Most of us would agree that we could be a little healthier; eat more fruits and vegetables, exercise more, get more sleep, etc.  But are we harming ourselves without realizing it through our high (and often hidden) sugar consumption?

The American Heart Association (AHA) recommends that adults consume no more than 6 to 9 teaspoons of sugar a day (children and teenagers even less); however, according to the AHA many Americans are estimated to be eating up to 22 teaspoons of sugar every day (AHA, 2015).  That averages to be 765 grams of sugar every five days, while collectively Americans are consuming over 130 pounds of sugar each year.  Health professional have been aware for some time that excess consumption sugar may result in negative side effects, but recent research has uncovered some concerning facts regarding the impact sugar is having not only on our bodies but also our minds.  

Why is Sugar Bad for Us?

It has long been known that eating too much sugar or too many sugary foods can often lead to weight gain.  Research has linked excessive sugar consumption to a whole host of health problems including; obesity, diabetes, cardiovascular disease, high blood pressure, increased aging, acne, lowered immunity and even infertility.  In fact, some health professionals now believe it to be as harmful if not more so than salt after a clinical study showed that sugar contributed to high blood pressure more than sodium (Prasad et al, 2014).  This is of particular interest to the medical community as hypertension was a contributing factor in nearly 350,000 deaths in the US in 2009, and costs the nation more than $50 billion annually (Nicholls, 2014). 

Additionally, excess sugar consumption has recently been linked to several forms of cancer.  One study (Liu, et al., 2011) found that high levels of fructose (from high-fructose corn syrup, not fruit) stimulated the growth of pancreatic cancer cells.  Meanwhile, another study reported a correlation between high levels of glucose and breast cancer (Onodera, Nam, & Bissell, 2014).

There is also some evidence to suggest that there may be links between sugar consumption and mental health.  Research comparing individuals who ate a Western diet (processed or fried foods, refined grains, sugary products, and beer) and those who ate a ‘traditional’ diet (vegetables, fruit, meat, fish, and whole grains) found that those on the Western diet had significantly higher odds of developing depression and anxiety (Jacka et al, 2010).  Meanwhile, another study found that woman with lowered blood sugar levels due to exercise experienced significantly less anxiety than woman whose sugar levels were higher (Sun, Byung-Jun, & Seon-Rye, 2014). 

Understanding How Sugar Affects Your Brain

There are two important things to understand about sugar and the brain.  First of all, sugar is addictive.  Put simply, sugar consumption stimulates the release of dopamine in the brain.  Dopamine is a chemical responsible for regulating feelings of pleasure, and is therefore a key element in addiction (Tang et al, 2012).  The rush of pleasure you receive from eating sugary food leads you to crave more, and when you give in to the craving it begins once more, creating a vicious cycle.  Not surprisingly sugar has also been linked to overeating and binge eating, as the positive reinforcement offered by the release of dopamine overrides physical sensations of not being hungry, or having eaten enough (Ames, et al., 2014).   

The second way sugar affects the brain is in its interference with essential brain functioning.  Research has found that individuals, who have a diet high in sugar, experience a gradual loss of an extremely important chemical in the brain called brain-derived neurotrophic factor (BDNF) (Francis & Stevenson, 2011). BDNF is responsible for the creation of neurons at birth and throughout our lives as well as encouraging the growth of new synapses in our brains. Additionally, it plays an important role in learning and memory – particularly long term memory.  Researchers have reported that individuals experiencing a lowered level of BDNF due to a diet high in sugar and fat perform poorly on memory tests (ibid). 

Reduced levels of BDNF have also been linked to a range of cognitive disorders.  BDNF levels are typically critically low in individuals suffering from depression and schizophrenia, and since excess sugar has been found to lower BDNF in humans some researchers have suggested a correlation between the two (Suliman, Hemmings, & Seedat, 2013). 

There are also well established links between depression and type 2 diabetes (a disorder commonly caused by a long term intake of excess sugar that the body cannot adequately process), as well as links between type 2 diabetes and lower levels of BDNF suggesting the three could be correlated – with sugar at the core (Pan, Lucas, & Sun, 2010).  

Recent research suggests that sugar may affect the brains functioning in another way too – by impairing the blood brain barrier which is essential for proper cognitive functioning (Kanoski, S, Zhang, Y, Zheng, W & Davidson, T, 2010).  The side effects from this interference can impair an individual’s learning and memory, as well as potentially contributing to them developing Alzheimer’s disease (Kanoski & Davidson, 2011). 

Who is at Risk?

Anyone who consumes a high sugar diet is potentially at risk, but research suggests that it is particularly those individuals whose diet and lifestyle choices have led them to be overweight who are especially susceptible to experiencing one or more of these negative side effects (Pan, Lucas, & Sun, 2010). Our bodies simply aren’t designed to process the amount of sugar we are currently consuming, and when combined with other unhealthy lifestyle habits such as inactivity and a diet high in fat, we create a toxic environment within ourselves.

Furthermore, if you have a history of mental health issues such as depression, or if you suffer from it yourself you are at a heightened risk as the reduction of BDNF can exacerbate your symptoms (Suliman, Hemmings, & Seedat, 2013).  

What Can You Do?

