the brain have been found to be active amongst those with drug addiction (4).

Environmental influences:

As witnessed amongst other addictive traits, the effect of our environment and our learned behaviours can also play a significant role on our relationship with food. For example, an alcoholic or drug addict might succeed in rehab and come out feeling very motivated. However, on return to their environment, they will most likely experience cravings due to environmental cues.

This can be applied to food cravings, as the sight, smell or even discussion of food can trigger a desire that might not have been there. Similarly, if you live with others that bring certain foods into the homen, it can induce a desire for these foods that wouldn’t have been there had they not have been exposed to you. Have you ever started a diet, then someone at work offers you a biscuit and you cave? It is for this reason that some individuals find it easier to remove any triggers from their environment (4).

This is an interesting consideration as it is very hard to avoid sugar in today’s society. With so many chronic ailments associated with excessive sugar intake, should more be done to help us avoid the temptation?

So what can we do?

The research behind sugar addiction presents us with some compelling evidence. As a result, we can gain a better understanding of why we might have these tendencies to crave sugary foods. That being said, with the increased occurrence of chronic disease as a result of lifestyle factors like our diets, it is imperative that we do something to tackle our sugar cravings.

Finding ways to improve your nutritional education and keep yourself motivated and accountable can be incredibly helpful in tackling sugar addiction. Following a plan and using tools such as our Low Carb Program is a prime example of how you can make improvements.

References

  1. Bento, D. (2010) The phenomenon of drug craving. Clinical Nutrition. 40(3), 288-303.
  2. Avena et al. (2008) Evidence for sugar addiction: behavioural and neurochemical effects of intermittent, excessive sugar intake. Neuroscience and Biobehavioural Reviews. 32, 20-39.
  3. Fortuna, J, L. (2010) Sweet preference, sugar addiction and the familial history of alcohol dependence: shared neural pathways and genes. Journal of Psychoactive Drugs. 42(2), 147-151.
  4. Pelchat, M, L. (2009) Food addiction in human. The Journal of Nutrition. 139(3), 620-622.
  5. Davis et al. (2008) Reward sensitivity and the dopamine 2 receptor gene: a case control study of binge eating disorder. Progress Neuropsychopharmacology and Biological Psychiatry. 32(3), 620-628.
  6. Nisoli et al. (2007) D2 dopamine receptor (DRD2) gene Taq1A polymorphism and the eating-related psychological traits in eating disorders (anorexia nervosa and bulimia) and obesity. Eating and Weight Disorders. 12(2), 91-96.
  7. Fortuna, J, L. (2009) Nutrition for the Focused Brain. 1st Cincinnati: Cengage Publishing.
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