There is good news. Living a healthy lifestyle by incorporating a range of fresh fruits and vegetables into your diet, limiting your added sugar intake and exercising regularly will in most cases protect you from the damaging effects of sugar. In fact, even if you have a sweet tooth, many of the negative effects that arise from excess sugar consumption can be reversed. 

As well as limiting your intake of sugary beverages and foods, it pays to look carefully at the ingredients in some of the foods you buy.  Many packaged food items contain high amounts of sugar.  For example; flavored chips and crackers, cereals, canned fruit, sports drinks, fruit juices, and granola bars are all often extremely high in sugar.  Replacing sugar with natural sweeteners such as stevia or agave is also a good option.

Exercise is also extremely important as research has found that regular exercise actually increases levels of BDNF in the brain therefore encouraging neuron support and growth (Jimenez-Maldonardo et al, 2014).  This does not have to be intensive or extreme. Researchers found that frequent gentle aerobic exercise was proven to be the most effective at consistently producing BDNF (Schmolesky, M, Webb, D & Hansen, R, 2013).   

For further information about the harmful effects of sugar, or to find out more about the recommended daily intakes check out the American Health Associations website at www.heart.org. 

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References

American Health Association.  (2015).  Added Sugars.  Retrieved from, http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/HealthyEating/Added-Sugars_UCM_305858_Article. jsp

Ames, S., Kisbu-Sakarya, Y., Reynolds, K., Boyle, S., Cappell, C., Cox, M., Dust, M., Grenard, J., Mackinnon, D., Stacy, A. (2014).  Inhibitory control effects in adolescent binge eating and consumption of sugar-sweetened beverages and snacks. Appetite. 180, 180 – 192.

Francis, H, M., & Stevenson, R, J. (2011).  Higher reported saturated fat and refined sugar intake in associated with reduced hippocampal – dependent memory and sensitivity to interoceptive signals.  Behavioural Neuroscience. 125(6), 943 – 955.

Jacka, N., Pasco, A., Mykletun, A., Williams, L., Hodge, A., O’Reily, L., & Berk, M. (2010).  Association of Western and traditional diets with depression and anxiety in women.  The American Journal of Psychiatry. 167(3), 305 – 311. 

Jimenez-Maldonado, A., de Alvarex-Bullya, E., Montero, S., Melnikov, V., Castro-Rodriguez, E., Gamboa-Dominguez, A., * Murguia, J. (2014).  Chronic exercise increases plasma brain-derived neurotrophic factor levels, pancreatic islet size, and insulin tolerance in a TrKB-Dependent Manner.  Plos ONE. 9(12), 1 – 18. 

Kanoski, S., Zhang, Y., Zheng, W., & Davidson, L. (2010). The Effects of a High-Energy Diet on Hippocampal Function and Blood-Brain Barrier Integrity in the Rat. Journal of Alzheimer’s Disease. 21(1),  207 – 219.

Kanoski, S., & Davidson, T. (2011).  Western diet consumption and cognitive impairment: Links to hippocampal dysfunction and obesity. Physiology & Behaviour.  103(1), 59 – 68. 

Liu, H., Huang, D., McArthur, DL., Boros, LG., Nissen, N., & Heaney, AP. (2010).  Fructose induces transketolase flux to promote pancreatic cancer growth. Cancer Research.  70(15), 6368-6376.

Nicholls, H. (2014). More than salt, sugars may contribute to high blood pressure.  Retrieved from http://www.medicalnewstoday.com/articles/286795.php.

Onodera, Y., Nam, J.-M., & Bissell, M. J. (2014). Increased sugar uptake promotes oncogenesis via EPAC/RAP1 and O-GlcNAc pathways. The Journal of Clinical Investigation, 124(1), 367–384.

Pan, A., Lucas, M., & Sun, Q. (2010). Bidirectional Association Between Depression and Type 2 Diabetes Mellitus in Women. Archives of International Medicine. 170(21), 1884-1891. 

Prasad, D., Kabir, Z., Devi, K., Dash, A., & Das, B. (2014).  Cardiac risk factors and prevention. Subclinical atherosclerosis and silent myocardial ischaemia in patients with type 2 diabetes: a protocol of a clinico-observational study.  Open Heart. 1(1) Retrieved from http://openheart.bmj.com/content/1/1/e000100.full?sid=05c8b5c0-7796-4971-9e8e-1da00956f3a8

Robinson, S. (2013). Mental health: High blood sugar hits memory. General Practitioner, 42.

Schmolesky, M., Webb, D., & Hansen, R.  (2010). The Effects of Aerobic Exercise Intensity and Duration on Levels of BrainDerived Neurotrophic Factor in Healthy Men. Journal of Sports Science and Medicine. 12, 502-511.

Suliman, S., Hemmings, S., & Seedat, S. (2013).  Brain – derived Neurotrophic Factor (BDNF) protein levels in anxiety disorders: Systematic review and meta-regression analysis.  Frontiers in Integrative Neuroscience. 7(55). 

Sun, H., Byung-Jun, C., & Seon-Rye, K. (2014).  Comparison of the Effects of Exercise Participation on Psychosocial Risk Factors and Cardiovascular Disease in Women.  Journal of Physical Therapy Science.  26(11),  1795 – 1798.

Tang, W., Fellows, L., Small, D., & Dagher, A. (2012). Food and Drug Cues Activate Similar Brain Regions: A Meta-Analysis of Functional MRI Studies. Physiology & Behavior.  106(3), 317-324.